[mythtv] Problem with XvMC

Jerry Rubinow jerrymr at gmail.com
Sun Feb 12 19:59:32 UTC 2006

On 2/11/06, Chad <masterclc at gmail.com> wrote:
> On 2/11/06, Jerry Rubinow <jerrymr at gmail.com> wrote:
> > When I try using XvMC, I consistently get low frame rate and audio
> > skips.  If I use libmpeg2, no problem.  mythfrontend -v playback gives
> > repeating cycles of:
> >
> > prebuffering pause
> > waiting for prebuffer
> > video is 3-4 frames ahead of audio, skipping a/v wait
> > video is 3-4 frames ahead of audio, skipping a/v wait
> >
> > Every so often the frame rate is reported at 56-58 fps.  Other
> > settings are deinterlace bob, open gl vsync, realtime priority
> > threads, extra audio buffering.
> >
> > Source is 1280x720 over firewire.  XvMC driver is 7676.  Myth version
> > 8906M.  FX 5200 card.  CPU is low, around 50%.
> >
> > I'd like to try to understand possible causes of this and either give
> > any helpful information to someone who might be able to fix it, or
> > accept any helpful suggestions to try to further diagnose it myself.
> >
> > Thanks,
> > -Jerry
> > _______________________________________________
> I turned off opengl-vsync and I think that did it for me.
> Chad

Thanks Chad - that did it.  I could have sworn I'd tried that
combination at least once, but I guess in all the tinkering I must
have missed it.  I'd seen in the archives that drivers past 7676 had
problems with gl sync, and some had problems with XvMC, but I had
missed anything about people having problems with combining gl sync
and XvMC.  Is this a hardware limitation or a bug, and if a bug, with
nvidia's driver or Myth?

In any case, the display looks and sounds pretty steady now.  There is
one new problem which I hadn't seen mentioned anywhere before.  I'd
gone out to shovel snow this morning and left the tv playing the
Olympics hockey on CNBC.  When I came back in, the left 1/7th or 1/8
of the screen gets all pixellated when the scene is changing - the
faster it's changing, the more artifacts, and they lag a bit behind
the rest of the image.

As well, if I try to bring up an OSD (info, FF, etc), the whole screen
turns green until it goes away, at which point the regular image
returns (with the pixellation).  If I exit live mode and come back,
the problem (both of them) is (are) gone.

When the games switched from CNBC to USA this afternoon, I changed the
channel.  It was fine for at least an hour or more, and then the same
thing recurred.

Is this a known problem?  Since the first message in this thread, I've
upgraded to 0.19.  USA and CNBC are SD resolution.  Sound is fine when
this is happening, no abnormal messages issued with mythfrontend -v
playback when pixellation is going on.  Don't know if there's anything
at the point where the problem begins.


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