> * 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???] Two schemes #1 TV card dma drives an offscreen YUV buffer and the video card scales converts and overlays. This is preferred - less PCI bandwidth and arbitary scalers #2 TV card does RGB conversion and scaling > * 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. This is mostly useful for mpeg/dvd playback. It helps if the hardware on the capture device cannot do overlay too
