On Tue, Feb 20, 2001 at 01:56:49PM -0500, Peter Kaczowka wrote: > Regarding "offscreen surface support": > Other than the source code, is there any way to tell that you have "offscreen > surface support"? Not afaict, no. Without it, XvPutVideo still works (driver bugs aside, of course), it is just done a different way. > Is there anything returned from the Xv or V4L interfaces, or is there any > required setup? > Or does it "just work", so that when you start video using Video4Linux, the YUV > video goes to the offscreen surface? Yes, "just works" is the idea from the user program. Whether you can get it to work without tweaking the bttv driver or the v4l.c program is a different question though :o) > Before I attempt to put "offscreen surface support" into the i810 > driver: > > - is "mga" the best / simplest example? If not, which one? mga was the first (perhaps a creation of the mga driver writer to do overlay video?) most of the other drivers are (more or less) cut and paste of that driver. The mga also supports what they call 'texture surfaces' which use offscreen video memory, but not the hardware overlay. Most likely you'll find an i810DisplayVideo function that does the necessary hardware stuff. > > - what's the real advantage of using the offscreen surface? Well, XvPutImage seems to do the same thing 25 times a second that XvPutVideo does once (or once per resize/reclip anyway) PutImage does a copy of the data too, so the main benefit is performace. Drivers like tdfx can bilinear filter the overlay as it scales it, so the quality is improved too. The texture video stuff has the advantage that most video cards only support 1 hardware overlay and then only on the first head of a multihead setup - so with that you can potentially display more than 1 stream at once or display a stream on a different monitor. > XV_DONT_BLIT_THE_COLORKEY option > (see your other mail). Is that implemented in any other driver? AFAICT, it isn't in any driver yet. > - is anyone else adding this support to the i810 driver, or planning on doing > so? You tell me :o) I haven't the first clue about how or where X development/design takes place. I have spoken to at least 1 X driver developer who took some convincing that there was such a thing as offscreen surfaces, so talking to the maintainer may be the first step. -- Michael.
