Switching cameras
Roland from South Africa  [107 posts]
11 year

I have been playing with two USB webcams. I want to sequentially process two completely different images (I don't want to use mosaic.) but I notice that if I change the selected camera, the new camera powers up, and the old one powers down. The problem is that there is a delay of about three seconds as the image saturates, then stabilises.

What I want to do is break the USB power line and keep the cameras powered up. And make a small PCB with a relay per camera. The relay connects the data lines. I can now use the USB power line or a line from the parallel port, with a script, to control the relays and thus select a camera, with immediate display.

Does this sound feasible? Any shortcomings besides the extra work?

Steven Gentner from United States  [1446 posts] 11 year
Rather than fix it in hardware just select one camera using the main Camera button and Options Video tab, and then use the Marker or Camera properties module to switch to the next image and keep them both active.

Anything before the Camera module will then process the first image, anything after will then process the second camera image. You use these modules to switch camera image but keep both cameras active so that they can be accessed immediately.

Its not so much the power that is dropped but rather the directX subsystem that needs to initialize ... that's what takes a while to do when you switch.

Note that marker module can be used to save the current image to memory and bring out a saved or alternative image to be processed.


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