[mythtv-users] Got smooth playback? please post your setup & configuratio

Julian Edwards myth at julian-edwards.com
Mon Aug 7 10:08:16 UTC 2006

James Buckley wrote:
> I've been down this road before...
> I'm using an 37" LG 37LP1D. It takes 1360x768 @ 50Hz without a hitch
> (infact it's taken almost every modeline I've ever given it!). But
> it's getting the refresh to be exactly 50Hz which I find the hardest.
> On xtiming, if I type 50 for the refresh rate, when it's calculated it
> normally says something like "Actually 50.04". If I use a refresh like
> 49.98, I can get it to say 50, but I think the value is still being
> rounded. How important is it to get a perfect 50Hz refresh.
> Also, I think some of the jerkyness is caused by the rubbishy graphics
> card. If I run glxgears, it uses 100% CPU (basically as much as it
> can), and if I do some CPU intensive task (like opening openoffice.org
> <http://openoffice.org> :P) it stutters really bad. I think that may
> be causing some of the erratic stutters I get (on top of the generally
> stuttery playback), and may be leading to the prebuffer pauses.
> I think I need a decent (i.e. normal) graphics card. :(
> Thanks so far
There's nothing wrong with your graphics card!  glxgears doesn't use any
kind of vertical sync so will attempt to draw as fast as possible, hence
the high CPU load.

Like Wim said, you need a 50Hz modeline (yes, it's important to get
exactly 50Hz).  If you run X up with --logverbose 5 it will tell you
more about the modelines that it's using and what the vertical refresh
rate is.  In your X config, set VertRefresh to 50.0 and this will ensure
it'll only pick a 50Hz vertical refresh rate.  You will also need to use
OpenGL vsync in Myth.

I am using an interlaced 50Hz modeline through svideo TV-out and OpenGL
vsync, and it's perfectly smooth (I have interlacing issues but that's a
different matter!)


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