Sustainability of Digital Formats
 Planning for Library of Congress Collections

Format Description Categories >> Browse Alphabetical List>> Back

Identification and description

Full name	Windows Media 9 Audio Codec
Description	Audio bitstream produced by the Windows Media 9 audio codec.
Production phase	Generally used in files that represent a final-state format for end-user delivery.
Relationship to other formats
Used by	WMA_WMA9, Windows Media Audio file with WMA9 codec

Local use

LC experience or existing holdings
LC preference	See WMA

Sustainability factors

Disclosure	Proprietary. Developed by Microsoft.
Documentation	Specifications not disseminated.
Adoption	Not known to the compilers of this document; the WMA file format is widely adopted.
Licensing and patents	See ASF for link to pages covering licensing of Windows Media and the Advanced Systems Format.
Transparency	Depends upon algorithms and tools to read; will require sophistication to build tools.
Self-documentation	Not applicable
External dependencies	None
Technical protection considerations	Not applicable

Quality and functionality factors

Sound
Normal rendering	Good support.
Fidelity (high audio resolution)	From the codecs page at the Microsoft Windows Media web site (consulted September 1, 2010): "For use in most scenarios. This codec . . . supports VBR [variable bit rate] audio that enables even higher quality audio at smaller file sizes. Windows Media Audio 9 is backward-compatible with previous Windows Media Audio-compatible decoders." The site indicates that higher quality is provided by WMA9_PRO.
Multiple channels	None
Functionality beyond normal rendering	Not applicable

File type signifiers

Tag	Value	Note
Filename extension	Not applicable.
Internet Media Type	Not applicable.
Magic numbers	Not applicable.

Notes

General
History

Format specifications

• See Disclosure under Sustainability factors.

Useful references