[MPlayer-users] crash in motion_est_mmx.c, backtrace included

[Ivan Kalvachev]

2007/9/21, Ariel <asmplayer at dsgml.com>:
>
> On Wed, 19 Sep 2007, Carl Eugen Hoyos wrote:
>
> > Ariel writes:
> >
> >> Command line: -fs -framedrop -softvol -softvol-max 800 -af volume=12 -ao
> >> alsa -channels 6 -ni -vo xvmc:queue -vc ffmpeg12mc
[...]
> >> If there is other information you need let me know.
>
> > Does it happen with every MPEG2 sample you have? With some? Only with
> > one sample - then please upload to incoming.
>
> Only with samples that contain transmission errors. I snipped a section of
> the file, called it: crash_with_transmission_errors_and_xvmc and uploaded
> it to incoming.

It's my bug and I hope that the commit to ffmpeg svn have fixed it.
Unfortunately the uploaded sample file is not able to reproduce the
bug so I cannot very the fix on my own.

It happens when there is bitstream error in I-Frame, then ffmpeg
error_resilience tries to see if neighborhood blocks have changed from
previous frame with the intent to use the old blocks (aka when there
is no scene change). As xvmc doesn't allow direct access to the image
dsp.sad() reads some random memory region.
There is already check for xvmc that prevent other methods that access
the image directly, but I have missed this one.

In the sample there is broken I-frame, but probably there are not
enough valid block to try testing them.

Hope it works.