Sustainability of Digital Formats
 Planning for Library of Congress Collections

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RealAudio, AAC Codec

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Table of Contents
Identification and description
Local use
Sustainability factors
Quality and functionality factors (sound)
File type signifiers
Notes
Format specifications
Useful references
Format Description Properties
• ID: fdd000056
• Short name: RealAudio_AAC
• Content categories: sound
• Format category: bitstream encoding, file format
• Last significant update: 2004-05-03

Identification and description Explanation of format description terms

Full nameRealAudio, Version 10, AAC Codec
DescriptionRecommended by RealMedia for use when delivered bitrates greater than 128 kb/s. RealMedia promotional literature states "for consumer music services, as well as easy transfer and playback compatibility to the extensive range of portable and mobile devices that support AAC."
  Production phase  Generally a final-state (end-user delivery) format.
Relationship to other formats 
  Subtype ofRealAudio_10
  ContainsAAC (MPEG-2 Advanced Audio Coding)

Local use Explanation of format description terms

LC experience or existing holdingsSee RealAudio_10
LC preferenceSee RealAudio_10

Sustainability factors Explanation of format description terms

DisclosureSee RealAudio_10
  DocumentationSee RealAudio_10
AdoptionSee RealAudio_10
  Licensing and patent claimsSee RealAudio_10
TransparencySee RealAudio_10, and AAC (MPEG-2 Advanced Audio Coding).
Self-documentationSee RealAudio_10
External dependenciesSee RealAudio_10
Technical protection considerationsSee RealAudio_10

Quality and functionality factors (sound) Explanation of format description terms

Normal renderingGood support.
Fidelity (support for high audio resolution)Good; promotional literature says that this codec provides "the highest quality listening experience for consumer music services."
Support for multiple channelsSee RealAudio_10
Support for downloadable or user-defined sounds, samples, and patchesNot applicable
Functionality beyond normal video renderingSee RealAudio_10

File type signifiers Explanation of format description terms

Tag typeValueNote
Filename ExtensionraNote that streaming applications require an associated ram (RealMedia Metafile) file.
Internet Media TypeSee RealAudio_10 
Magic numbersSee RealAudio_10 

Notes Explanation of format description terms

General 
History 

Format specifications Explanation of format description terms

URLs

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Useful references

URLs
See RealAudio_10

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Last Updated: 03/ 7/2007