Sustainability of Digital Formats: Planning for Library of Congress Collections

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WMA (Windows Media Audio) File Format

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

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 end user 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, Windows Media Audio File with WMA9 Codec
    Has subtype WMA_WMA9_PRO, Windows Media Audio File with WMA9 Professional Codec
    Has subtype WMA_WMA9_LL, Windows Media Audio File with WMA9 Lossless Codec
    Has subtype WMA file-format variants defined by other audio codecs, not documented at this time.

Local use Explanation of format description terms

LC experience or existing holdings The Library of Congress has a small amount of Windows Media Audio files in its collections.
LC preference See the Library of Congress Recommended Formats Statement for format preferences for audio works.

Sustainability factors Explanation of format description terms

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 patents 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 Explanation of format description terms

Normal rendering Good support.
Fidelity (high audio resolution) Moderate to excellent; outcome will depend on codec selected and upon the type and level of compression.
Multiple channels Supported in WMA_WMA9_PRO
Support for 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 and format identifiers Explanation of format description terms

Tag Value Note
Filename extension wma
Internet Media Type audio/x-ms-wma
Selected from The File Extension Source. Also in LC implementation of Apache mime.types.
Magic numbers Hex: 30 26 B2 75 8E 66 CF 11 A6 D9 00 AA 00 62 CE 6C
ASCII: 0&²u.fÏ.¦Ù.ª.bÎl
For extension asf (see ASF), from Gary Kessler's File Signatures Table.
ASF GUID F8699E40-5B4D-11CF-A8FD-00805F5C442B
Globally Unique IDentifier for ASF_Audio_Media; from Advanced Systems Format (ASF) Specification.
Pronom PUID fmt/132
Wikidata Title ID Q2194

Notes Explanation of format description terms


Format specifications Explanation of format description terms

Useful references


Last Updated: 05/01/2023