[FFmpeg-devel] Timestamp issues in live RTP->mpegts bridges

[Michael Niedermayer]

On Tue, Jan 20, 2009 at 01:32:42PM +0100, Luca Abeni wrote:
> Hi Alexandre,
[...]
> > However I worked around that by putting an 'fwrite()' (conditioned by an 
> > environment variable) in my H263-specific parse_packet function, as 
> > suggested by Michael last week.
> > 
> > The generated flat H263 bitstream is played by mplayer, but too fast.
> > 
> > The output of ffmpeg -i is:
> > 
> >   Input #0, h263, from 'a.263':
> >     Duration: N/A, bitrate: N/A
> >       Stream #0.0: Video: h263, yuv420p, 176x144 [PAR 12:11 DAR 4:3], 
> > 29.97 tb(r)
> >   At least one output file must be specified
> > 
> > So it is wrongly guessing 29.97.
> 
> I suspect the frame rate is stored in the bitstream, and the codec is
> reading such value, which turns out to be wrong... I do not know if this
> is a bug in the decoder, or in the enocoder...
> This looks like something for the codecs guys: can you open an issue on
> the bugtracker, or send an email in a new thread describing this problem?
> (you will have to upload the H.263 bitstream on upload.ffmpeg.org, as
> indicated in the bugreport page).

there is no fixed framerate value in h263
there are timestamps and a fixed 30000/1001 timebase

a few printf/av_log() that print what the spec calls "temporal reference"
and the AVFrame.pts as well as wat ffmpeg.c does with it should shed some
light on where things go wrong

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The greatest way to live with honor in this world is to be what we pretend
to be. -- Socrates
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