[mythtv-users] OpenGL vsync broken on Xorg 7.1 or latest nVidia driver?

John P Poet jppoet at gmail.com
Tue Nov 14 03:08:51 UTC 2006


On 11/6/06, John P Poet <jppoet at gmail.com> wrote:
> On 11/6/06, Doug Larrick <doug at parkercat.org> wrote:
> > John P Poet wrote:
> > > I have been using OpenGL vsync ever since Doug added it to Myth.
> > >
> > > I just did a fresh install of FC6 on my frontend machine.  Ever since
> > > doing so, enabling OpenGL vsync causes a minor but consistant stutter
> > > of HD playback.  It is basically like a micro-second pause every
> > > second.  If I turn off OpenGL vsync, the problem goes away.
> > >
> > > Has anyone else noticed this?  If so, has anyone determine whether it
> > > is a Xorg 7.1 or an nVidia driver problem?  I tried going back on
> > > version of the nVidia driver, but that had no effect.  Unfortunately,
> > > I don't remember exactly which version of the nVidia driver I was
> > > running before.
> >
> > I'm running Xorg 7.1 (Debian) and nvidia 8776 on my main box with an
> > FX5200; no issues.
> >
> > I'm running Xorg 7.1 and nvidia 9625 (beta) on my dev box with an MX440
> > and have my choice between tearing (which I'd never seen from any nvidia
> > driver ever before) or high CPU usage (too high to watch HD), depending
> > on the sync-to-vblank settings in nvidia-settings.
> >
> > If I turn on something like Compiz things go to pot: I see maybe 10 fps
> > (that is, all the frames are displayed by Myth but only some of them
> > make it to the actual screen).  Not altogether surprising.
> >
> > You might measure your CPU consumption; if it's too high you'll see the
> > behavior you're describing as the non-realtime threads get starved.
> >
> > -Doug
>
> Thanks Doug.  I will play around with it some more.

Well... I reinstalled FC5 on my frontend, along side FC6.  On both FC5
and FC6 I am running a 2.6.18 kernel, and the latest nVidia binary
driver.

With OpenGL vsync turned on, horizontal tickers are smooth on FC5, but
jumpy on FC6.

I don't know what to make of this.  It could be an Xorg 7 issue, but I
guess other distributions with Xorg 7 do not have this problem.

John


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