[Ffmpeg-devel] MPEG decoder duplicates second last frame?

[Stefan Heinzmann]

--- Michael Niedermayer <michaelni at gmx.at> wrote:

> Hi
> 
> On Sun, Aug 13, 2006 at 12:04:34AM +0200, Stefan Heinzmann
> wrote:
> > 
> > --- Michael Niedermayer <michaelni at gmx.at> wrote:
> > 
> > > Hi
> > > 
> > > On Sat, Aug 12, 2006 at 08:08:07PM +0200, Stefan
> Heinzmann
> > > wrote:
> > > > Hi all,
> > > > 
> > > > the MPEG decoder seems to duplicate the frame before
> the
> > > > last. I've seen this on an MPEG1 video stream that
> was
> > > part
> > > > of an MPEG2(SS). The last frame is produced correctly
> > > when
> > > > calling av_video_decode with NULL.
> > > > 
> > > > The decode example shows this, too; it produces one
> ppm
> > > file
> > > > too much, and careful examination shows that there
> are
> > > two
> > > > files produced from the second last frame.
> > > > 
> > > > The ffmpeg application also produces one more frame
> on
> > > output
> > > > than what the original file contains.
> > > > 
> > > > Is this a known problem?
> > > 
> > > no, it has been fixed ages ago
> > 
> > Really? It seems to have come back then. svn update
> today,
> > build on linux x86 still produces the problem here.
> 
> ive already tried to reproduce it but no images from the
> mpeg files
> i tried are duplicate in the output, so iam sorry i cant
> help
> unless you provide enough info so it can be reproduced

Details are now entered into bugzilla as bug #554, although
the file to reproduce it with is too large for bugzilla,
unfortunately. I'll try to attach it in 4 pieces, which you
unfortunately have to assemble. I have no shorter example
with visible timecode, unfortunately, and in order to check
which frame gets duplicated the timecode is extremely handy.

If you use ffmpeg to transcode it to another mpeg file, the
new file has the additional frame, but on the newly generated
file the error can not be reproduced again, so ffmpeg reads
the correct frame count on the file it generated itself.

Both m2v and mpg files show the problem.

I hope this all makes sense.

Cheers
Stefan



		
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