[linuxtv-softmpeg] Coredumps

["Colin Paton" <ac2crp@blueyonder.co.uk>]

Hi,

I had some luck on Saturday in that one of the DVB-T channels here had very
bad reception. It was a good chance to test to see how softmpeg coped under
error conditions. It crashed fairly frequently :-(

It turned out that the video buffer size could be exceeded; I put in a check
before the memcpy where the video frame is copied into the buffer to stop it
overflowing. I did the same for audio.

Unfortunately reception has since improved on the channel so it is harder to
prove that this has improved things. I've left the machine running so far
since yesterday lunchtime on that channel, and things seem to be OK so far.
(I've deliberately commented out the call to d->codec->decode however in
order to try and confirm that things look OK, one by one).

I also noticed that the video buffer overflows (i.e. it tries to copy more
than 128k data into a single frame) sometimes when playing VDR files - so I
guess that something can't be quite right in the demultiplexing. It's quite
intermittent though which is a bit strange - doesn't always occur at the
same point in the same file.

Anyway - I'm going to leave it running, decoding audio only, and if that
works still when I get home from work today I'll re-enable video. I'll then
leave it running overnight again to see if it still crashes.

The timing fix you put in has made a world of difference - VDR recordings
are now, for the first time, watchable, pending the crashes!

The crashes I have experienced are strange ones, that don't seem to have
much reason to them. I suspect therefore that something is causing the stack
to be corrupted. Hopefully the buffer checks will make the code more robust.

Still get a crash when using the hardware decoder which I'll investigate
once software playback seems reliable. I managed to hang the complete
machine once when using the hardware decoder with the errored stream - erk.

Thanks once again for your work so far  - it's looking good!

Thanks,

Colin




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