Multiple USB Cameras

Sorry if this is in the wrong place.

I'm trying to use stereo vision in OpenCV however I've hit a snag. I'm guessing that since the USB ports are on the same bus when I try to activate the second camera it gives:

Code:

libv4l2: error turning on stream: No space left on device
VIDIOC_STREAMON: No space left on device

Similar situation happens when I open the Webcam Utility program twice each one set to a different camera.

I'm unsure if there is any obscure Linux magic to fix this issue.

Thanks!

 

It's better to see which /dev/video number are assigned to each camera. This way you should be use both cameras...
So, let's see. First connect one camera, then the other (system should be already on).

Then type:

Code:

dmesg | tail

Paste output here

 

One is dev/video3 and the other is dev/video4

 

I can get one camera working at a time but not both.

Finally got time to run dmesg here's the output:

They typically load up as video3 and video4. So likewise in openCV I use 3 and 4 for the camera index numbers.


I tried

Code:

rmmod uvcvideo
modprobe uvcvideo quirks=128

But was met with:
ERROR: module uvcvideo does not exist in /proc/modules

 

After running lsusb I noticed that there are two buses. Is bus 1 J24?

In other words the primary USB, WIFI, etc seems to be on bus 2 while lsusb shows that there is a bus 1. So I'm hoping bus 1 is the third USB port. If that's the case getting the adapter would fix the bandwidth issue of the webcam since (from what I've read) 1 camera can take about 60% of the bus bandwidth.

 

For future knowledge: Third usb port is on Bus 2. No idea what bus 1 is used for.

 

From my experience I think your intuition is correct: it's a bandwidth problem. Can you try using gvucview or something similar to reduce the resolution and/or framerate enough to get it working?

 

I did. The webcams can not go into a small enough resolution in the MJPG format to work together. Some lower res cameras will be needed.

 

Hello, how can i recognize a webcam trough my udoo quad, i cannot open it.

Please help me

 

It'll depend on the webcam. Not all work with Linux.

 

Waht jaeg said. It has to be a UVC compatible camera. What I've found is that most Logitechs (since they got bought by microsoft) are NOT UVC.

Basically if it says it requires Windows, you're screwed. If it says it works on Mac, you're good to go (Mac's also require UVC.)