[MPlayer-dev-eng] Removal of backing store

[Vladimir Mosgalin]

Hi Stephane Marchesin!

 On 2008.08.22 at 02:41:21 +0200, Stephane Marchesin wrote next:

> >> some recent drivers (notably the open source ones using EXA). There
> >
> > Have you checked it for intel, ati and radeonhd drivers?
> >
> I don't have the hardware, but it should make no difference.

Well.. If it makes a lot of difference on one card, at least it makes
sense to check out what it does for others.

> In nouveau, we have a port that is the hardware overlay, but it will
> transparently fallback to the blitter when run in composite

Hm. Why, is this driver limitation?
I'll check what happens on intel with compiz (though driver I'm using is
kinda old, 2.2.1, but it uses EXA).

And what exactly does composite has to do with backing store? Actually,
what cases are you talking about? Composite-enabled desktop which
doesn't use compiz or other stuff like that? Because I don't quite
understand why compiz-enabled desktop would need or use backing store
anyway - when windows are rendered to textures and the textures are kept
anyway and compiz renders in any order without actually making applications
redraw them, isn't that making backing store obsolete?

> > Well, I tried this on radeon X1900 card with fglrx 8.8, using
> > -vo gl:yuv=2:force-pbo, -vo xv and -vo x11 output drivers and
> > performance was identical in each case, with or without patch. Is this
> > patch nvidia-specific?
> >
> 
> OpenGL is not affected by backing store, so your benchmark is meaningless.

Well, I tried both xv and plain x11 too.

> However, this change is beneficial to:
> 1. drivers that use EXA and implement a hardware overlay which is able
> to fallback to a blitter/texture

Intel provides two xv adaptors, one for hardware overlay and one for
textured video. Not sure about fallback, probably there isn't (when you
specify adaptor directly).

> 2. drivers that have a real hw overlay where you waste vram

Radeon cards based on R5xx and higher can have hw overlay, but it's
never used (it's kinda crippled or something, and supposed to be
obsolete). In all cases, only textured video xv adaptor is provided by
driver.

IOW, are you sure your fix applies to anything but older nvidia cards?

-- 

Vladimir