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WMA (Windows Media Audio) File Format
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Format Description Properties
• ID: fdd000027
• Short name: WMA
• Content categories: audio
• Format category: file format
• Last significant update: 2007-04-07
Identification and description 
| Full name | WMA (Windows Media Audio) File Format |
| Description | File format based in ASF (Advanced Systems Format) that wraps an audio bitstream. This web site documents versions of the format that contain bitstreams encoded by Windows Media Audio 9. Some WMA files may also employ Windows Media Audio 7 and 8 codecs. |
| Production phase | Usually a final state format for enduser delivery; sometimes a middle-state format, e.g., a high-quality audio 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 | WMA_WMA9 (file with specific audio codec) |
| Has subtype | WMA_WMA9_PRO (file with specific audio codec) |
| Has subtype | WMA_WMA9_LL (file with specific audio codec) |
| Has subtype | WMA file-format variants defined by other audio codecs, not documented at this time. |
Local use
| LC experience or existing holdings | None |
| LC preference | General preference for recorded sound is WAVE_LCPM. Within the WMA family, WMA_WMA9_LL (lossless codec) is preferred. |
Sustainability factors
| Disclosure | Microsoft's proprietary ASF wrapper format is fully documented. For information about the disclosure of information about the bitstreams wrapped by WMA, see the descriptions of individual codecs listed under Relationships, above. |
| Documentation | For wrapper documentation, see ASF. See also citations in Useful references below. |
| Adoption | Widely adopted. |
| Licensing and patent claims | See ASF. |
| Transparency | See information on versions that incorporate different codecs: WMA_WMA9, WMA_WMA9_PRO, and WMA_WMA9_LL. |
| Self-documentation | See ASF |
| External dependencies | None |
| Technical protection considerations | See ASF |
Quality and functionality factors
| Normal rendering | Good support. |
| 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 | Supported in WMA_WMA9_PRO |
| Support for downloadable or user-defined sounds, samples, and patches | [Appears to be some support for MIDI_SD; 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)
• 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 05/21/2007
