[FFmpeg-devel] [PATCH]Reorder channels for some mov channel layouts

Carl Eugen Hoyos cehoyos at ag.or.at
Thu Jun 23 20:04:18 CEST 2011

Nicolas George <nicolas.george <at> normalesup.org> writes:

> Le quintidi 5 messidor, an CCXIX, Carl Eugen Hoyos a écrit :
> > Would that be sufficient for stream copy?
> > (I don't think so.)
> What would be the problem?
> The demuxer reads the tag, look-it up in the table, and sets the map in the
> context.
> The muxer looks at the map in the context, look-it up in the table, and
> writes the tag.

In this case, I prefer my solution;-)

> Anyway, insisting on stream copy rather than transcoding for PCM is rather
> moot, isn't it?
> > Sure, but I thought about moving it as soon as/if another codec needs it.
> 7- and 8-channels FLAC has also undefined channel layout and order, and
> would require external information for the mapping. But I suppose FLAC is
> not possible in this particular format anyway, is it?

No, I don't think so.

> By the way, what is the value of this CAFChannelLayoutTag when the codec
> encodes the channels by function rather than by number, like AAC or AC3?

The meaning of the tag is not depending on the codec (it has the same meaning
for AAC, ALAC and pcm), but pcm and its friends are the only cases that
currently need reordering.

Carl Eugen

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