[FFmpeg-devel] [PATCH] issue251, xvid within .ogm will not remux to .avi

Michael Niedermayer michaelni
Mon May 26 13:59:59 CEST 2008

On Mon, May 26, 2008 at 07:29:40AM +0100, M?ns Rullg?rd wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> > Hi
> >
> > The patch below will fix remuxing from some ogm. Iam not 100% sure that
> > this is the correct solution though ...
> I believe you, but could you please explain a little.

Where should i start ...

The mpeg4 stream in this ogm uses these infamous packed b frames which avi
with some demuxers needed.
This should make pts=dts of the packets.

Now, the first packet that comes out of the ogg demuxer for the video stream
had a pts=0
Then it returned 7 packets with pts=AV_NOPTS_VALUE
and then a packet with pts=7

This cannot be correct as there are just 6 distinct pts values between 0 and
7. (and packed b frames means the stream should behave as if pts=dts and
theres no frame reordering)

droping the first timestamp (or using -1) is the smallest change which fixes
the issue. I do not know what the correct timestamps are supposed to be. 
I do not even know if the "timestamps" in ogm are pts or dts ...
AFAIK there is no OGM spec?

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Many things microsoft did are stupid, but not doing something just because
microsoft did it is even more stupid. If everything ms did were stupid they
would be bankrupt already.
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