[FFmpeg-devel] AAC ALS (lossless) and SLS (scalable lossless)

Robert Swain robert.swain
Wed Mar 18 03:19:32 CET 2009

Hello Jethro,

On 18/3/09 02:09, Jethro Walters wrote:
> Was doing a little research on both AAC ALS and SLS. ALS is the official lossless format for AAC, and a completely separate codec to AAC. SLS is the extension to AAC that adds a lossless reproduction layer on top of the lossy AAC file, sort-of like WavPack's Hybrid lossy/lossless mode.
> Is there any plan to implement these formats in ffmpeg / libavcodec? I feel that having one or both in ffmpeg would give them more chance of moving more into the mainstream, but there seems to be little information around about both formats. Anybody know anything further? Before you ask, no I'm not volunteering to code these, as my coding skills are in dire need of improvement.

ALS has been proposed as a Summer of Code project again. There was some 
noise on FFmpeg-user about SLS recently. Someone wanted to demux the SLS 
data and feed it and the output of the LC AAC decoder into their own 
decoder. I'm not sure what their decoder is or what they intend to do 
with it.


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