[FFmpeg-devel] [PATCH] flv set pts

Michael Niedermayer michaelni
Tue Sep 30 21:30:27 CEST 2008


On Tue, Sep 30, 2008 at 12:00:59PM -0700, Baptiste Coudurier wrote:
> Michael Niedermayer wrote:
> > On Tue, Sep 30, 2008 at 11:28:45AM -0700, Baptiste Coudurier wrote:
> >> Hi,
> >>
> >> Michael Niedermayer wrote:
> >>> On Mon, Sep 29, 2008 at 07:56:17PM -0700, Baptiste Coudurier wrote:
> >>>> Baptiste Coudurier wrote:
> >>>>> Hi,
> >>>>>
> >>>>> $subject.
> >>>>>
> >>>> Scratch old patch, this one should be correct.
> >>> can you post some example input&output pts & dts values for some file
> >>> with b frames.
> >>> I suspicion would be that the patch is not completely correct but this
> >>> should be more obvious from a list of timestamps and frame types.
> >>>
> >> Well, I didn't find any having < 0 cts yet, however it has been said
> >> that cts is signed like in .mov, so code is assuming that.
> >>
> >> Files generated by FFmpeg does not have < 0 cts.
> >>
> >> Patch is doing the same as the .mov demuxer excepts that we cannot know
> >> in advance while we can in .mov, though it misses has_b_frames = 1, I
> >> can see, not harmful though.
> >>
> >> What do you think could be wrong ? I'll try to find a file in the mean time.
> > 
> > Well
> > if we take as example normal mpeg2 style IPB then
> >         IPBBPBB
> > dts:    0123456
> > pts:    1423756
> > would be correct
> > 
> > now if dts where increased by one:
> > 
> >         IPBBPBB
> > dts:    1234567
> > pts:    1423756
> > 
> > then this would be wrong, and not only the ones for the B frames
> > would be wrong but all would be. That is for example if the I frame
> > is feeded at time 1 into the decoder then it will be output at time 2 not 1.
> > 
> 
> Humm of course yes, and in your situation, cts will be -1 for the third
> frame to achieve dts 3 and pts 2, I don't see what you mean, the check
> is indeed for cts < 0.

well, i think the demuxer would output:

dts:    12-----
pts:    1423756

but this is wrong for the first 2 frames


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I hate to see young programmers poisoned by the kind of thinking
Ulrich Drepper puts forward since it is simply too narrow -- Roman Shaposhnik
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