[maemo-developers] [maemo-developers] SDL vertical blank (vbl) sync.

From: Juha Yrjölä juha.yrjola at nokia.com
Date: Mon May 29 17:20:42 EEST 2006
Kuisma Salonen wrote:

>> Hi I was wondering if anyone knows how to sync. the SDL_Flip to the 
>> vertical blanking of the display.
>> While it is nice to get 47+ FPS while memset'ing the display, I would 
>> rather be synced to the display and avoid the tearing at the cost of FPS.
> This is actually generic issue, not just SDL one. When you call 
> SDL_Flip() (or SDL_UpdateRects() etc) it "draws" local data to the 
> display HW, and this goes through X. Having synchronization in the 
> display driver would solve this. Anyway I am not the person to say more 
> about this as I am not enough aware of display HW internals to tell how 
> hard implementing this would be and whether it would even be possible.

Unfortunately we don't provide user-space with the vsync information (or 
"Tearing Effect" signal, as it's called in LCD land).

If there's large enough need for this, we might consider implementing 
the support.  The tearing effects should be minimal on the 770, however, 
because of the high (around 55 Hz) refresh rate of the display.


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