[Ffmpeg-devel] [BUG] no video transcoding

Michael Niedermayer michaelni
Wed Apr 25 11:32:35 CEST 2007


Hi

On Wed, Apr 25, 2007 at 11:21:59AM +0200, Baptiste Coudurier wrote:
> Hi
> 
> Michael Niedermayer wrote:
> > Hi
> > 
> > On Mon, Apr 23, 2007 at 10:55:06AM -0000, Wolfram Gloger wrote:
> >> Hi,
> >>
> >>> to comment a little more on this as it seem to be a popular bug ;)
> >>>
> >>> On Sun, Apr 15, 2007 at 08:13:37AM -0000, Wolfram Gloger wrote:
> >>> [...]
> >>>> Ok that's probably true -- although I maintain the patch is correct,
> >>> no it is not, cur_dts was approximately correct before and completely
> >>> wrong after the patch
> >> How so?  cur_dts was set to some more or less random packet's dts
> >> that was the last one parsed in av_find_stream_info().
> > 
> > and your proposed patch sets it to the first dts from av_find_stream_info()
> > that is equally random
> > 
> > audio time stamp ?, ?, ?, 5, ?, ?, 123456, 123457, ...
> > video time stamp ?, ?, ?, ?, ?, ?, 123456, 123457, ...
> > timestamp discontinuity           ^
> > 
> > the first dts here would be 5 and 123456
> > filling things in would lead to something like:
> > 
> > audio time stamp      5,      6,      7,      5,      6,      7, 123456, ...
> > video time stamp 123456, 123457, 123458, 123459, 123460, 123461, 123456, ...
> > 
> > that is not better than what you get with the last dts, actually its
> > worse
> > 
> > 
> >> Then the packet queue is flushed and the next packet read has a
> >> (sometimetimes significantly) smaller dts value.
> >> This leads to a hard error (dts < cur_dts) for valid DVB streams.
> >> It is just a matter of luck if you don't hit this situation.
> >>
> >> After the patch, cur_dts becomes AV_NO_PTS_VALUE -- how can that
> >> be "completely wrong".  Please elaborate.
> > 
> > its not completly wrong on its own but in combination with all the other
> > code it is
> > 
> > [...]
> >> I suspect that reverting 8465 will hide the problem, but
> >> please give me until tonight when I will allocate some time
> > 
> > time is no problem, i can wait, i just want a clean solution ...
> 
> Ok, so do we all agree on reverting r8465 for now until a clean solution
> is accepted ?

you have my approval for that ...

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I count him braver who overcomes his desires than him who conquers his
enemies for the hardest victory is over self. -- Aristotle
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