Xgl and direct rendering

[Matthias Hopf]

On Mar 01, 06 18:01:16 +0100, Roland Scheidegger wrote:
> Matthias Hopf wrote:
> >Yes, that's what I actually meant. I'm currently unsure whether this
> > is enough for the color conversion and resampling code (there are 
> >limitations with dependend texture lookups), but I guess it is. So 
> >ATI_fragment_shader might be supported in the future as well. Though 
> >there are more pressing issues ATM.
> There are no dependant texture lookups in that code (as the parameters
> for texture sampling are not dependant on the results of previously
> sampled textures, only generic math). Definitely doable (though I don't
> know if the chip is actually fast enough?)

I was already thinking about color correction. But right, doable, and I
do think it is fast enough.

> >It should be possible by moving the texture coordinate calculation to
> > the main program and let the interpolation unit do the rest. 
> >Additionally, we might have to bind the texture to two units. I don't
> > remember 100% of ATI's fp programming interface right now.
> Yes, exactly. Or maybe just use 3 textures, since basically this is
> essentially what it is anyway.

Texture setup and switching is costly, so one would like to avoid this
as much as possible. Though no real switching is involved here.
Right now in glitz setting up multiple coordinates for a single texture
isn't really supported. That can be changed, though.

> >This is non-planar. Could work for YUY2, but not for YV12.
> Certainly. planar yuv doesn't fit the description of a 3-component
> texture really, it's 3 single-component textures, that you stuff them 
> together doesn't change that - in fact it might be slower depending on 
> how texture caches etc. are organized than using triple-texturing. I 
> think most software can deal with both planar and packed xvideo.

Most media players only use YUY2 for WMV (binary only M$ codecs, that
is). ffmpeg creates YV12.

> >I consider hardware overlay broken by design. It has already given me
> > tons of nightmares.
> I wouldn't call it "broken by design" since it predates 3d accelerators 
> (not to mention pixel shaders!) where the hw simply was too slow for a 
> better design.

I mean nowadays :)

Matthias

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