Michael, I Think some of the other replies have given the correct information, but I'll try to sum it up.
First, when you do Xv you are not drawing to the screen as you know it as all. The data goes into a totally different buffer. This area is then "overlaid" on top of the normal framebuffer by the overlay hardware. This is why your framebuffer (desktop) is in RGB color but the data you send to Xv is YUV. Additionally the overlay can stretch or shrink the image on the screen without altering the actual data in memory. This of the overlay as a projector that projects on the top of your desktop. The projector can change the size of an image or alter it's colors without changing the input. Second, XImages and XvImages are client side images. When you do an XPutImage or XvPutImage you are putting the data into a server side image. There is no separate copy of each image inside the X server. So the fact that you are using 2 XImages means nothing. If the target of your put() is the same then the data is getting overwritten. This behavior is a little different since the i810 double buffers the overlay, but the point is that the number of XvImages you are using has nothing to do with what happens inside the server. They are just memory areas of a specific format. Third, the i810 only has one overlay engine. Think again of the projector... it can only project one image to one place. If you try to use it twice (which you should not be able to do if you grab the port as you are supposed to do) you make the projector point to one place then the other, back and forth. Last, The blue is the colorkey. If the projector is displaying on top of your desktop then you could never make a window be "on top" of the projected image. This would make it impossible to ever cover up a portion of your video window. The solution is the colorkey. The overlay only projects onto pixels that are of a specific color. All other pixels will not be covered up. The default colorkey is blue and when you do an XvPutImage the X server paints your actual window blue so that the overlay will draw "on top" of those pixels. When you point the overlay to the second window the first window still has the blue pixels in it so that is what you get. It would be nice to have a software fallback so that you could do as many Xv's as you wanted (slowly) but that isn't the way Xv was designed. You'll have to convert the YUV data into RGB and do a regular XShmPutImage in the second window. -Matt -----Original Message----- From: Michael Zayats [mailto:[EMAIL PROTECTED]] Sent: Thursday, October 18, 2001 3:46 AM To: [EMAIL PROTECTED] Subject: [Xpert]very strange XVideo behaviour (i810) well I am trying to draw 2 streams of yuv420 frames to 2 windows I am doing XvShmPutImage , once to first window and once to another once to first, once to another etc. I use separate shared memories for each window. I am doing it very slowly (usleep(3000000) between each draw). the strange thing is that when I draw to one of the windows the second goes BLUE! the more interesting is that if I get one of the windows behind something such that clipping eats it all) the second behaves normally and doesn't present anything blue. it seems to me that there is some problem in i810_video driver, I just can't think of anything else! (First guess was that I get Exposure events and doesn't respond to them, but after checking I know that I don't get them at all (only when I raise the window again)). any thoughs? Michael _______________________________________________ Xpert mailing list [EMAIL PROTECTED] http://XFree86.Org/mailman/listinfo/xpert _______________________________________________ Xpert mailing list [EMAIL PROTECTED] http://XFree86.Org/mailman/listinfo/xpert
