[SDL] Re: HW accelaration

Marco Salvi nao at libero.it
Tue Aug 17 21:52:24 PDT 1999


Hello Sam

On 17-Ago-99, you wrote:

>> Hi guys (and gals!) :)
>> I have, like usually, a couple of question.
>> I'm wondering cause SDL_GetVideoInfo can't detect
>> any HW acceleration in my S3 (virge dx).
> 
> DGA currently supports NO hardware acceleration.
> This will change with XFree86 4.0

Umh..so actually, no gfx board can perform hw blit (or other
hw accelaration) under SDl->DGA->X11?
Maybe I misunderstood your statement :)

> 
>> I know how to render a 640x480 screen from a 320x200 screen via cpu.
>> But I was looking for something smarter than just take a pixel and
>> to write it in a buffer 2 times (the same for each scanline..) :)
> 
> If the 320x200 screen is 8-bit, you can build a 32-bit lookup table
> which contains two pixels for every one original pixels.  The other
> advantage of this is that you get 16-bit depth support for free.
> Then, when you're finished with a scanline, you can double it using
> memcpy().
> 
> This is a very fast operation on modern systems, using software 
> surfaces.

thanks! it seems a very smart idea :)

ciao,
Marco




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