[Openchrome-users] Stair Step Video Tearing in Mythtv

[calinb]

Stair Step Video Tearing in Mythtv
I have a P4M800 Pro.  I'm running Mythtv and a 1280x720 RGB output to an analog monitor.  1080i source looks okay, but 720p and 480i contains "stair step" video tearing from lower left to about 2/3 of the way across the screen to the upper right.  The "steps" are large--it takes about seven of them to span the screen.  Like all sync to vblank problems, the tears are noticeable during pans, motion, and scene changes.

The stair step is strange because tearing in Nivida and Intel chipsets is horizontal across the screen as the video buffer is flipped while the screen is still being scanned (not sync'ed to the vblank).

If I comment out load dri in xorg.conf, DRM myth cannot use DRM sync and the tear occurs in a vertical line near the left side of the screen--no more steps.  For some reason RTC sync is not working in Myth on my system so it would be nice to get DRM working.  I don't know if this is an Openchrome problem or a DRM problem.

Is there an option I could put in xorg.conf to attempt to fix the tearing?

Thanks,

-Cal

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