[FFmpeg-devel] looping input and pts rollover

Michael Niedermayer michaelni at gmx.at
Tue May 22 16:03:26 CEST 2012

On Tue, May 22, 2012 at 03:38:38PM +0200, Nicolas George wrote:
> Le quartidi 4 prairial, an CCXX, Robert Nagy a écrit :
> > We had a short discussion on IRC regarding looping input.
> > 
> > The problem today is that lavfi does not guarantee proper handling of
> > rollover pts (which happens with e.g. looping input), which means that
> > either the filter graph needs to be flushed and reinit at the same
> > time as avcodec_flush_buffers.
> > 
> > From the discussion I think the general consensus was that graph
> > reinit would be to complicated, thus I believe we need to review the
> > filters.
> I told you my opinion about this last time you raised it, and it has not
> changed yet: rollovers should be corrected before entry into the filter
> system, or at words just after with a fixpts filter.
> That way, no need for anything, no reinit, no review, no duplicated code.

I consider rollovers a special case of timestamp discontinuities
(resets to 0 are not uncommon)

If you want to handle them in a fixpts filter, this filter will have to
correct all the streams together because if its done independantly
for audio and video each could get a slightly different correction
offset and end with AV desync

also one disadvantage of removing the discontinuities before the
filters is that it becomes impossible to preserve them. There was
at least 1 user who wanted that though i dont remember the exact
reason why. (it was somthing with cuting and concatenating of mpegs)


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I do not agree with what you have to say, but I'll defend to the death your
right to say it. -- Voltaire
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