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-   -   VSync problem on multi screen setup - Ubuntu 9.10 - GTX285 - 195.36.15 drivers (http://www.nvnews.net/vbulletin/showthread.php?t=150189)

Fenrir 04-20-10 03:50 AM

VSync problem on multi screen setup - Ubuntu 9.10 - GTX285 - 195.36.15 drivers
 
Hi all,

Here is my current setup :

Ubuntu 9.10
195.36.15 drivers
2 GTX 285 graphic cards (one DVI, one VGA and one HDMI port)
4 screens (2 screens on each cards), all independents (no twinview)
Compiz disabled

On this setup, I have a custom OpenGL application running full-screen on all 4 screens (one application with 4 different contexts, based on the graphical engine OpenSceneGraph). My app is running at 60fps when VSync is on, it's the screens refresh rate.

When I enable "Sync to VBlank" in the Nvidia-settings, here is the current result :
- On the first screen of each cards (plugged on the DVI port), the VSync is perfect, no tearing.
- On the second screen of each cards (plugged on the VGA port), tearing is noticeable on the upper part of the screens (I have a line about 100 pixel far from the top of the screens).
=> Result : 2 screens without tearing, 2 screens with tearing in a specific location.

I have also tested on GTX285 cards with 2 DVI ports with the same result.
Another note : the 4 screens are the same, all plugged in VGA (using an adaptor when plugged in the card DVI ports).

Anyone knows how where this problem comes from ? And any idea how to solve it ?
Thanks in advance for your help.

Best regards,

jesmith 04-21-10 11:03 AM

Re: VSync problem on multi screen setup - Ubuntu 9.10 - GTX285 - 195.36.15 drivers
 
You can only sync to one monitor at a time. The fact that two seem to be sync'd is just luck.

This is a hardware thing. It's true of all cards, monitors, etc.

Fenrir 04-29-10 05:09 AM

Re: VSync problem on multi screen setup - Ubuntu 9.10 - GTX285 - 195.36.15 drivers
 
Sorry but you're wrong, we've configured Xorg to use 2 twinviews on the 4 screens and modified our app to use 2 contexts instead of 4 and we have a perfect VSync at 60Hz on the 4 screens. There is absolutely no tearing.

Cheers,


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