[FFmpeg-devel] [PATCH]lavf/mov: Support alac extradata in wave atom
michael at niedermayer.cc
Mon Aug 3 21:57:50 CEST 2015
On Mon, Aug 03, 2015 at 10:32:02AM +0000, Carl Eugen Hoyos wrote:
> 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.
it is safe if ffio_ensure_seekback() is used with appropriate
arguments before these x bytes are read
(or the stream is seekable or ...)
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
No snowflake in an avalanche ever feels responsible. -- Voltaire
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