[Xorg] Re: Damage/Composite + direct rendering clients

[Eric Anholt]

On Mon, 2004-05-17 at 11:02, Alex Deucher wrote:
> --- Keith Packard <keithp at keithp.com> wrote:
> > 
> > Around 9 o'clock on May 17, Alex Deucher wrote:
> > 
> > > Many video overlays support alpha blending with the graphics layer,
> > > it's just that support was never implemented since xfree86 never
> > > supported it.
> > 
> > Composite doesn't really expose things in a way that would make this 
> > hardware capability usable.
> > 
> > Instead, it expects the video to be painted into the window pixmap so
> > that 
> > those pixels can be composed to form the screen image.
> 
> Sorry for my composite ignorance.  Couldn't we just have Xv ignore
> composite and just use the video engine's native blending abilities to
> blend video with the graphics layer?  or add composite "support" to Xv
> by just passing it the required gamma value and letting the hardware
> take care of the rest?

With composite you really want to be able to get at the pixels to be
displayed so that transformations can be applied to them before
displaying them, rather than just putting them up as the last
transformation to be applied to the screen before display, as the
overlay scaler would do.  I've found that the 3d hardware solves the XV
problem pretty well in Xati (and gives you as many XV ports as you
want), though it lacks the controls typically associated with YUV
conversion using the overlay scaler, like brightness/saturation.

-- 
Eric Anholt                                eta at lclark.edu          
http://people.freebsd.org/~anholt/         anholt at FreeBSD.org