[SDL] SDL_BlitSurface and getpixel(): Windows Vs Linux

Chris Thielen chris at luethy.net
Mon Jul 29 18:50:01 PDT 2002


On Mon, 2002-07-29 at 15:58, George wrote:
> Mandrake 8.2 with nvidia 2960 drivers
> 	getpixels test -> time needed = 8 seconds
> 	SDL_Blit test -> speed = almost good (constant at window/fullscreen mode!)
> 
> Windows ME with nvidia 29.42 drivers + direct X 8.1
> 	getpixels test -> not tested
> 	SDL_Blit test -> speed = unbelievably SLOW 
> 
> Windows XP with nvidia 29.42 drivers + direct X 8.1
> 	getpixels test -> time needed = 22 seconds !!!
> 	SDL_Blit test -> speed = almost good (at window mode)
> 			 	SUPERFAST at fullscreen mode

I'm no expert w/ SDL, but I think I can partially answer this. I assume
that with Mandrake your getpixel test is accessing pixels on a software
surface, and your Windows XP getpixel test is accessing pixels on a
hardware surface, that would explain the differences in those times.
Somebody correct me if I'm wrong. Is that what's going on? Do you have
software surfaces in Mandrake and hardware surfaces in Windows XP?
Because as far as I understand it, accessing pixels, like a getpixel
test would do, is much quicker to a software surface than to a hardware
surface, since it has to go through the PCI/AGI bus. Right?





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