[mythtv-users] Fixed!: Nvidia Sync to Vblank pegging cpu in X

Steven Adeff adeffs.mythtv at gmail.com
Mon Dec 18 13:44:10 UTC 2006

On 12/16/06, J. Miller <mythtv.org at elvenhome.net> wrote:
> I've been fighting the scourge of myth causing X to consume 100% of the
> CPU when Xv Sync to Vblank is turned on in nvidia-settings.  Everything
> works just fine with it unchecked but that is the only sync setting that
> gives me a perfect picture with no tearing.  Myth's native OpenGL sync
> still tears a little.  The problem turned out to be the modeline I was
> using.  It was a 1368x768 56Hz modeline which apparently triggered the
> issue.  I switched to a 1360x768 60Hz modeline and now everything works
> peachy.  X still starts consuming large amounts of CPU occasionally but
> it quickly drops back down to the 2-4% range.  I'm not 100% sure that it
> was the refresh but a modeline change did the trick.  Hopefully posting
> this here will help point others that have the same problem in a new
> direction.

Interesting. I have the same issue, that setting is the only way to
get tear-free output with Myth (though mplayer works fine without
it...). I've been using the NVidia default 1080p modeline, which I'd
hope would work correctly. Actually, come to think of it. I tried the
9xxx series drivers over the weekend. They seemed to work fine except
it kept using a 24Hz 1080p modeline, I couldn't force it to use a 30
or 60hz, and the 24hz caused MAJOR tearing, so the fact that it's
frequency related doesn't really surprise me. Perhaps I'll try one of
the custom modelines listed in the wiki to see if that fixes things.

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