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Old 01-30-07, 04:41 AM   #1
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Join Date: Jan 2007
Posts: 8
Default VSYNC <-> tearing: summary of the situation ?


Like others, I'm experiencing the "tearing" problem (horizontal "split" lines on high-motion video, including fast moving-around of windows) with my 7600GS and 1.0.9746 drivers (under FC6, Xorg 7.1.1 and KDE 3.5.5, to 1024x768 LCD VGA-conntected (non-DVI) projector).

Now, extensively going through the docs, Google, and this forum, I'm completely at a loss at what to do when/how...

To summarize it all:
- there is an environment variable __GL_SYNC_TO_VBLANK that affects nVidia driver...
- that may not be desirable to set in some situation (like when using "compositors"; i.e. Option "Composite" ??? )...
- which may be overriden with some XV_SYNC_TO_VBLANK variables set by some player (e.g. Mplayer/Xine)...
- or by nvidia-settings...
- but not knowing which X extensions (Xv, XvMC, OpenGL) gets affected by it...
I'M LOST !!!
(I'm currently at the point of trying all the possible combinations of this various settings, until I find the one that solves this "tearing" issue)

Is there any place I can find a "summary of the situation" (or "anti-tearing" howto), pouring light into my clouded thoughts ? :-D

Or could someone help (me) writing this kind of "howto" (by pointing me in the right direction in regards on how this entire Sync-to-VBlank works with nVidia drivers; see above "summary") ?

Maybe a list of short questions (and their answers) could help us:
- has the choice of the driver/extension used (Xv, XvMC, OpenGL, etc) any importance in regards with Sync-to-VBlank ? (I *would* say it should not, if I want to get rid of "tearing" when moving anything around in the Window manager)
- does the __GL_SYNC_TO_VBLANK environment variable affects all video rendering from the nVidia driver ? Or does it require to use the OpenGL driver/extension ?
- should 'nvidia-settings' then be used to enable Xv's Sync-to-VBlank (and does it affect XvMC) ?
- has the Xorg's "Composite" extension any influence on whether to enable Sync-to-Vblank or not ?
- AaronP mentions that "9629 and the new beta should now ignore sync-to-vblank for redirected windows." ( Does that mean that we should be able to rely on __GL_SYNC_... and 'nvidia-settings' ?
- Any other clue ?

Thank you for your answers ;-)

Cheers to all (and thank you for supporting the Linux community as well as you do) !

cdufour is offline   Reply With Quote