[SDL] SDL Performance once again

Mattias Karlsson betasoft at acc.umu.se
Thu Sep 7 11:45:50 PDT 2006


On Thu, 7 Sep 2006, Maxim Mozgovoy wrote:

> I have read a couple of discussions on this topic but still haven't formed a
> consistent picture in my mind.
>
> The question is simple: suppose I initialize SDL, and perform a simple loop:
>    Erase the whole screen
>    Blit a background image
>    Blit several sprites
>    Pefrorm flip

In this case, erasing the screen is not needed and depending on how much 
is covered by sprites SDL_UpdateRects may be faster than SDL_Flip.

> How many FPS should I get on a typical modern hardware (say, 1,5 GHz
> processor and a decent videocard; 1024*768*32b) under reasonable
> assumptions?
>
> I know it depends on hardware/software surfaces, fullscreen/windowed mode,
> etc., but still? In my case it is usually 70-80 FPS, no more (while I
> expected at least 150).

Playing around with testblitspeed should answer most of those questions. 
On X11 a quick back-of-the-envelope calculation gives around 100 FPS as 
a teoretical max. In practice, you will never get there more than a few ms 
at a time.

> One reply in the newsgroup was something like: "if you want to get speed 
> in SDL, you should use OpenGL, otherwise you execute a generic 
> cross-platform (slow) code". Is it really so? I mean if I want speed, I 
> should forget about all SDL functions for blitting and about third-party 
> routines for primitives (like SDL_prim), and begin to study OpenGL?

Or wait for SDL 1.3.

The problem with SDL 1.2 is that almost no blits is HW accelerated, while 
in OpenGL most of them are.




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