[Ffmpeg-devel] Re: I want to know what data set to AVCodecContext for H.264

Rich Felker dalias
Sun Jun 26 17:22:05 CEST 2005

On Sun, Jun 26, 2005 at 12:26:46PM +0200, bond wrote:
> > On Saturday 25 June 2005 11:54, bond wrote:
> > [...]
> > > its indeed often the case that mpeg-4 part2 encoders outputting to .avi
> > > place the vol together with the i-frames, because avi seems to require
> this
> >
> > wrong, avi doesnt require it, its just the way divx did it and everyone
> not
> > wanting to break compatibility did it that way too
> well i assume when you want to easily be able to cut such mpeg4-in-avi files
> placing the vol together with the i-frames is maybe not a must, but makes
> things easier. and as you said its a defacto "standard" to group the two
> together

It's just as easy to cut if the vol header is where it belongs: in the
extradata. The people who made divx are just stupid.

> > > but it has to be stored only once
> > > on a seperated place from the video data. ffmpeg doesnt do this, which
> is
> > > also one of the problems with its .mp4 muxing
> >
> > this is not true, ffmpeg does store the global headers like VOL at the
> correct
> > place when encoding mpeg4 it just doesnt support extracting these headers
> > during stream copy, so .mp4->.mp4 or mpeg4 encoding should be fine
> avi->.mp4
> > and mpeg4-es -> .mp4 are not
> ok, so my statement is true when doing direct stream copying. would be great

No, it's true when doing direct streamcopy from a broken container to
a good one, or vice versa. As long as both containers are good or both
are broken it should work fine..


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