On Thu, 11 Dec 2003 v4l@xxxxxxx wrote: > > Grab all frames (i.e. 25 QBUF and DQBUF per second) and copy only the > > ones you want, maybe on the basis of the timestamp or timecode returned. > > Even if your QBUF were *perfectly* rythmed, what counts is the video > > synchro signal, not the system clock. > > > > Hi, > > 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)... You need to use the temporal decimation register on the bt8x8 chip, to have the card drop frames. This is the only sure way you can get smooth dropping of frames, without capturing all frames and deciding what to drop yourself, which of course has the PCI bus problems you mentioned. The only thing is the temporal decimation register is a strange thing, and doesn't appear to work as described in the data sheet. I remember a thread on this list a long time ago, were we discussed it. I think someone actually managed to get it working correctly and had a patch for the driver. I can't find any searchable archives for this list, but maybe there is some information out there.
