Actually I am wondering roughly the same thing. Can you hook up several
USB cameras/capture devices (AverTV for example) at one and have them
recognized as devices.
Michael
On Wednesday, April 11, 2001, at 02:38 PM, Rich Drewes wrote:
> Hello,
>
> I've been unable to get two USB CPIA cameras to work reliably on the
> same machine at more or less the same time. Either camera (/dev/video0
> or /dev/video1) will work fine by itself when the other camera is not
> being used--the problem arises when trying to use them at or near the
> same time. While it is possible to open /dev/video0 and /dev/video1
> simultaneously, if one device is in the middle of a VIDIOCMCAPTURE then
> opening the other device fails with a "device or resource busy error".
> If I coordinate the device openings to work around this problem (that
> is, not starting captures until both devices are successfully opened),
> then things fail if one card tries to do a VIDIOCMCAPTURE while the
> other is already doing a capture. I haven't found any V4L api docs
> anywhere that indicate that doing two captures at once on separate
> devices from separate processes is not permitted.
>
> I have experimented with protecting the actual capture with a shared
> memory semaphore so two processes never try to do a capture at the same
> time. This seems to work mostly, though there are enough lingering
> problems that I suspect that this may not be a proper solution. Does
> anyone have a recommended approach? Has anyone else gotten two USB cams
> working on the same machine reliably? If so, under what kernel/v4l
> driver version?
>
> I am on kernel 2.4.0. The cameras are generic USB CPIA cameras made by
> Ezonics. I have used a variety of test programs to explore the error
> behavior, but my main test environment is two "motion" processes (, each
> process controlling a camera. I have seen the same behavior with two
> concurrent gqcam processes as well, but it usually takes longer to
> manifest the problem with gqcam since gqcam spends a lot of time waiting
> between successive VIDIOCMCAPTURE calls and therefore the probability of
> both processes trying to do a VIDIOCMCAPTURE at the same time is lower.
> Eventually, however, an error will occur.
>
> Any suggestions will be appreciated.
>
> Rich
>
>
>
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