Ragga Muffin <ragga@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> writes: > Aaron Solochek <leko@xxxxxxx> wrote: > > > I was wondering what the difference between overlay and grabdisplay are, > > in terms of preformance. I am running AcceleratedX 5, and I think that > > means I can't do overlay. I have a g400max, and was wondering, > > basically, what the optimal setup would be. > > In overlay mode the video is copied directly to the framebuffer, thus > the need for cpu intervention is minimal. > I'm not quite sure what grabdisplay is, but it seems to involve > copying data from the bus to memory to display so it can be quite slow. > > Whether you can do overlay is, AFAIK, dependent on the videograbber board > and not so much related to which Xserver you are running. (IIRC, AccelX > worked fine here with a bt848 card and a Matrox G200). > > For xawtv, you need to run v4l-conf as root once to set things up for > overlay. Seems there's a confusion in the following mails between: * grabdisplay: make a huge memcpy of each frame to the X server (only way to play with export DISPLAY (hope you have a 100Mbps Ethernet network :-) ) Following are local only: * overlay flavour 1: by some magic way, the card grabs directly to the video ram and without cpu intervention, the image is refreshed (in RGB mode I think). It must cause a slight performance loss though because the bandwidth on PCI bus is not infinite (try putting four TV cards to see what happens). [how does that thing scale???] * overlay flavour 2: XvImages and friends; here the card grabs to a special shared memory segment (can be in YUV format). The image is not converted to RGB before sending to VGA, and is hardware scaled. I can't see a valid reason to use this one (which requires a X4.0.1 setup) compared to the previous. * overlay flavour 3 (analog): the VGA card output is filtered by an analog overlay that replaces a keycolor by an analogic signal. -- Emmanuel Michon Ingénieur en développement logiciel REALmagic France Mobile: 0662834836 GPGkeyID: D2997E42
