[MPlayer-dev-eng] flv A/V sync broken

Michael Niedermayer michaelni at gmx.at
Tue Feb 20 12:12:52 CET 2007


On Tue, Feb 20, 2007 at 12:07:20PM +0100, Michael Niedermayer wrote:
> Hi
> On Tue, Feb 20, 2007 at 04:18:35AM +0200, Uoti Urpala wrote:
> > On Tue, 2007-02-20 at 02:41 +0100, Michael Niedermayer wrote:
> > > > I tested that sample and saw desync when playing without -correct-pts.
> > > > It seems to work with -correct-pts. I haven't verified the exact cause
> > > > but flv uses a libavformat demuxer and those generally do not work well
> > > > without -correct-pts because of timestamp ordering.
> > > 
> > > flv1 doesnt support b frames so there should be no out of order timestamps
> > 
> > I checked what was causing it. Seems that demux_lavf sets a fps value
> > but it doesn't match the timestamps. It sets sh_video->fps to 29.9700298
> > which makes video.c use a constant 1/fps frame duration, but average
> > distance between frame timestamps is longer.
> ok so what should demux lavf set fps too if not the guessed fps? exact values
> are not available for several containers
> and i thought someone said that the fps value doesnt matter ...

also avi sets fps to the value in the header while avi can contain skiped
frames aka longer frames then 1/fps, and i know that avis with skiped frames
where working last time i saw one


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

it is not once nor twice but times without number that the same ideas make
their appearance in the world. -- Aristotle
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