[FFmpeg-devel] [PATCH] Incorrect ASF duration

[Henrik Gulbrandsen]

On Fri, 2008-04-18 at 05:15 +0200, Michael Niedermayer wrote:
> On Fri, Apr 18, 2008 at 01:05:52AM +0200, Henrik Gulbrandsen wrote:
> > This is similar to the Ogg problem. The stream duration is not identical
> > to the PTS of the last packet if the packet duration is non-negligible.
> > 
> > The attached examples show the result of
> > 
> >     ffmpeg -i video.mp4 -vcodec wmv2 -f asf video.wmv
> >     ffplay -stats video.wmv > report.txt 2>&1
> > 
> > before and after the patch. As before, video.mp4 is exactly 24 seconds
> > long, at 10 fps. Notice the "Duration: 00:00:23.90" for stats given with
> > the current code base!
> 
> This shows that there is likely a bug in the asf demuxer or asf muxer,
> what makes you belive it is the muxer that needs correction.

As I wrote, the stream duration is not identical to the PTS of the last
packet if the packet duration is non-negligible. This is how the current
muxer handles it, which indicates that correction is not a bad thing.

> What i see is a 50% chance of fixing a bug and a 50% chance of introducing
> a new bug instead.

And a 50% chance of doing both at the same time :-)

There may of course still be an even number of mutually negating bugs
left in the code, but I think this is a step in the right direction.
However, the original patch did introduce an indexing bug, since I
happened to miss that the duration variable was also used further down
in the same function. An updated patch is attached.

> I suggest you use some "official" asf encoder and encode a video of known
> length and then check what is written in the file.

I couldn't bring myself to read the EULA of an official encoder, but for
what it's worth, both my phone and Windows Media Player gives the length
of the WMV file created by the original code as 00:23. After my patch,
the length is given as 00:24, so I think demuxer bugs are irrelevant...

> Also i suspect that the regression test checksums will change by such
> a change to the muxer thus would need to be updated by your patch.

A separate patch with test changes is attached.

/Henrik

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