- which (cheap!) video-in device should be used?
USB cameras are low-bandwidth and so can't accomodate big resolutions. Even if you get 240*320, then if it is YUV-4:2:0, then 2 out of 3 YUV color channels are encoded at 120*160 (!!!)
actually using 4:2:0 chroma samples (Cb,Cr) are swapped every other line, so each chroma channel is effectively 160*60. 4:2:2 chroma is subsampled at a 2:1. this is really a trivial amount of data loss and you look at it everyday and never notice. DVD and PAL DV25 is 4:2:0, NTSC DV is 4:1:1, broadcast TV is 4:2:2 and so is HDTV. the Y is the really critical data as far as clarity goes. as long as the processing is 4:2:2 everything is usually ok.
We like analog cameras. Find the right shop for buying those (probably not "consumer electronics" shops). Then use a capture card such as a PCI BTTV. You can get 480*640 @ 30 fps and such.
yet another example of 4:2:2 ;)
cgc