Sustainability of Digital Formats: Planning for Library of Congress Collections
Sustainability of Digital Formats: Planning for Library of Congress Collections |
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | RealAudio, AAC Codec |
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| Description | Audio compression codec recommended 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." The Wikipedia article on RealAudio (consulted February 15, 2011) states that the codec is MPEG-4 HE-AAC (see Notes below). |
| Production phase | Generally a final-state (end-user delivery) format. |
| Relationship to other formats | |
| Used by | RealAudio_10, RealAudio, Version 10 |
| LC experience or existing holdings | See RealAudio_10 |
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| LC preference | See RealAudio_10 |
| Disclosure | See RealAudio_10 |
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| Documentation | See RealAudio_10 |
| Adoption | See RealAudio_10 |
| Licensing and patents | See RealAudio_10 |
| Transparency | See RealAudio_10, and AAC_MP4 Advanced Audio Coding, MPEG-4. |
| Self-documentation | See RealAudio_10 |
| External dependencies | See RealAudio_10 |
| Technical protection considerations | See RealAudio_10 |
| Sound | |
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| Normal rendering | Good support |
| Fidelity (high audio resolution) | Good; promotional literature says that this codec provides "the highest quality listening experience for consumer music services." |
| Multiple channels | See AAC_MP4 |
| Support for user-defined sounds, samples, and patches | Not applicable |
| Tag | Value | Note |
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| Filename extension | Not applicable. |
See RealAudio_10 |
| Internet Media Type | Not applicable. |
See RealAudio_10 |
| Magic numbers | Not applicable. |
See RealAudio_10 |
| Microsoft FOURCC | raac |
For the LC-AAC codec (RealAudio 9); this fourcc code will appear in the RealAudio_10 file wrapper |
| Microsoft FOURCC | racp |
For the HE-AAC codec (RealAudio 10); this fourcc code will appear in the RealAudio_10 file wrapper. |
| Pronom PUID | See note. | PRONOM has no corresponding entry as of July 2022. |
| Wikidata Title ID | See related format. | See RealAudio Version 10 |
| General | There are two HE-AAC profiles, as described in the Wikipedia article on AAC (consulted in February 2011): (1) High Efficiency AAC Profile defined in 2003, uses AAC-LC, SBR, and (2) High Efficiency AAC v2 Profile, defined in 2006, uses AAC-LC, SBR, PS. The compiler of this description does not know which HE profile is used by RealAudio, unless the FOURCC codes for "HE" and "LC" simply refer to these two profiles. |
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| History |
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