Sustainability of Digital Formats
 Planning for Library of Congress Collections

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RealAudio, RealAudio 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: fdd000055
• Short name: RealAudio_RA
• 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, RealAudio Codec
DescriptionRecommended by RealMedia for use when delivered bitrates are 128 kb/s or less, for lower bandwidth streaming.
  Production phase  Generally a final-state (end-user delivery) format.
Relationship to other formats 
  Subtype ofRealAudio_10
  ContainsRealAudio codec, not separately documented

Local use Explanation of format description terms

LC experience or existing holdingsRealAudio, including versions earlier than 10 and using the RealAudio codec, is used as streaming format for most audio presented in American Memory, with a target data rate oriented to users with dial-up modems.
LC preferenceConsiderations of quality and sustainability mean that WAVE_LPCM is preferred over RealAudio; considerations of sustainability mean that MP3 is preferred.

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
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)Moderate; promotional literature says that this codec is "renowned for delivering near CD quality at 64 kbps."
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