[MPlayer-dev-eng] Re: [PATCH] dvr-ms fixes for pts, key frame detection and seeking

Michael Niedermayer michaelni at gmx.at
Fri Feb 9 02:35:27 CET 2007


On Thu, Feb 08, 2007 at 11:02:53AM -0600, John Donaghy wrote:
> >
> >This sounds like a totally wrong approach. Aren't we talking about
> >mpeg video here? In which case, the video codec has a nominal
> >framerate stored in the video headers, which should be followed in the
> >absence of container-level timestamps. Yes it's ugly for the demuxer
> >to have to dig into codec-level data, but that's what you have to do
> >when writing a demuxer for an incestuous container. It's just like for
> >ogg/vorbis...
> I dont understand why you think this is a wrong approach. The timestamps are
> in the container. There are both the normal ASF timestamps, which sort of
> work but give you AV sync issue among other things, and then there are the
> dvr-ms specific timestamps which you pretty much have to use or else the AV
> does not sync well especially with HD content. The timestamps in both
> streams do not start at zero (I think because it's from a pvr app) so when
> using the framerate from the codec I cant see any way to sync the audio and
> video. (This is basically what happens in the libavformat asf demuxer and
> the result is that AV sync for dvr-ms files is often way off for HD content)

i cant follow your reasoning, mpeg-ps provides timestamps starting at random
values and does not even have to provide them for all I frames but rather just
once in a while, and lavf has no problems producing correct timestamps for that
by parsing MPEG-ES headers in an AVParser, so any dvr-ms issues would likely
be in the asf demuxer providing wrong timestamps (compared to missing ones)

do you have a dvr-ms sample which shows the problem with lavf?

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Observe your enemies, for they first find out your faults. -- Antisthenes
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