[Ffmpeg-devel] [Ffmpeg-devel-old] Re: avi out is buggy

[Michael Niedermayer]

Hi

On Monday 09 May 2005 18:38, Rich Felker wrote:
> On Mon, May 09, 2005 at 02:31:54PM +0200, Michel Bardiaux wrote:
> > Erik Slagter wrote:
> > >On Mon, 2005-05-09 at 11:24 +0000, Thomas Herrmann wrote:
> > >>>stream copy from mpeg to avi isnt synchronizable, mpeg has timestamps,
> > >>>avi does not, so frame drop / audio resampling might be needed but its
> > >>>not possible with stream copy
> > >>>
> > >>>-> bug closed / invalid
> > >>
> > >>Ok, but your answer does not help me to generate usable video file.
> > >>
> > >>I was asking what output format and/or ffmpeg options should I use to
> > >>transcode
> > >>a MPEG file containing a MPEG2 video stream and an AC3 audio stream to
> > >> a video
> > >>file (avi, mpg, mov, ... ???) containing a h264 video stream and a
> > >> ac3/aac audion stream?
> > >>
> > >>I tried:
> > >>
> > >>ffmpeg -i sample_w_ac3.mpg -vcodec h264 -acodec copy -sameq -hq out.avi
> > >>
> > >>which leads to asynchronous output, so does:
> > >>
> > >>ffmpeg -i sample_w_ac3.mpg -vcodec h264 -acodec aac -sameq -hq out.avi
> > >
> > >How about using mp4 output container (which does understand timestamps).
> >
> > Since the posted commands produce a desynched avi from a file that is
> > said to play correctly in mplayer, one could deduce that the streams in
> > it are not inherently synchronized, but the synchro is maintained by the
> > timestamps themselves; in other words, as Michael wrote, at places there
> > are too many or not enough audio samples. Obviously that cant be done if
> > acodec=copy.
>
> Actually it can. Just leave 0byte packets in the avi to serve in place
> of timestamps. I thought lavf already did this..

hmm yes it should, but it cant drop frames, so it still wont work unless you 
set the framerate to a large enough value

[...]
-- 
Michael