[FFmpeg-devel] Audio Video Sync issue with dvr-ms files

Michael Niedermayer michaelni
Tue Jun 12 02:11:24 CEST 2007


On Mon, Jun 11, 2007 at 03:15:03PM -0400, Jonathon Elwood wrote:
> On 6/10/07, Michael Niedermayer <michaelni at gmx.at> wrote:
> > [...]
> >
> > hmm, i dont think theres a clean way to detect it, and there also shouldnt
> > be any need to except for debuging (and for that a simple static int should
> > do)
> > or is there some case iam missing?
> > [...]
> Using your debug statement I'm able to see the real keyframes and this
> allowed me to learn two things about DVR-MS files.  First, dvr-ms
> files don't have timestamps on keyframes, there is always a timestamp
> on the segment right before a keyframe however.  Second, not all
> DVR-MS timestamps are sequencal.  The only reliable timestamps are the
> timestamps in the segment before the keyframes.

the timestamps are likely something like PTS, these are not sequential
in case of b frames, and they MUST NOT be sequential in case of b frames

mpeg with b frames does not store frames in display order, instead all non
b frames get delayed during decoding

PTS:            031254867
stored        : IPBBPBPBB
decoder output:  IBBPBPBBP


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Many that live deserve death. And some that die deserve life. Can you give
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even the very wise cannot see all ends. -- Gandalf
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