Bug#538082: Segmentation fault in avg_pixels8_xy2_altivec()

[Reinhard Tartler]

Christian E. Böhme <monodhs at gmx.de> writes:

> Running any of the various video playback programs such as vlc or gxine
> (I happen to use the latter) has them crash due to invalid memory access(es)
> from within the /usr/lib/altivec/libavcodec.so.52 du jour.
>
> As an example, open and play the video file that is available via the
> attached torrent (these are the only files that cause the errors, BTW).
> Executing gxine from withing gdb, in particular, yields the following
> lines at a crash:
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0x35a51480 (LWP 2996)]
> 0x0e07a8b4 in avg_pixels8_altivec () from /usr/lib/altivec/libavcodec.so.52
>
> The behaviour is reproducible in that it causes a crash but varies in the
> time it takes for the seg fault to occur (usually within the fist two to three
> minutes, occasionally longer) unless a fast forward or backward (via the
> progress bar slider simultaneously acting as a random access control)
> is attempted in which case the program bombs immediately.

The location of the crash indicates that it happens in altivec specific
code, this means you need an altivec capable machine to track it down,
which I don't have access to.

As a quick workaround, you can disable the file
/usr/lib/altivec/libavcodec.so.52, which will make applications fallback
to /usr/lib/libavcodec.so.52 and thus, use the non-altivec version of
libavcodec.

In any case, please try to produce a full backtrace of such a
crash. Also, we need all information requested from
http://ffmpeg.org/bugreports.html in order to forward the bug
upstream. The most important things missing here is the example file and
the full backtrace.

No, I will not download that movie via bittorrent. See the page for
instruction how to create small example excerps (for the case the
problem occurs only with some particular files, which I expect)

-- 
Gruesse/greetings,
Reinhard Tartler, KeyID 945348A4