[FFmpeg-devel] [PATCH] flv set pts

[Michael Niedermayer]

On Tue, Sep 30, 2008 at 01:02:53PM -0700, Baptiste Coudurier wrote:
> Michael Niedermayer wrote:
> > 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
> > 
> 
> Yes, that is true, what can we do about that ?
> It's sad not to set pts for correct files, what do you suggest ?

iam fine with the patch if it also prints some warning that the past
timestamps might have been wrong

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

No human being will ever know the Truth, for even if they happen to say it
by chance, they would not even known they had done so. -- Xenophanes
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