[FFmpeg-devel] [RFC/PATCHES] AAC LATM decoder

Janne Grunau janne-ffmpeg
Sun Oct 17 12:39:33 CEST 2010


I'm too annoyed by LATM in MPEG-TS to get the chained demuxers working.
The last annoyance which triggered my capitulation was that multiple LATM
frames are packed into a single PES packet.

Based on one of Paul Kendall's libfaad LATM decoder patches I wrote a
decoder using FFmpeg's AAC decoder.

I know that it's technically unclean but it's vastly simpler and less
annoying for the AAC LATM usage we see. All current digital TV
transmission use only a single stream in LATM. I have even samples with
multiple LATM elementary stream in MPEG-TS for a single program.

One (currently theoretical) advantage of the decoder approach over the
demuxer approach is that it could avoid the copying of the unaligned
aac data by passing the GetBitContext to the AAC decoder.

I've committed a version of this patch to MythTV's libavcodec copy. So
we will see in the next days if it causes trouble or doesn't work with
certain real life streams.


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