[MPlayer-dev-eng] Xvideo Extension

[Shachar Raindel]

On Fri, 6 Aug 2004 07:47:34 -0500, Billy Biggs <vektor at dumbterm.net> wrote:
> Amir Bukhari (ufz6 at rz.uni-karlsruhe.de):
> 
> > > Well, Xvideo uses the overlay feature of the video cards to draw the
> > > video on the screen. That means most of the time the video is never
> > > converted, but stored in some yuvbuffer on the video card. This data
> > > is never merged with the screen data but gets converted, scaled and
> > > overlayed during the display process.
> >
> > OK this during display process, where it done? In Video Card or in
> > Xvideo Extension.
> 
>   It's done in hardware by the video card.  The image data is never
> stored in the framebuffer in RGB.  It is converted to RGB as it is sent
> to the monitor.  It does not fit in the model of COMPOSITE/DAMAGE.  The
> overlay will draw video wherever it sees its colour key (usually blue)
> in the framebuffer, but it cannot do any of the scaling, rotation, or
> translation that you want to do in your X server.
> 
>   There is discussion going on about what to do with XVIDEO by Keith
> Packard and Eric Anholt, you might want to talk to them.  One option is
> to implement XVIDEO by always using OpenGL: the Mac platform has fancy
> alpha blending and does not support overlay hardware, for example.
> However, there are some advantages to overlay surfaces, so it is
> unclear if maybe some method should be supported.  One idea is to do
> something complicated like only use th overlay when the image is
> perfectly square and opaque, and then fall back to OpenGL otherwise, but
> this might be to complicated.
> 
I remeber hearing something about drawing Xv video on OpenGL ovelays,
where the card scales and stretch the video correctly. Check google
for this.