Sustainability of Digital Formats
Planning for Library of Congress Collections
Sustainability of Digital Formats
|
|
|
|
| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | AVI (Audio Video Interleaved) |
| Description | File format for moving image content that wraps a video bitstream with other data chunks, e.g., audio. |
| Production phase | Often a middle-state format, e.g., the video source when producing lower-resolution streaming versions; sometimes a final state format for enduser delivery. |
| Relationship to other formats | |
| Subtype of | RIFF (Microsoft Resource Interchange File Format) |
| Has subtype | AVI_Cinepak, AVI, Cinepak Codec |
| Has subtype | AVI_DivX, AVI, DivX codec |
| Has subtype | AVI_DV, AVI, DV Digital Video |
| Has subtype | AVI_Indeo, AVI, Indeo Codec |
| Has subtype | AVI_MJPEG, AVI, MJPEG Codec |
| Has subtype | AVI_J2K, AVI, JPEG 2000 Codec |
| Has subtype | AVI files containing streams produced by other video codecs, including uncompressed and lossless video, not documented at this time. |
| Has subtype | AVI_OpenDML (format extensions). Not documented at this time. |
| May contain | WAVE, WAVE Audio File Format |
| May contain | MP3_CBR, MP3 Audio Encoding, Constant Bit Rate |
| LC experience or existing holdings | American Memory produced AVI_Indeo files in 1992 and 1993, using version 3.1 or 3.2 of the Indeo codec, at 15 fps and 320x240 pixels, and yielding a data rate of about 188 Kb/s. These AVI files were retired and replaced by MPEG-1 and QuickTime files in 1994 and 1995. |
| LC preference | No preference has been established for video wrappers. Discussion in the Motion Picture, Broadcasting, and Recorded Division during 2004-06 has suggested that losslessly compressed JPEG 2000 frame images would be a good encoding option for reformatted video. Wrapper alternatives for these images and accompanying audio include MXF, AAF_1_1, and MJP2_FF. Encoding preferences for file-based lossy compressed video are less clear, but there is interest in bitstreams that conform to or approximate MPEG-2-422 (4:2:2 Profile) at Main Level (aka MPEG-2 422@ML) or MPEG-2-MP (Main Profile) at Main Level (aka MPEG-2 MP@ML). These may also be wrapped in MXF, AAF_1_1. The investigation of options continues. |
| Disclosure | Fully documented. Proprietary file format developed by Microsoft and IBM as part of RIFF, the Resource Interchange File Format for Windows 3.1. For information about the disclosure of information about the bitstreams wrapped by AVI, see the descriptions of individual codecs listed under Relationships, above. |
| Documentation | Specifications available from third parties; for example, the Multimedia Programming Interface and Data Specifications 1.0 (Issued as a joint design by IBM Corporation and Microsoft Corporation, August 1991), is available online from http://www.kk.iij4u.or.jp/~kondo/wave/mpidata.txt and other sites. Additional information may be found at John McGowan's AVI Overview (http://www.jmcgowan.com/avi.html) and http://www.opennet.ru/docs/formats/avi.txt. Documentation of the OpenDML extensions available from Morgan Multimedia (http://www.morgan-multimedia.com/download/odmlff2.pdf). Some additional citations in Useful references below. |
| Adoption | Widely adopted for video production and filemaking. Adoption may not extend to all permitted codecs and other features. One commentator wrote in 2000 that the introduction of Microsoft's Advanced System Format or ASF had "pushed to one side" the OpenDML effort, which dates from 1996-97. |
| Licensing and patent claims | [Unknown, probably none] |
| Transparency | See information on the codecs incorporated in AVI files: MJPEG, Indeo_3, Indeo_5, Cinepak, and DivX_5. |
| Self-documentation | Technical information in header chunks (e.g., hdrl, movi, and others); descriptive metadata may appear in a RIFF INFO chunk. |
| External dependencies | None |
| Technical protection considerations | None |
| Normal rendering | Good support. |
| Clarity (support for high image resolution) | Moderate to good, given that this is a format typically used for compression and that most implementations do not support interlaced video. Outcome will depend on the type and level of compression, and the encoder used. Extent of use of uncompressed video bitstream unknown. High resolution work is limited in the Windows environment due to file size limits (2 GB with FAT 16 technology; theoretical 8 GB with later technologies). The OpenDML extensions were intended to increase quality in professional applications by supporting the representation of interlaced video (60 fields per second), 24 fps for content from motion picture film, and other features. |
| Fidelity (support for high audio resolution) | Good to excellent, given that the options for audio are those available in the MP3_CBR and WAVE formats. |
| Support for multiple sound channels | [Limited to mono and stereo sound?] |
| Functionality beyond normal video rendering | [Support for text streams?] |
| Tag type | Value | Note |
| Filename Extension | avi | |
| Internet Media Type | video/vnd.avi | From http://www.iana.org/assignments/wave-avi-codec-registry. No examples found in IANA MIME Media Types. |
| Internet Media Type | video/avi video/msvideo video/x-msvideo image/avi application/x-troff-msvideo audio/avi | Selected from The File Extension Source. |
| Magic numbers | Hex: 52 49 46 46 xx xx xx xx 41 56 49 20 4C 49 53 54 ASCII: RIFF....AVILIST | From Gary Kessler's File Signatures Table. |
| Microsoft FOURCC | Varies according to the video codec selected; see the Microsoft registry. | |
| Microsoft WAVE format registry | Varies according to the audio codec selected; see the Microsoft registry. |
| General | |
| History | Format created by Microsoft and introduced with Windows 3.1. In its first version, picture size was limited to 160x120 pixels and 15 frames per second; over time, capabilities were extended to larger picture sizes and higher frame rates. |
URLs
Multimedia Programming Interface and Data Specifications 1.0, issued as a joint design by IBM Corporation and Microsoft Corporation, August 1991; available online from http://www.kk.iij4u.or.jp/~kondo/wave/mpidata.txt and other sites.
Print
URLs
• John McGowan's AVI Overview (http://www.jmcgowan.com/avi.html)
• John McGowan's AVI Audio and Video Codecs (http://www.jmcgowan.com/avicodecs.html)
• http://www.opennet.ru/docs/formats/avi.txt
• Documentation of OpenDML extensions (http://www.morgan-multimedia.com/download/odmlff2.pdf)
• AVI-RIFF information from the Microsoft Developer Site
(http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wcegmm/html/wcegmm_dshow_avi_riff_form.asp)
• List of chunks in a RIFF-AVI file (http://pvdtools.sourceforge.net/aviformat.txt)
• Microsoft registry of FOURCC codes and WAVE format indicators (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnwmt/html/registeredfourcccodesandwaveformats.asp). The archived 2001 version of this registry is at http://www.microsoft.com/whdc/archive/fourcc.mspx.
• Gary Kessler's File Signatures Table (http://www.garykessler.net/library/file_sigs.html).
• Microsoft's MSDN Library Archive (http://msdn.microsoft.com/archive/default.asp).
• Internet Assigned Numbers Authority (IANA) documents regarding Internet Media Type/MIME Type (http://www.iana.org/assignments/media-types/) and an AVI codec registry (http://www.iana.org/assignments/wave-avi-codec-registry).
• McGill University Multimedia Signal Processing site (http://www.tsp.ece.mcgill.ca/MMSP/Documents/AudioFormats/WAVE/Docs/MMREG.H) and their page documenting the WAVE format (http://www.tsp.ece.mcgill.ca/MMSP/Documents/AudioFormats/WAVE/Docs/MMREG.H).
Print
|
|