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

Alex Converse alex.converse
Wed Mar 18 14:49:08 CET 2009

On Tue, Mar 17, 2009 at 10:09 PM, Jethro Walters
<turkeyman121 at yahoo.co.uk> wrote:
> Hey guys.
> 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.
> Regards,
> Jethro Walters

At this point ALS has picked up very little steam in the wild and
probably won't be seen in FFmpeg anytime soon. A subset of SLS is
currently getting a push under the name HD-AAC. I imagine if it takes
off FFmpeg will get support for it. Right now we can play the LC core
of SLS files.

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