[FFmpeg-devel] [PATCH] code to parse mpeg4audio extradata

[Michael Niedermayer]

On Thu, Mar 27, 2008 at 03:04:38PM +0100, Michael Niedermayer wrote:
> On Thu, Mar 27, 2008 at 10:30:43AM +0100, Baptiste Coudurier wrote:
> > Hi,
> > 
> > Michael Niedermayer wrote:
> > > On Thu, Mar 27, 2008 at 12:42:56AM +0100, Baptiste Coudurier wrote:
> > >> Hi,
> > >>
> > >> Michael Niedermayer wrote:
> > >>> On Wed, Mar 26, 2008 at 10:14:47PM +0100, Andreas ?man wrote:
> > >>>> Michael Niedermayer wrote:
> > >>>>> On Wed, Mar 19, 2008 at 04:54:03PM +0100, Baptiste Coudurier wrote:
> > >>>>>> Hi,
> > >>>>>>
> > >>>>>> Here is a patch that adds parsing of mpeg4audio extradata, and retrieve
> > >>>>>> needed infos for decoders (only mp3on4 atm, but will be needed for aac),
> > >>>>>> and will be used by mov demuxer ideally to correctly compute sample rate
> > >>>>>> and channels.
> > >>>>>> Also extract common mpeg4audio code from aac_parser.c.
> > >>>>> Iam fine with this in priciple but i am unsure if the code does not maybe
> > >>>>> rather belong to libavformat.
> > >>>> If the AAC decoder should reuse the code i don't think it could belong
> > >>>> in lavf.
> > >>> Please elaborate
> > >>> my idea was that the mp4 demuxer would use this code to extract the various
> > >>> thing from the mp4 atoms in .mp4 and set things like sample_rate,...
> > >>> But maybe i misunderstood something?
> > >>>
> > >> Yes, the code will also be used by mp3on4 and aac decoders to fetch
> > >> sample rate, channels, sbr info from extradata. All decoders using
> > >> MPEG-4 audio system will do that basically.
> > > 
> > > From what you say it sounds like this clearly belongs in the mp4 demuxer
> > > and not in every decoder which could be stored in mp4.
> > > 
> > 
> > Huh, I don't understand.
> > How are decoders supposed to parse extradata, AAC GASpecificConfig for
> > example ? Duplicate the code ?
> 
> extradata should contain
> GASpecificConfig/CelpSpecificConfig/HvxcSpecificConfig/... (only one of
> these should be there)
> 
> The surrounding parts belong to the demuxer. The first 5? bits are yet

After thinking about this again, iam not sure anymore, .mp4 really is a mess
maybe it is simpler in practice to parse this in the decoders. Especially
if one consideres raw audio streams. So iam fine with the patch in principle
ill review it again in a moment.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Democracy is the form of government in which you can choose your dictator
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