How to open several cameras from the same USB port in Ubuntu
Hi!
I have a headset with 3 cameras. One USB output. I am using Python 2.7 on Ubuntu 16.04 and OpenCv 3.3.1-dev I can't read from the 3 cameras at the same time that use the same USB port.
I have this error: vidioc_streamon: No space left on device
Do you know how I can solve this problem. I have tried with read(), grab()/retrieve(). Always the same error.
Thank You
if the problem is bandwidth (one usb2 port can "just so" handle a single webcam), you can try to reduce the resolution of your cams.
(and 3.3.1 is quite old)
how does that device work, even ? does it concat 3 images to a single one ? (like e.g. a Zed does)
or do you try to access 3 VideoCaptures with 0,1,2 device id's ?
The resolution of the cameras are 200x200, 200x200 and 1280x720. Even if I only try with the two 200x200 cameras I have the same error. Maybe I could try to use a more recent OpenCV version. What is the more recent compatible version for Python 2.7?
I am trying to access with VideoCapture with 0,1,2 device id's. It works when I open only one. I tried with read, grab and retrieve. But I always have the same issue. I don't know if it concats 3 images in a single one.
Let me know if you need other informations. I am doing a project in a lab, and opening the 3 cameras at the same time is mandatory.
Thank you
PS: I am using this device: https://pupil-labs.com/store/
btw, is it usb2 or usb3 ?
i don't think, updating software will help (though pip has pretty recent releases),
sounds more like an usb bandwidth problem.
It is usb3. Yeah I agree. I think it is a banwidth problem. But I don't know how to handle it. Do you have any idea?
sorry, not really.
I already met this
vidioc_streamon: No space left on deviceerror message. It caused by the underlying V4L driver, not OpenCV related.It occurs when several cameras are connected, but it isn't a bandwidth problem (I had it with two webcams on different USB ports).
I don't remember how I solved it, google this error message for ideas for solutions.
Some more ideas: to be sure to open the same camera for the same variable, it's best to use the camera identifier in Linux (something like
/dev/v4l/by-id/lefteyecamera) than the device number (0,1,2...).You might also try to test the provided example code to see if the camera works with your hardware and then use their code as a base for your project. If you can get the image buffer, transforming it to OpenCV matrix or Numpy array is trivial.
I have already google this message error, but I haven't found any solutions.. What I know is that they are using uvc to open their cameras. I have tried but it didnt work for now. I have other issues. I will try with the camera identifier and I will let you know.
Ok, but how do you handle with this V4L driver? With their demo software they can open the 3 cameras at the same time, using uvc but I don't understand how
Thank you for your help
Where/how do you find the camera indentifier in Linux?
I success open the 3 cameras with uvc Library. Now I have an array of: (720,1280,3). How can I transform it into an OpenCV RGB Image?