[FFmpeg-user] ffmpeg treats m4v as container not elementry video format

[Francois Visagie]

> -----Original Message-----
> From: ffmpeg-user-bounces at ffmpeg.org [mailto:ffmpeg-user-
> bounces at ffmpeg.org] On Behalf Of Carl Eugen Hoyos
> Sent: 23 January 2013 10:43
> To: ffmpeg-user at ffmpeg.org
> Subject: Re: [FFmpeg-user] ffmpeg treats m4v as container not elementry
> video format
> 
> 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 not check.) 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 find it.
> 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).

Got it, thanks for the thorough explanation.