Capturing multiple webcams (uvcvideo) with OpenCV on Linux

Question

I am trying to simultaneously stream the images from 3 Logitech Webcam Pro 900 devices using OpenCV 2.1 on Ubuntu 11.10. The uvcvideo driver gets loaded for these.

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Answer 1

I had this exact problem, using three logitech quickcam pro 9000 cameras (using ubuntu). I could read from two, but not three. In my case, I wasn't using opencv, but was accessing the cameras through V4L2 directly, using memory-mapped IO. Simply put, there was not enough USB bandwidth to allocate three buffers.

I was reading in the uncompressed frames, however. As soon as I switched the format to MJPEG, the data was small enough, and I could read from the three cameras. I used libjpeg to decode the MJPEG stream.

I haven't looked into how to change the image format using OpenCV, but I do know that it needs to be MJPEG to fit all that data.

Before I switched to MJPEG, I spent a lot of time trying to access each camera one at a time, streaming a single frame before switching to the next. Not recommended!