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Re: [SDL] DirectAccess to Video Memory [was: Hello, new member reportin

Subject: Re: [SDL] DirectAccess to Video Memory [was: Hello, new member reporting]
From: Antonio Marcos
Date: Sun, 1 Feb 2009 16:58:06 -0800 PST
> As Mason Wheeler said, you can't do anything special
> with DMA, though,
> no colorkeying, no nothing. If it can't be done with
> memcpy(), it
> can't be done with DMA.

Yes, thats what I believed :) my intention is to get the image ready to 
display, and THEN DMA it to the card. But yes, if the sprite is already at the 
vRAM great, it will make it "ready" (the number crunching) using the gpu.. 
before that is just loading time.. disk to RAM.. DMA to vRAM, the user will 
just see it once, probably at the start of the game, or level.. but I believe 
you were talking about RAM to vRAM bandwidth.. not vRAM to vRAM... well, sorry 
for any misunderstanding :)


--- Em dom, 1/2/09, Pierre Phaneuf <pphaneuf@xxxxxxxxx> escreveu:

> De: Pierre Phaneuf <pphaneuf@xxxxxxxxx>
> Assunto: Re: [SDL] DirectAccess to Video Memory [was: Hello, new member  
> reporting]
> Para: amcmr2003@xxxxxxxxxxxx, "A list for developers using the SDL library. 
> (includes SDL-announce)" <sdl@xxxxxxxxxxxxxxxx>
> Data: Domingo, 1 de Fevereiro de 2009, 13:50
> On Sat, Jan 31, 2009 at 7:14 PM, Antonio Marcos
> <amcmr2003@xxxxxxxxxxxx> wrote:
> 
> > I dont get the point of DMA then :( probably because I
> dont know whats this number crunching doing... but I dont
> get whats the point of DMA if the whole data have still to
> go through the gpu...
> 
> DMA is to send data from the main RAM to the video RAM. So
> in the case
> of this example, where we wanted to top out the capacity of
> the GPU,
> we'd use DMA (well, by "we", I mean the video
> card driver) to put the
> sprites *once* in video RAM, then use the GPU to blit it at
> various
> locations on the screen in the fastest possible way.
> 
> As Mason Wheeler said, you can't do anything special
> with DMA, though,
> no colorkeying, no nothing. If it can't be done with
> memcpy(), it
> can't be done with DMA.
> 
> -- 
> http://pphaneuf.livejournal.com/


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