AVI Overview
        by John F. McGowan, Ph.D.
                      (c) 1996-1998, John F. McGowan


What is in this Overview?

       - Overview of Video for Windows, ActiveMovie, and AVI

       What is AVI?


       WHAT'S NEW

       - How to play an AVI file?
                    - DOS
                    - Windows
                    - Macintosh
                    - Unix
                    - VAX/VMS
                    - Amiga
                    - OS/2

       - How to convert AVI to various audio/video formats.
                    - MPEG (.MPG Files)
                    - QuickTime (.MOV or .MooV)
                    - Animated GIFs (GIF89a)
                    - Microsoft ASF (Active Streaming Format)
                    - Sequence of Still Images in Separate Files
                    - Smacker (.SMK Files)
                    - Progressive Networks RealMedia Streaming Format (.RM Files)

       - How to convert other audio/video formats to AVI
                    - QuickTime (.MOV or .MooV)
                    - Sequence of Still Images in Separate Files
                    - Autodesk Animation (FLI or FLC)
                    - MPEG (.MPG)
                    - Animated GIF (.GIF)

       - How to Convert a Sequence of Still Images in One Format to a Sequence in Another Format

       - Authoring AVI Files

                CREATING AVI FILES

                    - How to capture screen to AVI files
                    - Multimedia Authoring Tools to Create AVI Files
                    - How to import AVI files into Lightwave               
                    - How to create AVI files from analog video (Video Capture Cards)
                             - From VHS tapes and video cameras
                             - From Hi8 tapes and video cameras
                             - Video Capture under Video for Windows
                             - Video Capture Cards
                             - What to do about horizontal tearing in the video?
                             - Hard Drive Video Capture Issues
                             - Video Capture Cards with Windows NT Drivers
                    - How to create AVI files from Television
                    - How to Create Morph Effects for AVI Files


                    - How to change frame rate of AVI files
                    - How to crop an AVI file
                    - How to edit AVI files
                             - VidEdit
                             - Personal AVI Editor
                             - MGI VideoWave 
                             - Corel Lumiere Suite for 32-bit Windows
                             - Ulead Media Studio Pro
                             - Adobe Premiere
                             - in:sync SpeedRazor
                             - Asymetrix Digital Video Producer (DVP)
                    - How to create NTSC (or PAL) Safe AVI
                    - The Phantom Final Frame when Viewing an AVI
                    - Binary File Editors for Viewing and Editing AVI
                    - RIFF and AVI Parser/Viewers
                             - VidTrace
                             - Microsoft RIFFWALK
                    - Editing and converting WAV files
                    - Editing and converting Sound Files on Macintosh

                    - How to output AVI files to videotape
                    - Size limits on AVI files
                    - How to Fix Problem with AVI files from CorelMove 4.0

       Installation, Configuration, and Other Issues


                       - Where to get the 16-bit Video for Windows for Windows 3.x
                       - Reinstalling Microsoft's Video-for-Windows in Windows 95
                       - How to get ActiveMovie 1.0
                       - Installing and configuring AVI Codecs in Windows NT 4.0
                       - How to give AVI files a different extension in Windows 3.1
                       - How AVI Files are Handled in Windows 95

                    INFORMATION SOURCES
                       - Bibliography of sources of information on Video for Windows and AVI
                       - Internet Newsgroups with Information on AVI and Video 


                       - PC Video Card and Video Chips
                                         - Video Cards with Windows NT Drivers
                       - How to embed an AVI file in a Microsoft Word Document
                       - Microsoft's Changing Names
                       - Answers to miscellaneous other frequently asked questions about AVI 

                       -  AVI and Your Health (Eye Strain)

        AVI and the WORLDWIDE WEB
               - Effective use of video on a Web page
               - How to embed an AVI file in a Web page
               - Configuring Netscape Navigator 3.0x to Display AVI Files
        - Netscape Navigator Plug-ins to play AVI
               - Configuring Internet Explorer 3.0x to Display AVI Files
               - Sending AVI by E-Mail or Network News Postings
               - How to encrypt AVI Files

               - MIME types of AVI
               - Configuring Web Servers to Handle AVI Files
                         - Apache
                         - CERN (or W3C)
                         - NCSA HTTPd
                         - Microsoft Internet Information Server 3.0
                         - Netscape Enterprise Server 3.0

               - AVI and Java
               - AVI and VRML
               - AVI and NetShow
               - Converting AVI to Microsoft Active Streaming Format (ASF) Files
               - Sources of AVI Video Clips on the Web
               - Low Bit Rate AVI for the Web

               - Limitations of AVI and Video for Windows over Networks
               - NetShow
               - Microsoft's Changing Names
               - Internet Video Standards and Pseudo-Standards

               - Video for Windows compressors and decompressors
                         - The Old Guard
                               - Full Frames (Uncompressed)
                                      - Color Formats
                               - Indeo 3.2/3.1
                               - Microsoft Run Length Encoding
                               - Microsoft Video 1
                               - CinePak
                               - Motion JPEG
                               - Editable MPEG
                          - The New Wave 
                               - VDOWave (VDOLive)
                               - Indeo Video Interactive (Indeo 4.1)
                               - Indeo Video Interactive (Indeo 5.0)
                               - ClearVideo (aka RealVideo)
                               - SFM (Surface Fitting Method)
                               - QPEG
                               - H.261
                               - H.263
                                        - Microsoft H.263
                                        - Vivo Software H.263
                                        - Intel I263 H.263
                               - MPEG-4
                               - Lightning Strike (Infinop)
                               - VxTreme

               - Which codec is best?
               - How to determine which codecs are installed
               - How to determine which codec was used to compress an AVI file
               - Microsoft Four Character Codes (FOURCC)
               - Color Formats
               - Video Compression Technologies
                        Run Length Encoding
   Vector Quantization
                        Discrete Cosine Transform
                        Frame Differencing
                        Motion Compensation

               - Audio Codecs
               - How to determine which Audio Codecs are Installed




                   THE OLD REGIME

                       - Windows Multimedia System
                       - Video for Windows
                       - Wave (Waveform Audio)
                       - AVI file format
                                - RIFF Files
                                - Original AVI File Format
                                - OpenDML AVI File Format Extensions
                                - Where to get the exact specification of AVI?
                                - AVI and Windows Bitmaps (DDB, DIB, ...)
                    THE NEW WAVE

                       - ActiveMovie
                       - GUID's and AVI
                       - DirectShow (ActiveMovie 2.0)
                       - DirectDraw
                       - MMX
                       - ActiveX
                       - Microsoft's Changing Names

                    HOW TO PROGRAM IN WINDOWS
                       - Playing an AVI file within a Windows Application
                       - Reading and Writing an AVI file within a Windows Application


                      SOURCE CODE
                       - Where to get C source code for an AVI Player Including Many Codecs
                       - Where to get C source code for a JPEG Encoder or Decoder
                       - Where to get C source code for an H.263 Video Encoder or Decoder
                       - Where to get C source code for an MPEG Video Encoder or Decoder
                       - Where to get C/C++ Source Code for Wavelet Image Compression

                      TECHNICAL INFORMATION 
                       - Where to get an explanation of Color, Color Spaces, Gamma and All That
                       - Where to get Detailed Information on Graphics File Formats?
                       - Where to get Detailed Information on Audio File Formats?

                       - Internet Video Standards
                              - MIME
                              - RTP (Real Time Protocol)
                              - RSVP (Resource Reservation Protocol)
                              - IP Multicast
                              - UDP (User Datagram Protocol)
                       - What is a driver?
                       - GDI Device Drivers
                       - DirectDraw Hardware Abstraction Layer
                       - Virtual Device Drivers
                       - Windows NT Driver Model
                       - Win32 Driver Model (WDM)
                       - Setup Information Files


               ABOUT THE AUTHOR

               - John McGowan is a software engineer with experience
in digital audio and video on PC/Windows, Unix/X Windows, and
PowerMacintosh platforms.  He has developed commercial MPEG-1 and
MPEG-2 player software.  His experience includes development,
optimization, and implementation of audio, video, and still image
compression and decompression algorithms in C/C++ on Intel, MIPS,
SPARC, and PowerPC based platforms.  He has also developed Microsoft
Windows user interface software.  He has a Ph.D. in physics from the
University of Illinois at Urbana-Champaign and a B.S. in physics from
the California Institute of Technology.

               - John McGowan's Home Page


In no event shall John McGowan or other contributors be liable for direct, indirect, special, incidental or consequential damages arising out of the use or inability to use information, softwares, bitstreams and other data found on or referenced by the AVI Graphics Overview. Permission to copy and distribute this document is granted so long as the title, author's name, URL, and this disclaimer are retained. Any additions or modifications made to the original should be clearly marked as such. The author welcomes and encourages suggested changes and additions to the overview. Contributors will be credited.
Return to Top

What's New

(November 12, 1997) Microsoft has a new NetShow distribution NetShow 2.1 NetShow 2.1 adds support for RealNetworks (formerly Progressive Networks) RealVideo and RealAudio, NetShow clients for Windows 3.1, MacOS, and the Linux, Solaris, SunOS, and HP-UX versions of Unix, and TheaterServer for streaming broadcast-quality video over highbandwidth networks such as ATM and fast Ethernet. Microsoft has invested in RealNetworks within the last few months. (October 30, 1997) Wolfgang Hesseler writes about his AVI viewer for DOS: Hello, I just wanted to let you know that I've released the new QuickView 2.20. Besides supporting more hardware and MOV files it supports the QPEG codec. Please update your FAQ. Thanks. (September 8, 1997) Microsoft distributes Advanced Streaming Format (ASF) Specification for a "Public Design Review". Microsoft ASF Page (September, 1997) Lernout and Hauspie Speech Products forms a strategic partnership with and receives investment capital from Microsoft. $45 million in some reports. BT Alex Brown acted as financial advisor. Lernout and Hauspie audio codecs are used in Microsoft's NetShow product. (September, 1997) avi2mpg1 released. A Windows 95/NT console application to convert AVI to MPEG-1. (August 5, 1997) Microsoft acquires VxTreme (wavelet based streaming video) for its NetShow product line. VxTreme Inc. Intel's Indeo Video Interactive 5.0 software is now available on Intel web site. Wolfgang Hesseler announces version 2.13 of QuickView, an AVI player for DOS (July 28, 1997) MainConcept announces version 1.1 of MainActor shareware. MainActor can convert between AVI and many video, animation, and image formats. (July 9, 1997) Marcus Moenig of MainConcept writes: John, well here comes the press release of v1.1 We now support full MPEG-I and MPEG-II without audio. So you can now convert MPEG into AVI and vice versa. I dont want to get on your nerves on what MainActor can and cannot do but we also support full Motion JPEG for AVIs. Even interlaced JPEG from Miro and FAST hardware can now be read and written by MainActor. ---End--- RAD Game Tools announces a new version of their Smacker utilities, including the ability to read and write AVI files with optimized 8 bit color palettes. (June 27, 1997) Return to Top

What is AVI?

AVI stands for Audio Video Interleave. It is a special case of the RIFF (Resource Interchange File Format). AVI is defined by Microsoft. AVI is the most common format for audio/video data on the PC. Return to Top

Windows Multimedia System

In Win16 and Win32, Microsoft created a partially unified system for handling multimedia. This system consists of the high level Media Control Interface or MCI Application Programming Interface (API) and associated MCI drivers. Playback of AVI files can be controlled through the high level MCI API and the MCIAVI.DRV MCI driver. The Windows Multimedia System also provides a number of low level API's such as the WAVE API for waveform audio and associated device drivers such as the WAVE device drivers for sound cards. Under Windows NT 4.0, the MCI and low level API's are stored in the file WINMM.DLL The API's are: MCI (high level API - useful for AVI playback) joy (joystick devices) midi (MIDI devices) mixer (MIXER devices) wave (waveform audio input and output devices) mmio (low level functions to parse RIFF files) time (timers etc.) aux (auxiliary sound device) When a program loads the MCIAVI driver, the Multimedia System has the intelligence to locate and invoke the appropriate MCI driver (MCIAVI.DRV in 16-bit Windows or MCIAVI32.DLL in 32 bit windows) and pass the MCI commands such as MCI_PLAY to the MCI driver. The MCIAVI driver then calls Video for Windows to decompress the video, GDI (or another graphics API) to display the decoded frames, and WAVE to output the decoded audio samples. A dump of the functions exported by winmm.dll under NT 4.0 generated with the Microsoft DUMPBIN.EXE utility follows: Microsoft (R) COFF Binary File Dumper Version 5.00.7022 Copyright (C) Microsoft Corp 1992-1997. All rights reserved. Dump of file winmm.dll File Type: DLL Section contains the following Exports for WINMM.dll 0 characteristics 31EC70B4 time date stamp Tue Jul 16 21:48:52 1996 0.00 version 2 ordinal base 197 number of functions 197 number of names ordinal hint name 3 0 CloseDriver (000026CE) 4 1 DefDriverProc (00005AF4) 5 2 DriverCallback (0000254E) 6 3 DrvGetModuleHandle (00001D37) 7 4 GetDriverModuleHandle (00001D37) 8 5 MigrateAllDrivers (00013E79) 9 6 MigrateMidiUser (00013E60) 10 7 MigrateSoundEvents (00011A3C) 11 8 NotifyCallbackData (0000B2C2) 12 9 OpenDriver (00002036) 13 A PlaySound (00008ACB) 2 B PlaySoundA (00008ACB) 14 C PlaySoundW (00009AE1) 15 D SendDriverMessage (00001000) 16 E WOW32DriverCallback (0000C448) 17 F WOW32ResolveMultiMediaHandle (0000CC3C) 18 10 WOWAppExit (00009D3F) 19 11 aux32Message (0000C507) 20 12 auxGetDevCapsA (0000A3FD) 21 13 auxGetDevCapsW (00008C77) 22 14 auxGetNumDevs (00006AE4) 23 15 auxGetVolume (0000A4A1) 24 16 auxOutMessage (00008BFF) 25 17 auxSetVolume (0000A4C9) 26 18 joy32Message (0000C768) 27 19 joyConfigChanged (0000AE40) 28 1A joyGetDevCapsA (0000A99A) 29 1B joyGetDevCapsW (0000AB40) 30 1C joyGetNumDevs (0000AB96) 31 1D joyGetPos (0000ABAA) 32 1E joyGetPosEx (0000ABFD) 33 1F joyGetThreshold (0000AC5C) 34 20 joyReleaseCapture (0000ACA8) 35 21 joySetCapture (0000ACFC) 36 22 joySetThreshold (0000AE06) 37 23 mci32Message (00007566) 38 24 mciDriverNotify (00007006) 39 25 mciDriverYield (00008727) 40 26 mciExecute (0000D92C) 41 27 mciFreeCommandResource (000035CE) 42 28 mciGetCreatorTask (0000DCD5) 43 29 mciGetDeviceIDA (0000DCA3) 44 2A mciGetDeviceIDFromElementIDA (0000DBC6) 45 2B mciGetDeviceIDFromElementIDW (0000DBF5) 46 2C mciGetDeviceIDW (00005372) 47 2D mciGetDriverData (0000158B) 48 2E mciGetErrorStringA (0000DA46) 49 2F mciGetErrorStringW (0000352F) 50 30 mciGetYieldProc (0000E1F3) 51 31 mciLoadCommandResource (00002A75) 52 32 mciSendCommandA (000015D4) 53 33 mciSendCommandW (000014A1) 54 34 mciSendStringA (00004927) 55 35 mciSendStringW (00004A24) 56 36 mciSetDriverData (000058BD) 57 37 mciSetYieldProc (000034C9) 58 38 mid32Message (0000BDFD) 59 39 midiConnect (0001019E) 60 3A midiDisconnect (0001018C) 61 3B midiInAddBuffer (0001004A) 62 3C midiInClose (0000FF42) 63 3D midiInGetDevCapsA (0000FCCC) 64 3E midiInGetDevCapsW (0000FC71) 65 3F midiInGetErrorTextA (0000FDEB) 66 40 midiInGetErrorTextW (0000FDB2) SetInfo (0000EBF4) 140 8A mmioStringToFOURCCA (0000ED9A) (00008BC5) Under Windows 3.x and Windows 95, the DLL MMSYSTEM.DLL (short for MultiMedia System) contains the multimedia API's. Return to Top

Video for Windows

Video for Windows is an entire system for handling video in Microsoft Windows. It was part of MS Windows 3.1 The original Video for Windows is a collection of 16 bit windows utilities, dynamic link libraries, and other components. The AVI file and file format is a central part of Video for Windows. Microsoft Visual C++ 5.0 has a Video for Windows include file Vfw.h which contains the various API's that make up Video for Windows: * COMPMAN - Installable Compression Manager. * DRAWDIB - Routines for drawing to the display. * VIDEO - Video Capture Driver Interface * * AVIFMT - AVI File Format structure definitions. * MMREG - FOURCC and other things * * AVIFile - Interface for reading AVI Files and AVI Streams * MCIWND - MCI/AVI window class * AVICAP - AVI Capture Window class * * MSACM - Audio compression manager. Microsoft released a Video for Windows 1.0 for Windows 3.1 in November 1992, followed by Video for Windows 1.1. There have been several versions of Video for Windows 1.1 identified by a trailing alphabetical character such as 1.1e The last and most recent version of Video for Windows 1.1 for Windows 3.x is Video for Windows 1.1e This is available by ftp from Microsoft. Microsoft has provided a 32-bit version of Video for Windows for Windows 95, while threatening to replace Video for Windows with ActiveMovie. This version has 32 bit versions of the Video for Windows codecs such as CinePak. Other DLL's in the Video for Windows 95 are also 32-bit How much of the Video for Windows in Windows 95 is 32 bit code is not clear; many of the codecs are clearly 32 bit codecs. Nor is it clear how much has been changed or modified besides the convesion to 32-bit code. Windows NT 3.5, 3.51 and Windows NT 4.0 include a Video for Windows for NT. Presumably this is strictly 32-bit. It is not clear how much code is shared between the NT Video for Windows and the Windows 95 Video for Windows. Note that hardware device drivers are different between Windows 95 and NT 3.5/3.51/4.0. ActiveMovie 1.0 and DirectShow (formerly ActiveMovie 2.0) are 32-bit successors to Video for Windows for both Windows 95 and Windows NT. These support AVI files. ActiveMovie started out life under the code name Quartz; early Beta releases of ActiveMovie were known as Quartz. ActiveMovie 1.0 is bundled with Windows 95b (OEM Service Release 2.x) and Internet Explorer 3.x/4.x for Windows 95. It can also be downloaded and installed in Windows 95 separately. Note that ActiveMovie 1.0 does NOT completely replace Video for Windows. For example, ActiveMovie 1.0 does not provide a video capture mechanism. Video capture still uses Video for Windows capture drivers. ActiveMovie 1.0 is a 32 bit software component that can run in NT's user mode. It runs under Windows NT 4.0 as well as Windows 95. DirectShow (ActiveMovie 2.0) will supposedly add a number of new features including video capture support, kernel mode streaming, and miscellaneous other features. VIDEO FOR WINDOWS under WINDOWS NT 4.0 Under NT 4.0, Video for Windows is implemented as a collection of 32-bit DLL's in the Microsoft 32-bit Common Object File Format or COFF format. These are usually located in the \WINNT\SYSTEM32 directory where Windows NT stores most of the system DLL's, drivers, and so forth. MSVFW32.DLL ( Microsoft Video for Windows DLL - NT 4.0 ) AVIFIL32.DLL ( AVIFILE API for Reading and Writing AVI Files and Streams ) AVICAP32.DLL ( AVI Capture Window Class ) MCIAVI32.DLL ( Video for Windows MCI Driver ) MSACM32.DRV ( Microsoft Audio Compression Manager ) MSACM32.DLL ( more Microsoft Audio Compression Manager ) MSRLE32.DLL ( Microsoft RLE Video Codec ) IR32_32.DLL ( Intel Indeo 3.2 Video Codec ) MSVIDC32.DLL ( Microsoft Video 1 Codec ) ICCVID.DLL ( Cinepak for Windows 32 - Radius ) What is in MSVFW32.DLL? MSVFW32.DLL includes the DRAWDIB, Installable Compression Manager or ICM, and MCI Windows components of Video for Windows. Other components are stored in other DLL's. This is a dump of the functions exported by MSVFW32.DLL Version 4.00 Microsoft (R) COFF Binary File Dumper Version 5.00.7022 Copyright (C) Microsoft Corp 1992-1997. All rights reserved. Dump of file msvfw32.dll File Type: DLL Section contains the following Exports for MSVFW32.dll 0 characteristics 31EC70E9 time date stamp Tue Jul 16 21:49:45 1996 0.00 version 2 ordinal base 47 number of functions 47 number of names ordinal hint name 3 0 DrawDibBegin (00001E14) 4 1 DrawDibChangePalette (00008C30) 5 2 DrawDibClose (0000888A) 6 3 DrawDibDraw (000010A6) 7 4 DrawDibEnd (00008BEC) 8 5 DrawDibGetBuffer (00008EFC) 9 6 DrawDibGetPalette (00002F97) 10 7 DrawDibOpen (00003E0A) 11 8 DrawDibProfileDisplay (00003EBA) 12 9 DrawDibRealize (00001D49) 13 A DrawDibSetPalette (00001C0D) 14 B DrawDibStart (00002EEB) 15 C DrawDibStop (00002F42) 16 D DrawDibTime (00008C2B) 17 E GetOpenFileNamePreview (0000C7DC) 18 F GetOpenFileNamePreviewA (0000C7DC) 19 10 GetOpenFileNamePreviewW (0000C6A5) 20 11 GetSaveFileNamePreviewA (0000C7EC) 21 12 GetSaveFileNamePreviewW (0000C7CC) 22 13 ICClose (000035E0) 23 14 ICCompress (00004CE5) 24 15 ICCompressorChoose (00005F61) 25 16 ICCompressorFree (00005615) 26 17 ICDecompress (00004D4B) 27 18 ICDraw (0000106A) 28 19 ICDrawBegin (00001B95) 29 1A ICGetDisplayFormat (00004D8E) 30 1B ICGetInfo (00004C60) 31 1C ICImageCompress (00005A96) 32 1D ICImageDecompress (00005D2A) 33 1E ICInfo (00002FEB) 34 1F ICInstall (00004574) 35 20 ICLocate (0000372E) 36 21 ICMThunk32 (0000841C) 37 22 ICOpen (0000337C) 38 23 ICOpenFunction (00003B53) 39 24 ICRemove (0000488B) 40 25 ICSendMessage (00001000) 41 26 ICSeqCompressFrame (000059A7) 42 27 ICSeqCompressFrameEnd (00005907) 43 28 ICSeqCompressFrameStart (000056E4) 44 29 MCIWndCreate (0000C988) 45 2A MCIWndCreateA (0000C988) 46 2B MCIWndCreateW (0000C8CC) 47 2C MCIWndRegisterClass (0000C83F) 48 2D StretchDIB (00009D13) 2 2E VideoForWindowsVersion (000041D1) Summary 8000 .data 3000 .rdata 2000 .reloc 3000 .rsrc 11000 .text VIDEO FOR WINDOWS FOR WINDOWS 95 Microsoft distributed a new Video for Windows for Windows 95 while emphasizing Quartz/ActiveMovie/DirectShow in its marketing. Video for Windows 95 Files MSRLE32.DLL (32-bit Microsoft RLE Video Codec) IR32_32.DLL (32-bit Indeo 3.2 Video Codec) ICCVID.DLL (32-bit Radius Cinepak Video Codec) MSVIDC32.DLL (32-bit Microsoft Video 1 Video Codec ) MSVIDEO.DLL (16-bit Video for Windows DLL) MCIAVI.DRV (16-bit AVI Video MCI Driver) AVIFILE.DLL (16-bit AVIFILE) AVICAP.DLL (16-bit AVICAP) AVICAP32.DLL (32-bit AVICAP) MSVFW32.DLL (32-bit Video for Windows DLL - with VfW API) AVIFIL32.DLL (32-bit AVIFILE) SUMMARY Video for Windows 1.0 (Windows 3.x) Video for Windows 1.1 (a-e) (Windows 3.x) Video for Windows (Windows 95 - has 32-bit codecs and other 32-bit DLL's) Video for Windows (Windows NT 3.5, 3.51, and 4.0) Quartz (Betas of ActiveMovie) (Windows 95) ActiveMovie 1.0 (Windows 95 and NT 4.0) ActiveMovie 2.0 (DirectShow) (probably Windows 97/98/Memphis and NT 5.0) Return to Top


The Microsoft Windows audio (sound) input/output system, commonly referred to as Wave or WAVE, predates Video for Windows, which is wrapped around WAVE in various ways. The audio tracks in AVI files are simply waveform audio (or WAV) data used by the wave system. Video for Windows parses the AVI files, extracts the WAV data, and pipes the WAV data to the WAVE system. Video for Windows handles the video track if present. Traditionally, audio input and output devices such as Sound Blaster Cards have a WAVE audio input/output driver to play WAV (waveform audio) files. The simplest waveform audio files consists of a header followed by Pulse Coded Modulation (PCM) sound data, usually uncompressed 8 or 16 bit sound samples. WAVE also provides a mechanism for audio codecs. See elsewhere in the AVI Overview for further information on audio codecs and audio compression. WAVE is present in Windows 3.1 and Windows 95. A different WAVE system is present in Windows NT 3.5, 3.51, and 4.0 At least the hardware device drivers for sound cards must be different in NT. ActiveMovie appears to be replacing WAVE. Return to Top

What is the AVI File Format?

AVI Files are a special case of RIFF files. RIFF is the Resource Interchange File Format. This is a general purpose format for exchanging multimedia data types that was defined by Microsoft and IBM during their long forgotten alliance. Kevin McKinnon writes: In fact, RIFF is a clone of the IFF format invented by Electronic Arts in 1984. They invented the format for Deluxe Paint on the Amiga, and IFF quickly became the standard for interchange on that platform, maintained eventually by Commodore right up 'til it's demise. EA also ported Deluxe Paint to the PC platform and brought IFF with it. IFF even used the 4-character headers (FourCC), though at the time it was simply called a LONGWORD that some clever people decided to pair into four charcter because they looked good in #define's. ;) RIFF is so close to IFF that the good IFF parser routines will (mostly) correctly parse RIFF files. ----End of Kevin---- Further information on the IFF format is available at: http://www.ipahome.com/gff/textonly/summary/iff.htm

RIFF Files

RIFF files are built from (1) RIFF Form Header 'RIFF' (4 byte file size) 'xxxx' (data) where 'xxxx' identifies the specialization (or form) of RIFF. 'AVI ' for AVI files. where the data is the rest of the file. The data is comprised of chunks and lists. Chunks and lists are defined immediately below. (2) A Chunk (4 byte identifier) (4 byte chunk size) (data) The 4 byte identifier is a human readable sequence of four characters such as 'JUNK' or 'idx1' (3) A List 'LIST' (4 byte list size) (4 byte list identifier) (data) where the 4 byte identifier is a human readable sequence of four characters such as 'rec ' or 'movi' where the data is comprised of LISTS or CHUNKS.

AVI File Format

AVI is a specialization or "form" of RIFF, described below: 'RIFF' (4 byte file length) 'AVI ' // file header (a RIFF form) 'LIST' (4 byte list length) 'hdrl' // list of headers for AVI file The 'hdrl' list contains: 'avih' (4 byte chunk size) (data) // the AVI header (a chunk) 'strl' lists of stream headers for each stream (audio, video, etc.) in the AVI file. An AVI file can contain zero or one video stream and zero, one, or many audio streams. For an AVI file with one video and one audio stream: 'LIST' (4 byte list length) 'strl' // video stream list (a list) The video 'strl' list contains: 'strh' (4 byte chunk size) (data) // video stream header (a chunk) 'strf' (4 byte chunk size) (data) // video stream format (a chunk) 'LIST' (4 byte list length) 'strl' // audio stream list (a list) The audio 'strl' list contains: 'strh' (4 byte chunk size) (data) // audio stream header (a chunk) 'strf' (4 byte chunk size) (data) // audio stream format (a chunk) 'JUNK' (4 byte chunk size) (data - usually all zeros) // an OPTIONAL junk chunk to align on 2K byte boundary 'LIST' (4 byte list length) 'movi' // list of movie data (a list) The 'movi' list contains the actual audio and video data. This 'movi' list contains one or more ... 'LIST' (4 byte list length) 'rec ' // list of movie records (a list) '##wb' (4 byte chunk size) (data) // sound data (a chunk) '##dc' (4 byte chunk size) (data) // video data (a chunk) '##db' (4 byte chunk size) (data) // video data (a chunk) A 'rec ' list (a record) contains the audio and video data for a single frame. '##wb' (4 byte chunk size) (data) // sound data (a chunk) '##dc' (4 byte chunk size) (data) // video data (a chunk) '##db' (4 byte chunk size) (data) // video data (a chunk) The 'rec ' list may not be used for AVI files with only audio or only video data. I have seen video only uncompressed AVI files that did not use the 'rec ' list, only '00db' chunks. The 'rec ' list is used for AVI files with interleaved audio and video streams. The 'rec ' list may be used for AVI file with only video. ## in '##dc' refers to the stream number. For example, video data chunks belonging to stream 0 would use the identifier '00dc'. A chunk of video data contains a single video frame. Alexander Grigoriev writes ... John, ##dc chunk was intended to keep compressed data, whereas ##db chunk nad(sic) to be used for uncompressed DIBs (device independent bitmap), but actually they both can contain compressed data. For example, Microsoft VidCap (more precisely, video capture window class) writes MJPEG compressed data in ##db chunks, whereas Adobe Premiere writes frames compressed with the same MJPEG codec as ##dc chunks. ----End of Alexander The ##wb chunks contain the audio data. The audio and video chunks in an AVI file do not contain time stamps or frame counts. The data is ordered in time sequentially as it appears in the AVI file. A player application should display the video frames at the frame rate indicated in the headers. The application should play the audio at the audio sample rate indicated in the headers. Usually, the streams are all assumed to start at time zero since there are no explicit time stamps in the AVI file. The lack of time stamps is a weakness of the original AVI file format. The OpenDML AVI Extensions add new chunks with time stamps. Microsoft's ASF (Advanced or Active Streaming Format), which Microsoft claims will replace AVI, has time stamp "objects". In principle, a video chunk contains a single frame of video. By design, the video chunk should be interleaved with an audio chunk containing the audio associated with that video frame. The data consists of pairs of video and audio chunks. These pairs may be encapsulated in a 'REC ' list. Not all AVI files obey this simple scheme. There are even AVI files with all the video followed by all of the audio; this is not the way an AVI file should be made. The 'movi' list may be followed by: 'idx1' (4 byte chunk size) (index data) // an optional index into movie (a chunk) The optional index contains a table of memory offsets to each chunk within the 'movi' list. The 'idx1' index supports rapid seeking to frames within the video file. The 'avih' (AVI Header) chunk contains the following information: Total Frames (for example, 1500 frames in an AVI) Streams (for example, 2 for audio and video together) InitialFrames MaxBytes BufferSize Microseconds Per Frame Frames Per Second (for example, 15 fps) Size (for example 320x240 pixels) Flags The 'strh' (Stream Header) chunk contains the following information: Stream Type (for example, 'vids' for video 'auds' for audio) Stream Handler (for example, 'cvid' for CinePak) Samples Per Second (for example 15 frames per second for video) Priority InitialFrames Start Length (for example, 1500 frames for video) Length (sec) (for example 100 seconds for video) Flags BufferSize Quality SampleSize For video, the 'strf' (Stream Format) chunk contains the following information: Size (for example 320x240 pixels) Bit Depth (for example 24 bit color) Colors Used (for example 236 for palettized color) Compression (for example 'cvid' for CinePak) For audio, the 'strf' (Stream Format) chunk contains the following information: wFormatTag (for example, WAVE_FORMAT_PCM) Number of Channels (for example 2 for stereo sound) Samples Per Second (for example 11025) Average Bytes Per Second (for example 11025 for 8 bit sound) nBlockAlign Bits Per Sample (for example 8 or 16 bits) Each 'rec ' list contains the sound data and video data for a single frame in the sound data chunk and the video data chunk. Other chunks are allowed within the AVI file. For example, I have seen info lists such as 'LIST' (4 byte list size) 'INFO' (chunks with information on video) These chunks that are not part of the AVI standard are simply ignored by the AVI parser. AVI can be and has been extended by adding lists and chunks not in the standard. The 'INFO' list is a registered global form type (across all RIFF files) to store information that helps identify the contents of a chunk. The sound data is typically 8 or 16 bit PCM, stereo or mono, sampled at 11, 22, or 44.1 KHz. Traditionally, the sound has typically been uncompressed Windows PCM. With the advent of the WorldWide Web and the severe bandwidth limitations of the Internet, there has been increasing use of audio codecs. The wFormatTag field in the audio 'strf' (Stream Format) chunk identifies the audio format and codec.

OpenDML AVI File Format Extensions

The Open Digital Media (OpenDML) Consortium has defined an OpenDML AVI File Format Extensions which extend AVI to support a variety of features required for professional video production. These include support for fields (not just frames), file sizes larger than 1 GB, timecodes, and many other features. Microsoft has reportedly incorporated OpenDML AVI support in DirectShow 5.1 (ActiveMovie 5.1). It is also used by various professional video applications for the PC, in particular Matrox's DigiSuite software. The Open Digital Media Consortium AVI File Format Extensions add new lists and chunks to the AVI file which contain extra data such as timecodes not incorporated in the original AVI standard. OpenDML appears to have been spearheaded by Matrox to improve AVI for professional video authoring and editing. Matrox makes a variety of PC video products such as DigiSuite for professional and broadcast video authoring and editing. The OpenDML AVI File Format Extensions are primarily for the Motion JPEG AVI files used for professional video authoring and editing. The OpenDML effort seems to have been pushed to one side with the advent of ActiveMovie, NetShow, Advanced (formerly Active) Streaming Format (ASF) Files, and other Microsoft initiatives. On Oct. 2, 1997, the OpenDML AVI File Format Extensions Version 1.02 specification document (dated February 28, 1996) was available at the Matrox Electronic Systems, Ltd. web site at: http://www.matrox.com/videoweb/odmlff2.htm The specification is in Adobe Portable Document Format (PDF). Since Matrox seems to rearrange their site from time to time and one can't always find the specification, I've included a link to a copy of the PDF version of the specification on my web site. PDF OpenDML AVI File Format Extensions Specification Document Get Adobe Acrobat Reader (PDF Viewer)

Where to get the exact AVI specification?

Microsoft Visual C++ 5.0 has a Video for Windows include file Vfw.h which gives the exact AVI data structures such as the various headers used in AVI files. The file also has comments explaining the structure of the AVI file. Video for Windows refers to the AVI Format by the mnemonic AVIFMT. At one time, the format information was apparently stored in an AVIFMT.H header file. The format information now appears consolidated in Vfw.h In addition to the Video for Windows header files, Chapter Four of the Video for Windows Programmer's Guide, "AVI Files", gives a detailed specification of the AVI file format. Return to Top

AVI and Windows Bitmaps (DDB, DIB, ...)

Microsoft Windows represents bitmapped images internally and in files as Device Dependent Bitmaps (DDB), Device Independent Bitmaps (DIB), and DIB Sections. Uncompressed 'DIB ' AVI files represent video frames as DIB's. Various multimedia API's that work with AVI use Windows bitmapped images. Prior to Windows 3.0, Windows relied on Device Dependent Bitmaps for bitmapped images. A DDB is stored in a format understood by the device driver for a particular video card. As the name suggests, DDB's are not generally portable. The structure of a DDB is: typedef struct tagBITMAP { // bm LONG bmType; /* always zero */ LONG bmWidth; /* width in pixels */ LONG bmHeight; /* height in pixels */ LONG bmWidthBytes; /* bytes per line of data */ WORD bmPlanes; /* number of color planes */ WORD bmBitsPixel; /* bits per pixel */ LPVOID bmBits; /* pointer to the bitmap pixel data */ } BITMAP; Usually the pixel data immediately follows the BITMAP header. (BITMAP header)(Pixel Data) The HBITMAP handles used by GDI are handles to Device Dependent Bitmaps. The GDI function BitBlt and StretchBlt are actually using Device Dependent Bitmaps. With Windows 3.0, Microsoft introduced the Device Independent Bitmap or DIB, the reigning workhorse of bitmapped images under Windows. The DIB provided a device independent way to represent bitmapped images, both monochrome and color. Windows retains DDB's despite the introduction of the DIB. For example, to use a DIB, you might call: hBitmap = CreateDIBitmap(...) CreateDIBitmap creats a DDB from a DIB, returning the GDI HBITMAP handle of the DDB for further GDI calls. At a low level, Windows and GDI are still using DDB's. The DIB files have a standard header that identifies the format, size, color palette (if applicable) of the bitmapped image. The header is a BITMAPINFO structure. typedef struct tagBITMAPINFO { BITMAPINFOHEADER bmiHeader; RGBQUAD bmiColors[1]; } BITMAPINFO; The BITMAPINFOHEADER is a structure of the form: typedef struct tagBITMAPINFOHEADER{ // bmih DWORD biSize; LONG biWidth; LONG biHeight; WORD biPlanes; WORD biBitCount DWORD biCompression; /* a DIB can be compressed using run length encoding */ DWORD biSizeImage; LONG biXPelsPerMeter; LONG biYPelsPerMeter; DWORD biClrUsed; DWORD biClrImportant; } BITMAPINFOHEADER; bmiColors[1] is the first entry in an optional color palette or color table of RGBQUAD data structures. True color (24 bit RGB) images do not need a color table. 4 and 8 bit color images use a color table. typedef struct tagRGBQUAD { // rgbq BYTE rgbBlue; BYTE rgbGreen; BYTE rgbRed; BYTE rgbReserved; /* always zero */ } RGBQUAD; A DIB consists of (BITMAPINFOHEADER)(optional color table of RGBQUAD's)(data for the bitmapped image) A Windows .BMP file is a DIB stored in a disk file. .BMP files prepend a BITMAPFILEHEADER to the DIB data structure. typedef struct tagBITMAPFILEHEADER { // bmfh WORD bfType; /* always 'BM' */ DWORD bfSize; /* size of bitmap file in bytes */ WORD bfReserved1; /* always 0 */ WORD bfReserved2; /* always 0 */ DWORD bfOffBits; /* offset to data for bitmap */ } BITMAPFILEHEADER; Structure of Data in a .BMP File (BITMAPFILEHEADER)(BITMAPINFOHEADER)(RGBQUAD color table)(Pixel Data) The Win32 API documentation from Microsoft provides extensive information on the data structures in a DIB. In Windows 95 and Windows NT, Microsoft added the DIBSection to provide a more efficient way to use DIB's in programs. The DIBSection was originally introduced in Windows NT to reduce the number of memory copies during blitting (display) of a DIB. Return to Top

Meet the Codecs

The video data in an AVI file can be formatted and compressed in a variety of ways. Video for Windows 1.1e comes with several compressors: Intel Indeo (version 3.2) Microsoft Video 1 Microsoft RLE (Run Length Encoding) CinePak AVI is not restricted to these compressors. They are the compressors provided with Video for Windows. These compressors are the Old Guard, the video codecs from the early days of Video for Windows and Quicktime (CinePak originated with the Macintosh and Quicktime). During this period the focus of video was playback from hard drives and CD-ROM's. The advent of the WorldWide Web and Internet Mania has created a New Wave of audio and video codecs, trying to apply "advanced" technologies such as sophisticated motion estimation and compensation, wavelets, fractals, and other techniques to achieve extremely low bitrates (such as 28.8 Kbits/second for phone lines) for the Internet.

The Old Guard

Full Frames (Uncompressed)

Users can store AVI files with uncompressed frames. No codec is required for this. The Four Character Code (FOURCC) for this is 'DIB ', DIB for the Microsoft Device Independent Bitmap. NOTE: Unfortunately, at least three other Four Character Codes are somtimes used for uncompressed AVI videos: 'RGB ' 'RAW ' 0x00000000 ( a FOURCC whose hexadecimal value is 0 )
Color Formats
Not all uncompressed bitmap images and AVI frames are the same! A variety of color formats for image pixels exist. Some of these color formats are essentially standard and supported on all systems. Some color formats (such as 8 bit grayscaleY8) require special drivers to display or capture. Color Formats are also known as IMAGE FORMATS or PIXEL FORMATS. Some components of Microsoft Windows identify Color Formats with a Four Character Code (FOURCC) such as 'RGB8' or 'YUY2'. Some components such as the Windows Device Independent Bitmap or DIB do not use Four Character Codes for color formats. 24 BIT RGB (DE FACTO STANDARD) 24-bit RGB is the most well-known color format. All common graphics programs support 24-bit RGB. In 24 bit RGB a pixel is represented as three bytes, one byte for the red component, one byte for the green component, and one byte for the blue component. 255 0 0 (a bright red pixel in 24 bit RGB) 0 255 0 (a bright green pixel in 24 bit RGB) 0 0 255 (a bright blue pixel in 24 bit RGB) 0 0 0 (a black pixel in 24 bit RGB) 255 255 255 (a white pixel in 24 bit RGB) 128 128 128 (a gray pixel in 24 bit RGB) ... and so forth. Other color formats include: 8 bit grayscale Y8 9 bit YUV9 12 bit BTYUV 4:1:1 12 bit YUY12 16 bit YUY2 4:2:2 8 bit RGB (uses a color palette) 15 bit RGB (16 bits with most significant bit zero, 5 bits for red, 5 bits for green, and 5 bits for blue) 16 bit RGB (16 bits with 5 bits for red, 6 bits for green, and 5 bits for blue) (24 bit RGB - described above) 32 bit RGB (most significant byte is zero, 8 bits for red, 8 bits for green, and 8 bits for blue)
Original DIB Color Formats
In the Windows 3.1 Software Development Kit, DIB's were defined to allow values of 1,4,8, and 24 bits per pixel in the biBitCount field of the BITMAPINFOHEADER. The biCompression field was allowed the values BI_RGB, BI_RLE4 (for run length encoding of 4 bit per pixel images), and BI_RLE8 (for run length encoding of 8 bit per pixel images). That was it. This original specification of the DIB provided the 8 bit RGB and 24 bit RGB color formats described above. The original DIB specification had no support for 16 bit per pixel formats, 32 bit per pixel formats, or special encodings like YUV. Not surprisingly, the original formats and specification of the DIB are the most widely supported in software.
New DIB Color Formats and More Complexity
Microsoft added support for 16 bit per pixel and 32 bit per pixel images to the DIB specification. These formats are identified by setting the biBitCount field in the BITMAPINFOHEADER of the DIB to 16 or 32. An uncompressed AVI file that stores images using the RGB 15, RGB 16, or RGB 32 color formats stores the video frames as DIB's using these "new" color formats. By default, the Microsoft 16 bit per pixel format is actually RGB 15 where one bit is unused, 5 bits for red, 5 bits for green, and 5 bits for blue. This was done because the 15-bit RGB or 5-5-5 format was used in 16-bit-per-pixel color video cards. Hardware designers found it easier to build chips using a 5-5-5 pixel format with one bit unused than the slightly higher resolution 5-6-5 color format. The Microsoft 32 bit per pixel format has the most significant byte of the pixel set to zero. Then 8 bits for red, 8 bits for green, and 8 bits for blue. This is RGB 32 bit. Why do this? The 32-bit pixels in this format are DWORD aligned on 32 bit boundaries in this format which is more efficient for operations and memory transfers under a 32 bit processor architecture than the unaligned 24-bit RGB format. Microsoft also added a new value for the biCompression field of the BITMAPINFOHEADER called BI_BITFIELDS. If biCompression is set to BI_BITFIELDS, then the color table is three DWORD (32 bit) masks giving the bits used for the red, green, and blue components of a pixel. In this way, a "custom" format such as RGB 5-6-5 (5 bits for Red, 6 bits for Green, and 5 bits for Blue) can be defined. This is 16-bit RGB. Although Four Character Codes (FOURCC's) such as 'RGB8' are used to identify different Color Formats in some parts of Microsoft Windows, the DIB data structures don't use FOURCC's, rather they use combinations of biBitCount and biCompression. In addition to 16-bit and 32-bit formats, Microsoft also defined a mechanism for custom encodings such as YUV, YUY2, and so forth. Manufacturers can register the new format with Microsoft. Microsoft also concocted a JPEG-DIB specification for wrapping the JPEG still image compression standard in a DIB. The JPEG DIB specification is virtually unused, having lost to the JFIF JPEG file format. JPEG images in general use, such as on Web pages, are JFIF's not JPEG DIB's.
YUV Color Space and Color Formats
YUV is the color space used in the European PAL broadcast television standard. PAL was originally introduced in Britain and Germany in 1967. PAL is used by most European nations and many nations around the world. The United States and Japan use the NTSC standard. France and a few other nations use the SECAM standard. Y refers to the luminance, a weighted sum of the red, green, and blue components. The human visual system is most sensitive to the luminance component of an image. Analog video systems such as NTSC, PAL, and SECAM transmit color video signals as a luminance (Y) signal and two color difference or chrominance signals (the U and V above). If, R, G, and B are the red, green, and blue values, then: Y = 0.299 R + 0.587 G + 0.114 B U = 0.493 (B - Y) V = 0.877 (R - Y) U is very similar to the difference between the blue and yellow components of a color image. V is very similar to the difference between the red and green components of a color image. There is evidence that the human visual system processes color information into something like a luminance channel, a blue - yellow channel, and a red - green channel. For example, while we perceive blue-green hues, we never percieve a hue that is simultaneously blue and yellow. This may be why the YUV color space of PAL is so useful. To exploit this, digital color formats such as YUV9 or YUY2 exist that represent pixels as levels of Y, U, and V.
Both BMP still image files and AVI files may be saved in many different color formats. While 24 bit RGB is almost universally supported, there is no guarantee that your graphics software or AVI playback drivers will support some of the less well-known color formats. You may need to get special software, drivers, or even hardware to use some of these formats. For example, all of the color formats listed above are supported by hardware and software drivers with the miro miroMEDIA PCTV TV Tuner and Video Capture card. Some of these, like 8 bit grayscale Y8, are not widely known or supported. In general, video capture drivers allow selection of the color format used when the video (AVI file) is captured. These color format options should be accessible through the video capture software application. In Microsoft's VidCap and VidCap32 video capture applications, the user may select the color format through Options | Video Format... Return to Top

Microsoft Run Length Encoding

Microsoft Run Length Encoding uses the Four Character Code MRLE [drivers32] VIDC.MRLE=MSRLE32.DLL in Windows 95 [drivers] VIDC.MRLE=MSRLE.DLL in Windows 3.x Return to Top

Microsoft Video 1

Microsoft Video uses the Four Character Code MSVC [drivers32] VIDC.MSVC=MSVIDC32.DLL in Windows 95 [drivers] VIDC.MSVC=MSVIDC.DLL in Windows 3.x NOTE: The Four Character Code CRAM is also used for Microsoft Video 1. Return to Top

Intel Indeo 3.1/3.2

Indeo uses the Microsoft Four Character Codes IV31 and IV32, originally for Indeo 3.1 and Indeo 3.2, but these are usually now mapped to Indeo 3.2 [drivers32] VIDC.IV31=IR32_32.DLL VIDC.IV32=IR32_32.DLL in Windows 95 [drivers] VIDC.IV31=IR32.DLL VIDC.IV32=IR32.DLL in Windows 3.x Indeo 3.x uses Vector Quantization based image compression. Return to Top


CinePak is the most widely used Video for Windows codec. CinePak reportedly provides the fastest playback of video. While Indeo 3.2 provides similar or slightly superior image quality for same compression, Indeo decompression is much more CPU intensive than CinePak. CinePak was originally developed for the Mac and licensed to Apple by SuperMac. It is now free with Video for Windows. It is also free with Apple's QuickTime. There are at least three CinePak codecs in existence: CinePak by SuperMac (the original, 16 bit) CinePak by Radius (newer, better?, 16 bit) CinePak by Radius[32] (32 bit version of Radius CinePak, shipped with Windows 95) Peter Plantec's Caligari TrueSpace2 Bible strongly recommends using the Radius codec for superior results when generating AVI files from TrueSpace. Cinepak uses the Microsoft Four Character Code CVID [drivers32] VIDC.CVID=ICCVID.DLL in Windows 95 [drivers] VIDC.CVID=ICCVID.DRV in Windows 3.x Cinepak uses Vector Quantization based image compression and frame differencing. Vector Quantization Return to Top

Motion JPEG

Most PC video capture and editing systems capture video to AVI files using Motion JPEG video compression. In Motion JPEG, each video frame is compressed separately using the JPEG still image compression standard. No frame differencing or motion estimation is used to compress the images. This makes frame accurate editing without any loss of image quality during the editing possible. The standards situation for Motion JPEG is complicated since at one time there was no industry standard for Motion JPEG. Microsoft has a Microsoft Motion JPEG Codec and a JPEG DIB Format. The OpenDML Avi File Format Extensions (another standard for extending AVI to support professional video features) includes Motion JPEG support. See the Paradigm Matrix site below for more information on these standards. Motion JPEG codecs usually use the Four Character Code 'MJPG'. Motion JPEG is used for editing and authoring, but rarely for distribution. Usually, once the video has been edited, it is compressed further using CinePak or another codec for distribution. Because Motion JPEG does not use frame differencing or motion estimation, better compression is possible with other codecs. A software Motion JPEG codec for Windows NT and Windows 95 is available from Paradigm Matrix at: http://www.pmatrix.com/Goodies.htm The Paradigm Matrix Motion JPEG codec uses the Four Character Code MJPG. Motion JPEG uses the Block Discrete Cosine Transform (DCT) for image compression. Return to Top

Editable MPEG

At least two companies defined schmes to wrap editable MPEG (I frames only MPEG) in AVI files. Xing Technology's editable MPEG AVI uses the Four Character Code XMPG. Sigma Designs defined an AVI format using the Four Character Code MPGI. Editable MPEG consists of only MPEG I frames. This omits the MPEG motion estimation. It is very similar to Motion JPEG. By wrapping I frames only MPEG in AVI, editable MPEG works with standard Video for Windows editing and authoring applications such as Adobe Premiere. Xing Technologies http://www.xingtech.com/ Sigma Designs MPEG Extensions to AVI File Format (Draft 1.1 by Sigma Designs) Return to Top

The New Wave

Recently (5/18/97), there has been a proliferation of new Video for Windows codecs. A few like H.261 have been around for a while, but most represent implementations of new or improved technologies such as wavelets. Many are targetted toward low bitrate video over the Internet. For lack of better terminology, I refer to these as the New Wave to differentiate them from the older codecs like Cinepak included with Video for Windows 1.1e (the last release prior to Windows 95). Microsoft appears to be developing or licensing some of these codecs as part of NetShow, NetMeeting, and other Microsoft initiatives.

VDOWave or VDOLive from VDONet

VDONet http://www.vdonet.com/ 4009 Miranda Ave., Suite 250 Palo Alto, CA 94304 Voice: (415) 846-7730 FAX: (415) 846-7900 markets a wavelet based video codec which includes a Video for Windows (32 bit) implementation. Microsoft has licensed VDOWave as part of the NetShow product. There are two versions of the VDOWave codec. VDOWave 2.0 is a fixed rate video codec which uses the Microsoft Four Character Code VDOM. This codec adds the line [drivers32] vidc.vdom=vdowave.drv to the SYSTEM.INI file in Windows 95. VDOWave 3.0 is a "scalable" video codec. This codec uses the Microsoft Four Character Code (FOURCC) VDOW and adds the line [drivers32] VIDC.VDOW=vdowave.drv to the Windows 95 SYSTEM.INI files. In NetShow 2.0, the standalone Client Setup installs a VDOWave decode-only codec. The NetShow 2.0 Tools Setup installs a VDONet VDOWave encoder. In some of my tests, VDOWave appears significantly superior to MPEG-1 and the other block Discrete Cosine Transform based codecs at low bitrates. VDONet uses the trademark VDOWave for its wavelet based video codec. VDONet uses the trademark VDOLive for its VDOLive On-Demand Product Line. This includes the VDOLive On-Demand Server, the VDOLive tools including VDOCapture and VDOClip, and the VDOLive Player. Sometimes VDOLive and VDOWave are used interchangably by users and in some company literature. VDONet also has a VDOPhone product for real-time videoconferencing. Based on the company documentation, published reports, and viewing the technology, VDOWave appears to be a combination of wavelet based image compression and motion compensation or frame differencing. Return to Top

What is Indeo Video Interactive?

Indeo Video Interactive, Indeo 4.1, is a new version of Indeo from Intel based on a "hybrid wavelet algorithm" according to Intel. This is a different compression algorithm than Indeo 3.2 which is included with Video for Windows. Indeo 3.2 uses Vector Quantization. Indeo Video Interactive supports a number of features in addition to the new compression algorithm such as transparency. Indeo Video Interactive can be installed as a Video for Windows codec or in the new ActiveMovie environment from Microsoft. For further information on Indeo Video Interactive http://www.intel.com/pc-supp/multimed/indeo/index.htm How to program "sprites" in Indeo Video Interactive? Some of Intel's marketing material touts the ability to add sprites to applications using Indeo Video Interactive. Most of Intel's technical documentation on Indeo and the API's for using Indeo Video Interactive neglects to explain what Intel means by "sprite". There is a brief mention in the Overview document for Indeo Video Interactive. Indeo "sprite" means TRANSPARENCY. Indeo Video Interactive supports TRANSPARENCY. Indeo has transparent pixels to create transparent backgrounds to implement effects such as chroma-keying. The well-known example of chroma-keying is the television weather forecaster standing in front of a satellite weather picture. The forecaster stands in front of a blue screen (sometimes a green screen) and video gadgetry replaced the blue color with another video signal. Anything that is not the blue "key" color is left unchanged. In Indeo jargon a "video sprite" is a foreground object such as the mythical weather-caster on a transparent background. Your application can then provide a bitmap image or even another video as a background in the transparent areas of the image. This provides a crude mechanism for the video to change depending on interactions with a user. Look up the API's in Intel's documentation for TRANSPARENCY to implement video sprites. How to identify an AVI file that uses Indeo Video Interactive for the video compressor? Video for Windows identifies different video compressors through four character codes. For example, 'cvid' is the four character code for the widely used CinePak compressor. The four character code is found in the video stream header 'strh' in the AVI file. Indeo Video Interactive (Indeo 4.1) uses the four character code 'iv41' If Indeo Video Interactive is not installed installed Video for Windows will report an error, indicating that it cannot find the compressor for 'iv41'. The specific message appears to be: "Video not available, cannot find 'vids:iv41' decompressor." NOTE: Indeo 4.1 claims to implement a hybrid wavelet transform. Some of the behavior of the codec at low bitrates differs from other wavelet based image and video compressors such as VDOWave, Infinop's Lightning Strike, and some public domain wavelet compression software. In particular, at low bitrates, I have seen the characteristic checkerboard pattern of 8x8 pixel blocks seen in block based transform coding methods such as MPEG-1. I'm not sure what Intel means by hybrid wavelet transform. In general, at low bitrates, image and video compression schemes using the Discrete Wavelet Transform (DWT) exhibit a blurring at the edges of objects and also "ringing" artifacts near edges. They do not exhibit the blocking artifacts, checkerboard pattern in extreme cases, seen in block Discrete Cosine Transform based image and video compression. Return to Top

Indeo Video Interactive 5.0

Intel is now (8/1/97) distributing an Indeo Video Interactive 5.0 Beta software on their web site. Indeo 5.0 claims to use a new better wavelet compression algorithm for improvied video quality.
http://developer.intel.com/ial/indeo/video/beta/index.htm Return to Top

ClearVideo (aka RealVideo)

ClearVideo is a video codec from Iterated Systems( http://www.iterated.com Iterated has also licensed the ClearVideo technology to Progressive Networks, makers of RealAudio, under the name RealVideo. You can (or could at one time) download a Video for Windows demo of ClearVideo from the Iterated Web site. This includes a demo Video for Windows codec that allows both encoding and decoding The video can only be played on the same machine with the demo encoder. This codec works with Video for Windows applications such as Media Player and VidEdit. Fractal video encoding appears to be very slow (computationally intensive). The video is similar or somewhat superior to MPEG-1 in quality. ClearVideo uses Fractal Image Compression. Iterated is the main (only?) producer of commercial fractal image and video compression technology. The Video for Windows evaluation version of ClearVideo installs [drivers32] VIDC.UCOD=CLRVIDCD.DLL in SYSTEM.INI in Windows 95. Return to Top

SFM (Surface Fitting Method)

Crystal Net Corporation (http://www.crystalnet.com/ seeks to license a technology called SFM or Surface Fitting Method. This is supposed to be a low bitrate video technology for ISDN and POTS (Plain Old Television Service) bitrates. They have a Video for Windows demo to download from their Web site. SFM used the Microsoft Four Character Code (FOURCC) SFMC. The demo installs (actually the instructions tell you to manually install): [drivers32] VIDC.SFMC=SFMdemo.dll in Windows 95. The demo does not include an encoder which presents problems in evaluating the technology. However, SFM appears to be some sort of edge detection based encoding technology. White Pine's Enhanced CU-See Me desktop videoconferencing product uses Crystal Net's SFM under the name White Pine Color Software Codec. NEC has reportedly licensed SFM for its Network Video Audio Tool (NVAT). (February, 1998) Crystal Net also reportedly has relationships with Shepherd Surveillance and Winnov. (February, 1998) Return to Top


Q-Team Dr. Knabe produces a Video for Windows codec known as QPEG. Currently (6/27/97), QPEG supports 8 bit color. Q-Team plans 16 and 24 bit color, MMX support, and other additional features in the future. Sample AVI/QPEG files and Video for Windows QPEG codecs for Windows 3.x and Windows 95/NT are available at the Q-Team web site. http://www.q-team.de/ Q-Team is also working on MPEG-4 for the PC. Return to Top


H.261 is an international standard, widely used for video conferencing in the 128 Kbits/second to 384 Kbits/second range. This is a block Discrete Cosine Transform method. Actually, H.261 was the first international standard developed using the block Discrete Cosine Transform and motion compensation. MPEG-1, which is probably better known, followed the H.261 effort. Intel's ProShare videoconferencing product installs a Video for Windows H.261 codec. NOTE: I've never generated an AVI files with Intel's H.261, so it may only be used for Intel ProShare videoconferencing and not with AVI. Microsoft has a Microsoft H.261 Video for Windows 32 bit codec. [drivers32] VIDC.M261=MSH261.DRV in Windows 95. Return to Top


H.263 is another international standard, based on the Block Discrete Cosine Transform (DCT) and motion compensation. H.263 has a number of improvements, mostly in the area of motion compensation, over the earlier H.261 standard. It is targeted toward very low bitrate video compression. Microsoft's NetShow 2.0 installs a Microsoft H.263 video codec. Microsoft H.263 uses the Four Character Code M263. [drivers32] VIDC.M263=msh263.drv in Windows 95. The Microsoft H.263 video codec is one of several "keyed" codecs installed by NetShow. Others are Vivo H.263 and Duck's TrueMotion 2.0. These codecs will not encode video as AVI files, although they apparently will create Microsoft ASF files or provide compression for streaming video products such as Microsoft's NetMeeting videoconferencing. See the section on NetShow for more information on the NetShow video codecs. Some versions of the msh263.drv driver will crash when trying to encode an AVI file from VidEdit or similar applications. Other versions of msh263.drv don't crash but give an "Unable to begin compression" message box. Vivo Software Inc. markets streaming H.263 and G.723 audio for the Web under the brand name VivoActive. Vivo has its own file format called .VIV which can be embedded in web pages. Vivo provides a player called VivoActive player and an authoring tool for creating .VIV files called VivoActive Producer. Microsoft NetShow installs a "keyed" codec that identifies itself as Vivo H.263 Video Codec[32] which installs [drivers32] VIDC.VIVO=IVVIDEO.DLL in Windows 95. Vivo H.263 uses the four character code 'VIVO'. The Vivo Software Web Site: http://www.vivo.com/ Intel distributes an Intel "I263" H.263 video codec at there web site as part of the NetCard product. This installs [drivers32] VIDC.I263=C:\WINDOWS\I263_32.DLL VIDC.I420=C:\WINDOWS\I263_32.DLL in Windows 95. As of Dec. 27, 1998, this codec could be found at: http://support.intel.com/support/createshare/camerapack/CODINSTL.HTM Note that Intel, like Microsoft, seems to rearrange their web site constantly. Unlike the keyed Microsoft H.263 video codecs, this codec can be used to encode AVI's through Microsoft VidEdit 1.1 (and presumably other video editing products). How well this codec in fact implements the H.263 standard is not clear. Telenor R&D of Norway distributes the source code for an H.263 encoder and decoder that will reportedly compile and run under Windows. This is a standalone application not a Video for Windows codec or ActiveMovie filter. See elsewhere in the AVI Overview for a link to the Telenor web site. Return to Top


Microsoft's NetShow 2.0 installs a Video for Windows codec for MPEG-4. MPEG-4 is a new international standard that has not been officially released as yet. Microsoft is deeply involved in the MPEG-4 standardization effort. Microsoft has been using its MPEG-4 for the Microsoft NBC Business Video broadcasting over the Internet. Adding to confusion in true Microsoft fashion, there are two versions of each NetShow video codec. The NetShow 2.0 Player (Client) installation program installs codecs that provide only decoding functionality. The MPEG-4 video codec installed by NetShow 2.0 Player can only playback an MPEG-4 AVI. The MPEG-4 video codec installed by the NetShow 2.0 Tools can encode AVI files with MPEG-4 video compression. If you want to author MPEG-4 compressed AVI, make sure to get and install the NetShow 2.0 Tools, not just the NetShow 2.0 Player. MPEG-4 uses the Microsoft Four Character Code (FOURCC) MPG4. [drivers32] VIDC.MPG4=msscrc32.dll Return to Top

Lightning Strike (Infinop)

Infinop markets a wavelet based video codec called Lightning Strike Streaming Video. A Lightning Strike video decoder compatible with Microsoft NetShow can be dowloaded from the Infinop web site. There are several sample Lightning Strike Video files at the Infinop site. The Lightning Strike encoder does not seem to be generally available. http://www.infinop.com/ Return to Top


VxTreme was acquired by Microsoft in September of 1997. Microsoft has invested in numerous low bitrate audio and video companies during the second half of 1997, include VxTreme, VDONet, Progressive Networks/RealNetworks, and Lernout and Hauspie Speech Products. Although I have not seen a Video for Windows implementation of VxTreme (12/20/97), I thought that I should include this codec. Undoubtedly, it will be ported to Video for Windows and/or ActiveMovie if this has not already happened. VxTreme(http://www.vxtreme.com/ markets a video codec that is usually identified as a wavelet based codec. A VxTreme player, a Plug-In for Internet Explorer and Netscape, is available at the VxTreme Web site. VxTreme has some very impressive demos of QCIF (160x120) talking heads material on their Web sites. The subjective image quality during scenes with small changes is quite good, much superior to the block Discrete Cosine Transform based codecs and probably VDONet's VDOWave. Text such as movie titles and credits appears to encode very well. Preserving the sharp edges of text is a major problem in block Discrete Cosine Transform based encoders such as the JPEG still image compression standard and the MPEG video compression standard. In general, wavelet image compression encounters problems with sharp edges as well. VxTreme clearly uses some sort of motion compensation or frame differencing. Image quality drops dramatically during periods with rapid changes. I viewed a number of movie trailers encoded with VxTreme for 28.8 Kbits/second such as the trailer for "Goldeneye". These trailers contain many scene changes and motion. Video quality is poor, hardly superior to competitors such as H.261 or Microsoft's MPEG-4. The talking heads material at 28.8 looks almost natural. VxTreme may be a combination of the Discrete Wavelet Transform (??) and motion compensation. The preservation of sharp edges suggests something beyond the vanilla Discrete Wavelet Transforms described in the technical literature on wavelet based image and video compression. Return to Top

How to determine which Video for Windows decompressors are installed on a PC?

In the SYSTEM.INI file, there is a section [drivers] which will contain some lines as follows: [drivers] VIDC.MSVC=msvidc.drv VIDC.YVU9=isvy.drv VIDC.IV31=indeor3.drv VIDC.RT21=indeo.drv VIDC.CVID=iccvid.drv VIDC.MRLE=msrle.drv AVI files contain a four character code (such as 'IV31' or 'CVID') in the stream header for the video stream. This four character code identifies the video compressor used for the video stream. For example, 'CVID' is the identifier for CinePak (formerly Compact Video) compression. Video for Windows prefixes the four character code with VIDC. and uses it to look up the video decompressor driver in SYSTEM.INI iccvid.drv is the driver for CinePak in the example above. Note: These are 16-bit drivers. Windows 95 adds a section [drivers32] for 32 bit drivers. There are 32 bit versions of the Video for Windows drivers. See below (and notice that the 32 bit drivers have different names from the 16 bit drivers). [drivers32] vidc.cvid=iccvid.dll ; Cinepak for Windows 32 vidc.iv31=ir32_32.dll vidc.iv32=ir32_32.dll vidc.msvc=msvidc32.dll vidc.mrle=msrle32.dll WINDOWS 95 In Windows 95: (1) Open the Control Panel (2) Double click on the Multimedia Icon (applet) (3) Select the "Advanced" Tab (4) Under the Multimedia Drivers icon, double click on the Video Compression Codecs icon to open it. This gives a list of installed video codecs. Return to Top

How to determine which codec was used to compress an AVI file

LOW LEVEL WAY THAT WORKS ON ANY OPERATING SYSTEM WITH A FILE EDITOR! A low level way to find out is to view the avi file with an editor, for example the standard EDIT command in DOS will work. Search for the four character code vids (usually lower case). vids indicates a VIDeo Stream. vids is immediately followed by the four character code for the compressor used for the AVI file. For example, a full frames (uncompressed) AVI will contain the string: vidsDIB An AVI compressed using Microsoft Video 1 will contain the string: vidsmsvc And so forth. See elswhere in this overview for information on the Microsoft Four Character Codes. WINDOWS 95 In Windows 95 (or Windows NT 4.0): Left click on the avi file's icon. This brings up a menu of items. Select Properties. Click on the Details tab in the Properties sheet. Look under Video Format in the Details. This will list the compression used. Return to Top

Which compressor is best?

CinePak is the most widely used. CinePak reportedly provides the fastest playback of video. While Indeo 3.2 provides similar or slightly superior image quality for same compression, Indeo decompression is much more CPU intensive than CinePak. CinePak was originally developed for the Mac and licensed to Apple by SuperMac. It is now free with Video for Windows. It is also free with Apple's QuickTime. There are at least three CinePak codecs in existence: CinePak by SuperMac (the original, 16 bit) CinePak by Radius (newer, better?, 16 bit) CinePak by Radius[32] (32 bit version of Radius CinePak, shipped with Windows 95) Peter Plantec's Caligari TrueSpace2 Bible strongly recommends using the Radius codec for superior results when generating AVI files from TrueSpace. CinePak is the best codec to use to insure ease of playback. Few people will have problems or need to install special codecs or software to play an AVI compressed with CinePak. CinePak is based on Vector Quantization and Frame Differencing to achieve video compression. Other technologies such as the Block Discrete Cosine Transform and Motion Compensation can achieve superior compression (smaller files for the same subjective visual quality). Codecs that beat CinePak H.263 (probably H.261) Block DCT/Motion Compensation MPEG-4 Video Verification Model Block DCT/Motion Compensation Indeo Video Interactive (Indeo 4.x) "hybrid wavelet" VDONet's VDOWave Discrete Wavelet Transform/Motion Compensation Iterated System's RealVideo or ClearVideo Fractal Compression Although not integrated into AVI, the MPEG-1 digital video standard with IPB frames outperforms CinePak. The block DCT/Motion Compensation based codecs seem to perform 1.5 - 2.0 times better than CinePak. VDOWave, a wavelet based codec, seems somewhat better than this. Return to Top

Microsoft Four Character Codes (FOURCC)

A Four Character Code or FOURCC is a four byte code defined by Microsoft as part of Video for Windows to identify various types of video data. Microsoft defined FOURCC's to uniquely identify pixel layouts and video compressor types in Video for Windows. For example, the FOURCC 'CVID' identifies the CinePak (formerly Compact Video) video compressor. AVI files contain the FOURCC for the video compressor in the video stream header. In addition to codecs, Four Character Codes identify the pixel layouts used in uncompressed images and video. For example, codes such as 'YUY2' identify layouts of pixels in YUV space (as opposed to RGB). These codes are used in interfacing with graphics cards. For example, the S3 ViRGE/VX chip supports the YUY2 pixel layout. YUY2 is popular because it refers to the 4:2:2 format used in CCIR-601 (D1) digital video. Video for Windows, Display Control Interface (DCI), and Direct Draw all use FOURCC's. Incomplete List of Four Character Codes for Video for Windows Codecs DIB Full Frames (Uncompressed) RGB Full Frames (Uncompressed) RAW Full Frames (Uncompressed) 0x00000000 Full Frames (Uncompressed) 0x00000000 indicates the hexadecimal value of the Four Character Code is zero. A Four Character Code 'AAAA' has hexadecimal value 0x41414141 where 0x41 is the ASCII code for 'A'. Some video capture and editing products will use the non-standard FOURCC 0x00000000 for uncompressed AVI video instead of the easier to understand 'DIB ' or 'RGB ' or 'RAW '. MSVC or CRAM or WHAM Microsoft Video 1 MRLE Microsoft Run Length Encoding IV31 Indeo 3.1/3.2 IV32 Indeo 3.1/3.2 CVID CinePak (Radius) ULTI Ultimotion (IBM) MJPG Motion JPEG (Microsoft, Paradigm Matrix, video capture companies) IJPG Intergraph JPEG CYUV Creative YUV YVU9 Intel Indeo Raw YUV9 XMPG Editable (I frames only) MPEG (Xing) MPGI Editable MPEG (Sigma Designs) VIXL miro Video XL MVI1 Motion Pixels SPIG Radius Spigot PGVV Radius Video Vision TMOT Duck TrueMotion S DMB1 Custom Format Used by Matrox Rainbow Runner IV41 Indeo Interactive (Indeo 4.1 from Intel) IV50 Indeo 5.0 UCOD ClearVideo (Iterated Systems) VDOW VDOWave (VDONet) SFMC Surface Fitting Method (CrystalNet) QPEG Q-Team Dr.Knabe 's QPEG video compressor H261 H.261 M261 Microsoft H.261 VIVO Vivo H.263 M263 Microsoft H.263 I263 Intel "I.263" H.263 MPG4 Microsoft MPEG-4 Extensive information on Microsoft's Four Character Codes (FOURCC) may be found at Dave Wilson's The Almost Definitive FOURCC Definition List Return to Top

Video Compression Technologies

There are several underlying technologies used by different Video for Windows Codecs. For example, Indeo 3.2 and Cinepak both use Vector Quantization. The international standards MPEG-1, MPEG-2, MPEG-4, H.261, and H.263 all use a combination of the block Discrete Cosine Transform (DCT) and motion estimation/compensation. Several of the New Wave codecs use wavelet transform based image compression (the Discrete Wavelet Transform or DWT). Other technologies include Fractal Image Compression, represented by Iterated Systems. Some general comments on image and video compression: (1) Image compression may be lossless where no information is lost during the compression process. The image produced by the decompression (also known as decoding) process is identical bit by bit with the original image. The widely used GIF format is a lossless image and video (GIF89a or animated GIF) compression format. LOSSLESS COMPRESSION (2) Image compression may be lossy where information is lost during the compression process. These schemes exploit limitations of the human visual system. Some errors are undetectable by the human eye. Even though two images are different at the bit by bit level, the human viewer cannot distinguish them. Some errors are detectable by the human eye but acceptable. Some errors are detectable and very annoying. The widely used JPEG image compression standard is a lossy compression scheme. LOSSY COMPRESSION (3) Within lossy image and video compression, a compression scheme may be perceptually lossless, in which case the human viewer cannot distinguish between the original image or video and the decompressed compressed image or video which has errors introduced by the lossy compression. Most lossy image and video compression have some sort of quality factor or factors. If the quality is good enough, then the image will be perceptually lossless. PERCEPTUALLY LOSSLESS COMPRESSION (3) JPEG's and MPEG's and other lossy compression of images and video are often compressed beyond the point of perceptual losslessness, but the compressed images and video are still acceptable to the human viewer. If the compression and decompression degrades the image in a way that is very similar or identical to the natural degradation of images that might occur in the world then the human visual system will not object greatly. Loss of fine detail in an image is often acceptable because humans perceive objects in the natural world with widely varying levels of detail depending on how close the human viewer is to the object and whether the human viewer is looking directly at the object or not. The human viewer sees less detail if an object is further away. When a human viewer looks directly at an object, the viewer uses a small very high resolution part of the retina. If an object is to one side of the direction of view, the viewer is using lower resolution parts of the retina. Human beings are also used to certain natural forms of degradation such as rain, snow, and fog. Note that in all these natural viewing situation, the human viewer will still perceive sharp edges and lines in an image regardless of the level of detail. The human viewer will usually perceive the objects as the same object despite the variations in level of detail. A horse is a horse is a horse. NATURALLY LOSSY COMPRESSION (4) Sufficiently low quality lossy compression will introduce visual artifacts that are highly annoying to the human viewer. An example is the blocking artifacts visible in highly compressed MPEG video and other block Discrete Cosine Transform based image compression codecs. At some point the lossy compression will introduce artifacts that are very unnatural and are perceived as new objects in the scene or spurious lines within the image. The human visual system is very sensitive to lines or edges. One of its main functions appears to be to detect and characterize physical objects such as other people, potential threats such as predators, food plants, and other things. Objects in the visual system are dilineated by edges. Anything such as a codec algorithm that destroys or creates an edge in an image is noticed, particularly if the edge is interpreted as the border of an object by the human visual and cognitive system. UNNATURAL LOSSY COMPRESSION All of the widely used video codecs are lossy compression algorithms. At sufficiently high compression most of them will have problems with the edges in the image. Vector quantization, block Discrete Cosine Transform, and wavelet based image and video compression inherently do not mathematically represent the intuitive notion of an edge or line. THE POINT: In using and selecting video codecs, the author of an AVI file (or a compressed digital video in general) needs to achieve NATURALLY LOSSY COMPRESSION or better. Once the compression introduces noticable AND unnatural artifacts, the video is of very limited use even in cases where some features and objects are recognizable. A basic description of video compression technologies follows. I have tried to avoid the dense mathematics found in most of the technical video and image compression literature. Return to Top

Run Length Encoding

VIDEO CODECS THAT USE RUN LENGTH ENCODING Microsoft RLE (MRLE) Run length encoding is also used to encode the DCT coefficients in the block Discrete Cosine Transform (DCT) based international standards MPEG, H.261, H.263, and JPEG. STRENGTHS AND WEAKNESSES 1. Works for bilevel or 8 bit graphic images such as cel animation. 2. Not good for high resolution natural images. OVERVIEW Run length encoding encodes a sequence or run of consecutive pixels of the same color (such as black or white) as a single codeword. For example, the sequence of pixels 77 77 77 77 77 77 77 could be coded as 7 77 (for seven 77's) Run length encoding can work well for bi-level images (e.g. black and white text or graphics) and for 8 bit images, particularly images such as cel animations which contain many runs of the same color. Run length encoding does not work well for 24 bit natural images in general. Runs of the same color are not that common. Return to Top

Vector Quantization

VIDEO CODECS THAT USE VECTOR QUANTIZATION Indeo 3.2 Cinepak Indeo 3.2 and Cinepak both use vector quantization. As with most digital video, Indeo and Cinepak work in the YUV color space (not RGB for example). STRENGTHS AND WEAKNESSES 1. The encoding process is computationally intensive. Still cannot be done in real time without dedicated hardware. 2. The decoding process is very fast. 3. Blocking artifacts at high compression. 4. Generally, block Discrete Cosine Transform and Discrete Wavelet Transform based image compression methods can achieve higher compression. OVERVIEW The basic idea of Vector Quantization based image compression is to divide the image up into blocks (4x4 pixels in YUV space for Indeo and Cinepak). Typically, some blocks (hopefully many) are similar to other blocks although usually not identical. The encoder identifies a class of similar blocks and replaced these with a "generic" block representative of the class of similar blocks. The encoder encodes a lookup table that maps short binary codes to the "generic" blocks. Typically, the shortest binary codes represent the most common classes of blocks in the image. The Vector Quantization (VQ) decoder uses the lookup table to assemble an approximate image comprised of the "generic" blocks in the lookup table. Note that this is inherently a lossy compression process because the actual blocks are replaced with a generic block that is a "good enough" approximation to the original block. The encoding process is slow and computationally intensive because the encoder must accumulate statistics on the frequency of blocks and calculate the similarity of blocks in order to build the lookup table. The decoding process is very quick because it is lookup table based. In Vector Quantization, the lookup table may be called a codebook. The binary codes that index into the table may be called codewords. Higher compression is achieved by making the lookup table smaller, fewer classes of similar blocks in the image. The quality of the reproduced approximate image degrades as the lookup table becomes smaller. Vector Quantization is prone to blocking artifacts as compression is increased. Vector Quantization is an entire sub-field in signal and image processing. It goes well beyond the brief description above and is applied to other uses than video compression. The standard reference book on Vector Quantization is: Vector Quantization and Signal Compression A. Gersho and R. Gray Boston, MA : Kluwer, 1992 Like many image and signal processing books, this is heavy on abstract math.

A Simple Example

Consider the following 4 by 4 blocks of pixels. Each pixel has a value in the range of 0-255. This is a grayscale image for simplicity. (Block 1) 128 128 128 128 128 128 128 128 128 128 128 128 128 128 128 128 (Block 2) 128 127 128 128 128 128 128 128 128 128 127 128 128 128 128 128 (Block 3) 128 127 126 128 128 128 128 128 127 128 128 128 128 128 128 128 In practice, the blocks will look the same to a human viewer. The second and third blocks could be safely replaced by the first block. By itself, this does not compress the image. However, the replacement block (Block 1) could be represented by a short index into a lookup table of 4x4 blocks. For example, the index, in this case, could be 1. Lookup Table[1] = 128 128 128 128 128 128 128 128 128 128 128 128 128 128 128 128 The original image could be converted into a lookup table and a series of indexes into the lookup table, achieving substantial compression. In video, the same lookup table could be used for many frames, not just a single frame. Return to Top

Discrete Cosine Transform

VIDEO CODECS THAT USE DCT Motion JPEG Editable MPEG MPEG-1 MPEG-2 MPEG-4 H.261 H.263 H.263+ STRENGTHS AND WEAKNESSES 1. Blocking artifacts at high compression. 2. Ringing at sharp edges. Occasional blurring at sharp edges. 3. Computationally intensive. Only recently has it been possible to implement in real time on general purpose CPU's as opposed to specialized chips. OVERVIEW The Discrete Cosine Transform (DCT) is a widely used transform in image compression. The JPEG still image compression standard, the H.261 (p*64) video-conferencing standard, the H.263 video-conferencing standard and the MPEG (MPEG-1, MPEG-2, and MPEG-4) digital video standards use the DCT. In these standards, a two-dimensional (2D) DCT is applied to 8 by 8 blocks of pixels in the image that is compressed. The 64 (8x8 = 64) coefficients produced by the DCT are then quantized to provide the actual compression. In typical images, most DCT coefficients from a DCT on an 8 by 8 block of pixels are small and become zero after quantization. This property of the DCT on real world images is critical to the compression schemes. In addition, the human eyes are less sensitive to the high frequency components of the image represented by the higher DCT coefficients. A large quantization factor can and usually is applied to these higher frequency components. The de-facto standard quantization matrix (a matrix of 64 quantization factors, one for each of the 64 DCT coefficients) in the JPEG standard has higher quantization factors for higher frequency DCT coefficients. The quantized DCT coefficients are then run-length encoded as variable length codes that indicate some number of zero coefficients followed by a non-zero coefficient. For example, a run-length code might indicate 4 zero coefficients followed by a non-zero coefficient of level 2. Short variable length codes (e.g. 0110) are used for common combinations of runs of zero and levels of the non-zero coefficient. Longer variable length codes (e.g. 0000001101) are used for less common combinations of runs of zero and levels of the non-zero coefficient. In this way, substantial compression of the image is possible. The Discrete Cosine Transform itself is best explained as a 1 dimensional (1D) DCT first. The 2D DCT is equivalent to performing a 1D DCT on each row of a block of pixels followed by a 1D DCT on each column of the block of pixels produced by the 1D DCT's on the rows. The one dimensional Discrete Cosine Transform is applied to a block of N samples (pixels in an image or sound pressure samples in an audio file). The Discrete Cosine Transform is an NxN matrix whose rows are sampled cosine functions: DCT(m,n) = sqrt( (1 - delta(m,1) ) / N ) * cos( (pi/N) * (n - 1/2) * (m-1) ) where DCT(m,n) is the 1D DCT Matrix m,n = 1,...,N pi = 3.14159267... N = number of samples in block delta(m,1) = 1 if m is 1 0 otherwise cos(x) = cosine of x (radians) * = multiply Naively, performing a DCT on a block of N samples would require N*N multiplies and adds. However, the DCT matrix has a recursive structure that allows implementation with order N log(N) multiplies and adds (many fewer). This makes the DCT practical for implementation on current CPUs and DSPs. Return to Top

Frame Differencing

VIDEO CODECS THAT USE FRAME DIFFERENCING CinePak STRENGTHS AND WEAKNESSES 1. Generally can achieve better compression than independent encoding of individual frames. 2. Errors accumulate in successsive frames after a key frame, eventually requiring another key frame. (see below) OVERVIEW Frame Differencing exploits the fact that little changes from frame to frame in many video or animation sequences. For example, a video might show a ball flying through the air in front of a static background. Most of the image, the background, does not change from frame to subsequent frame in the scene. In frame differencing, the still image compression method such as vector quantization is applied to the difference between the frame and the decoded previous frame. Often, most of the difference is zero or small values which can be heavily compressed. Most often, frame differencing uses "key frames" which are frames compressed without reference to a previous frame. This limits accumulated errors and enables seeking within the video stream. In the widely used CinePak, a key frame is often set every 15 frames. CinePak movies usually use frame differencing combined with vector quantization. If the compression scheme is lossy (vector quantization is lossy), errors will accumulate from frame to frame. Eventually these errors will become visible. This necessitates key frames! Return to Top

Motion Compensation

VIDEO CODECS THAT USE MOTION COMPENSATION ClearVideo (RealVideo) Fractal Video Codec from Iterated Systems VDOWave from VDONet VxTreme MPEG-1,2, and 4 H.261 H.263 H.263+ STRENGTHS AND WEAKNESSES 1. Motion compensation achieves high video compression in video generally superior to frame differencing. 2. The encoding phase of motion compensation (known as motion estimation) is computationally intensive. MPEG-1 with IP and B frames cannot be encoded in real time without dedicated hardware, a silicon implementation of motion estimation. 3. The motion compensation scheme used in the international standards MPEG, H.261, and H.263 works best for scenes with limited motion such as talking heads. In general, video with heavy motion such as sports video is hard to compress with motion compensation. OVERVIEW Motion Compensation codes for motion within a scene such as a ball moving across a background. The block Discrete Cosine Transform (DCT) based international video standards MPEG-1, MPEG-2, MPEG-4, H.261, and H.263 use motion compensation. Iterated Systems ClearVideo (Real Video) fractal Video Codec, VDOWave from VDONet, and VxTreme's video codec use forms of motion compensation. Motion Compensation refers to a number of ideas and algorithms. The motion compensation method used in MPEG and related international standards (H.261 and H.263) is described below. This motion compensation works for translational motion only. This is suited for objects moving across a background or panning of the camera. It does not work well for spinning objects, resizing objects, or camera zooms. Alternative forms of motion compensation exist which handle rotational, scaling, skewing, and other kinds of motion in a scene. Recognizing objects such as a flying ball in a scene is an unsolved problem in image processing and understanding. A way to exploit the motion of the ball to achieve image compression is to partition the image into blocks (16x16 pixels in MPEG-1). Code a "motion vector" for each block which points to the 16x16 pixel block in a previous (or future) frame that most closely approximates the block being coded. In many cases this reference block will be the same block (no motion). In some cases this reference block will be a different block (motion). The encoder need not recognize the presence of a ball or other object, only compare blocks of pixels in the decoded and reference frames. COMPRESSION IS ACHIEVED BY SENDING OR STORING ONLY THE MOTION VECTOR (AND A POSSIBLE SMALL ERROR) INSTEAD OF THE PIXEL VALUES FOR THE ENTIRE BLOCK. Note that the reference block can be anywhere in the image. The coded or "predicted" blocks must form a partition or tiling of the image (frame) being decoded. A reference block can be any 16x16 pixel block in the reference frame (image) that most closely approximates the coded or "predicted" block. The reference frame must be decoded prior to the current frame being decoded. However, the reference frame need not be PRESENTED before the current frame being decoded. In fact, the reference frame could be a future frame!! MPEG allows for this through so-called B (bi-directionally predicted) frames. In the example of the ball in front of a static background, no motion occurs in most of the blocks. For these cases, the motion vectors are zero. Motion compensation for these blocks is then equivalent to frame differencing, where the difference between the block and the same block in a previous (or future) frame is coded. For the block or blocks containing the moving ball, the motion vectors will be non-zero, pointing to a block in a previous (or future) frame that contains the ball. The displaced block is subtracted from the current block. In general, there will be some left over non-zero values, which are then coded using the still image compression scheme such as Vector Quantization, the Block Discrete Cosine Transform, or the Discrete Wavelet Transform. MPEG style motion compensation does not require recognition of the ball. An encoder simply compares the block being coded with displaced blocks in the reference frame (a previous or future frame). The comparison can use mean squared error or some other metric of differences between images. The encoder selects the displaced block with the smallest mean squared error difference! At no point has the encoder recognized an object in the image. In MPEG, the motion vectors are encoded as variable length codes for greater compression. The encoding process is called Motion Estimation. This finds the motion vector (or vectors) for each block. The decoding process is called Motion Compensation. Motion Compensation achieves greater compression than simple Frame Differencing. ILLUSTRATIVE EXAMPLE: Predicted Region Reference Region (the current frame being decoded) (a previously decoded frame) _________ _________ | | | | | | | * | | | | * | (moving ball) | 4 | -4 | | | | | | | | | | _________ _________ | | | | | | | 0 | 0 | | | | (no change) | | | | | | | | | | | | _________ _________ The asterisk (*) represents a ball flying across the scene from right to left. Four blocks with associated motion vectors (4, -4, 0, and 0). The upper left block looks like the upper right block in the reference region (where the ball was). The upper right block looks like the upper left region in the reference region. The lower left and lower right blocks were unchanged. In this simple example, the vertical displacement is zero and is ignored. In this simple example, the region can be decoded using the motion vectors alone. In more general cases, there is an error between the frame predicted using motion vectors alone and the actual frame. This error is coded using a still image compression scheme such as the block Discrete Cosine Transform (DCT). In this simple example, the previously decoded frame is also previous in the presentation order. The previously decoded or reference frame precedes the current frame in time. In general, keep in mind the distinction between decode order and presentation order. The reference frame could be a future frame. Return to Top

Audio Codecs

The sound tracks in an AVI file are Microsoft Waveform Audio (WAV) files. The Waveform Audio files can be uncompressed PCM (Pulse Code Modulated) audio or compressed with many different audio codecs (compressor/decompressors). The windows multimedia system uses the terms WAVE or waveform audio to refer to audio that consists of digitally sampled sound. In contrast to notes of music as in MIDI, another type of audio incorporated in the Windows multimedia system. The WAV, WAVE, or waveform audio system (different authors use all three to refer to the Microsoft Windows audio system) predates Video for Windows. Video for Windows was wrapped around WAVE. Various compromises were made to insure backward compatibility with existing WAVE applications, drivers, and files. Keep this in mind as there are various differences between the audio system and the video system described in other sections of this overview. To play a waveform audio (WAV) file or the sound track of an AVI compressed with a codec, the codec must be installed in the Audio Compression Manager under Windows. Windows PCM files (uncompressed) are always supported. The Audio Compression Manager (ACM) is the software system in Windows that manages waveform audio codecs and filters. Different audio codecs are identified with different waveform audio tags, 32 bit numbers. Wave audio format tags are registered with Microsoft. The following list of registered wave audio formats if from the mmreg.h file in the Win32 SDK. mmreg.h is the Registered Multimedia Information Public Header File /* WAVE form wFormatTag IDs */ #define WAVE_FORMAT_UNKNOWN 0x0000 /* Microsoft Corporation */ #define WAVE_FORMAT_ADPCM 0x0002 /* Microsoft Corporation */ #define WAVE_FORMAT_IBM_CVSD 0x0005 /* IBM Corporation */ #define WAVE_FORMAT_ALAW 0x0006 /* Microsoft Corporation */ #define WAVE_FORMAT_MULAW 0x0007 /* Microsoft Corporation */ #define WAVE_FORMAT_OKI_ADPCM 0x0010 /* OKI */ #define WAVE_FORMAT_DVI_ADPCM 0x0011 /* Intel Corporation */ #define WAVE_FORMAT_IMA_ADPCM (WAVE_FORMAT_DVI_ADPCM) /* Intel Corporation */ #define WAVE_FORMAT_MEDIASPACE_ADPCM 0x0012 /* Videologic */ #define WAVE_FORMAT_SIERRA_ADPCM 0x0013 /* Sierra Semiconductor Corp */ #define WAVE_FORMAT_G723_ADPCM 0x0014 /* Antex Electronics Corporation */ #define WAVE_FORMAT_DIGISTD 0x0015 /* DSP Solutions, Inc. */ #define WAVE_FORMAT_DIGIFIX 0x0016 /* DSP Solutions, Inc. */ #define WAVE_FORMAT_DIALOGIC_OKI_ADPCM 0x0017 /* Dialogic Corporation */ #define WAVE_FORMAT_YAMAHA_ADPCM 0x0020 /* Yamaha Corporation of America */ #define WAVE_FORMAT_SONARC 0x0021 /* Speech Compression */ #define WAVE_FORMAT_DSPGROUP_TRUESPEECH 0x0022 /* DSP Group, Inc */ #define WAVE_FORMAT_ECHOSC1 0x0023 /* Echo Speech Corporation */ #define WAVE_FORMAT_AUDIOFILE_AF36 0x0024 /* */ #define WAVE_FORMAT_APTX 0x0025 /* Audio Processing Technology */ #define WAVE_FORMAT_AUDIOFILE_AF10 0x0026 /* */ #define WAVE_FORMAT_DOLBY_AC2 0x0030 /* Dolby Laboratories */ #define WAVE_FORMAT_GSM610 0x0031 /* Microsoft Corporation */ #define WAVE_FORMAT_ANTEX_ADPCME 0x0033 /* Antex Electronics Corporation */ #define WAVE_FORMAT_CONTROL_RES_VQLPC 0x0034 /* Control Resources Limited */ #define WAVE_FORMAT_DIGIREAL 0x0035 /* DSP Solutions, Inc. */ #define WAVE_FORMAT_DIGIADPCM 0x0036 /* DSP Solutions, Inc. */ #define WAVE_FORMAT_CONTROL_RES_CR10 0x0037 /* Control Resources Limited */ #define WAVE_FORMAT_NMS_VBXADPCM 0x0038 /* Natural MicroSystems */ #define WAVE_FORMAT_CS_IMAADPCM 0x0039 /* Crystal Semiconductor IMA ADPCM */ #define WAVE_FORMAT_G721_ADPCM 0x0040 /* Antex Electronics Corporation */ #define WAVE_FORMAT_MPEG 0x0050 /* Microsoft Corporation */ #define WAVE_FORMAT_CREATIVE_ADPCM 0x0200 /* Creative Labs, Inc */ #define WAVE_FORMAT_CREATIVE_FASTSPEECH8 0x0202 /* Creative Labs, Inc */ #define WAVE_FORMAT_CREATIVE_FASTSPEECH10 0x0203 /* Creative Labs, Inc */ #define WAVE_FORMAT_FM_TOWNS_SND 0x0300 /* Fujitsu Corp. */ #define WAVE_FORMAT_OLIGSM 0x1000 /* Ing C. Olivetti & C., S.p.A. */ #define WAVE_FORMAT_OLIADPCM 0x1001 /* Ing C. Olivetti & C., S.p.A. */ #define WAVE_FORMAT_OLICELP 0x1002 /* Ing C. Olivetti & C., S.p.A. */ #define WAVE_FORMAT_OLISBC 0x1003 /* Ing C. Olivetti & C., S.p.A. */ #define WAVE_FORMAT_OLIOPR 0x1004 /* Ing C. Olivetti & C., S.p.A. */ // // the WAVE_FORMAT_DEVELOPMENT format tag can be used during the // development phase of a new wave format. Before shipping, you MUST // acquire an official format tag from Microsoft. // #define WAVE_FORMAT_DEVELOPMENT (0xFFFF) Return to Top

How to determine which Audio Codecs are Installed

View the SYSTEM.INI file. In Windows 95, 32 bit Audio Codecs are listed in the [drivers32] section. [drivers32] msacm.lhacm=lhacm.acm msacm.l3codec=l3codecb.acm msacm.msg723=msg723.acm msacm.msnaudio=msnaudio.acm The string msacm stands for Microsoft Audio Compression Manager (ACM). This is the system software component that manages audio codecs (and other audio components) in 16 bit Windows and in Win32. The different codecs are identified by a string of arbitrary length such as msnaudio for Microsoft Network Audio. Note that this differs from Video for Windows where everything is a Four Character Code. The audio codecs in the example above were installed in Windows 95 by Microsoft's NetShow streaming audio/video product. The Audio Compression Manager (ACM) is in the process of being displaced by ActiveMovie. In Windows 95, (1) Open the Control Panel (2) Double Click on the Multimedia Icon (3) Select the Advanced tab (4) Under the Multimedia Drivers icon, double click on the Audio Compression Codecs icon to see a list of installed audio codecs. This information is the same as the information stored in the SYSTEM.INI file (see above). Return to Top


Active Movie is a new multimedia architecture for Windows 95 and Windows NT (4.0 and after). ActiveMovie includes support for playing AVI, Quicktime (.MOV), and MPEG files. ActiveMovie is apparently intended to supersede Video for Windows. ActiveMovie 1.0 ships with the OEM Service Release 2 (OSR2) of Windows 95. It did not ship with prior releases of Windows 95 but was available separately through the ActiveMovie SDK. ActiveMovie 1.0 is also bundled with Microsoft's Internet Explorer for Windows 95 and NT 4.0 Internet Explorer can be downloaded from the Microsoft web site at: http://www.microsoft.com/ie/ Active Movie 1.0 can be downloaded by itself from the Microsoft Internet Explorer site. (6/6/97) ActiveMovie 1.0 appears to be a 32 bit software component that runs under both Windows 95 and Windows NT 4.0 user mode. ActiveMovie provides at least three different programming interfaces: - The ActiveMovie ActiveX Control - ActiveMovie Component Object Model (COM) interfaces - The OM-1 MPEG MCI (Media Control Interface) command set Amongst other things, the ActiveMovie ActiveX Control can be embedded in HTML Web pages and programmed via VBScript or JavaScript. It can also be programmed using Visual C++ or Visual Basic as part of applications. The ActiveMovie COM interaces can be accessed through Visual C++ or Visual Basic. ActiveMovie supports a subset of the Media Control Interface (MCI) commands familiar to Video for Windows programmers. These commands can be accessed through the mciSendCommand(...) and mciSendString(...) functions in C/C++. ActiveMovie 1.0 does NOT provide video capture. Windows 95 with ActiveMovie 1.0 continues to use the Video for Windows video capture system and drivers. ActiveMovie 2.0 (renamed DirectShow in 1997) will provide a new, alternative mechanism for video capture. According to information distributed by Microsoft at the WDM Device Driver Conference in April, 1997, ActiveMovie 2.0 will use the WDM Stream Class under Memphis (formerly Windows 97) and Windows NT 5.0 to implement video capture. This is subject to possible change since neither Memphis nor NT 5.0 has been released (7/27/97). Extensive information on ActiveX and ActiveMovie is available at the Microsoft Web site. ActiveMovie 1.0 SDK Documentation at (6/28/97): http://www.microsoft.com/devonly/tech/amo v1doc/ Return to Top

GUID's and AVI

GUID stands for Global Unique IDentifier. In Microsoft's Component Object Model (COM) morass, an object oriented programming model that incorporates MFC (Microsoft Foundation Classes), OLE (Object Linking Embedding), ActiveX, ActiveMovie and everything else Microsoft is hawking lately, a GUID is a 16 byte or 128 bit number used to uniquely identify objects, data formats, everything. Within ActiveMovie, there are GUID's for video formats, corresponding to the FOURCC's or Four Character Codes used in Video for Windows. These are specified in the file uuids.h in the Active Movie Software Developer Kit (SDK). ActiveMovie needs to pass around GUID's that correspond to the FOURCC for the video in an AVI file. With proper programming, this should be hidden from end users but ActiveMovie programmers need to know about GUID's. Return to Top


DirectShow is Microsoft's new name for ActiveMovie 2.0 Microsoft has shifted to marketing ActiveMovie as an integral part of DirectX. Apparently DirectShow (ActiveMovie 2.0) will be released to the general public as part of Direct X 5.0. Return to Top


DirectDraw, one of the components of DirectX, is a new Applications Programming Interface (API) that is part of Windows 95 and Windows NT 4.0. DirectDraw allows programs to directly access video memory and other hardware features in video display cards. Direct Draw also defines new device drivers for graphic/video display adapters to supersede the GDI display drivers. DirectDraw needs the new device drivers. DirectDraw consists of a new API and new hardware drivers known as the Direct Draw Hardware Abstraction Layer (HAL). In the Windows 3.1 Graphic Device Interface (GDI), an application program never writes directly to the memory in a display card. It writes to a buffer in main memory within Windows. GDI invokes a GDI video device driver and copies the image from main memory to the video memory of the video card. This multiple copying of the image inevitably slows down the display. The DirectDraw API provides a mechanism allowing appliation programs to write directly into the video card's memory. It also provides a mechanism to access various special features in video cards such as color space conversion, hardware scaling, z-buffering, alpha blending, and so forth. Video card manufacturers must provide a DirectDraw driver for DirectDraw to work with their card. Microsoft's ActiveMovie uses DirectDraw to achieve faster playback of AVI, Quicktime, and MPEG files. There is extensive information on the DirectDraw and DirectX API's at the Microsoft Web site. The DirectX 3 SDK can be downloaded from the Microsoft Developer Online Web site (6/28/97): http://www.microsoft.com/msdn/ Select Microsoft SDKs from the Technical Information section, or point your browser at: http://www.microsoft.com/msdn/sdk/ Versions of DirectX - DirectX 1 - DirectX 2 - DirectX 3 - DirectX 3A (latest as of 2/18/97) - DirectX 5.0 (in development?) - DirectX 6.0 (mentioned occasionally by Microsoft) Return to Top

What is a driver?

Most often, driver refers to a software component that handles control and communication with hardware in a computer. Most but not all hardware device drivers run in a privileged mode such as the Ring Zero mode of the Intel 80x86 processors. Microsoft Windows uses the term driver to refer to several different software components. - Hardware Device Drivers - Windows 3.x or 95 Virtual Device Drivers (VxD's) - not all VxD's access hardware - Microsoft Windows Installable Drivers such as - Media Control Interface or MCI Drivers - Video for Windows Codecs (Compressor/Decompressors) - Audio Codecs (Compressor/Decompressors) Hardware Device Drivers include MS-DOS device drivers, DOS Terminate and Stay Resident Programs that access hardware, Windows 3.x and 95 VxD's (Virtual Device Drivers) that access hardware, Windows DLL's that access hardware but do not run in Ring Zero, Windows NT kernel-mode device drivers, and the new Win32 Driver Model (WDM) drivers for Memphis/Windows 98 and NT 5.0 Microsoft Windows Installable Drivers are Ring Three (Windows 95) or user-mode (Windows NT) Dynamic Link Libraries (DLL's) with a single entry point DriverProc(). MCI drivers, Video for Windows Codecs, Microsoft Audio Compression Manager Codecs, and a variety of other software components are Installable Drivers. Some installable drivers are hardware drivers. Return to Top

GDI Device Drivers

In Windows 3.1, and to a lesser extent Windows 95, the Graphic Device Interface or GDI is the system that handles graphic display, including putting bitmaps on the display monitor. Amongst other things, GDI defines a set of GDI functions that application programs call such as BitBlt(...) to display graphics on the screen. GDI also controls printers and other graphic output devices. Windows NT also provides a GDI system, but the underlying hardware device drivers are different. Windows 3.1 GDI drivers won't work under NT. Application programs written using the GDI API will usually work under NT. GDI is device independent. To achieve this, GDI uses GDI device drivers loaded dynamically as needed. The most commonly used GDI device driver is the DISPLAY device (for display monitors). In Windows 3.1, this is specified by lines such as: display.drv=SUPERVGA.DRV in the SYSTEM.INI file. SUPERVGA.DRV is a generic super vga graphic display adapter driver shipped with Windows 3.1 SUPERVGA.DRV is a GDI Device Driver The printer driver is another common GDI device driver. In Windows 3.1 or Windows 95 without DirectDraw, GDI handles display of video frames on the display monitor. GDI defines a set of standard functions exported by GDI Device Drivers. A GDI Device Driver can also report that it does not support a particular function. Standard Functions for GDI Device Driver Entry Name Description 01 BitBlt Transfer bits from src (source) to dest (destination) rect (rectangle) 02 ColorInfo Converts between logical and physical colors. . . . 30 BitmapBits Sets, retrieves, copies bitmap data. Video card manufacturers write and provide GDI Device Drivers for video cards. When Video for Windows plays an AVI file, Video for Windows usually uses the Media Control Interface (MCI) driver for AVI files (MCIAVI.DRV). The MCI driver will call GDI to display each decoded frame of video and WAVE to output the decoded audio to the sound card. In Windows 95 or NT 4.0, ActiveMovie 1.0 has "renderers" which can invoke GDI or DirectDraw depending on the situation to display the decoded video frames. There are also audio renderers to output the decoded audio from an AVI, QuickTime, or MPEG file. Return to Top

Direct Draw Hardware Abstraction Layer

DirectDraw is a replacement for GDI for Windows 95 and Windows NT 4.0. See elsewhere in this overview for sections on GDI and DirectDraw. The Direct Draw Hardware Abstraction Layer (HAL) defines Direct Draw device drivers for graphics/video display adapters. Graphics and video card manufacturers provide DirectDraw device drivers. For Direct Draw to work it must have these device drivers. DirectDraw also defines a DirectDraw Applications Programming Interface (API), a standard set of function calls invoked by applications. The DirectDraw API in turn calls the Direct Draw HAL to access the graphics/video display adapter. ActiveMovie can invoke DirectDraw for video output under Windows 95 and Windows NT 4.0. Return to Top

Virtual Device Drivers

In Windows 3.x and Windows 95, Virtual Device Drivers or VXD's are usually the hardware device drivers. They run in a privileged mode of the Intel 80x86 processor known as Ring Zero. Video display adapters and video capture cards usually have an associated VXD written by the card or chip manufacturer. Note that some Windows device drivers are implemented as Dynamic Link Libraries (DLL's) that do not run in the privileged, Ring Zero, mode of the 80x86 processor or as MS-DOS programs that access hardware. These device drivers are not VXD's. There are some things that only VXD's can do. Most PC hardware, especially with high bandwidth requirements, use VXD's. Device drivers for video display adapters are rarely a single VXD. Often the Device Driver Interface (DDI) is implemented as a Dynamic Link Library which does not run at Ring Zero. Only parts of the device driver that need to run at Ring Zero are in the VXD. A full video display device driver is often built of several files, frequently including one or more VXDs. VXD's are usually found in the \WINDOWS\SYSTEM directory. VXD's will not work for hardware under Windows NT 3.51 or NT 4.0 Windows NT has its own Windows NT Driver Model for device drivers. In "Memphis", formerly Windows 97, and NT 5.0, Microsoft is attempting to provide a common driver model known as WDM or Win32 Driver Model so that the same drivers can be used in both Memphis and NT. Return to Top

Windows NT Driver Model

Windows NT (3.51, 4.0) has its own system of hardware device drivers. While NT can often run Windows 3.x and Windows 95 applications, NT cannot use Windows 3.x or Windows 95 device drivers (the Virtual Device Drivers or VxD's). For most people working with AVI, or video in general, the main point to remember is that different drivers are needed for NT than Windows 95 (or Windows 3.x). Most hardware manufacturers provide both Windows 3.x, 95, and NT drivers. TOOLS Programmers will need the Windows NT DDK (Device Driver Kit) to develop Windows NT drivers. This is available in a subscription to Microsoft Developer Network (Professional). http://www.microsoft.com/msdn/ Return to Top

Win32 Driver Model (WDM)

The Win32 Driver Model (WDM) is a new device driver system for Memphis (formerly Windows 97) and Windows NT 5.0 The notion is that the same device drivers will work under both Memphis and NT 5.0 WDM is largely the Windows NT Driver Model used in NT 3.51 and 4.0 It is still under development. Video display card and video capture card companies will presumably be providing WDM drivers for Memphis and NT 5.0 in the future. Memphis is supposed to be backward compatible so that Windows 95 Device Drivers will still work under Memphis. Similarly, NT 4.0 Device Drivers will still work under NT 5.0 A WDM Device Driver will work under both Memphis and NT 5.0. Return to Top

Setup Information or INF Files

When a video codec or hardware device driver is installed under Windows 3.x, Windows 95, or Windows NT, Windows uses a special file known as a Setup Information file. This is also known as a Device Information file in the case of device drivers. These files have the extension .INF and are also known as INF files. When a user installs a codec or device driver through the Control Panel, the user points the Windows system to a directory containing an INF file and the various files, such as VxD's or DLLs, to be installed. A Setup Information, Device Information, or INF file contains directives that tell Windows how to install the new software or hardware. These include changes to the Windows Registry, names and locations of files to install, and other things. If you are providing a hardware or software product, you may need to create an INF file to install your product, driver, etc. End users are often unaware of the INF file. Indeed, its purpose is to hide the complexity of installing hardware or software. But it is good to be aware that these files exist and Windows needs them to properly install many drivers, codecs, and so forth. Where AVI is concerned, there are frequently INF files for video codecs, video display adapters, and video capture cards. Return to Top


MMX or Multimedia Extensions to the Pentium instruction set are 57 new instructions that accelerate some graphics, imaging, and multimedia operations. Multimedia often involves small data types such as 8 bit or 16 bit pixels that can be processed in parallel. For example, in principle, a 32 bit instruction could operate of four 8 bit pixels in parallel. A simple example would be adding four 8 bit pixels in parallel. The MMX instructions add clipping for underflow and overflow situations. 255 0 0 255 Normal addition of four 8 bit pixels backed in 32 bits + 0 0 0 255 ------------- 255 0 1 0 255 0 0 255 MMX style clipping of overflow + 0 0 0 255 -------------- 255 0 0 255 Intel developed the MMX instructions and added them to recent versions of the Pentium chip known as the P55C or Pentium with MMX. The MMX instructions were also added to the Pentium Pro. The Pentium Pro with MMX was code named Klamath, but called the Pentium II when actually shipped in 1997. MMX can accelerate various graphics and multimedia operations. It can accelerate video codecs. In particular, the block Discrete Cosine Transform used in JPEG, Motion JPEG, H.261, H.263, H.263+, MPEG-4, MPEG-1, and MPEG-2 can be accelerated using MMX instructions. Initially compilers have not supported generation of MMX instructions, so critical portions of the multimedia algorithms must be hand-coded in Pentium assembler using the MMX instructions. An MMX version of a codec may be able to encode and decode an AVI file (for example) faster on a PC with MMX. DOCUMENTATION ON MMX Further information on MMX is available at the Intel Web site for developers: http://developer.intel.com/sites/developer Click on the Literature Center link, then select "Pentium Processor with MMX" from the pull down list of products. This information is dated August 1, 1997. The Intel Web site changes from time to time. In addition to various on-line documentation at the Web site, Intel has some manuals on MMX: Intel Architecture MMX Technology Developers Manual (Order No. 243013) Intel Architecture MMX Technology Programmer's Reference Manual (Order No. 243007) TOOLS FOR WORKING WITH MMX Intel provides an MMX Technology Macro Package for use with the Microsoft Macro Assembler (MASM). This can be downloaded from: http://developer.intel.com/design/perftool/mmx1mac/ Intel markets an Intel C/C++ compiler plug-in for Microsoft Visual C/C++ 4.x/5.0. This plug-in includes "special compiler intrinsics" to support MMX. These allow a programmer to use the call syntax of C functions instead of manually coding in assembly language. Example of an "instrinsic" __m64 _m_pmaddwd(__m64 m1, __m64 m2) http://developer.intel.com/design/perftool/icl24/ The Intel C/C++ compiler plug-in is available on the VTune CD-ROM. VTune is discussed below. Intel markets a product called VTune for profiling programs on the Intel architecture at the machine instruction level. VTune includes support for the MMX instructions and has been used to profile and optimize MMX code. The VTune CD-ROM includes a number of other Intel freebies and products such as the Intel C/C++ compiler plug-in that may be useful developing MMX software. http://developer.intel.com/design/perftool/vtune/ Return to Top


NOTE: ActiveX is NOT ActiveMovie. There is an ActiveMovie ActiveX control, but ActiveX is far more than this. ActiveX is a stripped down version of OLE (Object Linking and Embedding) targetted for the World Wide Web. An ActiveX component or control is a software component written in Visual Basic, Visual C++, or Java that conforms to the ActiveX API. This API is a variant of OLE, designed to create small objects that can be dowloaded over the Internet. An ActiveX object or control may reside on a Web page to be downloaded and run when Microsoft's Internet Explorer views the page. An ActiveX control can be the ActiveMovie ActiveX control which plays AVI and other video formats supported by ActiveMovie. An ActiveX control can be an entertaining animation, a game like tic tac toe, anything. In this sense, ActiveX objects are similar to Java applets. Unlike Java applets, once an ActiveX control has been downloaded once it remains on the downloading machine and can be used again without being dowloaded again. Also unlike Java, ActiveX controls are tied to a particular architecture, Windows 95 or Windows NT. It is not clear how much support Microsoft will give for ActiveX on non-Windows platforms. Java applets are compiled to a Java bytecode that will run on any platform with a Java virtual machine implemented. Java applets will run on Windows 3.1, Windows 95, Windows NT, PowerMacintosh, Linux, Sun, and various other Unix platforms. There is extensive information on ActiveX at the Microsoft Web site. The ActiveX SDKs can be downloaded from the Microsoft Developer Online Web Site (6/28/97): http://www.microsoft.com/msdn/ Select Microsoft SDKs from the Technical Information section or point your browser at: http://www.microsoft.com/msdn/sdk/ Netscape Fans: ScriptActive is a Netscape Plug-In that adds support for ActiveX to Netscape. ScriptActive Web Site Return to Top

Playing an AVI File within a Windows Application

Programmers can play an AVI File within a Windows application by several means. The simplest traditional way is to use the Media Control Interface (MCI). Video for Windows includes an MCI driver mciavi.drv for AVI files. Within the Windows API, programmers can use two C language API functions, mciSendString(...) and mciSendCommand(...), to communicate with the MCI driver. mciSendString(...) sends MCI command strings such as "play from 0 to 100" to the MCI driver. mciSendCommand(...) sends MCI command messages, a straight C type interface, to the MCI driver. The syntax for mciSendString is: MCIERROR mciSendString(LPCTSTR lpszCommand, LPTSTR lpszReturnString, UINT cchReturn, HANDLE hwndCallback); The pointer lpszCommand points to the MCI command string such as "play from 0 to 100". Consult the Microsoft SDK documentation for more details. The syntax for mciSendCommand is: MCIERROR mciSendCommand(MCIDEVICEID IDDevice, UINT uMsg, DWORD fdwCommand, DWORD dwParam); where uMsg is an MCI command message such as MCI_PLAY defined in an include file. Consult the Microsoft SDK documentation for more details on MCI command messages. mciSendString(...) and mciSendCommand(...) are essentially equivalent. The MCI driver should convert the MCI command string to an MCI command message internally. The MCI command strings provide a more English like interface to MCI. For C++ programmers, Microsoft provides a window class MCIWnd to wrap the MCI operations. Quoting the Microsoft SDK documentation: Microsoft sayeth.... MCIWnd is a window class for controlling multimedia devices. A library of functions, messages, and macros associated with MCIWnd provides a simple method to add multimedia playback or recording capabilities to your applications. Using a single function, your application can create a control that plays devices such as video, CD audio, waveform audio, MIDI (Musical Instrument Digital Interface), or any device that uses the Media Control Interface (MCI). Automating playback is also quick and easy. Using a function and two macros, an application can create an MCIWnd window with the appropriate media device, play the device, and close both the device and the window when the content has finished playing. ... end Microsoft sayeth. Consult the Microsoft documentation for more details on MCIWnd. ActiveMovie appears intended to supersede MCI. ActiveMovie includes a restricted subset of MCI for (partial) backward compatibility. However, Microsoft appears to want developers to switch over to new API's such as ActiveX and ActiveMovie, built on top of Microsoft's Component Object Model (COM) object oriented framework. Return to Top

Reading and Writing an AVI file within a Windows Application

The Microsoft Windows Win32 SDK (Windows NT and Windows 95) includes a set of functions and macros known as AVIFile for reading, writing, and manipulating RIFF files including AVI files within a Windows program. These functions are contained within a Dynamic Link Library avifile.dll. The AVIFile functions include: AVIFileInit(...) AVIFileOpen(...) AVIFileReadData(...) AVIFileWriteData(...) AVIFileExit(...) and many many others. Consult Microsoft documentation for details. Return to Top

Where to get C Source Code for AVI Player Including Many Codecs

Marc Podlipec's Xanim is a free AVI Player for X Windows and Unix. Most of Xanim is available in source code format. The Xanim home page is: http://xanim.va.pubnix.com/ Unfortunately, Xanim's Cinepak and Indeo support is only available in object module (binary format). Return to Top

Where to get Detailed Information on Graphics File Formats

Programmers often need to know the details of the many graphics file formats, both still image and moving. There are a number of Web sites, books, and other resources that provide detailed information on the many still image and video/animation graphics file formats. Wotsit's File Format Collection http://wotsit.simsware.com/ and http://www.ipahome.com/gff/textonly/summary/ Return to Top

Where to get Detailed Information on Audio File Formats

On the Internet, Guido Van Rossum distributes an Audio Formats FAQ (in two parts) to the alt.binaries.sounds.misc, alt.binaries.sounds.d, and comp.dsp USENET newsgroups. On the Web: http://www.cs.ruu.nl/wais/html/na-dir/audio-fmts/.html Return to Top

Where to get C Source Code for a JPEG Encoder or Decoder?

Maybe you want to write your own Motion JPEG codec for AVI. It happens. The Independent JPEG Group, also known as IJG, distributes the source code for a JPEG encoder and decoder. The IJG code is incorporated in many JPEG viewers, is optimized, is free. This is available by anonymous ftp from the UUNET FTP archive. ftp://ftp.uu.net/graphics/jpeg/ Return to Top

Where to get C Source Code for an H.263 Video Encoder or Decoder?

Telenor Research distributes a free H.263 video encoder and decoder. The code is not optimized. Note that H.263 is subject to a variety of patents and Telenor includes a disclaimer with the code. http://www.fou.telenor.no/brukere/DVC/h263_software/ Return to Top

Where to get C Source Code for an MPEG Video Encoder or Decoder?

The MPEG Software Simulation Group or MSSG distributes the C source code for MPEG-1 and MPEG-2 video encoders and decoders. This code is not optimized. Go to the MPEG site below and look for MSSG. http://www.mpeg.org/ Return to Top

Where to get C/C++ Source Code for Wavelet Image Compression?

Geoff Davis distributes a C/C++ source code for wavelet still image compression of grayscale images, the Wavelet Image Construction Kit. This code is made available for research purposes. http://www.cs.dartmouth.edu/~gdavis/ Also see the SPIHT demonstration programs, http://ipl.rpi.edu/SPIHT/ Return to Top

Where to get an Explanation of Color, Color Spaces, Gamma, and All That

Charles Poynton maintains an FAQ on Color and an FAQ on Gamma. This is posted in USENET newsgroups regularly and is available on the Web. http://www.inforamp.net/~poynton/notes/colour_and_gamma/ColorFAQ.html Return to Top

Internet Video Standards and Pseudo-Standards

There are a number of Internet standards and proposed standards for sending video and multimedia over IP based networks. These are mostly described in Internet Engineering Task Force (IETF) Requests For Comments (RFC's). Programmers and others needing the details of the standards and proposed standards can find the RFC's at a variety of on-line RFC repositories such as the Information Sciences Institute: http://www.isi.edu/rfc-editor/ What should you look for? There are thousands of RFC's, most of which do not relate directly to video. Below are some families of protocols used with video and representative RFC's for these families. I have tried to include the most important RFC's. MIME (Multipurpose Internet Mail Extensions) MIME is a protocol for attaching multimedia data such as images, sound, and video to Internet mail. RFC 1521 MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies. RFC 1522 MIME (Multipurpose Internet Mail Extensions) Part Two: Message Header Extensions for Non-ASCII Text (why do it only once?) RFC 2045 MIME Part One RFC 2046 MIME Part Two RFC 2047 MIME Part Three RFC 2049 MIME Part Five RTP (Real Time Protocol) RTP is a protocol for insuring timely delivery of "real-time" data such as video. Video frames must be delivered in a timely manner in order to be displayed evenly and periodically. The TCP protocol does not provide this functionality. See the discussion of UDP (User Datagram Protocol) below for more on the limitations of TCP. RFC 1889 RTP: A Transport Protocol for Real-Time Applications RFC 1890 RTP: Profile for Audio and Video Converences with Minimal Control RFC 2029 RTP Payload Format of Sun's CellB Video Encoding RFC 2032 RTP Payload Format for H.261 Video Streams RFC 2035 RTP Payload Format for JPEG-Compressed Video RFC 2038 RTP Payload Format for MPEG1/MPEG2 Video RFC 2190 RTP Payload Format for H.263 Video Streams RFC 2198 RTP Payload for Redundant Audio Data RSVP (Resource Reservation Protocol) The Resource Reservation Protocol guarantees a certain bandwidth to a particular data stream. Video and other "real-time" data typically require a minimum bandwidth consistently for acceptable quality and performance. If the bandwidth is not available, the video skips frames or worse. The original TCP/IP Internet was designed primarily for non "real-time" data, often text such as e-mail messages. With e-mail, if a network becomes congested and it takes a long time to transmit a message, there is little problem. The user's e-mail arrives a little late. In many cases, the user never notices. Real-time video does not have this luxury. RSVP is one possible mechanism to add "Quality of Service" (QoS) to the Internet. RFC 2205 Resource ReSerVation Protocol (RSVP) - Version 1 Functional Spec RFC 2206 RSVP Management Information Base using SMIv2 RFC 2207 RSVP Extensions for IPSEC Data Flows RFC 2210 The Use of RSVP with IETF Integrated Services IETF is reportedly working on a standard for mapping RSVP to Asynchronous Transfer Mode (ATM) Quality of Service (QoS) A number of products supposedly support RSVP. RSVP is not widely used (Nov. 25, 1997) hence some caution is prudent with claims of RSVP support. Products Cisco's Internetwork Operating System (IOS) for Cisco Routers Ascend's GRF Routers Version 12.0 of Bay Networks BayRS Router Microsoft NetMeeting videoconferencing software Intel ProShare videoconferencing software First Beta Version of Microsoft's Windows NT 5.0 Operating System Internet Service Providers (ISP's) GTE Corporation's Internetworking Division (formerly BBN Corporation), a major Internet Service Provider, has a service trial of RSVP. (Nov. 25, 1997) MCI Telecommunications reportedly will enable RSVP on its very-high-bandwidth Backbone Network Service (vBNS) next year (1998). IP Multicast IP packets support so-called "multicast addresses". A multicast address is an an address that represents a group of machines. Machines may dynamically join and leave the multicast group. Multicasting allows simultaneous transmission of a packet to all machines in the group without duplication of the packet. For video data, this allows the equivalent of broadcast channels over a network. For example, a live speech could be sent to one multicast address while a different video program was sent to a different multicast address. A machine joins the appropriate multicast group to receive the "broadcast channel". In principle, multicasting reduces the load that video places on a network since only one packet is sent to multiple viewers. Without multicasting, a separate duplicated packet is sent to each viewer. Ethernet and some other network technologies support multicast in hardware. Ethernet "frames" have multicast Ethernet addresses. Implementing IP multicast on a single Ethernet, a single IP "subnet", is a straightforward mapping from the multicast IP addresses to the Ethernet multicast addresses. IP Multicast becomes quite complex when the machines in the multicast group are located on separate subnets and the IP multicast packets are routed by networks routers. The routers need to know whether a particular subnet contains machines belonging to a particular multicast group. Since machines join and leave the multicast groups over time, the routers must detect these changes to properly route multicast IP packets. Much of the difficulty in IP multicast involves development and implementation of routing protocols for multicast IP packets. Multicast has been implemented on the Internet throught the Multicast Backbone (MBONE) which uses the mrouted daemon to implement the Distance Vector Multicast Routing Protocol (DVMRP). Various video programs such as NASA Space Shuttle mission video, IETF meetings, and other technical conferences are frequently "multicast" over the MBONE. RFC 1112 Host extensions for IP multicasting RFC 1054 Host extensions for IP multicasting Note: RFC's 1112 and 1054 describe the Internet Group Management Protocol (IGMP) for management of multicast groups. RFC 1075 Distance Vector Multicast Routing Protocol RFC 1584 Multicast Extensions to OSPF RFC 2117 Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification UDP (User Datagram Protocol) UDP is a very simple protocol layered on top of IP. An IP packet contains the IP addresses of the sending and receiving machines on the network. The IP packet has no mechanism to identify separate sending and receiving processes on the machines. UDP adds "ports" which effectively identify sending and receiving processes. An IP address can have many ports. The pair of sending and receiving ports is called a "connection" in the language of TCP/IP. Proprietary and experimental streaming video protocols are usually layered on top of the UDP protocol rather than the TCP (Transmission Control Protocol) protocol. Why UDP instead of TCP? While TCP guarantees delivery of a stream of data, something that IP alone does not, TCP does not guarantee timely delivery of the data. To insure delivery of data, TCP resends a packet if the TCP protocol software does not receive an acknowledgement from the receiver before the TCP retransmission timeout expires. TCP uses an "adaptive retransmission algorithm" that may choose a long timeout when the network is slow. As a result TCP may wait a long time before retransmitting the packet. With video, packets of video data must be delivered quickly to prevent an underflow in the buffer of the receiving video player resulting dropped frames. The video player runs out of video data to display. Video networking protocols implemented with UDP often add a fixed timeout to retransmit packets before the buffer of the receiving video process, the video player, underflows. Such a protocol may also adjust the buffer size to compensate for delays and congestion in the network. RFC 768 User Datagram Protocol Return to Top

AVI and Your Health (Eye Strain)

Note: This is not intended as medical advice. If you are experience visual problems, see a qualified professional. Sustained use of computers probably causes a variety of visual problems. The most common problems appear to be "burning eyes" and focusing problems. Currently, computer monitors are usually placed around two feet from the user's eyes. This is much closer than the natural resting focus distance of the eyes, which is somewhere between ten feet and infinity. Also computer monitors are much dimmer and lower contrast than natural objects which forces the eyes to work harder to focus effectively on the monitor. This is one of the reasons paper remains a more comfortable medium for reading than computer monitors. Prolonged focusing at short distances probably causes a variety of visual problems. Computer users should look away from their monitor and rest their eyes, focusing at a distance, every few minutes. Many users do this without even realizing that they are doing it. Desktop video such as AVI probably presents greater risks than traditional computer uses such as reading. With static media such as text documents or still images, when the user looks away from the monitor and looks back, nothing changes, no information is missed. There is no penalty to looking away from the monitor to rest your eyes, focus at a distance, and so forth. With video, the video will change while the user is looking away. The user misses something, perhaps a critical event. Thus, users tend not to look away from desktop video, keeping their eyes focused on the screen for long periods of time. Computer animators who work with computer video, often for long periods, have reported these problems for years. Thus, people are very unlikely to watch two hour movies on computer monitors two feet from their eyes. Digital video will likely migrate to the same location as the television, at least ten feet away. Some Resources on Computers and Your Eyes "Reducing eyestrain from video and computer monitors " by Charles Poynton http://www.inforamp.net/~poynton/notes/reducing_eyestrain/index.html IBM's Healthy Computing - Vision Page Note: Keep in mind that IBM sells computers. http://www.pc.ibm.com/us/healthycomputing/ergoviso.html Return to Top

Miscellaneous Questions about AVI and Video for Windows

What is most recent version of Video for Windows? Most recent version of Video for Windows for Windows 3.1 appears to be Video for Windows 1.1e. (10/2/96)

Where can I get the 16-bit Video for Windows 1.1e runtime?

This is the Video for Windows for Windows 3.x In a pinch, it will also work under Windows 95. Windows 95 includes a version of Video for Windows that has 32 bit video codecs and possibly other changes specific to Windows 95. See elsewhere in this Overview for information on re-installing Video for Windows for Windows 95. From Microsoft, ftp://ftp.microsoft.com/softlib/mslfiles/WV1160.EXE (Note the file name is all upper case) Return to Top

How to import AVI files into Lightwave

Lightwave is a powerful 3D animation program from NewTek. Originally developed for the Amiga, Lightwave has been ported to Windows 95 and Windows NT. BurntPixels produces a plug-in for Lightwave 5.0 called AVILoad 2.1 that enables direct importing of AVI files into Lightwave animations. AVILoad 2.1 is available for Lightwave 5.0 for Windows 95 and NT. See the AVILoad Web site for further details. http://www.en.com/users/bforce/ For further information on NewTek and Lightwave, see the LightWave Web site: http://www.newtek.com/ Return to Top

How to give AVI files a different extension in Windows 3.x

It is possible to give an AVI file a different file extension, for example VID. Microsoft Windows can be configured so that Windows treats this file the same as a file with the AVI extension. For example, double clicking on a .VID file in File Manager will play the .VID file just the same as a .AVI file. In Windows 3.x, edit the WIN.INI file, usually in the \WINDOWS directory. There is a section [Extensions] which associates file extensions with applications. For example, this section will typically include a line such as: [Extensions] AVI=mplayer.exe /play /close ^AVI which causes Media Player (mplayer.exe) to be invoked when the user double clicks on a file with extension AVI. For VID, add a line VID=mplayer.exe /play /close ^VID Media Player is an MCI (Media Control Interface) application. It will attempt to play the .VID file through MCI. At this point however, MCI would not recognize VID although Media Player would be invoked. There is also a section [mci extensions] which contains lines such as: [mci extensions] AVI=AVIVideo ( tells MCI to use the MCI driver refered to as AVIVideo for files with the extension AVI) For the VID example, add VID=AVIVideo to the [mci extensions] section in WIN.INI The WIN.INI file is used mainly for configuring the higher levels of Windows: the graphical user interface and the desktop. Many applications install their configuration or installation information in sections within WIN.INI Names such as AVIVideo are defined in the [mci] section in the SYSTEM.INI file, also usually in the \WINDOWS directory. SYSTEM.INI is used mainly for configuring the lower levels of Windows: the device drivers, VxD's, and so forth. [mci] AVIVideo=mciavi.drv ( where mciavi.drv is the AVI MCI Driver ) Thus, many file extensions can refer to AVIVideo which in turn refers to the MCI Driver for AVI files. The MCI Driver processes MCI commands and may in turn invoke other drivers or DLL's such as the Video for Windows decompressors. Return to Top

How AVI Files are Handled in Windows 95

If a user double-clicks on an AVI file icon in Windows 95, Windows 95 will invoke an AVI player. In Windows 95 OEM Service Release 2, Windows 95 will invoke the ActiveMovie Control to play the AVI file. ActiveMovie 1.0 ships with OEM Service Release 2 which is configured to use ActiveMovie for AVI, Quicktime, and MPEG files. Windows 95 has file extensions and file types. .AVI is a file extension. File extensions are mapped to file types. AVIFile is a file type. The information on file extensions and file types is stored in the Windows 95 System Registry. More than one file extension can be mapped to the same file type. For example, the .AIF and .AIFF file extensions are both mapped to AIFFFile, the file type for the Apple AIFF audio file format. The file type contains information on how to play the file (which application to use) and other information. This information is all stored in the Windows 95 Registry. A user can view and also edit the information on file types through the Windows Explorer applet. Select the Options... item from the View Menu of Windows Explorer. Select the File Types tab from the Options property sheet. This gives a list box of registered file types. There are buttons to add, remove, or edit a File Type. The AVIFile File Type is identified as "Movie Clip(AVI)" in this list box of registered file types in Windows 95 OEM Service Release 2. In the Windows 95 Registry, "Movie Clip(AVI)" is a string in the "AVIFile" file type "key". Windows Explorer displays the string "Movie Clip(AVI)", not AVIFile, the name of the "key". A user can change how Windows 95 handles an AVI file by editing the "Movie Clip(AVI)" File Type in the File Types through Windows Explorer. For example, a user can select an alternative AVI file player. In Windows 95 OEM Service Release 2, the File Type includes a Content type (Multipurpose Internet Mail Extension or MIME type). The Content type (MIME type) tells Microsoft Internet Explorer how to handle a file from a Web site. The original Windows 95 retail version did not include the Content (MIME) type. This extra feature could be added by installing the MS Plus! add-on to Windows 95. Some OEM versions of Windows 95 prior to OEM Service Release 2 supported the Content (MIME) type. The Windows 95 Registry can be viewed using REGEDIT, the Windows 95 Registry editor. The registry "keys" for file extensions and file types are stored in the HKEY_CLASSES_ROOT "key". Although REGEDIT can also edit the registry, the registry is rather complex and this drastic action should be avoided. Use the Windows Explorer applet. This applet knows how to modify the keys in the Windows 95 Registry. The Windows 95 Registry is a binary database stored in two files: SYSTEM.DAT and USER.DAT. Internally, the database is structured very similarly to a hierarchical file system such as the DOS/WINDOWS file system. A Windows 95 Registry "key" is essentially a folder that contains other "keys" or "values". The "values" have a name and associated data. The data are text strings such as "Movie Clip(AVI)" or binary numbers. The Registry Editor represents keys with a folder icon and values with different icons. The Registry Editor closely resembles the Windows Explorer. The registry contains a key in the top level HKEY_CLASSES_ROOT key called .avi, for the .avi file extension. All keys contain a default "value" with the name (Default). In the .avi key, the (Default) value has the associated ASCII text string data "AVIFile". In Windows 95 OEM Service Release 2, there is an additional value named "Content Type" with the associated ASCII text string data "video/avi", the MIME type for AVI files. This additional information is used by the Internet Explorer. The (Default) value in the .avi key references the AVIFile key, also in HKEY_CLASSES_ROOT. This key contains a number of other keys and values. The (Default) value for the AVIFile key has the data "Movie Clip(AVI)" which the Windows interface uses to identify the files to users. The AVIFile key is an example of a file type key. The "shell" key in the AVIFile key specifies what happens when a user double-clicks on an AVI file. In Windows 95 OSR2, the (Default) value for the shell key is "play". The shell key contains two subkeys:open and play. These keys specify possible actions to perform. The (Default) value indicates that the "play" action will be used. The open and play keys each contain a key called command. The (Default) value for the command subkey of play is "rundll32 amovie.ocx RunDLL /play /close %1". rundll32 is a program that runs a 32 bit Windows Dynamic Link Library or DLL as an Application. The command executes amovie.ocx, the ActiveMovie Control, as an application. Controls such as amovie.ocx are actually DLLs. /play tells the control to play the file and /close tells the control to close after finishing playing the file. In versions of Windows 95 without ActiveMovie, the command keys are configured to invoke Media Player, mplayer.exe. Return to Top

How can I play an AVI file?


On DOS, the shareware program QuickView by Wolfgang Hesseler can play AVI files (including sound). QuickView 1.03 is available through the simtel sites such as ftp://info.nic.surfnet.nl/mirror-archive/software/simtel-msdos/graphics/qv103.zip You can get the latest version of QuickView (2.13 on 7/28/97) from Wolfgang Hesseler's Home Page

Microsoft Windows

Windows 3.x, Windows 95, and Windows NT are usually configured so that double clicking on the icon for an AVI file will invoke an AVI player application. Video for Windows includes an application known as Media Player that can play AVI files as well as other multimedia data types. ActiveMovie 1.0 inclues an ActiveMovie ActiveX control that can play AVI, Quicktime, and MPEG video as well as other multimedia data types. On Windows 3.x, Media Player is MPLAYER.EXE. This is a 16 bit Windows 3.x application. Windows 95 can run both the 16 bit Media Player and a 32 bit Media Player. There is also a Media Player on Windows NT 4.0 This is MPLAY32.EXE MediaPlayer can be invoked by typing mplayer.exe at the DOS command prompt or through the Run... item in the Windows 3.x Program Manager or the start menu for Windows 95 or Windows NT 4.0 The ActiveMovie ActiveX control on Windows 95 is amovie.ocx. This can be executed as a standalone application using the commands Rundll32 amovie.ocx. ActiveMovie is only available for Windows 95. It will not work on Windows 3.x Windows NT 5.0 should add an ActiveMovie implementation. ActiveMovie 1.0 is shipped with the Windows 95 OEM Service Release 2.

Power Macintosh

On the Macintosh, Microsoft's Internet Explorer (Web Browser) can play AVI files directly. There is also an application AVI->QuickTime that can convert AVI files to QuickTime .MooV files on the Macintosh. Microsoft's Internet Explorer 3.01 (on 6/4/97) for the Macintosh may be downloaded from the Microsoft web site at: http://www.microsoft.com/ie/ MacZilla is an inexpensive shareware Netscape Navigator Plug-In for the Macintosh that plays QuickTime .MOV, Video for Windows AVI, and MPEG-1 files. MacZilla can also play Sun Audio .AU, Microsoft .WAV, and MPEG Layer 2 Audio .MP2 files. If you pay the fee, MacZilla will send you a STANDALONE player (not a Netscape Plug-In) for the Macintosh. The MacZilla URL is: http://maczilla.com NOTE: I personally experienced a lot of crashes with MacZilla on my Macintosh. (6/4/97)


Xanim by Marc Podlipec is a free X Windows based AVI Player for Unix. Much of Xanim is available as source code!! The Xanim home page is: http://xanim.va.pubnix.com/ Mark Podlipec writes: Below is some up-to-date information about XAnim, the unix X11 AVI player. Thanks, Mark ---- Latest revision: XAnim Official Web sites: http://xanim.va.pubnix.com/home.html http://smurfland.cit.buffalo.edu/xanim/home.html http://www.tm.informatik.uni-frankfurt.de/xanim/ AVI Video and Audio Codecs Supported: + AVI Video Codecs supported: + IBM Ultimotion (ULTI) + JPEG (JPEG) + Motion JPEG (MJPG) + Intergraph JPEG (IJPG) + Microsoft Video 1 (CRAM/WHAM/MSVC) + Radius Cinepak (CVID) + Intel Indeo R3.1 (IV31) + Intel Indeo R3.2 (IV32) + Intel RAW YUV9 (YUV9) + Creative CYUV (CYUV) + Uncompressed (RGB ) + Run length encoded (RLE8) + Editable MPEG (XMPG) + AVI Audio Codecs supported: + PCM (0x0001) + MS ADPCM (0x0002) + ULAW (0x0007) + DVI/IMA ADPCM (0x0011)

Digital Equipment Corporation's VAX/VMS

On VAX/VMS, Xanim (see above) has been ported and works on VMS.


TapAVI 1.5 Picasso AVI Animation Player AVI Player for 020+ KS2.0 Picasso-II (variety of Amiga) http://www.ziplink.net/~wingell/ibrowse/tapavi.html There appears to be an Amiga version of the XAnim AVI Player. The TapAVI documentation in fact says that in general XAnim is better but TapAVI is better for certain uses. xanim for the Amiga appears to be available in a file xanim6.lha from Aminet. As of (5/16/97) have not located a URL.


OS/2 has built-in support for AVI files ... up to a point. OS/2 has had built-in AVI support since OS/2 2.0 in 1992. However, it cannot play all Windows style AVI files. Practice Corporation markets an extension for OS/2 called AnPoCODEC which adds support for playback of Windows-style AVI files, including AVI's compressed with RLE (Microsoft RLE), CVID (Cinepak), and MSVC (Microsoft Video 1). Practice also markets QUickMotion which adds support for playing QuickTime video files. http://www.practice.xo.com/ At least two other programs exist that are claimed to be OS/2 AVI Players. Calliope DMP 1.41 Return to Top

AVI and NetShow

NetShow is a relatively new product from Microsoft for distributing streaming video over the Internet. NetShow includes a NetShow server for Windows NT and NetShow players (both NT and Windows 95). NetShow uses the Active Streaming Format (ASF) for video streams over the Internet. ASF adds time stamps for synchronization, error correction codes, and other features that AVI lacks. The NetShow family of products includes utilities to convert AVI files to ASF files. Microsoft has licensed a number of low bitrate video technologies for NetShow including Vivo's H.263, Iterated Systems/Progressive Networks/RealNetworks RealVideo/ClearVideo fractal codec, and VDONet's VDOWave. Microsoft has purchased VxTreme, possibly the best wavelet based video codec. Microsoft has used their implementation of the uncompleted international standard MPEG-4 for NetShow. NetShow, including the server, is available at the Microsoft web site. NetShow has a number of components: the NetShow Player, the NetShow Tools, and the NetShow Server. The NetShow Player is a simple client for audio and video playback over networks. The NetShow Tools are a collection of tools and software components for creation of content, especially the ASF files. The NetShow Server is a server that runs under Windows NT for broadcasting audio and video streams over networks. The NetShow 2.0 Player Installation and the NetShow 2.0 Tools Installation both install Video for Windows codecs, the NetShow codecs. Only the NetShow 2.0 Tools codecs appear to support encoding. You must install the NetShow Tools to create AVI or ASF files compressed with the new "low bitrate" NetShow codecs! The NetShow 2.0 Player (Client) Setup installs: Codec Name ( line in SYSTEM.INI ) (Video Codecs) Vivo H.263 decoder/keyed encoder ( vidc.vivo=ivvideo.dll ) VDONet VDOWave decoder ( vidc.vdom=vdowave.drv ) Microsoft MPEG-4 decoder ( vidc.mpg4=msscmc32.dll ) ClearVideo decoder ( vidc.ucod=clrviddd.dll ) Duck TrueMotion decoder/keyed encoder (vidc.tr20=tr2032.dll ) (Audio Codecs) Vivo G.723.1 / Siren decoder ( msacm.vivog723=vivog723.acm ) Frauenhofer MPEG Layer III Audio Codec ( msacm.l3acm = l3codeca.acm ) Lernout and Hauspie Audio Codecs ( msacm.lhacm = lhacm.acm ) Voxware MetaSound/MetaVoice decode/keyed encode (msacm.voxacm119=vdk32119.acm) The NetShow 2.0 Tools Setup also installs: (NetShow 2.0 Player Codecs with Encoder) Microsoft H.263 keyed encoder ( vidc.m263=msh263.drv ) The NetShow 2.0 Player Codecs appear to lack the functionality to compress video. While they can be invoked from within some video editing programs such as Asymetrix Digital Video Producer 4.0, they produce uncompressed AVI's. These AVI's list the four character codes for the NetShow codec (such as VDOM for VDOWave) in the AVI Header but not in the video stream header within the AVI file. The video stream header uses the value 0 for the video compression indicating no compression. The NetShow 2.0 Player Codecs are invisible from Microsoft VidEdit 1.1 (Video | Compression Options ... menu selection). I believe this is because VidEdit queries the codecs to determine if they support compression and only lists the codecs that can actually compress video. In contrast, some applications such as Asymetrix Digital Video Producer 4.0 will list all codecs, both those that can compress and those that only decompress. The NetShow 2.0 Tools Codecs can compress video. You can create compressed AVI files with the VDOWave and MPEG-4 codecs from NetShow 2.0 Tools. These are actually compressed and use the VDO four character code or MPEG-4 four character code both in the AVI header and in the video stream header. However, the so-called "keyed encoders" which are Microsoft H.263, Vivo H.263, and Duck TrueMotion, cannot create compressed AVI files if invoked from a Video for Windows video editing application such as Asymetrix Digital Video Producer. The "keyed encoders" appear to be used only for creating Microsoft ASF files compressed with Vivo H.263, Microsoft H.263, or Duck TrueMotion. Microsoft VidEdit 1.1 will list all NetShow 2.0 Tools Codecs under the Video | Compression Options ... menu selection if no AVI file is loaded. Once an AVI file is loaded, some of the NetShow 2.0 Tools Codecs disappear from the list. Other video editors such as Asymetrix Digital Video Producer list all NetShow 2.0 Tools Codecs at all times. NetShow tries to use a real-time Internet Protocol called MMS to transfer video over the Internet. If it cannot use MMS, it will use TCP (Transmission Control Protocol) or HTTP (HyperText Transport Protocol). MMS appears to be a Microsoft proprietary real time protocol and a competitor to RTP (Real Time Protocol) or RTCP (Real Time Control Protocol). The Microsoft NBC Business News channel distributes video over the Internet using these technologies. NetShow also claims to support multicast IP over Networks. I've not personally seen this work. The NetShow 2.0 server administrative user interfaces contain panels for configuring multicast channels. http://www.microsoft.com/netshow/ Return to Top

How to convert an AVI file to a Microsoft ASF File?

Microsoft has defined yet another audio/video/multimedia file format to support streaming audio and video over the Internet. This is ASF (formerly Active Stream Format and now Advanced Streaming Format). These files have the extension .asf or .asx. They are used as part of Microsoft's NetShow video server and client over the Internet. The NetShow authoring tools include a DOS command line utilitity: VidToAsf which converts AVI files to ASF files, preserving whatever compression was used. Like AVI, ASF files support many compression schemes. For more information including software: http://www.microsoft.com/asf/ http://www.microsoft.com/netshow/ Return to Top

Sources of AVI Video Clips on the Web

What good is all this technology without something to watch? Accordingly, some sites with AVI content. The Official Babylon 5 Web Site has a large number of AVI files from the popular science fiction television show. http://www.babylon5.com Paul Bauer's Multimedia City contains a large list of sites with video clips. http://www.geocities.com/Broadway/2876/index.html Return to Top

Low Bit Rate AVI for the Web

A major limitation of video on the Web in general and AVI in particular is the limited bandwidth available. Currently most users with Plain Old Telephone Service (POTS) have 28.8 Kbits/second or 33.6 Kbits/second connections to their Internet Service Provider. The new generation of K56Flex and X2 modems from U.S. Robotics and Rockwell may eventually provide 50-60 Kbits/second over tradiational analog telephone lines. A Basic Rate Interface (BRI) ISDN connection provides 128 Kbits/second. Although very high speeds are possible within the LAN's and WAN's of major corporations and other well-endowed organizations, the so-called Intranet, the actual rates achieved over the world wide Internet are generally much less. Not necessarilly better than the rates for POTS or ISDN. For example, currently (7/20/97) a Web browser at NASA Ames Research Center in Mountain View, California can attach to my web site at an Internet Service Provider in nearby San Jose at a sustained data transfer rate of 15 KBytes/second or 120 Kbits/second. NASA Ames is home to the Federal Internet Exchange (FIX), the government's main switching center for the Internet, for the West Coast of the United States. This is the heart of the Silicon Valley. This is probably much better performance than more outlying parts of the Internet. This gives a sense of the current limitations of the broader Internet. These Internet rates are very low bitrates for video. The prevailing block Discrete Cosine Transform (DCT) based video codecs such as MPEG-1, H.261, and H.263 perform acceptably at 384 Kbits/second but frequently exhibit unnatural artifacts at 128 Kbits/second for 30 frame per second 320x240 pixel video. These block DCT based codecs match or exceed the performance of CinePak, the reigning king of AVI codecs. Ultimately, faster Internet connections and better codecs will combine to resolve this problem and allow convincing, realistic video over the Internet. In the meantime, Web authors planning to use video must provide highly compressed video at low bitrates. To do this, options are: - Use smaller frame sizes (e.g. 160x120 pixels) - Use lower frame rates (10 - 15 frames per second) - Push the standard codecs such as CinePak as far as possbile. - Use one of the newer codecs such as: VDOWave Indeo 4.1 H.263 This overview contains a detailed section on the many codecs available for AVI files: Video for Windows Codec Section This overview also has a section on effective video for the Web. Note that there are practical limits on how low resolution, frame rates, and video quality can be pushed before the video becomes ineffective. Effective Video for the Web Return to Top

Limitations of AVI and Video for Windows over Networks

AVI and Video for Windows were developed for playback of audio and video from hard disks and CD-ROMs on personal computers. They are also adequate for downloading a video file from a remote site on the Internet for subsequent playback from the computer's hard drive. They are not well suited for real-time or streaming video playback over networks. This means videoconferencing or broadcast video over networks. The AVI file format lacks time stamps embedded in the audio and video streams. There is no mechanism to resynchronize the audio and video streams if data is lost. In a network, sometimes packets are lost in which case the audio and video playback will lose track of the time. With time stamps, the application can resynchronize the audio and video playback. Microsoft has a new generation of products in the form of the Active/Advanced Streaming Format (ASF), NetShow, NetMeeting (videoconferencing), and ActiveMovie (DirectShow) with improved support for video over networks. Microsoft provides utilities for converting AVI to the new ASF format. Return to Top

How can I convert an AVI file to a sequence of bitmap images?


Microsoft's VidEdit video editor can convert AVI files to a sequence of Microsoft DIB files, such as test.avi --> test00.dib, test01,dib, etc. Further information on VidEdit is available in the section of the AVI Overview on editing AVI.


There is a freeware DOS program called AVIRIP that can convert non-compressed AVI files to a sequence of TGA (Targa), RAW, or DIB files. AVIRIP is available with the convmpg3 freeware toolkit for converting AVI to MPEG and MPEG to AVI. Further information on convmpg3 is available in the section of the AVI Overview on converting AVI to MPEG. Phade Software's MPEG Site has CONVMPG3 http://www.mpeg1.de/msdos.html

Jih-Shin Ho's Display

Display by Jih-Shin Ho Available at ftp://info.nic.surfnet.nl/mirror-archive/software/simtel-msdos/graphics/disp189a.zip or other Simtel mirror sites. This is a 32-bit MS-DOS program that can read and write many image and movie file formats.

DeBabelizer Pro

Equilibrium's DeBabelizer Pro for Windows 95 and NT 4.0 reads and writes about 90 common and not-so-common image formats. DeBabelizer Pro also reads and writes AVI files. DeBabelizer Pro can read an AVI file and export it as a sequence of still images in the many image formats that it supports. DeBabelizer Pro has many other features beside file format conversions. Equilibrium has a demonstration version of DeBabelizer Pro on its Web site. This is definitely demonstration version. The demo version plasters the word Equilibrium all over any images that it processes. DeBabelizer Pro ($595 Suggested Retail Price) Equilibrium 475 Gate Five Road, Suite 225 Sausalito, CA 94965 1-800-524-8651 or (415) 332-4343 http://www.equilibrium.com/ Return to Top

Smacker (.SMK Files)

Smacker is a special 8-bit color video format from RAD Game Tools used for video and computer games. Smacker files usually use the file extension .SMK RAD Game Tools provides free Smacker Utilities at their Web site: http://www.radgametools.com/ The utilities can convert an AVI file to a Smacker video file (.SMK file). The Smacker utilities calculate a good 8 bit palette for the input video. Return to Top

Progressive Networks RealMedia Streaming Format (.RM Files)

Progressive Networks has a streaming media format known as RealMedia with the file extension .rm using RealAudio audio compression and RealVideo video compression (RealVideo, also known as ClearVideo, is Iterated Systems fractal video compression). Progressive provides a product known as RealEncoder to author RealMedia files. RealEncoder can import AVI files! http://www.real.com/ Return to Top

How to convert a sequence of bitmap images to an AVI?


Microsoft's VidEdit software (16 bit Windows) can read in sequences of Microsoft .DIB files and convert them to an AVI file. More information on VidEdit is available in the section of the AVI Overview on editing AVI files.

Video for DOS

A shareware program called Video for DOS (VFD) can convert sequences of Targa files (.TGA) into AVI. (11/8/96) Video for DOS can be downloaded from http://www.dc.ee/Files/Graf Thanks to John Avis for information on Video for DOS.

AVI Constructor

Michael Caracena's AVI Constructor is a shareware program that Michael Caracena (Oct. 3, 1997) writes... The newest version of AVI Constructor can: - Make AVI files from bitmap (*.BMP), JPEG (*.JPG), and TARGA (*.TGA) files. - Insert audio from a .wav file into the AVI. - Extract images from any AVI. etc. AVI Constructor can be ordered and a demonstration version downloaded from: http://www.henge.com/~caracena

MainConcept's MainActor

MainConcept's MainActor can import sequences of BMP images and export them as an AVI video file. MainActor can import and export many other video and still image formats as well. http://www.mainconcept.de/

DeBabelizer Pro for Windows 95 and NT 4.0

Equilibrium's DeBabelizer Pro can read and write about 90 common and not so common image file formats. DeBabelizer Pro can also read and write AVI files. DeBabelizer Pro can read in sequences of image files in many formats and convert to an AVI file. Equilibrium has a demonstration version of DeBabelizer Pro on their web site. This is a demonstration version. It adds the words Equilibrium to any images or movies that it processes. DeBabelizer Pro ($595 Suggested Retail Price) Equilibrium 475 Gate Five Road, Suite 225 Sausalito, CA 94965 1(800) 525-8651 or (415) 332-4343 http://www.equilibrium.com/

Smacker Utilities

RAD Game Tools distributes free Smacker utilities at their Web site: http://www.radgametools.com/ The Graphics Processor can convert a sequence of bitmap images in several common bitmap image formats into an AVI file. NOTE: this AVI file uses an 8 bit color palette selected by the Smacker utilities for best picture quality. RAD Game Tools licenses a proprietary 8 bit video format called Smacker for use in video games. Their focus is on compression achieved through proper selection of an 8 bit color palette, rather than 24 bit color. Smacker is popular in the gaming industry. RAD Game Tools 850 South Main Street Salt Lake City, UT 84101 Voice: (801) 322-4300 FAX: (801) 359-6169

mkavi (PPM to AVI)

mkavi is a Unix utility with source code to convert sequences of Unix PPM (Portable Pixmap) files into AVI. As of 11/7/97, the documentation describes mkavi as alpha code. ftp://www.va.pubnix.com/staff/stripes/code/ Return to Top

How to convert QuickTime MOV files to AVI?

Power Macintosh:

Video for Windows (Macintosh) is a collection of utilities and extensions for the Macintosh that add support for Windows video file formats. One of the utilities is VfW Converter which can convert Quicktime MooV files to AVI files playable on the PC. VfW Converter is more powerful than Intel's smartvid PC application. It can convert video formats. For example, VfW Converter can convert a raw uncompressed 24 bit Quicktime Movie to a raw uncompressed 24 bit AVI Movie (or do various compressions). Uncompressed Quicktime and uncompressed AVI files use different video formats. VfW Converter also converts audio from Quicktime audio to AVI audio. The Video for Windows (Macintosh) file is usually called: video-for-windows-11p.hqx Apple's Quicktime Web site contains links to sources for Video for Windows (Macintosh) as well as other useful video utilities. Apple's QuickTime Web Site Video for Windows (Macintosh) has the virtue of being free, unlike: Adobe Premiere (Macintosh) ---reportedly can save QuickTime movies as AVI files.

On PC/Microsoft Windows:

TRMOOV.EXE (see below) can translate MOV to AVI, but I found problems playing back the AVI files on my 486 PC. It does not change the interleaving of the audio and video streams in the conversion from .MOV to .AVI. TRMOOV preserves the half-second interleave of QuickTime movies which is not appropriate for AVI. AVI wants each video frame interleaved with the audio for that frame. With the half-second interleave of QuickTime the audio will playback for a half-second while the video is frozen, followed by a half-second of video with no audio, repeated for the duration of the AVI playback. The interleave can be fixed using VidEdit. VidEdit contains algorithms to properly interleave the audio and video. Load the offending AVI file into VidEdit, Select File | Save As ... and give the file a new name. This triggers the interleave algorithm. VidEdit will reorganize the audio and video to interleave frames instead of half-seconds. Intel's SmartVid (see below) can convert .MOV to .AVI It appears to convert the audio video interleave from one format to another, something TRMOOV seems to have problems with. Return to Top

Converting Autodesk Animation Files (FLI or FLC) to AVI


Use Microsoft's VidEdit editor. This editor can read FLI or FLC files. Then save the files as AVI files. Launch VidEdit. Select File | Open ... This brings up the Open Video File dialog box. Under List Files of Type, select Autodesk Animation from the pulldown list. Then, choose File | Save As ... VidEdit will save the file as an AVI file. Further information on VidEdit is available in the section on editing AVI files, including where to get VidEdit.


MainConcept's MainActor for Windows 95 and OS/2 Version 1.00 can load Autodesk Animator FLI and FLC files and save in AVI format. For further information on MainActor, a shareware program that converts many video and animation formats, see: http://www.mainconcept.de/ or e-mail info@mainconcept.de Return to Top

Converting MPEG to AVI

CONVMPG3/VIDEDIT (FREE) Use the CONVMPG3.ZIP package of MPEG and AVI utilities. CONVMPG3 is available for download at the Phade Software MPEG site: http://www.mpeg1.de/msdos.html (1) Run DMPEG to convert MPEG-1 to a sequence of RAW still images. (2) Use RAWRIP to convert the sequence of RAW still images to a sequence of DIB's. (3) Use VidEdit to convert the sequence of DIB's to an AVI file. (or another video editor). VidEdit is not bundled with CONVMPG3, but is available elsewhere. Go to VidEdit Section The VidEdit section of the AVI Overview includes links to sites to download VidEdit. Ulead's MPEG Converter can convert MPEG-1 to AVI. Ulead is: Ulead 970 West 190th Street, Suite 20 Torrance, CA 90502 Voice: (800) 858-5323 FAX: (310) 523-9399 http://www.ulead.com/ Return to Top

Converting Animated GIF (GIF89a) to AVI

MainConcept's MainActor for Windows can load animated GIF files (GIF89a) and then save these files as AVI files. MainActor is available in a shareware version or as a fully functional paid-for version. On the Web: http://www.mainconcept.de/ By E-Mail: info@mainconcept.de Return to Top

How to Convert a Sequence of Still Images in One Format to a Sequence in Another Format

At this time, there are hundreds of different graphic file formats for still images, such as Windows BMP, Windows DIB, Targa, GIF, JPEG, Unix Portable Pixmap (PPM), and many others. In creating an AVI (or MPEG or MOV for that matter), some authoring programs may create a video as a sequence of still images in some graphic file format which is not supported by the graphic file sequence to AVI conversion utilities listed elsewhere in this Overview. Fortunately, there are freeware, shareware, and commercial programs which provide batch conversion of sequences of still images from one file format to sequences in another file format. For example, you might generate a sequence of Unix PPM format files with one utilitity and need to convert to a sequence of Windows BMP files.


WinJPEG is a shareware Windows utilitity from Pixel Vision. WinJPEG reads and writes most graphic file formats. It has a batch conversion feature. Pixel Vision Software Home Page (WinJPEG): http://www.pixvision.com/ Paint Shop Pro is a shareware and commercial Windows utility from Jasc Software. Paint Shop Pro reads and writes most graphic file formats. It has a batch conversion feature. The shareware version of Paint Shop Pro has a thirty (30) day evaluation period. Jasc Software Paint Shop Pro Page: http://www.jasc.com/psp.html

Power Macintosh

GraphicConverter is a shareware Power Macintosh utility with very extensive support for graphic file formats and some video formats. It can read and write roughly a hundred different file formats including some pretty obscure formats. It has a batch conversion feature. GraphicConverter Web Site: http://www.lemkesoft.de/


I've not identified a Unix utility with explicit batch conversion features. However, there are some utilities for bitmap conversion. The Portable Bitmap Utilities can easily be used for batch conversion through a script. PBMPLUS: Extended Portable Bitmap Toolkit by Jef Poskanzer A collection of utilities for converting to and from Jef Poskanzer's Portable Bitmap (PBM), Portable Greymap (PGM), and Portable Pixmap (PPM) file format. FREE and widely available on Unix systems. For example, to convert a GIF file to a TIFF file. 1. giftoppm myfile.gif 2. pnmtotiff myfile.ppm giftoppm is a utility program to convert GIF to PPM pnmtotiff is a utility program to convert PBM/PGM/PPM to TIFF The PBM utilities can be invoked from Unix scripts (Bourne Shell, Korn Shell, C Shell, Perl, etc.) for batch conversion of a sequence of bitmap images. PBMPLUS is available at a number of ftp sites such as: ftp://ftp.x.org/R5contrib/ There are many files in this directory. PBMPLUS is: pbmplus10dec91.tar pbmplus10dec91.tar.Z John Bradley's xv (shareware) xv is a Unix X-Windows shareware utility for viewing, manipulating, and converting bitmap images on Unix X-Windows systems. xv supports many common bitmap image file formats. The xv Version 3.10a Manual states: "Since xv has absolutely no command-line or batch conversion abilities..." xv is available from a number of sites such as: ftp://ftp.cis.upenn.edu/pub/xv Return to Top

How to convert AVI to QuickTime files?

Microsoft Windows

Intel's SmartVID, a DOS and Windows application, can convert .AVI to .MOV files. SmartVID is codec independent. This means that SmartVid preserves the video compression scheme from the source .AVI file. http://www.intel.com/pc-supp/multimed/indeo/smartvid.htm TRMOOV.EXE Windows 3.1 Program Converts AVI to QuickTime for Windows movie. The QTW movie will play on a Macintosh with QuickTime 1.5 or later. Note: My experiments converting some .MOV files to .AVI seem to playback ok, unlike the .AVI to .MOV conversion. Source: Found on CD-ROM with the "How to Digitize Video" book (see below). On Net: ftp://ftp.rahul.net/pub/jfm/avi/trmoov.exe Please Note: TRMOOV and SmartVid preserve the compressor used in the source file. For example, if the AVI file was compressed with CinePak, the MOV file will be compressed with CinePak. Since CinePak is supported by both Video for Windows and QuickTime this is not a problem. However, if the compressor exists only in Video for Windows or only QuickTime, then there will be a problem. Mainconcept's Main Actor can load many video and animation formats. It can also save many video and animation formats. The Windows version of Main Actor can load AVI and save the file as Quicktime. http://www.mainconcept.de


On the PowerMacintosh, the program AVI->QuickTime can convert AVI to QuickTime. At least, it can convert the video successfully for subsequent playback with Apple's MoviePlayer. I have seen problems with the audio. This application is available at various Web and ftp sites in the file avi-to-qt-converter.hqx One site with AVI->QuickTime is: ftp://mirrors.aol.com/pub/info-mac/gst/mov/avi-to-qt-converter.hqx Return to Top

How to convert AVI to animated GIF?

GIF Construction Set

Gif Construction Set from Alchemy Mindworks reportedly can convert an AVI file to an animated GIF file. Alchemy Mindworks, Inc. Web http://www.mindworks.com/alchemy/alchemy.html E-Mail: alchemy@mail.north.net FTP: ftp://ftp.mindworkshop.com/pub/alchemy

Microsoft GIF Animator

Microsoft's GIF Animator for Windows 95 product can reportedly convert AVI to animated GIFs (GIF89a format). Information on GIF Animator including a dowloadable version is available at the Microsoft Web site (11/7/96) on the Microsoft Image Composer page. Web http://www.microsoft.com/imagecomposer


MainActor, a shareware software product for Windows 95, Windows NT, and OS/2 reportedly can convert AVI to animated GIF. http://www.mainconcept.de/


Ulead reports that is has added AVI to GIF to Ulead's PhotoImpact GIF Animator 1.2 Beta (11/16/96) http://www.ulead.com/products/framens.htm Ulead Toll Free Number: 1-800-858-5323

Adobe Premiere

There is (Feb. 1998) a free plug-in for Adobe Premiere 4.x to convert AVI to Animated GIF. See the Adobe web site to download this and many other plug-ins for Adobe products: http://www.adobe.com/ Return to Top

How to convert AVI to MPEG?

AVI to MPEG Conversion at a Glance Company/Author(s) Product Price URL --------------------------------------------------------------------- Corel PhotoPaint $500? http://www.corel.com/ Ulead MPEG Converter $249 http://www.ulead.com/ Xing Technologies XingMPEG Encoder $89 http://www.xingtech.com/ XingMPEG Encoder 2 (May 6, 1997 release) CeQuadrat PixelShrink $199 http://www.cequadrat.com/ Vitec MPEG Maker $125 http://vitechts.com/ MainConcept MainActor shareware http://www.mainconcept.de/ avi2mpg1 Unknown freeware http://www.mnsi.net/~jschlic1/ Stefan Eckhart and others CONVMPG3 freeware kit http://www.powerweb.de/mpeg/msdos.html ------------------- Further information, reviews, and live links follow: The following posting from the comp.graphics.animation USENET newsgroup provides a good answer to this question. I have retained the header to insure proper credit to the author. Note: LW refers to the Lightwave 3D animation software package. From comp.graphics.animation Wed Oct 30 18:16:34 1996 Path: samba.rahul.net!rahul.net!a2i!news.PBI.net!news.mathworks.com!howland.erols.net!surfnet.nl!tudelft.nl!ne ws From: Valery Newsgroups: comp.graphics.animation Subject: Re: AVI to Mpeg converter Date: Mon, 28 Oct 1996 15:15:14 +0100 Organization: Technical University, Delft Lines: 58 Message-ID: <3274BFF2.2EDD@twi.tudelft.nl> References: <01bbc33f$05021880$d73d93cf@cube176a> Reply-To: V.V.Kritchallo@twi.tudelft.nl NNTP-Posting-Host: duti504b.twi.tudelft.nl Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (Win95; I) Mariusz Jesmanowicz wrote: > > Hi, I use LW to do animation, and basically I am not happy with any of the > compression engines aviable for avi. Those codes suck. So what I want to do > is make an UNCOMPRESSED AVI and then translate it to MPEG. anyone know of > any good converters to MPEG or hoe about plug-in for LW to be able to do > MPEG files from the start. > > Thank You Hi, you're right, every single AVI compression codec is lame. 5 years of the AVI format existance and zero progress so far. If you're talking about freeware or budget-priced MPEG codecs, it's a tough task, to find the damn thing. I'm busy in this area quite for a while already, and here are my findings: 1. XING's MPEG encoder is a classical name on the scene. Had compatibility problems before, not anymore, I believe. Can cost you $150 or more, not sure. Scan for 'XING' on the Net, you'll definitely find some tracks (www.xing.com doesn't show up). 2. Stefan Eckart's CMPEG (DOS) encoder is FREE and GOOD, and stays so for a couple of years already. Can have troubles converting some particular streams, but generally not worse than many commercial programs. (You need to make a TGA sequence first out of your AVI, though). Again, scan for CMPEG, or use my bookmarks found on the site Im introducing below. 3. To my surprise, Corel Photopaint 6 has got very decent built-in MPEG compression option. Open an AVI, Save As an MPEG, and see what happens (get some coffie, as it'll take a while ;) I checked it out on a stream where CMPEG gave up and the Corel's conversion did make a wonder. (If you like to see the result, download my 'Liquid Beatles' morph clip, 1 Mb: http://www.proteon.nl/synth_art/movies/cross.mpg). 4. Ulead's MPEG converter (www.ulead.com) seems to be the major player (priced below $250) on the Windows arena. I've heard good references about their MPEG's quality, but I feel that their biggest advantage is good integration with Windows and AVI format. If I'm not mistaken, a very slow codec. 5. Don't mess with DARIM Vision's codec (Korea). I've tried their demo, it produces low-quality crap. Though fast and cheap (you bet :-). See my MPEG clips, fractals, morphs, and in general lots of advanced graphics at http://www.proteon.nl/synth_art/ Hope this helps, Valery http://www.proteon.nl/synth_art/movies.html --------------------------------------------------------------- In addition to the above, there is MPEG Maker from VITEC-HTS (formerly Vitec Multimedia). Vitec is: Vitec 4366 Independence Court, Suite C Sarasota, FL 34234 Voice: (941) 351-9344 FAX: (941) 351-9423 http://vitechts.com CeQuadrat makes a software-only AVI to MPEG converter called PixelShrink. CeQuadrat is: CeQuadrat 1804 Embarcadero Road, Suite 101 Palo Alto, CA 94303 Voice: (415) 843-3780 FAX: (415) 843-3799 http://www.cequadrat.com/ And the freeware kit CONVMPG3, a collection of MS-DOS utilities that can be used to convert AVI to MPEG-1 or MPEG-1 to AVI. CONVMPG3 includes Stefan Eckhardt's CMPEG MPEG-1 encoder mentioned above but also includes utilities to generate the sequence of Targa files required by CMPEG. The URL for CONVMPG3 is: http://www.powerweb.de/mpeg/msdos.html avi2mpg1 is a freeware command line application for Windows 95/NT that can convert AVI to MPEG-1, supports audio, video, and interleaved audio/video. http://www.mnsi.net/~jschlic1/ MainConcept's MainActor product now (March 1997) includes add-on modules to output MPEG-1 and MPEG-2. With these add-on modules, MainActor can convert AVI to MPEG-1 or MPEG-2. Marcus Moenig at MainConcept provided an evaluation copy of the MPEG-1/2 modules. In tests, these modules could convert AVI files to MPEG-1 that could be played using the ActiveMovie software MPEG player shipping with Microsoft's Windows 95 OSR2. MainConcept is: MainConcept http://www.mainconcept.de The URL for Ulead is: Ulead MPEG Converter http://www.ulead.com/ On May 6, 1997, Xing announce a new product, the Xing MPEG Encoder 2 which accelerates MPEG encoding using Intel MMX instructions on PC's. The original Xing MPEG Encoder did not use MMX instructions. The Xing MPEG Encoder 2 can convert AVI and WAV files to MPEG-1. The URL for Xing is: Xing Technology Corporation http://www.xingtech.com/ For further information on the MPEG digital audio and video format see Tristan Savatier's comprehensive MPEG site: http://www.mpeg.org/ Return to Top

How to capture screen to AVI Files

Microsoft Camcorder

Microsoft distributes a free screen capture utility called Microsoft Camcorder (sometimes abbreviated MSCamcorder). Camcorder can save screen captures as AVI files or a .EXE file. http://www.microsoft.com/msoffice/office97/camcorder/default.htm


See the following posting from Greg Kochaniak dated 5/10/97 from the comp.archives.ms-windows.announce newsgroup. I have uploaded to Simtel.Net: http://www.simtel.net/pub/simtelnet/win95/mmedia/hycam119.zip ftp://ftp.simtel.net/pub/simtelnet/win95/mmedia/hycam119.zip 251872 bytes hycam119.zip HyperCam v1.19 AVI screen capture for Win95,NT HyperCam v1.19 captures the action from Windown 95 or NT screen in any graphics mode, including cursor movements and sound, and saves it to standard AVI movie files. Perfect for demonstrations, presentations and tutorials. Special requirements: Windows 95 or Windows NT. Changes: Fixed two problems: starting recording in 256 color mode would produce sometimes invalid AVI files (when, upon minimizing HyperCam window for recording, another window with a different palette would come to front and realize its palette). The other problem: selecting AVI file name with Browse button would not always work correctly. hycam119.zip has replaced hycam118.zip. Shareware. Uploaded by the author. Greg Kochaniak, Hyperionics gregko@hyperionics.com http://www.hyperionics.com/


TechSmith Corporation markets a Microsoft Windows product called SnagIt which can capture the screen to AVI files. SnagIt also can capture the screen to still image formats such as BMP. http://www.techsmith.com/ Return to Top

Authoring Tools to Create AVI Files

A wide variety of 2D and 3D animation applications as well as other multimedia authoring tools generate AVI files directly. This is especially true for Windows versions of applications, since Microsoft provides an API for creating AVI files. A list of applications that can create AVI files follows.

LightWave 3D 5.5 for Windows 95 and Windows NT

LightWave is a popular 3D modeling and animation program widely used in broadcast television. LightWave can do almost anything and supports third party plug-ins to add features that it lacks. NewTek Note: According to product literature on the NewTek Web site.

Caligari Truespace 1,2, and 3 for Windows

Caligari TrueSpace is a popular low-end 3D modeling and animation program. Traditionally, TrueSpace has been polygon based limiting its usefulness for modeling organic forms. TrueSpace 3.0 adds some organic features. Caligari Corporation Note: Confirmed from personal use of Caligari TrueSpace. http://www.caligari.com/

Fractal Design Ray Dream Studio for Windows

Ray Dream Studio is a suite of 3D modeling, animation, and rendering tools. Fractal Design Note: According to product literature on web site. http://www.fractal.com/

Macromedia Director 6.0 for Windows

Macromedia Director is a widely used authoring tool for creating interactive 2D animations such as presentations, multimedia for kiosks, prototypes of user interfaces, and similar uses. Director can also produce straight 2D animations appropriate for AVI files. Macromedia Note: According to product literature on the Macromedia Web site. http://www.macromedia.com/


Corel's CorelMOVE animation software can export AVI files. Return to Top

How to create AVI files from analog video:

Video Capture Cards

On Intel based PC's, use a video capture card to convert analog video from video tapes or video cameras to AVI files. A PC video capture card is typically either a 16 bit ISA bus card or a 32-bit PCI bus card that plugs into the 16 bit ISA or 32-bit PCI slots in your PC motherboard. 32-bit PCI bus cards are steadily replacing 16-bit ISA bus cards. Most video capture cards have either a composite video connector or both a composite video and an S-Video connector. Most video capture cards perform compression of the video in hardware or firmware on the video capture card before tranferring the compressed video over the ISA or PCI bus to the PC hard drive. Most video capture cards only capture video. They do not contain audio capture. Audio capture is done through the audio or sound card of the computer. It is increasinly common to have the audio input and output hardware built into the motherboard. The computer may not have a physically distinct sound card. Sound cards usually have a Microphone input jack, a Speaker or Headphone output jack, a Line input jack, and a Line output jack. Line input and the microphone input are not interchangable. The jacks use different electrical signals. Most users will use the microphone for input and speakers or headphone for output.

Video Capture in Video for Windows

Under Microsoft Windows, video capture cards come with a Video for Windows capture driver (CAPTURE DRIVER). The capture driver exports standard functions (including some dialog boxes for user interaction) that any Video for Windows software application can call. Any Video for Windows video capture application, including video editing applications that support video capture, can and must use this Video for Windows capture driver to capture video. Windows 3.x, Windows 95, Windows NT 3.51, and Windows NT 4.0 all use Video for Windows capture drivers. ActiveMovie 1.0 for Windows 95 and Windows NT 4.0 does not provide a mechanism for video capture, only video playback. Video for Windows continues to be the software component for video capture. The capture driver may consist of a single file or multiple files. The capture driver is identified by the name MSVIDEO (in the SYSTEM.INI file in Windows 3.x and Windows 95 for example). In Windows 3.x and Windows 95, the SYSTEM.INI file will contain a line such as MSVIDEO = C:\PROSHARE\ISVRPRO.DRV ISVRPRO.DRV is the name of the video capture driver used by Intel's Smart Video Recorder Pro in the Intel ProShare video-conferencing system. where MSVIDEO points to the top-level file that exports the standard Video for Windows functions for the capture driver. This file may in turn invoke other separate files that form the rest of the video capture driver. For example, the installation program for the miroMEDIA PCTV TV Tuner and Video Capture Card installs eleven (11) different files to support the Brooktree Bt848 video capture chip on the card. This card consists of some connectors, a few resistors and capacitors, and the Bt848 chip. In Windows 95, users can view and configure the video capture driver by selecting System in the Windows 95 Control Panel. Then select the Device Manager tab. System | Device Manager is actually a user friendly interface to the Windows 95 Registry which contains all of the information about a device such as names and locations of driver files, hardware resources used, and other data in a complex database. The Device Manager contains icons representing all the devices installed on the computer. The video capture card and associated driver will appear either in the "Sound, video and game controllers" category or "Other Devices". Each device has "Properties". Users can view and change the properties either by: (1) Click once on the device icon in System | Device Manager to select the device. (2) Click once on the Properties Button in System | Device Manager. OR (1) Double-click on the device icon in Device Manager. The Device Properties usually have a General, a Driver, and a Resources tab. The Driver and Resources Tabs may be absent in some cases. Users can usually determine the version of the device driver from the Driver tab of the Device Properties in System | Device Manager. The Driver tab usually lists all of the files installed on the system that make up the device driver. Use the Driver tab to install or update the video capture driver. The Driver tab contains a Change Driver... button. Clicking on the Change Driver... button will bring up a list box with the devices and drivers known to Windows 95. The relevant video capture card and driver may be in this list. The user may need to provide a disk or CD-ROM with the drivers and a Device Information (INF) file. If the driver is not on the list of available drivers, the user must click on the Have disk... button to load the drivers from the disk or CD-ROM using an INF file. The INF file contains the information telling Windows 95 how to install the capture driver, including which files to install where on the hard disk and what changes to make to the Windows 95 Registry and the INI files. Use the Resources tab to view and change the hardware resource settings: the IRQ levels used, the DMA channels used, and the I/O addresses used by the video capture card. It is not uncommon for a newly installed video capture card to have an IRQ conflict with other devices on the system. Often Windows 95 will detect the conflict but fail to resolve it. Windows 95 automatically assigns resources such as IRQ levels to devices such as video cards. Windows 95 is supposed to select IRQ levels that do not conflict. This does not always work. To fix, try deleting the device from the Device Manager and restarting Windows 95. TO DELETE A DEVICE FROM DEVICE MANAGER (0) Make sure that you have the installation CD-ROM or disks with the device driver software for the device BEFORE you delete it!!! (1) Click on the device icon in Device Manager. (2) Presss the delete button on your keyboard or click the Remove button on System | Device Manager. When Windows 95 restarts, it will again automatically detect the hardware, install the necessary drivers, and configure the hardware. If Windows 95 does not have the necessary drivers it will prompt the user for a disk or CD-ROM with the needed drivers. As above, the disk or CD-ROM will need a Device Information or INF file to tell Windows 95 how to install the needed drivers. On a second or third try, Windows 95 may get it right. Users must delete the device before restarting Windows 95 to force Windows 95 to auto-detect, otherwise it will simply use the information currently displayed in Device Manager. If deleting the device from Device Manager and restarting Windows 95 fails to fix the problem, the user can manually set the IRQ level and other resources through the Resources tab in the Device Properties in System | Device Manager. Uncheck the "Use automatic settings" check box. Then, the user can manually change the IRQ, DMA, and I/O settings. Note that this disables the automatic configuration of the device and can cause other problems. In some cases however there is no choice but to manually set the resources. In Windows 95, users may also view and configure some video capture device information by selecting the Multimedia icon (applet) in the Windows 95 Control Panel. Then select the Advanced Tab. Then select the Video Capture Devices icon from the icons in the Advanced Tab. This will show the installed Video for Windows capture drivers. The IRQ, DMA, and I/O resources usually cannot be set through the Multimedia icon; users must use System | Device Manager in the Control Panel. Typically, when a user installs the software for a video capture card, the installation will install the Video for Windows capture driver for the video card, Video for Windows if needed, non-standard Video for Windows compression drivers, and some video capture and editing applications. Microsoft shipped a simple Video Capture application called VidCap, a 16-bit application, with the original 16-bit Video for Windows (full, not run-time). There is also now a VidCap32, a 32-bit video capture application. Many other applications such as Adobe Premiere support video capture. The video capture drivers provide a Video Source dialog box for selecting the analog video input format, connectors, and other options. The Video Source dialog box varies from video card to video card. It can include options to adjust the brightness or color of the video image. The capture drivers also provide a Video Format dialog box for selecting the color format (image format or pixel format) of the image, the image size to capture (such as 320x240 or 160x120), whether to utilize hardware compression built into the video capture card, and miscellaneous other features. Users can access the Video Source and Video Format dialog boxes through their video capture software application. In VidCap, select the Options menu. Then Video Format... to get the Video Format dialog box. Video Source... to get the Video Source dialog box. See below for further discussion.

Analog Video Formats

Composite video signals are analog signals that combine luminance and chrominance (color) information in a single analog signal that can be transmitted over a single wire or stored in a single track on an analog magnetic tape. The NTSC video signals used by commercial television sets in the United States and Japan are an example of composite signals. Composite video is particularly prone to errors in reproducing exact colors due to the overlap of the color and luminance signals. Video professionals jokingly refer to NTSC as Never The Same Color. S-Video video signals separate the luminance and chrominance information into two separate analog signals that can be transmitted over two separate wires or stored in two separate tracks on an analog tape. S-Video is generally superior to composite video in reproducing colors correctly. The S-VHS and Hi8 video tape standards use S-Video. Ordinary VHS video tape uses composite NTSC signals. Thus, in general, using an S-VHS or Hi8 video camera with S-Video output to provide the analog video signal to the S-Video input of a PC video capture card will provide better video quality. A third type of video signal is component video. In component video, the luminance (Y) and two color difference signals (U and V or I and Q) are separated into three separate analog signals that can be transmitted over three separate wires or stored in three separate tracks on an analog tape, or digitized separately. Component video is used in professional video production and provides the best quality and the most accurate reproduction of colors. The professional Betacam SP video cameras use component video. The current generation of widely used PC video capture cards do not provide component video inputs.

Capture with Motion JPEG Compressed Video

Typical PC video capture cards store the digitized compressed video as an AVI file using Motion JPEG compression. Motion JPEG is used instead of other compression schemes because each frame is compressed separately. This allows frame accurate editing of the AVI file after capture. If a compression scheme that uses frame differencing - where a frame is stored as the differences between the frame and a previous frame (such as MPEG) - is used, it is difficult to edit the video. Typical PC video capture cards are bundled with non-linear video editing software such as Adobe Premiere which can be used to edit the Motion JPEG compressed AVI file and ultimately compress the edited AVI file using compression such as CinePak using frame differencing for maximum compression. PC video capture cards usually compress the video using a lossy compression scheme such as Motion JPEG or MPEG because uncompressed video places very high demands on the bandwidth of the ISA or PCI bus and on the bandwidth to the hard drive. In addition, uncompressed video can fill even very large hard drives very quickly.

Capture with Uncompressed Video (Color Formats)

A number of video capture cards such as those based on the Brooktree Bt848 and Bt848a video capture system chip save uncompressed video in alternative color formats to the common 24 bit RGB color format. Such as the 15 bit RGB color format or YUV9 color format. These formats represent a pixel with less than 24 bits, reducing bandwidth and storage requirements. Color formats may also be known as IMAGE FORMATS or PIXEL FORMATS. 24 bit RGB is almost universally supported. Other color formats may not be supported by graphics software, video editors, or playback drivers. Beware problems such as inability to play an AVI file or view a BMP may occur with AVI files or BMP still images created with some color formats. Color Formats Section PC video capture cards are usually bundled with application software and drivers to perform video capture such as Microsoft's VIDCAP.EXE (16 bit) or VIDCAP32.EXE (32 bit) or Intel's SMARTCAP.EXE or other similar software. Video capture drivers may provide the ability to select different color formats for uncompressed AVI video, such as RGB15 or YUV9. With Vidcap and Vidcap32, select Options | Video Format ... to set the color format for a video capture session and file. Video Format ... invokes a Video Format dialog box provided by the video capture driver; this dialog box differs from capture card to capture card. Users can usually use the Video Format dialog box to select the size (resolution) of the captured video (such as 320x240 or 160x120 pixels). Users usually can select the color format which may be identified as IMAGE FORMAT or PIXEL FORMAT. NOTE: Windows 95 and Windows NT require different device drivers. Most video capture cards have drivers for Windows 95. Only some have Windows NT drivers. Video capture cards that have Windows NT device drivers and therefore can be used under Windows NT are listed at the end of this section.

Recent Video Capture Cards (PCI)

Some current (1/11/97) popular PC video capture cards that generate AVI files are: Digital Processing Systems (DPS) makes high end video capture cards for the broadcast and studio markets. Some of these cards can capture video on the PC. Some of these cards are designed for Windows NT and include Windows NT device drivers. http://www.dps.com/ FAST AV Master PCI 60 field/60fps with Motion JPEG, Includes Ulead's Media Studio Pro digital video editing application. FAST Web Page Truevision Bravado 1000 50/60fps 32-bit PCI video capture board with Motion JPEG, Includes Adobe Premiere 4.2 Full Version Truevision Web Page MiroVideo DC30 PCI, complete non-linear video and audio editing for Windows 95, Includes Adobe Premiere 4.2 Full Version miro Web Page Azeena Vision 500 640x480 30 fps Motion JPEG PCI Capture Card Up to 3:1 compression. Azeena Web Page Hauppauge WinTV PCI TV-tuner and Video Capture Cards. This is a family of TV-Tuner and Video Capture cards. Built around the Brooktree Bt848 video capture chip. Hauppauge Web Page Winnov Videum AV, Half size ISA card, composite and S-Video input, claims to capture 352x240, 24 bit, AVI videos at 30 frames per second (must be compressed to fit across ISA bus - JFM) Winnov Web Page Intel Smart Video Recorder III, a 32-bit PCI card that uses Indeo video compression. Includes a composite (NTSC) video input and an S-Video input, RCA and S-Video cables, Asymetrix Digital Video Producer and Asymetrix WebPublisher. Intel Page U.S. Robotics markets the Bigpicture Video capture card and NTSC camera for about $249.99 (7/22/97). The video capture card is a PCI half card with a single RCA jack for the NTSC composite video in and a +5 Volt, 1 Amp power output jack for the NTSC camera. The video capture card uses the single Brooktree Bt848 chip, a complete video capture system on a single chip. Personally, I was impressed that they could get the entire video capture system on a single chip. More information on the Bt848 can be found at: Brooktree Bt848 Press Release Bigpicture can capture NTSC composite video at 30 frames per second at 320x240 or 160x120 resolution. Bigpicture also comes in versions with U.S. Robotics modems. The idea is that this can be a PC video phone. Bundled software includes Kai's Power GOO Special Edition, Asymetrix Digital Video Producer to capture and edit video, VDONet's VDOPhone (trial edition), and VDONet's VDOLive player. MINI-REVIEW I intalled the Bigpicture video capture system under Windows 95b (OEM Service Release 2) on a 200 MHz Pentium with MMX, 32 MB RAM, two Western Digital IDE hard drives (2GB and 5 GB), and a 12x CD-ROM. The installation was difficult due to resource conflicts. At first the video capture card appeared to conflict with the SupraExpress 336i PnP modem in my PC. After reinstalling a few times, the video capture card started to work, but the modem stopped working. A conflict between the modem (an ISA card modem) and the COM1 serial port was reported in the Windows 95 Device Manager (Control Panel | System | Device Manager tab). I fixed this by disabling the automatic settings on the modem and changing the IO address. I left the COM1 port (which I don't use) and the modem using the same IRQ (Interrupt Request) level. While the documentation provides some pointers on these conflicts, I found the problem frustrating and difficult to fix although I am moderately familiar with PC installation and configuration. Once fixed, the camera and video capture card worked fine. My modem seems to work fine. I can capture video and use the modem at the same time. U.S. Robotics 7770 North Frontage Road Skokie, IL 60077-2690 http://www.usr.com/

Old Video Capture Cards (ISA)

Some widely used older, 16-bit ISA cards, are: Video Spigot from Creative Labs - 16-bit ISA Card - RCA Jack for Composite (NTSC/PAL/SECAM) Video Input - S-Video Connector - Windows 3.x Drivers (16 bit) Media Vision Pro Movie Studio - 16-bit ISA Card - RCA Jack for Composite (NTSC/PAL/SECAM) Video Input - S-Video Connector - Windows 3.x Drivers (16 bit) Intel Smart Video Recorder Pro - 16-bit ISA Card - RCA Jack for Composite (NTSC/PAL/SECAM) Video Input - S-Video Connector - Windows 3.x Drivers (16 bit) - Version 2.20.061 (known to run under Windows 95) The Smart Video Recorder contains chips to accelerate and implement Intel's Indeo 3.x and YVU9 proprietary formats. These allowed it to capture video with Indeo compression on 486 machines even though Indeo encoding is very compute intensive. The special chips on the board encoded the video instead of the PC's CPU. Intel is no longer supporting the Intel Smart Video Recorder (Oct. 1997). Drivers and other support information are still available at the Intel web site. I've successfully installed and used the Intel Smart Video Recorder Pro on two different machines under Windows 95 with Driver Version 2.20.061 of the drivers for this card.

What to do about horizontal tearing in the video?

Tearing is a particularly common problem when capturing video from the output of an analog video tape such as a VCR. It can happen in other contexts as well. Analog video such as NTSC, PAL, and SECAM composite video has a sychronization signal at the end of each horizontal scan line and a vertical synchronization signal at the end of each frame. The motors and mechanical parts in the transport mechanism of a video tape player can slip slightly, causing the analog signals and horizontal synchronization signals to arrive at slightly incorrect times. Video monitors, capture cards, and other video equipment have a tolerance for jitter in the timing of the synchronization signals. Digital video capture cards can be very sensitive to the timing jitter in the output of video tape players. Tearing will occur because the synchronization is off. Capture cards are frequently more sensitive than analog video monitors and other analog video equipment which is designed to withstand distortions in the analog signals. Devices called Time Base Correctors (TBC) can adjust for jitter in the timing of the analog video synchronization signals and other distortions of the analog signals. TBC's are available as plug-in cards for PC's and as black boxes to be inserted between the video source and the video capture card. Time Base Correctors are available from: Prime Image Inc. http://www.primeimageinc.com/ Return to Top

Hard Drive Video Capture Issues

Digital video capture requires writing data to the PC hard disk at sustained very high data rates. The higher the resolution and quality of the digital video, the higher the data rate the hard disk must handle. 1. Defragment the hard disk. This allows the PC to write the digital video (the AVI file) to contiguous disk sectors without stopping to skip the drive head over used regions. 2. Scan the disk and fix any bad sectors if possible. 3. Conventional hard drives pause the drive heads for thermal recalibration which slows their ability to write data to the hard disk. Special AV (Audio/Video) hard drives (which cost more) disable the thermal recalibration during data writing. This supposedly allows an AV hard drive to capture higher video data rates. Note that you can capture video onto conventional hard drives. People do this all the time. But for very high end video capture, you may need a special AV drive.

Video Capture Cards with Windows NT Drivers

The DPS (Digital Processing Systems) Perception ISA video capture card. The DPS PVR-2500 Perception Video Recorder (PCI-bus) for Intel and DEC Alpha Windows NT workstations. An optional AD-2500 real time video capture daughter card adds component, S-Video, and composite video inputs to this high-end product. The AD-2500 is the actual capture card in this product which is a "digital video disk recorder system". The DPS HVR-2800 Hollywood Video Recorder (PCI and ISA). The PCI version is available for both Intel and DEC Alpha Windows NT workstations. The Hollywood is also a "digital video disk recorder system", more than a simple video capture card. DPS makes PC video products aimed at the studio and broadcast production markets. http://www.dps.com/ The Truevision Targa 2000 video capture card. http://www.truevision.com/ The Osprey 100 PCI Video Capture Card works under Windows NT as well as Windows 95. The Osprey Systems Division of Multimedia Access Corporation makes a line of video capture cards, all or some with drivers for Windows NT 3.51 and NT 4.0 The Osprey 100 is a PCI board based on the BrookTree Bt848 single-chip video capture device. The version of the Osprey 100 that I have seen has one S-Video input and two composite (NTSC or PAL) video inputs. The Osprey 100 has software and drivers for both Windows NT 3.51 and Windows NT 4.0 The NT software for the Osprey 100 (10/8/97) consists of the VidCap32 video capture application, a Video for Windows Capture Driver, and a Windows NT Device Driver for the Osprey. There are at least two versions of the software: 0.93(beta) and 0.95(beta). On 10/7/97, the 0.95(beta) was available by anonymous ftp from Osprey. The anonymous ftp site also contained directories for a 1.00 version of the software that could not be downloaded (10/7/97). The 0.95(beta) software from Osprey is a single Windows executable that easily installs VidCap32 and the drivers, also updating the NT taskbar, registry, and so forth. The Osprey 100 with the 0.95(beta) drivers captures video under NT 4.0 with both VidCap32 and the Progressive Networks RealEncoder software. At least in some of my experiments, VidCap32 exhibited some problems although it was possible to repeatedly capture AVI clips. Problems included flawed updating of the VidCap32 window and sluggish performance of the NT system until rebooted. The problems appeared intermittent. System Tested: (Micron Millenium PC) Intel Pentium 132 MHz with 48 MB RAM Phoenix BIOS Version 4.04 M-M Windows NT 4.0 (Build: 1381 Service Pack 2) Osprey 100 PCI Video Capture Card with 0.95(beta) drivers for Windows NT Diamond Multimedia Stealth64 Video 2001 PCI (2MB RAM) Creative Labs Vibra 16 ISA sound card with NT 4.0 Drivers Intel 82557 based 10/100 Ethernet PCI Network Interface Card (NIC) IDE CD-ROM (ATAPI 1.2) Dual Channel PCI IDE Controller Inexpensive NTSC video camera (bundled with LiveLan videconferencing product) http://www.osprey.mmac.com/ Return to Top

How to Create AVI Files from Television

To create an AVI file from your favorite television program, there are two approaches. Television is transmitted over radio frequency (RF) waves. The NTSC, PAL, or SECAM composite analog television signals are modulated onto high frequency radio waves to create the familiar television channels. In the United States, television channels 2 through 69 cover the range from 54 MHz to 806 MHz. An NTSC channel uses about 4 MHz of frequency range. Traditional analog Cable Television (CATV) works much the same except that the RF is sent over coaxial cables instead of the open air. A device usually referred to as a tuner can demodulate the television radio frequency signal and extract the NTSC, PAL, or SECAM composite analog signal. Television sets, Video Casette Recorders (VCR) and cable television set top boxes contain a tuner. The easy way to turn your favorite television show into an AVI is to record the show to a videotape using a VCR. The VCR can output the composite analog video signal to a video capture card in your PC (see the section on creating AVI from composite analog video). A number of companies market TV tuner cards for PC's. In this case you can feed the television radio frequency (RF) signal into the TV tuner card which will demodulate the NTSC, PAL, or SECAM signal. Use an associated video capture card to convert the demodulated composite analog video to an AVI files. ATI Technologies, for example, markets a PC TV Tuner. It is probably simpler to use a VCR than a PC TV Tuner card. A VCR circumvents the often painful installation problems with PC hardware. Return to Top

How to Create Morph Effects for AVI

Morphing is a technique for progressively transforming one image into another image, or one video sequence into another. For example, a video producer might morph one face into another. STOIK Software markets a tool called Morph Man for Windows 95 http://www.stoik.com/ Morph Man can create AVI files with a still image morphing into another still image, or one video sequence morphing into another. STOIK provides a demonstration version of Morph Man for evaluation purposes. Return to Top

Reinstalling Microsoft's Video for Windows in Windows 95

This requires the Windows 95 CD-ROM. One can either reinstall Windows 95 (probably not what you want to do) or manually remove Video for Windows and manually reinstall the files that make up Video for Windows under Windows 95. Truevision's Technical Support has a good note on how to do this. Although it does not appear to be copyrighted, I felt uncomfortable cutting and pasting it into the AVI Overview. The URL is http://www.truevision.com/Support/vfwwin95.html Return to Top

How to get Microsoft ActiveMovie 1.0

ActiveMovie is Microsoft's successor to Video for Windows. ActiveMovie 1.0 is shipped with OEM Service Release 2 of Windows 95. ActiveMovie 1.0 is also bundled with Microsoft Internet Explorer for Windows 95 and Windows NT 4.0. ActiveMovie 1.0 is available for Windows 95 and Windows NT. ActiveMovie 1.0 plays AVI, QuickTime, and MPEG files. IF YOU DON'T HAVE OEM SERVICE RELEASE 2 of 95! ActiveMovie 1.0 is incorporated in Internet Explorer. A full install of Internet Explorer can be downloaded from Microsoft's web site. Microsoft also provides a free download of just ActiveMovie 1.0. Both can be downloaded from the Microsoft Internet Explorer web site as described below: http://www.microsoft.com/ie/ Click on Internet Explorer for 95 and NT 4.0 link to get to the download area. There is a pulldown list of products. (6/6/97). Select "Active Movie 1.0 for Windows 95 and NT 4.0" to get just ActiveMovie 1.0 Click the "Next" button. This brings up a page to select the language from another pulldown list. Pick your language (e.g. U.S. English). Click the "Next" button. This brings up a list of links to download sites for amov4ie.exe Dowload this executable and run. It installs Active Movie 1.0 Return to Top

Installing and Configuring AVI Codecs in NT 4.0

The Microsoft Windows NT 4.0 applications and operating systems are configured through the NT Registry, which is similar to the Windows 95 Registry. Although Windows NT 4.0 and Windows 95 share a desktop user interface, there are some significant differences between the NT 4.0 Registry and the Windows 95 Registry. In NT 4.0, the 32 bit video codecs do not appear to be listed in a [drivers32] section in the SYTEM.INI file. This differs from Windows 95. The Video for Windows configuration information appears to be stored almost exclusively in the NT Registry in NT 4.0. The NT Registry can be viewed and modified through the Control Panel or through the REGEDT32 Registry Editor. Use the Control Panel unless you really know what you are doing. You can view and change which audio and video codecs are installed through the Multimedia icon in the Windows NT 4.0 Control Panel (in My Computer). This works much the same as the Multimedia icon in the Windows 95 Control Panel (in My Computer). Double click on the Multimedia icon to launch the Multimedia applet. Select the Devices tab within the Multimedia applet. This tab gives a list of installed multimedia drivers including hardware device drivers, MCI drivers, and audio and video codecs. It includes two sections: (cute icon)Video Compression Codecs (cute icon)Audio Compression Codecs Double-click on these to view the installed audio and video codecs. There are buttons to Add.. or Remove... multimedia devices including the audio and video codecs. To Add a video codec, click the Add... button. This gives an Add dialog box with a List of Drivers. You may select from a list of drivers that the system knows about, such as "Cinepak", or select "Unlisted or Updated Driver". If you need to use "Unlisted or Updated Driver" you will need a directory on a floppy disk, CD-ROM, or your hard drive containing the needed drivers and an INF (Setup Information ) file. Depending on what you are doing, the needed directory may be on a floppy provided with a product, on the Windows NT installation CD-ROM, or constructed manually by you or someone else. The INF file provides directives for installing the driver including changes to the Registry. Windows read the INF file and follows the directives. You may need a different (NT specific) INF file to install under Windows NT 4.0 than Windows 95. The 32 bit video codecs are installed in the \WINNT\SYSTEM32 directory used for 32 bit drivers, analogous to the \WINDOWS\SYSTEM directory in Windows 3.x NOTE: Using the Remove... button to remove a codec does not remove the codec files from the hard drive. Nor does the codec disappear from the list of codecs displayed when Add... is selected. Remove... appears to simply disable the video codec so that it is not invoked. Use Add... to enable the codec after Remove... The other option to install a codec is to use an installation program that will appropriately update the NT Registry and copy the needed files to the correct directories in the NT file system (such as \WINNT\SYSTEM32). In many cases, you can get an install program from a Web site or other convenient source. In this case, you do not need to use the NT Control Panel. The install program does all of the work. NT 4.0 appears to be able to use the same 32 bit video codecs as Windows 95, for example Cinepak for Windows 32. Keep in mind that device drivers for hardware are different between Windows 95 (which uses VxD's) and NT 4.0. Only some parts of Windows 95 and NT 4.0 can use the same code. Return to Top

How to change frame rate of AVI files

You may want to change the frame rate of an AVI. For example, you may want to convert a video captured at 30 frames per second (NTSC) to 15 or 10 frames per second to reduce the size of the file. This type of conversion throws away frames; it does not play the AVI in slow motion. Video editors usually contain this function. For example, the free VidEdit video editor can convert the frame rate of AVI files. Select Video | Convert Frame Rate ... in VidEdit For more on video editors, see Video Editors Return to Top

How to crop an AVI file

Microsoft VidEdit 1.1 can crop an AVI file, that is create another AVI file with a rectangular region of the original AVI file: Select Video | Crop ... in VidEdit Undoubtedly, many other AVI video editors can crop AVI files. Microsoft VidEdit 1.1 has the special virtue of being free and available on the Web. For more on video editors, see Video Editors Return to Top

How to edit AVI files:

Several applications exist to edit (cut, paste, etc.) AVI files. Such applications are known as video editors. Sometimes such digital video editors are called non-linear editors, in contrast to traditional videotape or film based editing. Video editors range from very simple applications to very sophisticated applications.

Video Editor Features

Common video editor features include: * cut, paste, and deleting video sequences * selecting video codec and compression settings * selecting audio codec and compression settings * converting video frame rate * converting audio sampling rate * adjusting synchronization of audio and video * converting color depth of video (24, 16, or 8 bit usually) * converting to NTSC or PAL safe colors * adding transitions and other special effects * applying image processing filters to video * adding text and subtitling * much more in high end video editors....


The full 16 bit (Windows 3.x) Video for Windows from Microsoft (not the "Run Time") shipped with a simple video editing program VidEdit. VidEdit can cut, paste, concatenate, add sound, and do many other things to AVI files. VidEdit can be downloaded from a number of sites on the Internet. WARNING: While VidEdit, a 16 bit Windows application, works under Windows NT and Windows 95, I found that it cannot see the Video for Windows codecs distributed with Microsoft NetShow 2.0 (such as the Microsoft MPEG-4 codec, Vivo H.263, etc.). Other editors such as Asymetrix Digital Video Producer (DVP) CAN see these compressors. By "see", I mean that none of the NetShow specific codecs is in the list of codecs under Video | Compression Options... in VidEdit. This means that you cannot create an AVI using the NetShow codecs from within VidEdit; you need to use another video editor. VidEdit does recognize the following 32 bit Video for Windows codecs: Intel Indeo (R) Video Interactive [32] Intel Indeo (R) Video R3.2 [32] Intel Indeo Raw R1.2 [32] Microsoft Video 1 [32] Cinepak Codec by Radius [32] Indeo video 5.0 [32] As far as I can tell Microsoft is not currently distributing VidEdit. However, a file winvid.zip is bouncing around the Net. This file includes the Video for Windows run time along with a number of Video Tools including VidEdit and VidCap (Microsoft's video capture tool). Disclaimer: I am not certain what the legal restrictions on VidEdit or winvid.zip are.

EarthStation 1 Archive of Windows Freeware and Shareware

Microsoft's VidEdit Video Editor is also available at: EarthStation1: Recommended Shareware and Freeware Page http://www.attention.net/wandarer/software.html The preceding link now contains links to mirror sites for the EarthStation 1 archive. The LaJolla Earthstation 1 mirror site is: http://earthstation1.simplenet.com/software.html Once you have reached the EarthStation 1 page, click on the Graphics link to jump to the Graphics Editors section. VidEdit is in this section. Scroll down a few pages to find VidEdit or use the find string on this page feature of your Web browser. Click to download VidEdit. There is also a mirror site at: http://mirrors.org.sg/earthstation/software.html

Alchemedia Inc. Shareware Page

The Alchemedia Inc. shareware page contains a file videdit.zip with VidEdit. http://www.alchemediainc.com/sharewar.html

Greg Hughes Home Page

winvid.zip is available from Greg Hughes home page: http://www.public.iastate.edu/~gregngng/ Note that I found this site hard to connect to although I was eventually able to download winvid.zip

Personal AVI Editor

FlickerFree markets an inexpensive/shareware avi editor for Windows called Personal AVI Editor. Personal AVI Editor ($49.95 + Shipping and Handling) http://www.flickerfree.com/index.html

MGI VideoWave

MGI Software Corporation (Toronto, Canada) markets a PC video capture and editing program called VideoWave. VideoWave supports AVI, QuickTime, and MPEG. Suggested price: $99 http://www.mgisoft.com/

Corel Lumiere Suite for 32-bit Windows

Lumiere is a new contestant in the PC video editing game. (May, 1997) Corel Lumiere Suite for 32-bit Windows List Price on Corel Web Site: $89 (US) Corel Corp. Ottawa, Ontario, Canada (800) 772-6735 (613) 723-3733 FAX: (613) 728-9790 http://www.corel.com/ Corel's Lumiere Web Page

Ulead Media Studio Pro

Ulead's Media Studio Pro ( around $300 ) http://www.ulead.com/

Asymetrix Digital Video Producer

Asymetrix's Digital Video Producer (DVP) Typical Retail Price: $69.95 (Sept. 1997) A simple digital video capture and editing program for Windows 95 and Windows NT. DVP is bundled with many video capture cards and is also available retail. More information is available at the Asymetrix Web site. http://www.asymetrix.com/

Adobe Premiere

Adobe Premiere is the reigning king of desktop video editing programs. Versions exist for both the PC/Windows and the Macintosh. Adobe Systems Premiere ( around $500 ) http://www.adobe.com/


in:sync produces SpeedRazor Mach 3.51 (5/16/97), a professional non-linear editing (NLE) video editor for Windows NT for the Broadcast industry. This can handle AVI as well as other formats. Speed Razor (not cheap) http://www.in-sync.com/ Return to Top

Editing and Converting WAV files

AVI and WAV files are closely related. WAV files are the sound file format, and frequently provide the source for the sound tracks in an AVI file.

CoolEdit (PC)

A good shareware sound editor and sound file format converter is Syntrillium Software's CoolEdit (Cool96) for Windows 3.1 and Windows 95. This supports many common sound file formats such as Apple's .aiff and Next/Sun .au files. http://www.syntrillium.com/10/index.htm

GoldWave (Windows 3.1/95/NT)

Another shareware sound editor and sound file format converter is GoldWave. http://www.goldwave.com/

Macromedia's SoundEdit16 (Macintosh)

Macromedia markets a sound editor for the Macintosh called SoundEdit16 + Deck II. SoundEdit can open and save in WAV format. For further information on SoundEdit, see the Macromedia Web site: http://www.macromedia.com/

Sound Forge

Sonic Foundry markets a digital sound editor for Windows called Sound Forge 4.0 (5/16/97) Sound Forge includes support for importing AVI video and editing the sound to synchronize with specific frames in the AVI file. http://www.dg.co.il/Forge/forge.htm

SpeedRazor (Windows NT 3.51 and 4.0)

in:sync produces SpeedRazor Mach 3.51 (5/16/97), a professional non-linear editing (NLE) video editor for Windows NT for the Broadcast industry. SpeedRazor can read and write WAV audio files. It has sophisticated multi-track stereo audio editing and mixing features. Speed Razor (not cheap) http://www.in-sync.com/

Editing and Converting Sound Files on the Macintosh

A Macintosh shareware utility SoundHack can read, write, and modify sound files on the Macintosh including Microsoft WAV format and AIFF. Macintosh users can use SoundHack to convert AIFF and other Macintosh sound files to the WAV format for integration in AVI. http://www.imuse.com/Soundhack.html Return to Top

How to output an AVI file to videotape:

AVI files generated with a video editor such as Premiere or a 3D Animation program such as Caligari TrueSpace can be output to videotape (e.g. a VHS tape) using a hardware device known as a scan converter. A scan converter converts the VGA signal intended for the computer monitor into an video signal, typically NTSC or S-Video. The video signal can then be input into a videotape recorder such as a VHS VCR. A scan converter may be a small box which resides between the computer and the monitor. It may be integrated into a video card. For example, ATI's new 3D XPRESSION+PC2TV video card includes NTSC and S-Video output as well as output to a conventional computer monitor. Configure the PC graphics in one of the modes supported by the scan conversion hardware and play the AVI file in full screen mode. Some manufacturers of scan converter (or similar) hardware: ATI Web Page VideoLogic Web Page PC Video Conversion claims to make a high quality scan converter called HyperConverter that converts from SuperVGA to broadcast quality NTSC/PAL video. Less than $5000. PC Video Conversion Return to Top

PC Video Chips and Cards

The current (6/21/97) generation of graphics controllers for PC's incorporate a number of hardware features to improve playback of video, including AVI. Video acceleration features have become standard in most chips. As a consequence video chip and card marketing has increasingly emphasized 3D graphics acceleration features in an effort to differentiate chips and cards from different manufacturers. These video acceleration features include hardware color space conversion and hardware scaling of video.

Color Space Conversion

Many video standards such as Indeo, CinePak, and MPEG operate in a luminance - chrominance color space such as YUV, YCbCr, etc. Computer monitors use RGB (Red/Green/Blue). The decoded video signals must be converted from YUV to RGB for display. Most video chips now provide dedicated hardware for this color space conversion.

Hardware Scaling

Displaying a video in a windows larger (or smaller) than the encoded aspect ratio involves duplication of pixels. Complex filtering operations can reduce or remove blocking artifacts when a video is scaled up in size. If scaling is performed in software using the PC's CPU, the scaling will absorb many CPU cycles, possibly resulting in degraded video playback depending on the speed of the CPU. Most video chips now provide dedicated hardware for scaling video.

Video Cards

PC video cards are printed circuit boards. Today (6/23/97), virtually all video cards are PCI cards, with a PCI bus connector along one side of the circuit board. The video card will have at least a DB-15 connector for the VGA cable to the computer monitor. Video cards have a chip variously known as a graphics controller, graphics accelerator, video chip, video controller, or something similar. The graphic controller is the heart and the brain of the video card. The card has one or more memory chips forming the video memory where the images are stored. The video memory is known as a framebuffer. Video cards have a RAMDAC (Random Access Memory Digital to Analog Converter) which convertes the digital image stored in the framebuffer into an analog signal for the RGB monitor. PC video cards have a ROM (Read Only Memory) with the VGA BIOS used during the PC boot process. There is also a clock that provides the timing signals for the entire board. Many video cards have a feature connector allowing an auxiliary card to be added to the main video card. The auxiliary card adds additional features such as hardware MPEG decoding. Although AVI should be independent of the video chips and cards used in a PC, there can sometimes be problems or technical issues specific to a particular chip. By far the most common PROBLEM is a subtle bug in a video chip driver or a subtle conflict between a video chip driver and another driver or piece of software on the PC. Downloading and installing the latest video driver from the chip or card maker's Web site is a frequently successful fix for these problems. ALSO, Windows 3.x and Windows 95 use different Device Drivers than Windows NT 3.51 or Windows NT 4.0 Windows 3.x and 95 use Device Drivers known as VxD's for low-level hardware access. NT uses its own device drivers. If you use a video card or other hardware on an NT machine, you need to be sure to use the NT drivers! A number of video card companies such as Diamond Multimedia and STB that buy or license the controller chips from other companies such as S3 frequently write video card/chip device drivers with additional features or better quality than the device drivers provided by the chip company. Links to video chip and video card makers follow:
ATI Technologies Diamond Multimedia STB Systems Inc. S3 Incorporated Tseng Laboratories Trident Microsystems Matrox Number Nine Cirrus Logic Rendition nVidia 3dFX 3dLabs A fairly comprehensive list of video chipsets, video cards, and miscellaneous other information may be found at: http://www.heartlab.rri.uwo.ca/vidfaq/chipset.tx t

Video (Display) Cards with Windows NT Drivers

Unfortunately, Windows 95 and Windows NT use different device drivers for the same hardware. While Windows 95 drivers are available for the vast majority of PC hardware, Windows NT drivers are harder to come by. Video cards with NT drivers are listed below: Number Nine Revolution 3D (Windows NT 4.0 Drivers) http://www.nine.com/ Return to Top

How to make AVI NTSC (or PAL) Safe

AVI files can represent colors that are not supported by the NTSC or PAL analog video standards. These colors correspond to synchronization and control signals in the NTSC or PAL video. Such AVI files cause problems if translated to NTSC or PAL video. Equilibrium's DeBabelizer Pro for Windows 95 and NT 4.0 reads and writes about 90 common and not so common image file formats as well as AVI files. In addition to translating between all of these formats, DeBabelizer Pro has a number of image processing functions. DeBabelizer Pro can remove colors from AVI files that are excluded by NTSC or PAL to create an NTSC or PAL safe AVI file. Equilibrium has a demonstration version of DeBabelizer Pro on its Web site. This is a demonstration version. The demonstration version adds the words Equilibrium (very large words) to all images and video that it processes. DeBabelizer Pro ($595 Suggested Retail Price) Equilibrium 475 Gate Five Road, Suite 225 Sausalito, CA 94965 1(800)524-8651 or (415) 332-4343 http://www.equilibrium.com/ Return to Top

The Phantom Final Frame when Viewing an AVI

When playing or viewing an AVI with a number of Microsoft Windows applications, you will see a "phantom" final frame. The "phantom" frame may appear as a blank frame or a duplicate of the last frame depending on the Windows application. For example, if you have a one second AVI file with 30 frames and you view this AVI file with Microsoft VidEdit 1.1, VidEdit will display positions that it numbers 0-30. The 30 position will appear as a blank frame. Note that 0-30 means 31 total positions; there is a "phantom" final frame. If you view the 30 frame AVI file with Microsoft Media Player, there will also be positions 0-30. In this case, position 30 is a duplicate of frame 29. What is this? The MCIAVI driver has a concept of the "end" or "position after the last frame in an AVI". In the 30 frame AVI example above, positions 0 through 29 are the actual frames in the AVI file. 0 is the first frame, 1 is the second frame, and 29 is the last (30'th) frame. Position 30 is the "end" or "position after the last frame in an AVI". The Microsoft Windows application, such as VidEdit 1.1 or Media Player, decides what to display for this "end" position. You can see this feature of the MCIAVI driver through the Media Player. Open an AVI file through Media Player. Then, type Ctrl-F5 to invoke a dialog box for entering MCI (Media Control Interface) string commands. set time format frames status length (would return 30 for the example above) seek to start status position (returns 0) seek to end status position (returns 30 - this is the "phantom" frame) seek to 29 (this is the true last frame in the AVI file) seek to 0 play status position (returns 30) In conclusion, the "phantom" final frame represents the position after the last frame in the AVI file. It is NOT a frame in the AVI file. Return to Top

Binary File Editors for Viewing and Editing AVI Files

Occasionally, you may need to view or edit an AVI file at the down and dirty byte level. Use a binary file editor for this. Many binary file editors, including quite a number of free ones, exist.


Harmony Systems offers HexEdit, a free binary editor for Windows NT and 95, that can be downloaded from their web site: http://www.hsys.com/hex.htm

SimTel Archives

The SimTel collection of ms-dos software includes a section with many binary file editors. There are many mirrors of the SimTel site. One is: http://oak.oakland.edu/simtel.net/msdos/binaryed.html

HEdit 2.1

Trial versions of HEdit, a binary file editor, both for Windows 95/NT and Windows 3.1 are available at: http://www.yurisw.com/hedit/

GNU Emacs (Unix)

The GNU Emacs editor from the Free Software Foundation has a hexadecimal mode. The GNU Emacs command to invoke this mode is hexl-mode. In GNU Emacs, type the META Key (ESC-x) Type: hexl-mode at the command prompt. The current buffer will switch into (Hexl) mode. On my Unix system (Sun), I found the Hexl mode a little sluggish at times. Sometimes I had to wait several seconds to get a response to scrolling or jumping to the start of the AVI file. Emacs modes are usually implemented in interpreted LISP; this may be the reason.

beav (Unix)

beav, a binary file editor and viewer, is available for Unix. beav displays the contents of a binary file as both hexadecimal and ASCII in side by side views. beav can edit as well as view binary files such as AVI files. Unix Prompt% beav file.avi

od (Unix)

od is a common Unix command. It is NOT an editor. od stands for Octal Dump. od file.avi | more (Octal Dump of AVI File) od -x file.avi | more (Hexadecimal Dump of AVI File) od -a file.avi | more (ASCII Dump of AVI File) Return to Top

RIFF and AVI Parser/Viewers


VidTrace is a 32-bit Windows console application for Windows 95 and Windows NT that I wrote to parse and display RIFF and AVI files. VidTrace displays the RIFF Forms, LISTS, and CHUNK. VidTrace also understands the AVI header format, audio stream header format, and video stream header format. Sample output of VIDTRACE some-file.avi RIFF (139086) AVI LIST (2004) hdrl avih (56) Microseconds Per Frame: 33333 30.000300 Frames Per Second Maximum Bytes Per Second: 1727488 Pad to Multiples of This Size: 6050647 Flags DWORD (hex): 710 FLAG: (AVIF_HASINDEX) AVI File Has 'idx1' chunk FLAG: (AVIF_ISINTERLEAVED) AVI File is Interleaved Total Frames: 239 Initial Frames: 23 Number of Streams: 2 Suggested Buffer Size: 57582 Width in Pixels: 160 Height in Pixels: 112 Scale (MAY BE UNUSED): 0 Rate (MAY BE UNUSED): 3220642425 Samples Per Second (MAY BE UNUSED): 3220642425 Start of AVI File (MAY BE UNUSED): 27920 Length of AVI File (MAY BE UNUSED): 4294967295 LIST (116) strl strh (56) Stream Type (Four Character Code): 'vids' 'vids' is Four Character Code for Video Stream Installable Compressor (Four Character Code): 'vdow' 'VDOW' is Four Character Code for VDONet VDOWave Video Codec Flags (hex): 0 Priority (MAY BE UNUSED) (hex): 0 Language Code (MAY BE UNUSED) (hex): 0 Initial Frames: 0 Scale: 33333 Rate: 1000000 Start: 0 Length: 239 Suggested Buffer Size: 1340 Quality: 0 Sample Size: 0 Frame (MAY BE UNUSED OR ABSENT): 0 0 0 2170023936 strf (40) Windows Bitmap Header Number of Bytes Required by Bitmap Structure: 40 Width of Bitmap in Pixels: 160 Height of Bitmap in Pixels: 112 Number of Planes: 1 Number of Bits Per Pixel (1,4,8,16,24, or 32): 24 Compression Mode (hex): 574f4456 COMPRESSION: Custom Compression 'VDOW' Size of Image in Bytes: 53856 Horizontal Resolution in Pixels per Meter: 0 Vertical Resolution in Pixels per Meter: 0 Number of Color Indices Actually Used by the Bitmap: 0 Number of Color Indices Considered Important to Display Bitmap: 0 LIST (92) strl strh (56) Stream Type (Four Character Code): 'auds' 'auds' is Four Character Code for Audio Stream Installable Compressor (Four Character Code): '' '' is Four Character Code for Uncompressed Audio Flags (hex): 0 Priority (MAY BE UNUSED) (hex): 0 Language Code (MAY BE UNUSED) (hex): 0 Initial Frames: 23 Scale: 1 Rate: 11025 Start: 0 Length: 87512 Suggested Buffer Size: 368 Quality: 0 Sample Size: 1 Frame (MAY BE UNUSED OR ABSENT): 0 0 0 2170023936 strf (16) Windows Waveform Audio Header Waveform Audio Format Type (hex): 1 Audio Format (WAVE_FORMAT_PCM): Microsoft Pulse Code Modulation Audio Number of Channels of Audio: 1 Samples Per Second: 11025 Required Data Transfer Rates (Bytes Per Second): 11025 Block Alignment in Bytes: 1 Bits Per Sample: 8 Size of Extra Format Information Appended to End of WAVEFORMATEX Structure (Bytes): -15736 vedt (8) JUNK (1688) LIST (104908) movi LIST (380) rec 01wb (367) LIST (380) rec 01wb (368) LIST (380) rec 01wb (367) . . . LIST (16) rec 00dc (4) idx1 (11840) DISP (21) DISP (20268) Download VIDTRACE

Microsoft RIFFWALK

Microsoft distributes a command line utility called RIFFWALK with the 16-bit Video for Windows 1.1e Development Kit that parses the structure of RIFF and AVI files, displaying the file structure in RIFF Forms, LISTS, and CHUNKS. Sample output of RIFFWALK some-file.avi 00000000 RIFF (00021F4E) 'AVI ' 0000000C LIST (000007D4) 'hdrl' 00000018 avih (00000038) 00000058 LIST (00000074) 'strl' 00000064 strh (00000038) 000000A4 strf (00000028) 000000D4 LIST (0000005C) 'strl' 000000E0 strh (00000038) 00000120 strf (00000010) 00000138 vedt (00000008) 000007E8 LIST (000199CC) 'movi' 0001A1BC idx1 (00002E40) 0001D004 DISP (00000015) 0001D022 DISP (00004F2C) 00021F56 The Video for Windows 1.1e Development Kit is included with the 16-bit SDK's in the Microsoft Developer Network CD-ROM's. Return to Top

Effective Use of Video on a Web Page

The limited bandwidth of the Internet is the bane of effective use of video on a Web page. Video clips on a web page need to be small. Even then downloading a video clip can take several minutes, hours over a 28.8 modem to someone's home. The longer the wait, the better the video should be! FIRST AND FOREMOST, tell a story!!! A video clip without a story is usually boring. A story can be told in 30 seconds, the duration of many television advertisements. Some stories can be told in less time. Because of the bandwidth limitations of the Internet, even 30 seconds is a big file, several megabytes. Characters, human personalities, sell. Sex sells. Violence sells. Talking heads (your company's CEO saying "Welcome to our great Website") tend to be boring. USE AUDIO! Sound makes a world of difference. Use base, lower frequencies in the soundtrack. Human beings are more sensitive to low frequency sound. A soundtrack with more base tends to sound "better" to most people. Most computer speakers are very cheap and don't reproduce high frequencies well anyway. You will likely cheat on higher frequencies to reduce bandwidth use by the audio as well. TECHNICAL ISSUES For widest distribution and ease of viewing: Provide video clips as AVI using the CinePak codec. For maximum distribution, also provide flattened QuickTime files again using the CinePak codec; these can be played on both PC's with QuickTime for Windows and on Macs. Provide MPEG-1 clips as well. Give the size of the video file in KBytes or MBytes in text as part of the link to the video file. This way the viewer can estimate how long it will take to download the file if they wish to. If you use less standard codecs or file formats to get smaller file sizes, provide links to download the needed viewers or codecs. Provide the AVI's with less standard codecs (e.g. VDOWave from VDONet) in addition to CinePak versions. Don't omit the CinePak versions. Video encoded at less than 15 frames per second usually looks very jerky to human viewers, like a slide show rather than smooth motion. The transition to smooth motion occurs somewhere in the range 15-17 frames per second. If motion is limited, frame rates below 15 may look acceptable, although often not. Image resolutions should be 320x240 or larger. In some cases, smaller sizes such as 160x120 may work. In general, most viewers find sizes smaller than 320x240 too small. DO NOT COMPRESS the video so much that unnatural artifacts such as blocking occur. In general loss of fine details appears natural to human viewers. This corresponds to changes in natural viewing conditions such as viewing an object at a distance or in poor lighting. Unnatural artifacts such as visible 4x4 pixel blocks or 8x8 pixel blocks jump out at most viewers and destroy the illusion of a natural image. For AVI, sound codecs aren't very standard. Avoid using audio compression, especially more exotic codecs. ADPCM may be ok. Again, if you use an audio codec, make sure to include a link on your website to download the codec. If possible, provide a version of the AVI without special audio codecs (and CinePak video). Uncompressed audio takes space. You ALMOST NEVER need to use the 44 KHz sampling rate. At most, use 22 KHz sample rate. Many people cannot hear the frequencies above 11 KHz (the sample rate is twice the highest frequency that the sampled audio data can represent faithfully). People who can hear frequencies between 11 KHz and 22 KHz are not very sensitive to these frequencies. See if the soundtrack works ok at 11 KHz 8 bit Mono (not Stereo). Use this low quality setting if you can get away with it (often this won't work). NOTE: You can select audio and video codecs, convert the frame rate, convert the audio sampling rate, and resize the video using video editor applications such as Adobe Premiere or VidEdit. See the section on video editors: Video Editors TO REPEAT: TELL A STORY!!! Many video clips in current (7/20/97) use on Web sites are very short, a few seconds, and really don't tell a story. These clips are boring! So are most talking heads (I have one on my Web site and it IS boring). Movie trailers, short television advertisements, etc. illustrate what is needed. If you don't have a story, think seriously about dropping the video. See elsewhere in this overview for information on authoring AVI files and converting to QuickTime and MPEG-1. Return to Top

How to embed an AVI file in a Web Page:

A Simple Hypertext Link

The simplest approach is to use the anchor tag < A HREF="http://www.somplace.com/movie.avi" > A Movie </A> In this instance, clicking on the link will cause the AVI file to be downloaded. The browser recognizes that the AVI file is not an HTML document. Typically, the browser invokes a helper application that can play the AVI file, such as Media Player under Windows 3.1. The movie will appear in a separate window. The browser may have a plug-in that provides support for AVI, in which case the video window will appear embedded in the HTML page. Web browsers such as Netscape and Internet Explorer know how to handle a file through a Content (MIME) type reported by the Web server. For example, the MIME type for AVI files is video/avi. The browser may contain a built-in decoder for this MIME type. For example, JPEG and GIF still image compression decoding and viewing is built into Internet Explorer and Netscape. The browser can be configured to invoke a helper application such as Media Player. Helper applications are invoked as separate applications with their own windows. The browser can be configured to use a "plug-in" instead of a helper application. A "plug-in" is a software component that extends the capabilities of the browser. The "plug-in" handles input and presents output embedded within the page. For example, a video plug-in's decoded video appears within the page, not as a floating window. In the case of a simple hypertext link, a browser with an AVI plugin will jump to a blank page with the AVI video appearing in a rectangle in the upper left corner of the blank page. The video is not embedded in the page with the hypertext link. It is necessary to use the Netscape EMBED HTML tag (see below) to produce a video embedded in the page. Using the EMBED tag is different from using a simple anchor A tag (hyptertext link). If the browser is unable to handle a MIME type (no built-in capability exists and no helper application or plug-in is specified), the browser will present a dialog box asking the user to select an application, save the file to disk, or cancel the operation. In both Internet Explorer and Netscape, the user can configure the browser to use helper applications or plug-ins as desired. Netscape now provides a Netscape plug-in known as LiveVideo to play AVI files. This plug-in should be installed in the \NETSCAPE\PLUGINS directory. For the Windows 3.1 (16 bit) version of Netscape this plug-in is named NPAVI16.DLL. Digigami provides a plug-in for Netscape Navigator (Windows) called CineWeb that adds playback of AVI, QuickTime .MOV, and MPEG files. The URL is: http://www.digigami.com/CineWebPress.html

Microsoft Internet Explorer HTML Syntax

Microsoft's Internet Explorer 2.0 added attributes to the IMG tag that allow for inline video (an AVI file actually embedded in the page rendered by the Web browser). These are the DYNSRC, CONTROLS, START, and LOOP attributes. For example, < IMG DYNSRC="movies/movie.avi" CONTROLS SRC="movies/movie.gif" > This will embed the movie in the page with some simple playback controls for the user to select. Browsers that do not support the DYNSRC attribute will use the SRC attribute and display the image movie.gif instead. Internet Explorer will ignore the SRC attribute. In the Microsoft spirit of a new API every week, Microsoft has added some new tags in Internet Explorer 3.0 and is discouraging use of the IMG tag and DYNSRC attribute. In Internet Explorer 3.0, Microsoft has added support for the Netscape EMBED tag, see the section on HTML for Netscape's LiveVideo below. Microsoft has also added a Microsoft specific OBJECT tag which does essentially the same things as EMBED and is overtly linked with Microsoft's OLE/COM/ActiveX environment. Naturally Microsoft recommends using the OBJECT tag. Unlike Netscape Navigator, Internet Explorer on Windows does not use plug-ins, either from Micrsoft or 3rd parties, to view AVI. Rather it invokes either the Video for Windows media player or the ActiveMovie ActiveX control. If necessary, Internet Explorer is able to effectively embed the applications in the Web page. Microsoft has a copyrighted white paper "File References on HTML Pages" on their Web site that provides a detailed description of referencing AVI files on HTML pages for viewing with Internet Explorer. http://www.microsoft.com/devonly/tech/amov1doc/amsdk008.htm Since Microsoft reportedly has $9 billion in cash for acquisitions, lawyers, and other fun - and I don't, I will refrain from simply incorporating the document here.

Netscape LiveVideo HTML Syntax

If you hunt around the Netscape Web site you will find the following detailed specification of the HTML syntax for embedding an AVI file in a Web page for use with the LiveVideo Plug-in. LIVEVIDEO SYNTAX DESCRIPTION LiveVideo plays video files in AVI format. (Currently for Windows 95 and NT only.) HTML SYNTAX EMBED - Use this tag to place AVI movies into your Web document. SRC=[URL] - The URL of the source AVI file. AUTOSTART=[TRUE|FALSE] - Setting the value to TRUE allows the AVI movie to begin playing automatically when the Web page is loaded. The default is FALSE. LOOP=[TRUE|FALSE] - Setting the value to TRUE allows the AVI movie to play continuously until the user clicks on the movie to stop it from playing or goes to another page. The default is FALSE. WIDTH=[# PIXELS] - Use this attribute to display the width of the AVI movie. HEIGHT=[# PIXELS] - Use this attribute to display the height of the AVI movie. Standard sizes for movies are 90x120, 120x160, 180x240, and 240x320 (all size references are HEIGHT x WIDTH). These are all standard sizes using the 4:3 aspect ratio. ALIGN=[TOP|BOTTOM|CENTER|BASELINE|LEFT|RIGHT|TEXTTOP|MIDDLE|ABSMIDDLE|ABSB OTTOM] - This attribute tells Netscape Navigator how you want to align text as it flows around the AVI movie. It acts similarly to the IMG tag. JAVA AND JAVASCRIPT FUNCTIONS play() - Starts playing the source file at the current location. stop() - Stops the currently playing video. rewind() - Rewinds the currently loaded video. seek(frame-number) - Sets the current frame of the video to the given frame number. Return to Top

Sending AVI by E-Mail or Network News

The original Internet e-mail system was designed for sending purely text messages using printable 7-bit ASCII codes (byte values from 0 to 127 that represent printable characters). Binary files such as AVI can include non-printing 7-bit ASCII control codes and values higher than 127. These cause problems. The Network News system was built on top of the Internet mail system. Network News postings use the same text format as mail messages with some additional headers for news postings. Network News postings use the same mechanisms to attach or embed binary files such as AVI to the message. There are two main ways to transfer binary files such as AVI by e-mail (and also the Network News system which is derived from e-mail). The older method is UUENCODE. UUENCODE is a utility that translates binary files into printable 7-bit ASCII codes that can be sent safely by e-mail. Simply include the uuencoded file in the body of the e-mail message. The modern method is to use MIME, the Mulipurpose Internet Mail Extensions. This is a standard for adding attachments to Internet e-mail, including binary files such as AVI. MIME supports a number of schemes, notable base64 encoding, to represent binary files as printable 7-bit ASCII characters. See the section on
MIME for more information. More modern e-mail software include built in support for uuencode and MIME. LESS COMMON METHODS btoa btoa (binary to ascii) is another Unix utility for encoding binary files to printable 7-bit ASCII files. btoa is less widely used than UUENCODE. BinHex Another method is to use the Macintosh program BinHex. Like UUENCODE, BinHex translates a binary file into printable 7-bit ASCII codes that can be transferred over mail networks. There are cases of AVI files being BinHex'ed and added to newsgroup postings as text MIME attachments. BinHex 4.0 files are identified by a first line: (This file must be converted with BinHex 4.0) followed by a blank line, followed by a colon, followed by the data. On the PC, (1) WinZip 6.2 (and later versions of WinZIP) can open and decode BinHex encoded files. WinZip 6.2 also opens and decodes uuencoded, XXencoded, and MIME (base64, plain/text, and quoted-printable) files. http://www.winzip.com/ (2) BinHex'ed files may be decoded using the PCBINHEX utility. For more information on BinHex, see: http://www.gis.at/infoalley/1095/31/what.html

Microsoft Internet Mail

In Microsoft's Internet Mail (included in Windows 95 OSR2 for example), click New Message to generate a new e-mail message. Select Insert | File Attachment to add an attachment, for example an AVI file. Select Format | Settings... to choose UUENCODE or MIME. Internet Mail defaults to MIME. One can also select UUENCODE. Internet Mail automates the binary file attachment process. Return to Top

How to Encrypt AVI Files

One option is to use the PGP (Pretty Good Privacy) program. PGP appears to have been developed to encrypt conventional e-mail messages, printable 7-bit ASCII characters which PGP's documentation calls "ASCII-Armored Text". You need to encode binary files such as AVI using a binary to printable 7-bit ASCII encoder such as UUENCODE or BinHex. Then, run PGP on the encoded text. In the case of E-Mail, there is a PGP-MIME standard for encrypted multimedia attachments to e-mail messages. PGP versions exist for Windows, Macintosh, and Unix. PGP includes extensive documentation on its use. PGP at MIT for Non-Commercial Uses Pretty Good Privacy, Inc. Editorial Comment: PGP almost certainly provides excellent protection against most would-be non-governmental codebreakers. PGP also emphasizes the threat of surveillance by the NSA, FBI, and other governmental agencies in its marketing literature, citing apparent efforts by the government to suppress public key cryptography in general and PGP specifically. For example, Phil Zimmerman, the PGP author, was the target of a government investigation relating to PGP. Spy agencies, both foreign and domestic, play such a major role in funding research into cryptography and in most companies and organizations involved in communications security that it is very difficult to know if ANY well-known cryptography algorithms, whether or not obviously associated with the NSA as in DES or the Clipper chip, is secure against these agencies. These agencies might have the sense to appear opposed to the use of an algorithm which they in fact know how to break, to make a high profile but ineffective effort to suppress such an algorithm while quietly dealing with algorithms which they cannot break. Return to Top

MIME types of AVI

MIME stands for Multipurpose Internet Mail Extension. This is a mechanism that was developed to support multimedia and other file type attachments to Internet e-mail. MIME defines MIME types that identify the data type of the attachment. The World Wide Web uses MIME types to identify the data type of files on Web sites. A MIME type consists of a type/subtype, for example image/jpeg for JPEG images. The MIME specification (IETF RFC 2046) specifies a type of video for video images. The specification defines video/mpeg as the MIME type for MPEG video. Beyond this, the MIME specification (IETF RFC 2048) specifies a mechanism for registering MIME types with the Internet Assigned Number Authority (IANA). As of 5/16/97, the following video subtypes were registered with IANA: video/mpeg video/quicktime video/vnd.vivo video/vnd.motorola.video video/vnd.motorola.videop Thus, AVI has never been officially registered with IANA. To view the complete list of registered MIME types: http://www.isi.edu/in-notes/iana/assignments/media-types/media-types More than one MIME type appears to be used in practice for AVI files. MIME types used for AVI: video/avi video/msvideo video/x-msvideo Note that according to the MIME specification the prefix "x-" indicates an unregistered, experimental MIME type. For extensive information on MIME, visit The MIME Information Page at: http://www.fwb.gulf.net/~dwsauder/mime.html Return to Top

Configuring Web Servers to Handle AVI Files

Web servers are configured to send a MIME type to Web browsers to indicate what to do with a file on the Web site that the browser is viewing. For example, the MIME type image/gif indicates to a browser that it is viewing a GIF file. Web servers must send the AVI MIME type(s) to Web browsers for files installed on the Web site. There are many Web servers. Probably many are automatically configured to send a MIME type for AVI files (files with the extension .avi). The folowing explains how this configuration is done for some of the more popular Web servers.

Apache httpd

The free Apache httpd Web server is one of the most popular (perhaps the most popular) Web server in use (May, 1997). This is a free implementation of the httpd daemon for Unix machines. Apache is frequently run on Sun workstations used as Web servers. By default, Apache httpd looks in a configuration file httpd.conf for directives that configure Apache. One of these directives is AddType AddType video/avi .avi The example above would configure the Apache Web server (the httpd Unix daemon) to send the MIME type video/avi to a Web browser for files with the file extension .avi on the Web site. The Apache httpd daemon includes a command line option -f to override the default httpd.conf file name and file location. The Web administrator can use this to set up an alternative configuration file. Apache allows users to add a file .htaccess in the root directory of their Web site which contains directives such as AddType. In this way individual users may add or override the configuration of the Web server. For example, my Web site did not send the x-world/x-vrml MIME type for .wrl (VRML) files. Netscape with Live3D expected to see this MIME type for VRML "worlds". I created a .htaccess file with addtype x-world/x-vrml .wrl With this, my browser would correctly view VRML files. The same could be done with AVI files. For further information on Apache, see the Apache Web site: http://www.apache.org/

CERN (or W3C) httpd

The CERN httpd is similar to Apache. The CERN httpd defaults to looking in a configuration file /etc/httpd.conf The configuration file contains configuration directives. One of these is AddType AddType .suffix representation encoding [quality] For example: AddType .html text/html 8bit 1.0 Extensive information on the CERN httpd web server, including a user manual, is available at: http://www.w3.org/Daemon/


The NCSA (National Center for Supercomputer Applications at my alma mater, the University of Illinois at Urbana-Champaign) HTTPd web server is similar to Apache and CERN. NCSA HTTPd looks in a resource configuration file conf/srm.conf (srm for Server Resource Map) You can add AddType configuration directives to this configuration file to add new MIME types or override the default MIME types used by NCSA HTTPd. AddType type/subtype ext1 ext2 ... extn For example: AddType text/plain txt doc or AddType video/avi avi Extensive information on NCSA HTTPd is available at: http://hoohoo.ncsa.uiuc.edu

Microsoft Internet Information Server

Microsoft Internet Information Server is a server providing HTTP (WWW), FTP, and Gopher services for Windows NT 4.0 Server. IIS handles the mapping from file extensions to MIME types through the Windows NT System Registry. To view and modify the MIME map: 1. Run the Windows NT Registry Editor Regedt32.exe 2. Look in the Windows NT Registry Key (Folder): HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\InetInfo\Parameters\MimeMap 3. The MimeMap Key contains a series of Registry Values (entries) of form: < mime type > , < filename extension > ,, < gopher type > 4. On my IIS server, the sole Registry Value (entry) for avi is: video/x-msvideo,avi,,>:REG_SZ: :REG_SZ: identifies a text string in the Registry editor. The IIS server will send the MIME type video/x-msvideo for files with the extension AVI. IIS also uses the entries: video/x-ms-asf,asf,,5:REG_SZ: video/x-ms-asf,asx,,5:REG_SZ: for the Microsoft Active (or Advanced) Streaming Format files. 5. IIS defaults to treating files as vanilla binary files if they are not explicitly listed in the MIME Map. 6. To add a new MIME type, in the Registry Editor - Select Add Value ... from the Edit menu. - Create a Registry Value of type REG_SZ (for a string) - Enter the MIME type information as above as the NAME of the Registry Value. - Leave the string blank.

Netscape Enterprise Server 3.0

Edit the mime.types file in the server's config directory. This will contains lines of the form: type=video/x-msvideo exts=avi These can also be of the form: type=video/x-msvideo exts=avi,vid,vvv when multiple file extensions map to the same MIME type. The server reads this file to associate the MIME type video/x-msvideo with files with the file extension avi. The Netscape help site is: http://help.netscape.com/ This includes many articles on the Netscape server including a discussion of MIME types and the mime.types file. Return to Top

AVI and Java

Plans for Java include a collection of Java Media and Communications API's (Application Programmer's Interfaces). These include the Java Media Framework (JMF for short). The first part of JMF is the Java Media Player, an API for synchronization, control, processing and presentation of compressed streaming and stored timed media including video and audio. A public specification for the Java Media Player has been released. According to this the Java Media Players will be designed to support many media types including AVI. A beta release of the JMF software is scheduled for the second quarter of 1997 and may be happening as of 5/15/97 (some rumors at least although I have not seen the software). For further information on Java Media Framework, see: http://java.sun.com/products/java-media/jmf/index.html For further information on Java, see the Java site: http://java.sun.com/ Return to Top


The Virtual Reality Modeling Language (VRML, often pronounced 'vermal') is the file format standard for 3D multimedia and shared virtual worlds on the Internet. VRML supports a "node" known as a MovieTexture. This allows a video (or movie) to be mapped onto the surface of an object. A MovieTexture node is referenced by the texture field of an Appearance node. Each object has an Appearance node. The VRML MovieTexture node includes a url field. The url field, as the name suggests, is the URL (Uniform Resource Locator) of a video file to map onto the surface of the VRML object. The VRML 2.0 specification requires that this video file must be in either MPEG-1 Systems (audio and video) or MPEG-1 video only format. AVI is not directly supported. It is necessary to convert an AVI file to MPEG-1 format to use the AVI file with VRML. This is VRML 2.0 VRML 97 may be different. For further information on VRML, see the VRML Consortium Web Site. http://www.vrml.org/ Return to Top

Configuring Netscape Navigator 3.01 to Display AVI Files

The following remarks apply to Netscape Navigator 3.01 for Windows 3.1, Windows 95, and Windows NT 4.0. Netscape Navigator displays .AVI files either through a helper application such as the Microsoft Media Player or a Netscape Plugin that supports AVI playback, such as the Netscape npavi16.dll and npavi32.dll plugins. A helper application is a separate application, executable, that is invoked by the Web browser. The helper application runs as a separate process with its own window or windows. The helper application is not tied to the Web page. A Netscape plugin is a dynamic link library that extends the capabilities of the Netscape Navigator. Typically the plugin will receive control over a region of the Web page displayed by the browser and display its output in that region. The output appears to be embedded in the Web page. To view and configure helper applications, select the General Preferences item from the Options menu of Netscape Navigator. Select the Helpers tab of the General Preferences. Helpers lists registered File types (MIME types), associated actions, and file extensions. Options | General Preferences | Helpers A File Type is a MIME type such as image/gif or video/avi. MIME stands for Multipurpose Internet Mail Extensions. MIME types are a mechanism to identify the data type of multimedia attachments to Internet e-mail messages. MIME types are also used by Web servers to identify to Web browsers the data type of multimedia files such as AVI files on Web sites. An action can be blank, Ask User, Browser, or a helper application such as Media Player (mplayer.exe). The blank action appears to be used in cases where a Plugin is installed and may be used for other cases as well. The Ask User action indicates to pop up a dialog asking the user what to do: save to disk, select an application, or cancel. Browser indicates that the File Type is supported by the browser. For example gif and jpeg decoding is built directly into Netscape Navigator. To view installed plugins, select About Plugins from the Help menu. This produces a listing of installed Plugins. The list has an entry for each currently installed Netscape Plugin. For example: NPAVI32 Dynamic Link Library MIME Type video/msvideo ... other information ... video/x-msvideo ... other information ... is the information presented for Netscape's npavi32.dll plugin in Netscape Navigator 3.0 on Windows NT 4.0 Server (Service Pack 2). Netscape Plugins are dynamic link libraries stored in a plugins directory. For example, \Program Files\Netscape\Navigator\Program\plugins\ Many Netscape plugins including the Netscape AVI plugins (npavi16.dll for 16 bit Windows and npavi32.dll for 32 bit Windows) can be dowloaded from the Netscape Web site. http://home.netscape.com/ Return to Top

Netscape Navigator Plug-ins to Play AVI Files

Netscape LiveVideo

Netscape Navigator 3.0 includes LiveVideo which supports playback of AVI files on Windows 3.x, Windows 95, and Windows NT platforms. This is implemented through the dynamic link libraries npavi.dll, npavi16.dll, and npavi32.dll. http://home.netscape.com/ You can download the latest Navigator 3.0 with LiveVideo from Netscape. Netscape also maintains pages with Netscape Plug-Ins, mostly from other companies. These include CineWeb by Digigami and MacZilla by Knowledge Engineering which provide AVI playback. To get to the Audio/Video Plug-Ins page (as of May 15, 1997), go to the Netscape Home Page. There is a graphical text "Get the latest Netscape Software". Underneath this text there is pulldown list of the many Netscape products. This initially reads "Pulldown to select products". Click on this to show the pulldown list (it is very long). Choose "Navigator Plug-Ins". Click on the Product Info icon under the pulldown list. This presents a page for Inline Plug-Ins. Select the Audio/Video option. This brings up a page of audio/video plugins that add support for various audio and video formats. CineWeb by Digigami and MacZilla by Knowledge Engineering are both in this list. These plug-ins are also available directly from their makers.

CineWeb by DigiGami

Digigami produces a Netscape Navigator Plug-in for Windows 95 and Windows NT called CineWeb that provides playback of AVI, QuickTime, and MPEG files. http://www.digigami.com/cineweb/

MacZilla by Knowledge Engineering

MacZilla is a Netscape Plug-in for the Power Macintosh that adds AVI, Quicktime, and MPEG playback. http://maczilla.com/ Return to Top

Configuring Internet Explorer 3.0x to Display AVI Files

The following applies to Internet Explorer on Windows 95 and Windows NT 4.0. The information may also work for Windows 3.1 Select the Options item from the View menu of Internet Explorer. Select the Programs tab. Within the Programs sheet, click on the "File Types ..." button. View (menu) | Options (item in menu) | Programs (tab) | File Types ... (button) Internet Explorer 3.0x uses the Windows 95 System Registry or Windows NT System Registry to determine what to do with a file. This is the same mechanism that the Windows 95 or NT 4.0 Desktop uses to determine which application to use when a user double clicks on a file icon. This is achieved through a Content or MIME type "value" (name and data pair) in the registry. See the section on how AVI is handled in Windows 95 for more details. The "File Types ..." brings up a list of file types and associated actions. This can be used to edit and modify the actions. Return to Top

How to embed an AVI file in a Microsoft Word Document?

Media Player acts as an OLE (Object Linking and Embedding) server. This means that application such as Microsoft Word that support OLE can embed a movie. With Word 6.0 (Microsoft seems to keep changing the user interface for Microsoft Word so I need to qualify which version of Microsoft Word), 1. Select Insert from the menu bar. This pulls down a long menu. 2. Select Object... from the pulldown menu. This pops up a dialog box. 3. Select the Create from File tab. 4. Select the AVI file from the file browser. 5. Select OK This inserts a link to the AVI file at the current location within the Microsoft Word document that you are editing. The first frame of the AVI file is displayed. Double click on the first frame of the AVI file to start playback. NOTE: With Word 6.0, this sequence of Word commands embeds a graphic of the first frame of the AVI file along with instructions to invoke Media Player on an external file in the Word document. The binary AVI file remains separate. Only the file specification and a graphic image of the first frame are actually inserted in the Word document. The on-line help documentation with Word 6.0 is misleading or outright false on this point. Other Windows applications that act as OLE clients will be able to do similar things with AVI files. Return to Top

Size limits on AVI files

An AVI file cannot be larger than the disk partition that contains it. Different filesystems have different maximum sizes for disk partitions. Under the 16 bit FAT (File Allocation Table) filesystem used by DOS, disk partitions are limited to a maximum size of 2GB (Gigabytes). In DOS, a hard disk is divided into 512 byte sectors. DOS Version 4 added support for 32 bit sector numbers. 2 raised to the 32 is roughly 4 billion, multiply this times 512 bytes in a sector to get the 2GB limit. FAT16 partitions are limited to 2GB, necessarilly limiting AVI files to a maximum size of 2GB as well. DOS versions prior to DOS 4 limited disk partitions to 32MB (Megabytes). These earlier versions of DOS used 16 bit sector numbers in all I/O routines. 2 raised to the 16th power is 64K, multiply this by 512 bytes in a sector to get the 32MB limit. Partitions using other filesystems such as the Windows NT File Systems (NTFS) may not be subject to the 2GB limit. The new FAT32 filesystem available with Windows 95 permits partitions larger than 2GB. Unfortunately, a 1 or 2 GB file size limit is hard wired into some of the code for the Microsoft Video for Windows. In particular, the RIFF parser code and MCIAVI (the MCI driver for AVI files) contain a 1 GB or 2 GB limit hard wired into them. Microsoft's Active Movie, which replaces Video for Windows, contains fixes for the 1-2 GB size limits hard wired into Video for Windows. Microsoft's OEM Service Release 2 (OSR2) incorporates FAT32. Earlier OEM releases and the retail version of Windows 95 (as of 2/15/97) do not include FAT32. Microsoft sayeth: "Neither MS-DOS 6.x nor retail versions of Windows 95 will recognize a FAT32 volume". To see if you have OSR2, go to the Control Panel, select the System icon, and click the General tab. It will say "4.00.950b". If there is no trailing letter or "4.00.950a", then you do not have OSR2. OEM versions of Windows 95 cannot be purchased separately as off the shelf software. They are bundled on systems created by companies like Dell, Compaq, and so forth. The retail version(s?) of Windows 95 can be purchased at software stores or through software resellers. I believe that there was some sort of beta release of FAT32 prior to OSR2, either a special version of Windows 95 or a way to install FAT32 in versions of Windows 95 that did not come with FAT32. OSR2 and FAT32 seem to have some problems. Some applications such as Corel's Paradox 7 fail on FAT32 volumes. See: Bug Net Web Site or search the Microsoft Knowledge Base for the keyword OSR2. The header for an AVI file includes a 32 bit AVI file length, imposing a restriction of 4GB on the AVI file size. The Open Digital Media (OpenDML) Consortium has defined OpenDML AVI File Format Extensions to add support for professional video functionalities to AVI. This includes a fix for the 4 GB limit. Microsoft has incorporated this extended version of AVI into ActiveMovie 1.0 from Microsoft. Return to Top

How to Fix Problem with CorelMove4.0 AVI Files

CorelMove 4.0 exports AVI files that cannot be played using Video for Windows 1.1 or the Windows 95 Video for Windows or ActiveMovie 1.0. Corel has a fix file that can be downloaded from their software library. The file is called "cmvfix.exe." The URL is... http://www.corel.com/products/graphicsandpublishing/draw4/library.htm Description text from the web page... Title: CMVFIX.EXE For CorelMOVE 4.0 AVI export correction CMVFIX.EXE by Corel Corporation 1994 contains these compressed files: CMV4FIX.EXE is a compressed file that contains fixes for CorelMOVE 4.0's AVI file exports. These are new replacement .DLLs. AVI4FIX.EXE is a Windows application that will allow you to correct older CorelMOVE 4.0 AVI files to work with MS-Video For Windows 1.1. If you create an AVI file AFTER installing the CMV4FIX update that accompanies this fix, then you will NOT be required to run this application. This will change the RLE compression in the CorelMOVE AVI files. Return to Top

Sources of Information on AVI and Related Topics:

TECHNICAL How to Digitize Video by Nels Johnson with Fred Gault and Mark Florence John Wiley and Sons, New York, 1994 ISBN 0-471-01440-0 Article "Digital Video File Formats" by Mark Florence Dr. Dobbs Sourcebook of Multimedia Programming, Winter 1994 Microsoft Software Development Kits (SDK) and Device Driver Kits (DDK) Microsoft's SDK's and DDK's are included with various products such as Visual C/C++ and in a subscription to the Microsoft Developer Network. Windows 3.1 Software Development Kit (SDK) Win32 Software Development Kit (SDK) Video for Windows Software Development Kit (SDK) Windows 3.1 Device Driver Kit (DDK) Windows NT Device Driver Kit (DDK) specifically, Windows Multimedia Programmer's Guide - includes overview of RIFF Video for Windows Software Development Kit (SDK) Programmer's Guide - includes overview of AVI RIFF Specification is available on World Wide Web at (11/7/96): http://www.seanet.com/HTML/Users/matts/riffmci/riffmci.htm DirectX Software Development Kit (SDK) - DirectX 3 SDK Contents - ActiveMovie 1.0 SDK Contents included with Visual C++ 5.0 Professional Edition and other Microsoft products. Practical Digital Video with Programming Examples in C Phillip E. Mattison John Wiley and Sons, Inc. New York ISBN: 0-471-31016-6 Multimedia Developer's Guide Paul Perry SAMS Publishing: A Division of Macmillan Computer Publishing Indianapolis, IN 1994 ISBN: 0-672-30160-1 Library of Congress Catalog Number: 93-86963 Information on Windows Multimedia using MCI, AVI, and Video for Windows. Dumps of Windows SDK references. Video Demystified: A Handbook for the Digital Engineer by Keith Jack HighText Publications Solana Beach, CA 1ed (C) 1993 by Brooktree Corporation ISBN: 1-878707 Library of Congress Catalog No.: 93-14705 A popular highly technical book on analog and digital video technology. Not much on AVI, Video for Windows, or PC Video but plenty of details on NTSC, PAL, SECAM, and other video topics. Now in a 2nd edition with new information on MPEG and H.26x Publishing Digital Video, 2nd. Edition by Jan Ozer Academic Press, 1997 Price: $34.95 Covers video capture on PC/Windows, video editing, windows video compression, and MPEG-1 compression for digital video and multimedia authors. Includes chapters on streaming audio and streaming video. The Windows NT Device Driver Book A Guide for Programmers by Art Baker (Cydonix Corporation) Prentice Hall, Upper Saddle River, New Jersey, 1997 Price: $44.95 An introduction to Windows NT Device Drivers with simple examples and source code. Does not use video display adapter drivers or video capture drivers as examples. Sticks with simple examples. BUSINESS and POP COMPUTING "Set-top boxing" by Edward W. Desmond, Fortune, November 10, 1997, p. 91 - Microsoft and WebTV (pretty thin) "Real Revolution" by Robert H. Reid, Wired, October, 1997, p. 122 - All about Progressive Networks (now renamed RealNetworks) and its CEO Rob Glaser, the purveyors of RealAudio streaming audio and RealVideo streaming video. Return to Top

Internet Newsgroups with Information on AVI and Video

Internet or USENET Newsgroups are a good source of current information on AVI and video. Some useful newsgroups are: VIDEO SPECIFIC NEWSGROUPS
rec.video.desktop comp.os.ms-windows.video comp.sys.ibm.pc.hardware.video comp.dcom.videoconf Videoconferencing OTHER USEFUL NEWSGROUPS comp.multimedia Broad coverage of multimedia including video. comp.compression Both technical discussions of compression algorithms and codecs, as well as end user issues such as utilities and configuration issues. Return to Top

Microsoft's Changing Names

Microsoft has an annoying tendency to rename API's, software components, products, and perhaps even entire companies. One has to wonder if this is good marketing or a symptom of politics within the colossus. This has happened to a number of video and video related products, most notably ActiveMovie. List of Changed Names --------------------- Quartz ( original codename for ActiveMovie ) Active Movie 1.0 ( new video software to replace Video for Windows) Active Movie 2.0 ===> DirectShow 2.0 ( March, 1997 ) The change to DirectShow seems analagous to Ford renaming the Mustang the Putt-Putt Mobile in 1967. ASF (Active Streaming Format) (new video file format, to replace AVI?) ASF (Advanced Streaming Format) Active is dropped in Sept. 1997 Somebody doesn't like Active???? (new Operating System to replace Windows 95) Memphis ==> Windows 97 ==> Windows 98 Progressive Networks, marketers of RealAudio audio compression for the Internet, was founded by Rob Glaser, a former top executive at Microsoft. In late 1997, Microsoft invested in Progressive Networks, reportedly acquiring an option to acquire 23% of the company. Progressive Networks renamed itself RealNetworks, possibly to improve the prospects of its Initial Public Offering (IPO). Progressive Networks (that was then) RealNetworks (this is now 12/20/97) RealNetworks has licensed and markets Iterated Systems fractal video codec under the name RealVideo. Iterated used to call their video codec ClearVideo. ClearVideo (that was then) RealVideo (this is now 12/20/97) Return to Top


A quick guide to acronyms, jargon, and techno-babble.

Microsoft software component for handling and displaying digital video, including AVI, MPEG, and QuickTime, for Windows 95 and Windows NT 4.0. Intended to replace Video for Windows. Renamed DirectShow.
Audio Compression-3. Usually marketed as Dolby Digital. A digital audio compression format from Dolby Laboratories. Incorporates "5.1" audio channels: left, right, center, left surround, right surround, and a base channel for more realistic three-dimensional sound. Used in DVD, GA-HDTV, laser discs, and movie theaters.
Asymmetric Digital Subscriber Line. A technology and standard to enable much higher bitrates between telephone company central offices and homes over the already installed copper telephone lines. One of a family of such technologies and standards collectively referred to as xDSL. May provide sufficient bandwidth for network video to homes.
Audio Video Interleave. Microsoft format for digital audio, video, and other multimedia data.
Advanced Streaming Format (formerly Active Streaming Format). A Microsoft file and data stream format for multimedia data including audio, video, still images, and other data types.
Applications Specific Integrated Circuit. A silicon chip customized for a specific application such as video compression.
Asynchronous Transfer Mode. Networking technology and standard frequently used for implementing high-speed Wide Area Networks over fiber optic cables.
Bitrate may refer to bits per pixel for compressed images or bits per second (such as 128 Kilobits/second) for compressed video.
Constant Bit Rate. In video coding, the bitrate of the compressed video is fixed at a certain rate. This usually results in variable perceived quality of the video.
The International Radio Consultative Committee. An international body responsible for a number of video standards, e.g. CCIR-601. Renamed ITU-R
The International Telephone and Telegraph Consultative Committee. An international body responsible for a number of communications standards, e.g. H.261. Renamed ITU-T.
short for compressor decompressor. Usually a software or hardware component that compresses and/or decompresses audio or video data. A hardware codec is usually a silicon chip.
Discrete Cosine Transform. Mathematical transform used in digital video compression. Used in JPEG, MPEG-1, MPEG-2, H.261, H.263, H.263+, and DV digital video compression.
Device Driver
A software component that handles direct interaction with a piece of hardware.
Dynamic Link Library. A type of software library in Microsoft Windows.
Digital Versatile Disc. High density optical storage discs. DVD used to distribute movies using MPEG-2 digital video and either Dolby Digital (AC-3) or MPEG-2 (Philips MUSICAM) digital audio.
European Broadcasting Union.
Electronics Industry Association. A trade organization responsible for a number of standards. For example, EIA Standard EIA-189-A, July 1976, Encoded Color Bar Signal
Federal Communications Commission. United States government agency that regulates television industry. Established the NTSC standard and the GA-HDTV standard.
Grand Alliance - High Definition Television. The new United States standard for High Definition Television based on the MPEG-2 digital video compression format and the Dolby Digital (AC-3) audio compression format.
A standard for digital video compression for videoconferencing. Uses the Discrete Cosine Transform.
A standard for digital video compression for videoconferencing. Uses the Discrete Cosine Transform.
A standard for digital videoconferencing over ISDN.
A standard for digital videoconferencing over TCP/IP networks.
A standard for digital videoconferencing over telephone lines.
Institute of Electrical and Electronics Engineers. An organization of engineers responsible for a number of electrical and electronics industry standards.
Internet Engineering Task Force. Body responsible for managing and establishing protocols for the Internet.
International Standards Organization. Operates under auspices of the United Nations. Responsible for many audio, video, and telecommunications standards.
International Telecommunications Union
Joint Photographic Experts Group. A body within the International Standards Organization (SI) that established the JPEG still image compression standard. JPEG is usually used to refer to compression of still images or video frames using the "baseline JPEG" compression algorithm using the Discrete Cosine Transform and Huffman coding.
A new standard under development by the JPEG committee for improved lossy still image compression. JPEG-2000 will probably use a different technology than the Block Discrete Cosine Transform used in baseline JPEG.
Media Control Interface. A Microsoft standard API for software control of multimedia devices and components. MCI includes API's for playback of AVI files and digital video devices (such as laser disc players).
Motion JPEG
A type of digital video in which the video frames are individually compressed using JPEG still image compression. A standard exists for Motion JPEG stored in AVI files.
Motion Pictures Experts Group. A body within the International Standards Organization (ISO) that established the MPEG-1, MPEG-2, and MPEG-4 digital audio and video compression standards. MPEG is also used to refer to video and audio clips compressed using the MPEG standards and the MPEG standards themselves.
Mean Squared Error. A statistical measure of error, used to determine quality of compressed images. Mathematically equivalent to Peak Signal to Noise Rate (PSNR).
National Television System Committee. The color analog television standard used in the United States, Japan, and a number of other countries. Adopted by United States in 1953.
Phase Alternation Line. The analog television standard used in Germany, England, and many other nations.
Plain Old Telephone Service. Analog copper wires between telephones and the phone company.
Peak Signal to Noise Ratio. A statistical measure of error, used to determine the quality of compressed images. Mathematically equivalent to mean squared error (MSE).
Quality of Service. In networking, QoS refers to various schemes to insure a certain quality, such as limiting or eliminating packet loss for video streams.
Red Green Blue. Color represented as red, green, and blue components. Most computer monitors use RGB pixels.
Original black and white television standard used in the United States. NTSC was designed to be compatible with RS-170 black and white television sets.
Sequentiel Couleur Avec Memoire or Sequential Color with Memory. Analog television standard developed in France. Used in France and some other nations.
Society of Motion Picture and Television Engineers.
The English word specification has a few meanings, or word senses. The Webster's New World Dictionary gives the following meaning: "2 [usually pl.] a)a detailed description of the parts of a whole b) a statement or enumeration of particulars, as to actual or required size, quality, performance, terms, etc. [specifications for a new building]".
The English word standard has a large number of meanings, or word senses. The Webster's New World Dictionary gives the following meaning: "4 the type, model, or example commonly or generally accepted or adhered to; criterion set for usages or practices [moral standards]". This is the closest dictionary meaning or word sense to the usage of engineers.
Video for Windows (VfW)
Microsoft Windows software component for handling and displaying video. Windows 3.x incorporates a 16-bit Video for Windows. Windows 95 and Windows NT both incorporate a 32-bit Video for Windows.
Variable Bit Rate. In video coding, the bitrate of the encoded video stream varies over time. Sometimes the video is encoded with a fixed quantization factor resulting in varying bitrates and varying perceived quality. Sometimes the video is encoded with a fixed perceived quality which usually results in varying bitrate.
Video Quality Experts Group. A committee within the International Standards Organization to establish a standard for measurement of the quality of compressed digital video.
Virtual Device Driver. A type of device driver for Microsoft Windows 3.x and Windows 95.
The color space used in the CCIR-601 digital video specification.
The color space used in the NTSC analog television standard.
The color space used in the PAL analog television standard.
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The following people have contributed ideas, suggestions, criticisms, and information to the AVI Overview: John Avis (information on Video for DOS) Jens Mutschke Q-Team Dr. Knabe GmbH John Whelan Dublin City University Victor Rutman Netvision Wolfgang Hesseler QuickView for DOS Marcus Moenig MainConcept Dave Wilson Rockwell/Brooktree Steve P. (no full last name, information on CorelMove 4.0) Dennis Strauch Tom Harding Practice Corporation Alexander Grigoriev Michael Caracena AVI Constructor Ashley Jacobs Mystech Associates Bernd Schoenes WashDC@aol.com (information on BinHex and AVI) Kevin McKinnon Dowco Computer Systems (info on IFF file format and RIFF) Tom Lane (Independent JPEG Group) Cindy Fuhrman Techsmith Corporation ted_klugman@usa.net (information on DMB1 four character code) Timothy Barr (information on Premiere AVI to GIF89a plug-in) Special thanks to: Desktop Video Expert Center/NASA Ames Research Center Return to Top NOTE: Suggestions, additions, and corrections are welcome. Please send to