Philipp Ineichen wrote:
Hi Peter In the meantime I changed the alternate setting from 3 to 1 in the cpia_usb_open function. Now, both cameras are able to set the alternate setting (interface = 1), but xawtv (gqcam as well) is still not able to display both streams! I think that there is enough USB bandwidth since I changed the alternate setting to 1. Am I right? That means that video4linux has troubles handling both cameras simultaneously?
As I indicated in an earlier post, there is a fairly simple userland solution to this problem: using semaphores to enforce exclusive access to the read system calls as I have done in my modification to the 'motion' V4L program (http://interstice.com/drewes/motion-2.6.2-with-semaphore.tgz). This doesn't reduce the total capture speed for all cameras though of course each camera captures at about half the speed it did individually. I have used this method to keep two USB cameras working simultaneously in a security application for weeks at a stretch without any problems. I agree that a system level solution would be desirable, so if anyone knows how to make that work, by all means, please advise. In the meantime, my advice: use semaphores. Rich
