[FFmpeg-devel] [PATCH] assdec: non monotone timestamps

Aurelien Jacobs aurel
Sat Sep 27 23:19:14 CEST 2008

On Sat, 27 Sep 2008 21:41:04 +0300
"Ivan Kalvachev" <ikalvachev at gmail.com> wrote:

> On 9/27/08, Aurelien Jacobs <aurel at gnuage.org> wrote:
> > Hi,
> >
> > When trying to stream copy the attached ASS file with the following command:
> >   ffmpeg -i test.ass -scodec copy test2.ass
> > I get some "error, non monotone timestamps". They are due to the fact that
> > this file contains several events with the same pts (this is perfectly
> > valid ASS). I guess that those events with equal pts should be packed in
> > the same AVPacket (the same way all the macroblocks from a video frame are
> > stored in a single packet).
> > Attached patch just implement this.
> >
> > Note that the matroska demuxer has the same problem, and I intend to fix
> > it soon.
> Just to be clear,
> You intent to make mkv demuxer concatenate multiple different packets
> stored in the mkv.ass format into one huge packet combining multiple
> file.ass lines. All lines in the packet would have same pts,


> but the lines may contain different duration than the one of the packet.

The AVPacket won't contain any display_duration for ASS tracks (just the
same as the raw ass demuxer).

> Would you also do the mkv muxer side changes - breaking multiple lines
> into multiple packets

Yes. Along with other fixes needed by the mkv muxer.
This is needed anyway to mux packets comming from the raw ass demuxer.

> or the mkv.ass specs already allow this?

No, it don't.


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