On Sun, Mar 05, 2006 at 09:56:20AM +0000, Dieter wrote: > It might be possible to set up X11 to avoid the overscan area. > Have to give that some thought. > > For non-X11 applications, (and even for X11 if it turns out to > be non-trivial to avoid the overscan area) it would be handy if > there was a way for the software mode and the actual hardware mode > to be different. The software would see fewer pixels so that it > wouldn't paint things in the overscan area. > > Given the limited resolution of standard resolution TVs, it > would be good to let the user fine tune the software mode > to match the actual overscan of their particular TV. > > Hmmm... This is basically just a different application of the > same capability in my previous posting. (Allowing the firmware > to talk at 640x480 and a fixed-frequency monitor to receive say > 1280x1024.) > In modesetter terms, there is a difference between overscan and blanking. Overscan is where the CRTC is not blanking, but where it isn't pumping out pixels either. It pumps out the overscan colour instead (VGA cmap stuff). Sadly this is still quite common as many hw makers don't provide enough blanking, or at least don't provide enough register space for a more complete range.
A good X driver on good hardware has everything adhering to the modeline you feed it. In the X modelines blanking and overscan are one and the same. Blanking is effectively the area between H/VDisplay and H/VSyncStart, and between H/VSyncEnd and H/VTotal. Play with the modeline if you want more or less blanking. FB has a similar sort of setup, although here the term margin is used for blanking as well (this is intended extra blanking, not necessary blanking in VESA terms). Here it might depend on the dac used, check its datasheet. If you're talking about the TV encoder, which will most likely be the device handing you RGB and composite sync, then the whole game changes. The modeline fed to the CRTC defines the framerate, and the TV encoder should handle the incoming mode at the given framerate (TV encoders usually don't have a framebuffer and can at most scale a few lines). The amount of blanking/overscan seen on a given TV is usually configurable in the encoders I2C config registers. The software for controlling that isn't generally present in Xorg, but this is where i have my unichrome.sf.net code aimed at. Luc Verhaegen. _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
