[FFmpeg-devel] MP4A-LATM support?

Michael Niedermayer michaelni
Tue Nov 24 11:24:03 CET 2009

On Fri, Nov 13, 2009 at 12:33:40PM +0100, Luca Abeni wrote:
> Luca Abeni wrote:
> [...]
>> a patch was recently posted to implement support for MP4A-LATM in RTP.
>> I am currently working on that patch, and I am trying to understand
>> what's the better way to implement such functionality...
>> In order to avoid duplicate work and to prepare a patch that is not
>> consistent with the rest of ffmpeg, I have some questions about
> [...]
> Ok, thanks to everyone who replied and provided links and information.
> After a little bit of reading, I think I now have an idea about this
> LATM stuff. Of course, it can be wrong, so please correct me if I
> misunderstood something. Anyway, this is my understanding of the situation:
> 1) LATM can be seen as a different bitstream syntax for AAC (I hope I
>    am not oversimplifying anything, here... :)
> 2) codecs in libavcodec will see the "regular" AAC bitstream (with codec
> 3) muxers and demuxers in libavformat will see the LATM bitstream
> 4) someone between codec and muxer is in charge of transforming the
>    bitstream in LATM (this can be a bitstream filter, I suppose)
> 5) how can the muxer know if the bitstream is "regular AAC" or LATM?
>    I think we need a "fake" codec ID (CODEC_ID_LATM, or something like
>    this) for identifying LATM streams. When the AAC stream is transformed
>    in LATM (or vice-versa) by the bitstream filter, the codec ID is changed
>    from CODEC_ID_AAC to CODEC_ID_LATM (or vice-versa).
> Is this correct/reasonable? I am starting to work on the RTP muxer assuming
> that some filter provides it with the LATM stream (and a LATM codec ID),
> which simplifies things a lot :).

did you read the thread with subj
"Re: [FFmpeg-devel] [PATCH] seperate parser from codec selection"
i think that also contains some related discussions


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

When you are offended at any man's fault, turn to yourself and study your
own failings. Then you will forget your anger. -- Epictetus
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