On Fri, 12 Dec 2003, Tuukka Toivonen wrote: > On Fri, 12 Dec 2003, Erik Slagter wrote: > > >> That's what I used before, and that works ok. The problem is that I'm using > >> 4 or more grabbers in one PC now, and capturing everything and skipping > >> frames causes too much data on the PCI bus, resulting in image distortion. > >> (distorted horizontal lines at random places, etc)... > >Yeah typical... You might try to play with card latency's, but probably > >you're just plain out of PCI bandwidth. > > Latency? Is there some BIOS setting or how it can be changed? Usually a bios setting, but you can also change it with setpci at run time. I wrote some more about this a while back, check the list archives. > And by the way, why wouldn't PCI bandwidth run out temporarily with just > one card, if several devices try to transfer data at once? What PCI does in The capture card has a buffer that will fill up while it waits for access to the PCI bus. If it has to wait too long, the buffer fills and you lose data. > this case, allow one device to transfer one word, then the next, and so on, > or is the bus allocated for a single device for a longer period? The latter. > My single TV card (bttv878) makes the horizontal garbage as described if I > use SCSI disk simultaneously, no matter whether synchronous or async mode > or whatever transfer speed the SCSI controller is set, or how small image > I'm capturing. (IDE works fine). What scsi card is it? It might be a poorly designed card, or a poorly designed driver. You might also have the latency on the scsi card set too high, letting it hold the PCI bus for too long.
