Apple Lossless Audio Coding: Difference between revisions
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Lossless audio coding using linear prediction with Golomb-Rice coding of the difference. Similar to FLAC, although the bitstreams are not compatible. Usually stored in an [[Apple QuickTime|MP4]] container, as a private extension since it is not part of the MPEG-4 standard. | Lossless audio coding using linear prediction with Golomb-Rice coding of the difference. Similar to FLAC, although the bitstreams are not compatible. Usually stored in an [[Apple QuickTime|MP4]] container, as a private extension since it is not part of the MPEG-4 standard. | ||
=== Frame Header === | |||
{| border="1" | |||
! Syntax !! Number of bits !! Semantics | |||
|- | |||
| channels || 3 || Number of channel -1 (Should be the same than in extradata ???) | |||
|- | |||
| ??? || 4 || ??? | |||
|- | |||
| ??? || 12 || ??? | |||
|- | |||
| hassize || 1 || the output sample number is stored in the header | |||
|- | |||
| wasted_bytes || 2 || unknow (same as flac ???) | |||
|- | |||
| isverbatim || 1 || if 1, the data is not compressed | |||
|- | |||
| if (hassize) { || || | |||
|- | |||
| outputsamples || 32 || number of samples | |||
|- | |||
| } || || | |||
|} | |||
[[Category:Lossless Audio Codecs]] | [[Category:Lossless Audio Codecs]] | ||
[[Category:Audio Codecs]] | [[Category:Audio Codecs]] |
Revision as of 10:14, 14 May 2006
- FOURCCS: alac
- Company: Apple
- Technical Description: http://craz.net/programs/itunes/alac.html
Lossless audio coding using linear prediction with Golomb-Rice coding of the difference. Similar to FLAC, although the bitstreams are not compatible. Usually stored in an MP4 container, as a private extension since it is not part of the MPEG-4 standard.
Frame Header
Syntax | Number of bits | Semantics |
---|---|---|
channels | 3 | Number of channel -1 (Should be the same than in extradata ???) |
??? | 4 | ??? |
??? | 12 | ??? |
hassize | 1 | the output sample number is stored in the header |
wasted_bytes | 2 | unknow (same as flac ???) |
isverbatim | 1 | if 1, the data is not compressed |
if (hassize) { | ||
outputsamples | 32 | number of samples |
} |