[mythtv] MPEG-4 trouble on SMP

[Benjamin Binford]

On Thu, Oct 31, 2002 at 10:01:45AM -0500, Isaac Richards wrote:
> On Wednesday 30 October 2002 10:35 pm, Samit Basu wrote:
> > Hi -
> >
> > I've got a strange problem with mythtv when I use MPEG-4 encoding.
> > Recordings
> > work fine, as do playbacks, but when I watch live TV, the video is
> > corrupted.  It looks
> > mostly fine, but there are blocking artifacts -- blocks of color, white and
> > black that
> > fade in and out periodically.  I don't have the same problem with rtjpeg,
> > and the problem
> > doesn't go away with reduced capture resolution (I tried down to 320 x
> > 200). I'm running
> > on a dual 1GHz PIII, and the artifacts go away when I run a non-SMP kernel.
> > (hence
> > the subject line)...  I looked at the rwlocks in RingBuffer.cpp, but wasn't
> > familiar
> > enough with the code to spot the problem (e.g., why is a read-lock used in
> > the Write
> > method?).  Any ideas?
> 
> Probably thread-safety issues in libavcodec that are exposed when running SMP.  
> Anyone feel like checking that out?
> 

I'm not sure if it will help, but when I use ffmpeg's command line tools to record an mpeg4 stream I don't see this behavior. I'm using version 0.4.5 of ffmpeg- I'm not sure when the code was spliced into mythtv, but maybe they've tweaked something since then?