[FFmpeg-user] ffmpeg treats m4v as container not elementry video format
Carl Eugen Hoyos
cehoyos at ag.or.at
Wed Jan 23 09:42:45 CET 2013
Francois Visagie <francois.visagie <at> gmail.com> writes:
> > You have to add the extradata to the output file:
> > $ ffmpeg -i input -vcodec copy -f m4v -vbsf dump_extra out.m4v
> What is this extradata and why does it need to be added in this
> instance and not normally when using iDevice format? Thanks.
The extradata is always required for MPEG4 decoding.
(That is what I assume because of the report, I did
If a "real" container (like mov) is chosen for
output, the muxer places the extradata into the
header of the output file where decoders will
If instead of a "real" container "m4v" (MPEG-4
elementary stream as opposed to mov variant "ipod")
is chosen, no extradata can be written by the muxer,
it gets lost and decoding is impossible.
The bitstream filter apparently takes the extradata
and places it into the first packet of the
videostream (or something similar).
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