This is probably due to my limited understanding of writing Xv apps but how do you keep the app from drawing the colorkey itself? isn't it
I simply assume that the app will, some way or the other, in the end use the XAA accelerator functions. As I said, my method is not bullet-proof.
just an X rectangle? is there an Xv function that the app uses or does
it just draw a rectangle and paint it the colorkey color? How does the
sis driver do it (if it does)? what does the output look like with no
colorkey drawn?
The depends. Earlier versions of mplayer (0.9) left the background visible (ie didn't overwrite the window at startup); later versions paint the window black at start, for what reason ever.
The real application for this feature is, of course, not a generic app like mplayer but a specially written app that utilizes the blue-screen technique for displaying a background and a video which is chroma-keyed, such as a weather forecast where the presenter stands in front of a blue wall and the viewer sees a weather map instead of the blue background. A real-life application of this kind (using SiS hardware and my driver) is installed at a local government's exhibition in Austria; visitors are presented a virtual TV interview person on screen and are being filmed during that interview. Afterwards they can watch the interview (which is being cut in real-time) and see themselves in a beautiful TV studio, while the cabin where the interview took place has a simple plain green background wall.)
does Xv even work without a colokey?
Yes, at least on SiS hardware. There are 16 combinations of src and dst combination (video-ROPs) available, include the standard one (video if background = colorkey) and all possible combinations of chroma- and colorkey (which monstly aren't so useful after all).
> I thought that's how the overly worked it overlays the video data based > on regions painted with the colorkey.
That's one of 16 possible ways.
I suppose in global alpha mode though (on radeon), it will blend the video with whatever the graphics layer shows so if I could get rid of that rectangle of color, I'd get a nice blend with the desktop and any windows over or under it.
I think it will be like that: If the alpha stuff is activated, the video overlay doesn't care about the colorkey anymore. Or perhaps you need to change the ROP (if such a thing is on Radeon) to ignore the colorkey. Do you see the entire video (if alpha avtive) even if another window covers a part of the video window?
Thomas
-- Thomas Winischhofer Vienna/Austria thomas AT winischhofer DOT net http://www.winischhofer.net/ twini AT xfree86 DOT org
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