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List:       freedesktop-xorg
Subject:    Re: Xgl/Xegl future?
From:       Eric Anholt <eta () lclark ! edu>
Date:       2005-08-24 18:39:55
Message-ID: 1124908795.91625.11.camel () leguin
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On Wed, 2005-08-24 at 10:59 -0600, Brian Paul wrote:
> Eric Anholt wrote:
> > On Wed, 2005-08-24 at 17:49 +0200, Matthias Hopf wrote:
> > 
> >>On Aug 22, 05 14:56:12 -0400, Michel Dänzer wrote:
> >>
> >>>On Mon, 2005-08-22 at 19:23 +0200, Matthias Hopf wrote:
> >>>
> >>>>On Aug 22, 05 01:01:37 -0400, Michel Dänzer wrote:
> >>>>
> >>>>>On Sun, 2005-08-21 at 21:08 -0400, Owen Taylor wrote:
> >>>>>
> >>>>>>In order to do a good job with a GL-based compositing manager you need:
> >>>>>>
> >>>>>> - Redirection of OpenGL and Xvideo clients
> >>>>>
> >>>>>This is true whether the compositing manager is GL based or not.
> >>>>
> >>>>But an OpenGL based Xserver can use the graphics hardware for scaling
> >>>>and color conversion of XV surfaces (that's what I've been working on).
> >>>
> >>>So can a GL based compositing manager.
> >>
> >>No. Not with current Xservers. No way to get YUV / YUY2 data in native
> >>format. This isn't easily possible to implement, either, as the PutImage
> >>call does not have to completely fill a Window, and RGB data can be
> >>drawn over it afterwards as well.
> > 
> > 
> > Obviously a GL compositing manager wouldn't be doing the YUV to RGB
> > conversion, since the compositing manager is at the wrong level.  It
> > should be done in the XV handler of the driver in the DDX.  It's been
> > done in several KAA (aka EXA) drivers before, using the graphics
> > hardware for scaling.
> > 
> > GL isn't needed to do this.
> 
> Just FYI, there's the GL_MESA_ycbcr_texture extension that let's you 
> pass a YCbCr texture image to GL.  The YCbCr -> RGB conversion is done 
> by the hardware when the texture is applied to a polygon.
> 
> Arbitrary color-space conversion can also be done with fragment 
> programs nowadays.
> 
> Using the GL hardware for that kind of stuff seems pretty interesting.

Yep, I know.  We use the same hardware to do the same thing in the KAA
stuff.  What I'm trying to say is that GL isn't necessary to do it,
though it can do it as well.

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

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