[mythtv-users] Latest Intel Drivers and HD on G915 (works) and G965 (video tearing)

[Doug Larrick]

Calin Brabandt wrote:
> I compiled the latest Intel graphics drivers from
> www.intellinuxgraphics.org.  The modesetting is a
> welcome addition to the drivers and my G915 board
> seems to be working well on either my 720p DFP or
> 1440x900 LCD VGA monitor.  There's still no XvMC in
> the drivers, however.
> 
> Unfortunately, my G965, unlike the G915,has a bad case
> of video tearing.  Mythfrontend -v playback reports
> that both boards are using DRM sync and OpenGL sync
> doesn't appear to work with the drivers.  I think DRM
> sync is close to working on the G965 but it's sync'ing
> in the wrong place.  With 1080i video, the video tear
> is always about 1/4 of the way down the screen and
> with 720p playback, it's about 1/8 of the way down. 
> Without DRM sync, Myth uses RTC sync and the tearing
> is all over the place on either board.  Using the
> G915, and DRM sync, the video is correctly
> synchronized with vblank and a pleasure to watch.

I've noticed this problem on my G965 as well.  I am able to use OpenGL
vsync on my system, and it happens there as well.

My understanding is that the G965 has no video overlay hardware, and so
does its drawing using a texture (3D hardware).  My further
understanding is it makes no attempt to sync to vertical retrace
internally.  That's OK; we don't need it to.

Unfortunately there's not a whole lot to be done from the MythTV side --
we're told by DRM or OpenGL "OK, now, go!" and we then display the video
frame as quickly as we can.  My guess is that by the time we get the
vertical retrace there's not enough time for the combined work that
MythTV and the driver need to do -- either this work is taking too long,
or the signal is arriving late.

The G965 driver is still under some fairly heavy development, so there's
hope to get this fixed.

-Doug

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