[FFmpeg-cvslog] r15206 - in trunk/libavformat: matroskadec.c matroskaenc.c

Michael Niedermayer michaelni
Fri Sep 5 15:58:23 CEST 2008

On Fri, Sep 05, 2008 at 12:47:06PM +0300, Uoti Urpala wrote:
> On Fri, 2008-09-05 at 03:10 +0200, Michael Niedermayer wrote:
> > convergence_duration of 10 means that in 10 timebase units from now the
> > output of the decoder when started with this frame will match what it
> > would have been when started from the very first frame.
> > 
> > that is if 5 minutes ago there was a subtitle that has a display duration
> > of 7 min then convergence_duration could be 2min for the current
> > subtitle packet because if we stat decoding now we will be missing this
> > subtitle and thus output will differ for 2 min. Of course if this past
> BTW how do you expect this to work in practice for subtitles (I assume
> you do expect it could work in some case since subtitles are explicitly
> mentioned in the documentation)? This is a field in a demuxer packet,
> but typically there is no packet right after a seek where you could set
> it. 

> Do you expect the demuxer to generate a dummy packet whose only
> meaningful information is the value of this field? 

no, the idea was more to preserve this information when remuxing
maybe this isnt the best way, if you have a better idea we surely
can remove this field again
Similar to this field we also could add a display duration that would
then match the maroska-ass durations.

Both these fields could be filled in by demuxer or parser and be used
by the muxer.
Without such fields muxers would have to extract this information from
the codec specific bitstream, that would work most of the time but not
always, also it means more codec specific code in muxers, thought that
can be shared.


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The worst form of inequality is to try to make unequal things equal.
-- Aristotle
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