RealAudio, RealAudio Codec

Sustainability of Digital Formats Planning for Library of Congress Collections

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RealAudio, RealAudio Codec

Table of Contents

Identification and description
Local use
Sustainability factors
Quality and functionality factors
File type signifiers
Notes
Format specifications
Useful references

Format Description Properties

ID: fdd000055
Short name: RealAudio_RA
Content categories: sound
Format Category: encoding
Other facets: unitary, binary, sampled
Last significant update: 2011-02-15
Draft status: Partial

Identification and description

Relationship to other formats
Full name	RealAudio, RealAudio Codec
Description	Audio compression codec recommended 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.
Used by	RealAudio_10, RealAudio, Version 10

Local use

LC experience or existing holdings	RealAudio, 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 preference	See RealAudio_10

Sustainability factors

Disclosure	See RealAudio_10
Documentation	See RealAudio_10
Adoption	See RealAudio_10
Licensing and patents	See RealAudio_10
Transparency	See RealAudio_10
Self-documentation	See RealAudio_10
External dependencies	See RealAudio_10
Technical protection considerations	See RealAudio_10

Quality and functionality factors

Sound
Normal rendering	Good support
Fidelity (high audio resolution)	Moderate; promotional literature says that this codec is "renowned for delivering near CD quality at 64 kbps."
Multiple channels	Not investigated
Support for user-defined sounds, samples, and patches	Not applicable

File type signifiers

Tag	Value	Note
Filename extension	Not applicable.	See RealAudio_10
Internet Media Type	Not applicable.	See RealAudio_10
Magic numbers	Not applicable.	See RealAudio_10
Microsoft FOURCC	lpcJ and 14_4	Reported in Wikipedia for IS-54 VSELP (RealAudio 1)
Microsoft FOURCC	28_8	Reported in Wikipedia for G.728 LD-CELP (RealAudio 2)

Notes

General	A number of additional Microsoft FOURCC values are reported in the Wikipedia RealAudio article (consulted February 17, 2012). Some are reported in RealAudio_AAC, RealAudio_LL, and RealAudio_MC. Others include dnet: Dolby AC3 (RealAudio 3), sipr: Sipro Lab Telecom ACELP-NET (RealAudio 4/5), cook: G2/Cook Codec (RealAudio 6), and atrc: Sony ATRAC3 (RealAudio 8).
History

Format specifications

See Disclosure under Sustainability factors.

Useful references

URLs

Wikipedia article RealAudio (http://en.wikipedia.org/wiki/RealAudio).

Last Updated: Friday, 17-Feb-2012 14:40:55 EST