Xgl/Xegl future?

Michel Dänzer michel at daenzer.net
Thu Aug 25 20:05:04 PDT 2005

On Thu, 2005-08-25 at 18:30 +0200, Matthias Hopf wrote:
> On Aug 24, 05 10:59:28 -0600, Brian Paul wrote:
> > >>>>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.
> Yes, but as soon as we want an abstraction layer (in this case OpenGL),
> this isn't easily accessible, as several hardware vendors chose to not
> convert YUV to RGB on PutImage, but during scanout (using color keying
> for selecting the YUV framebuffer).

We're not talking about overlays (which will be little use with
compositing) but about using the 3D engine to do the colourspace
conversion and scaling.

Earthling Michel Dänzer      |     Debian (powerpc), X and DRI developer
Libre software enthusiast    |   http://svcs.affero.net/rm.php?r=daenzer

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