[Ffmpeg-devel] Re: [PATCH] non conformance to 3GP format (3GP TS 26.244 v 6.5.0 2006/06) 2nd try

[Michael Niedermayer]

Hi

On Sun, Aug 06, 2006 at 10:13:09PM +0200, Baptiste Coudurier wrote:
> Hi
> 
> Michael Niedermayer wrote:
> >> [...]
> >>
> >> Michael, do you think we should keep using AVI fourcc ? The more I read
> >> specs and the more I feel we should not do that and strictly mux
> >> according to specs.
> > 
> > hmm, where do we use avi fourcc in mov/mp4 except if theres no mov fourcc
> > maybe?
> 
> Yes when there is no mov fourcc. Personnaly I would prevent using them
> except manually when they use vtag.

what about requireing -strict -1 ?


> 
> >> [...]
> >> -    }
> >> +    /* FIXME not sure, ISO 14496-12 specifies either 1 or 2, no samples found where channels > 2 */
> >> +    if (track->mode == MODE_MOV || (track->mode == MODE_MP4 && track->enc->channels < 2))
> >> +        put_be16(pb, track->enc->channels);
> >> +    else
> >> +        put_be16(pb, 2); /* Reserved */
> > 
> > does the spec just not specify how to store streams with more then 2 channels
> > or does it explicitly say that >2 channels audio should have 2 in the channels
> > field?
> 
> 
> Quoting ISO 14496-12:
> "template unsigned int(16) channelcount = 2;"
> 
> "ChannelCount is either 1 (mono) or 2 (stereo)"
> 
> Would mean 2 is default value.
> 
> Like I said I'm not sure. Im looking for ISO 14496-3 AMD 3 which
> specifies mp3on4, mp3 5:1. Maybe they override specs for mp4, maybe not.
> 
> All mp3on4 5:1, vorbis 5:1, aac 5:1 samples I could find have 2 for
> channelcount, while mov with 5:1 from apple have 6 as channelcount.

hmm, hmmmmmm :(
i still think channel count is the count of channels and not 2 ...
so unless this breaks something my vote would be to store the correct
number of channels, after all the specs you quote dont say store 2 if
there are more then 2 channels they just dont say anything about more
then 2 ...


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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