[cpia] Re: 2 cameras streaming at once?

[WJ Vlothuizen]

> Now your question: is this really necessary? I have a parport and a
> usb-camera right now. On PIII-350 I get no visible performance
> degradation if I have gqcam open with both. So I guess unless you don't
> want to do serious video-capturing on a smp-machine streaming will not
> gain you that much. But who wants to do that with a bunch of
> CPiA-cameras anyway? In short right now it is a desktop driver for a
> desktop camera.

The reason why I would favor streaming and double buffering is that I
use the camera's to provide vision for a robot, where I want a high
update rate and every bit of performance counts. I entirely agree with
you that this is not the way most people will use these cameras. Instead
of a interrupt driven scheme I would envision the use of a kernel thread
that works when incoming data and an outgoing buffer are available, and
otherwise goes to sleep.
Further experiments on my side show that the driver *always* fails after
a hub disconnect. I don't know whether the CPiA-driver could sense such
a disconnect and reinitialize the camera, but the disconnect should not
be there in the first place. After some reading on www.usb.org I removed
the EMI-control components on the USB formcard: this clearly improved
the results, but the problem still remained. I have never seen a
disconnect when using one camera, so there seems to be some mutual
electrical influence (I don't think this is a software issue).

Regards,
Wouter Vlothuizen