[FFmpeg-devel] [PATCH]lavf/mov: Support alac extradata in wave atom
Carl Eugen Hoyos
cehoyos at ag.or.at
Mon Aug 3 12:32:02 CEST 2015
Paul B Mahol <onemda <at> gmail.com> writes:
> > Attached patch fixes ticket #4747 for me,
> > I don't know how to detect that the wave
> > atom contains no frma / alac atom...
> And that is mentioned because?
The file from ticket #4747 does not contain an
alac atom which is required for alac decoding.
Instead it contains the necessary data in the
wave atom (where you normally would find the
alac atom). To distinguish, it would be
necessary to look "into" the wave atom to know
if it contains an alac atom or not.
I meanwhile found that the mpeg demuxer
sometimes seeks eight bytes back which I will
probably copy. The alternative, iiuc, would be
to copy the whole wave atom into a buffer and
call mov_read_default() from the wave_read()
function with that buffer.
But this should not be necessary if somebody
can confirm that it is ok to seek back x bytes
in a demuxer.
As an alternative the current version could
also be committed, I am not sure.
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