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WMV (Windows Media Video) File Format
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Format Description Properties
• ID: fdd000091
• Short name: WMV
• Content categories: moving image
• Format category: file format
• Last significant update: 2007-08-07
Identification and description 
| Full name | WMV (Windows Media Video) File Format |
| Description | File format based in ASF (Advanced Systems Format) that wraps a video bitstream. This web site documents versions of the format that contain bitstreams encoded by Windows Media Video 9, which is also known as VC-9. Some WMV files may also employ Windows Media Video 7 and 8 codecs. |
| Production phase | Often final state format for enduser delivery; sometimes a middle-state format, e.g., a high-quality video representation for archiving or as a source when producing lower-resolution streaming versions. |
| Relationship to other formats | |
| Subtype of | ASF (Microsoft Advanced Systems Format) |
| Has subtype | WMV_WMV9 (file with specific video codec) |
| Has subtype | WMV_WMV9_PRO (file with specific video codec) |
| Has subtype | WMV file-format variants defined by other video codecs, not documented at this time. |
Local use
| LC experience or existing holdings | None |
| LC preference | For audio, WAVE_LPCM is preferred.
For file-based compressed video, bitstreams encoded as MPEG-2 (various profiles, the higher the better) or MP4-FF_2 (MPEG-4, various encodings and profiles, the higher the better) are preferred.
For uncompressed or losslessly compressed video, which is generally preferred to lossy compressed, MXF may be preferred as a wrapper; this topic will be developed in a future investigation. |
Sustainability factors
| Disclosure | Microsoft's proprietary ASF wrapper format is fully documented. For information about the disclosure of information about the bitstreams wrapped by WMV, see the descriptions of individual codecs listed under Relationships, above. |
| Documentation | For wrapper documentation, see ASF. See also citations in Useful references below. |
| Adoption | Unknown to the compilers of this page. News coverage in early 2004 reported that the underlying encoding (VC-9, presumably the same as WMV9_PRO) received "provisional approval" for use in DVD systems, where it will coexist with MPEG-2. |
| Licensing and patent claims | See ASF. |
| Transparency | See information on versions that incorporate different codecs: WMV_WMV9 and WMV_WMV9_PRO. |
| Self-documentation | See ASF |
| External dependencies | None |
| Technical protection considerations | See ASF |
Quality and functionality factors
| Normal rendering | Good support. |
| Clarity (support for high image resolution) |
Moderate to excellent, given that this is a format used for compression. Outcome will depend on the type and level of compression; Microsoft promotional materials state that WMV_WMV9_PRO can deliver "ultra-high" quality, including HDTV (High Definition TeleVision). As of 2004, a 720p HDTV signal can be encoded as 1280x720 pixels per frame; in later years, it will be possible to encode 1080p. |
| Fidelity (support for high audio resolution) | Moderate to excellent; outcome will depend on codec selected and upon the type and level of compression. |
| Support for multiple sound channels | 5.1 surround sound supported in WMV_WMV9_PRO |
| Support for downloadable or user-defined sounds, samples, and patches | [Not investigated at this writing.] |
| Functionality beyond normal rendering | [Support for various elements offered by ASF] |
File type signifiers
Notes
Format specifications
URLs
• Advanced Systems Format (ASF) Specification from Microsoft (as of April 5, 2007, this was revision 01.20.03, December 2004; http://www.microsoft.com/windows/windowsmedia/format/asfspec.aspx)
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Useful references
URLs
• Menu that provides access to Introduction to Digital Media and Windows Media 9 Series (http://www.microsoft.com/windows/windowsmedia/technologies/overview.aspx)
• Codecs 101 (http://www.microsoft.com/windows/windowsmedia/howto/articles/codecs.aspx)
• Advanced Encoding Techniques with Windows Media 9 Series (http://www.microsoft.com/windows/windowsmedia/howto/articles/AdvancedEncoding.aspx)
• Overview of the ASF Format (http://msdn2.microsoft.com/en-us/library/aa390652.aspx)
• Architecture of Windows Media Rights Manager (http://www.microsoft.com/windows/windowsmedia/howto/articles/drmarchitecture.aspx)
• Windows Media Licensing(http://www.microsoft.com/windows/windowsmedia/licensing/licensing.aspx)
• Microsoft video codecs and related matters discussed in 2006 by Microsoft vice president Amir Majidimehr (http://www.edn.com/index.asp?layout=article&articleid=CA6391444&industryid=22043)
• IANA MIME Media Types (http://www.iana.org/assignments/media-types/)
• Gary Kessler's File Signatures Table (http://www.garykessler.net/library/file_sigs.html)
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Last updated: 08/20/2007
