rbaleksandar's profile - activity

I have two Logitech Pro 9000 webcams. I have discovered a strange behaviour in cv::VideoCapture::set() when setting the frame size (width and height) for my captures resulting in the infamous error

libv4l2: error turning on stream: No space left on device
VIDIOC_STREAMON: No space left on device
ERROR: Could not read from video stream

for my second camera. In order to fix it I have to reduce my frame size almost 2 times from the initial one. Now here is the interesting thing:

• Version 1 (without using cv::VideoCapture::set()) - I manage to get both cameras up and running at 15fps (I tried with 20fps but I get the error I have mentioned above) with a resolution of 640x480, which seems to be a sort of a hidden default for those cameras (I was unable to find in the source code of cv::VideoCapture where this is set) if you don't specify these. The two values are retrieved by using cv::VideoCapture::get(CV_CAP_PROP_FRAME_WIDTH) and cv::VideoCapture::get(CV_CAP_PROP_FRAME_HEIGHT) respectively. Here is a small example:

  // The indices are 1 and 2 since 0 is my built-in webcam (I'm using a notebook)
  cv::VideoCapture cap1(1);
  cv::VideoCapture cap2(2);
  
  if(!cap1.isOpened())
  {
    std::cout << "Cannot open the video cam [1]" << std::endl;
    return -1;
  }
  
  if(!cap2.isOpened())
  {
    std::cout << "Cannot open the video cam [2]" << std::endl;
    return -1;
  }
  
  // Set both cameras to 15fps
  cap1.set(CV_CAP_PROP_FPS, 15);
  cap2.set(CV_CAP_PROP_FPS, 15);
  
  double dWidth1 = cap1.get(CV_CAP_PROP_FRAME_WIDTH);
  double dHeight1 = cap1.get(CV_CAP_PROP_FRAME_HEIGHT);
  double dWidth2 = cap2.get(CV_CAP_PROP_FRAME_WIDTH);
  double dHeight2 = cap2.get(CV_CAP_PROP_FRAME_HEIGHT);
  
  // Here I display the frame size that OpenCV has picked for me - it is 640x480 for both cameras
  std:: cout << "cam[1] Frame size: " << dWidth1 << " x " << dHeight1 << std::endl;
  std::cout << "cam[2] Frame size: " << dWidth2 << " x " << dHeight2 << std::endl;
  cv::namedWindow("cam[1]",CV_WINDOW_AUTOSIZE);
  cv::namedWindow("cam[2]",CV_WINDOW_AUTOSIZE);
  
  while(1)    
  {    
    cv::Mat frame1, frame2;    
    bool bSuccess1 = cap1.read(frame1);    
    bool bSuccess2 = cap2.read(frame2);
  
    if (!bSuccess1)
    {
      std::cout << "Cannot read a frame from video stream [1]" << std::endl;
      break;
    }
  
    if (!bSuccess2)
    {
      std::cout << "Cannot read a frame from video stream [2]" << std::endl;
      break;
    }
  
    cv::imshow("cam[1]", frame1);
    cv::imshow("cam[2]", frame2);
  
    if(cv::waitKey(30) == 27)
    {
      std::cout << "ESC key is pressed by user" << std::endl;
      break;
    }
  }
  

This example is working without any issues.

• Version 2 (using cv::VideoCapture::set()) - if I take the exact same values that I retrieve using cv::VideoCapture::get() and use them with cv::VideoCapture::set() to setup the exact same parameters the above mentioned error occurs:

  cv::VideoCapture cap1(1);
  cv::VideoCapture cap2(2);
  
  if(!cap1.isOpened())
  {
    std::cout << "Cannot open the video cam [1]" << std::endl;
    return -1;
  }
  
  if(!cap2.isOpened())
  {
    std::cout << "Cannot open the video cam [2]" << std::endl;
    return -1;
  }
  
  cap1.set(CV_CAP_PROP_FPS, 15);
  cap2.set(CV_CAP_PROP_FPS, 15);
  
  // Values taken from output of Version 1 and used to setup the exact same parameters with the exact same values!
  cap1 ...

Hello!

I have two Logitec Pro 9000 webcams connected to my 64bit Debian notebook. I want to do some stereo-vision and so far it is working great (stereoCalibrate etc.). As you know if the data output is too great (resolution and framerate) you get (especially when using USB cameras) the infamous error:

libv4l2: error turning on stream: No space left on device
VIDIOC_STREAMON: No space left on device
ERROR: Could not read from video stream

I have discovered that for some reason that

cv::VideoCapture::set(CV_CAP_PROP_FRAME_HEIGHT, some_value)

and

cv::VideoCapture::set(CV_CAP_PROP_FRAME_WIDTH, some_value)

don't seem to be working. If I run 2 VideoCapture-s simultaneously I see that the default resolution for these two cameras is 640x480, which I see when I call the cv::VideoCapture::get() equivalent of those two methods I mentioned above. I have to limit the framerate to 15 in order to avoid that libv4l2 related error. Below I have two versions of a very simple program where I set my framerate to 15 and in the second version I also set the exact same resolution that I get when I call cv::VideoCapture::get(CV_CAP_PROP_FRAME_WIDTH/HEIGHT) in the first version:

• Version 1 (working, no manual setup of the resolution, only framerate):

  VideoCapture cap1(1);
  VideoCapture cap2(2);
  
  if(!cap1.isOpened())
  {
    cout << "Cannot open the video cam [1]" << endl;
    return -1;
  }
  
  if(!cap2.isOpened())
  {
    cout << "Cannot open the video cam [2]" << endl;
    return -1;
  }
  
  cap1.set(CV_CAP_PROP_FPS, 15);
  cap2.set(CV_CAP_PROP_FPS, 15);
  
  double dWidth1 = cap1.get(CV_CAP_PROP_FRAME_WIDTH);
  double dHeight1 = cap1.get(CV_CAP_PROP_FRAME_HEIGHT);
  double dWidth2 = cap2.get(CV_CAP_PROP_FRAME_WIDTH);
  double dHeight2 = cap2.get(CV_CAP_PROP_FRAME_HEIGHT);
  
  cout << "cam[1] Frame size: " << dWidth1 << " x " << dHeight1 << endl;
  cout << "cam[2] Frame size: " << dWidth2 << " x " << dHeight2 << endl;
  namedWindow("cam[1]",CV_WINDOW_AUTOSIZE);
  namedWindow("cam[2]",CV_WINDOW_AUTOSIZE);
  
  while(1)    
  {    
    Mat frame1, frame2;    
    bool bSuccess1 = cap1.read(frame1);    
    bool bSuccess2 = cap2.read(frame2);
  
    if (!bSuccess1)
    {
      cout << "Cannot read a frame from video stream [1]" << endl;
      break;
    }
  
    if (!bSuccess2)
    {
      cout << "Cannot read a frame from video stream [2]" << endl;
      break;
    }
  
    cv::addText(frame1, "cam[1]", Point2f(10,25), cv::fontQt("FONT_HERSHEY_SCRIPT_SIMPLEX", 15, cv::Scalar(255,0,0)));
    cv::addText(frame2, "cam[2]", Point2f(10,25), cv::fontQt("FONT_HERSHEY_SCRIPT_SIMPLEX", 15, cv::Scalar(255,0,0)));
    imshow("cam[1]", frame1);
    imshow("cam[2]", frame2);
  
    if(waitKey(30) == 27)
    {
      cout << "ESC key is pressed by user" << endl;
      break;
    }
  }
  

• Version 2 (not working, manual setup framerate, manual setup of the resolution results in error I've mentioned at the beginning of my question once I try to capture from the second camera):

  VideoCapture cap1(1);
  VideoCapture cap2(2);
  
  if(!cap1.isOpened())
  {
    cout << "Cannot open the video cam [1]" << endl;
    return -1;
  }
  
  if(!cap2.isOpened())
  {
    cout << "Cannot open the video cam [2]" << endl;
    return -1;
  }
  
  cap1.set(CV_CAP_PROP_FPS, 15);
  cap2.set(CV_CAP_PROP_FPS, 15);
  
  // Values taken from output of Version 1
  cap1.set(CV_CAP_PROP_FRAME_WIDTH, 640);
  cap1.set(CV_CAP_PROP_FRAME_HEIGHT, 480);
  cap2.set(CV_CAP_PROP_FRAME_WIDTH, 640);
  cap2.set(CV_CAP_PROP_FRAME_HEIGHT, 480);    
  
  double dWidth1 = cap1.get(CV_CAP_PROP_FRAME_WIDTH);
  double dHeight1 = cap1.get(CV_CAP_PROP_FRAME_HEIGHT);
  double dWidth2 = cap2.get(CV_CAP_PROP_FRAME_WIDTH ...

Hello!

I have two Logitec Pro 9000 webcams connected to my 64bit Debian notebook. I want to do some stereo-vision and so far it is working great (stereoCalibrate etc.). As you know if the data output is too great (resolution and framerate) you get (especially when using USB cameras) the infamous error:

libv4l2: error turning on stream: No space left on device
VIDIOC_STREAMON: No space left on device
ERROR: Could not read from video stream

I have discovered that for some reason that

cv::VideoCapture::set(CV_CAP_PROP_FRAME_HEIGHT, some_value)

and

cv::VideoCapture::set(CV_CAP_PROP_FRAME_WIDTH, some_value)

don't seem to be working. If I run 2 VideoCapture-s simultaneously I see that the default resolution for these two cameras is 640x480, which I see when I call the cv::VideoCapture::get() equivalent of those two methods I mentioned above. I have to limit the framerate to 15 in order to avoid that libv4l2 related error. Below I have two versions of a very simple program where I set my framerate to 15 and in the second version I also set the exact same resolution that I get when I call cv::VideoCapture::get(CV_CAP_PROP_FRAME_WIDTH/HEIGHT) in the first version:

• Version 1 (working, no manual setup of the resolution, only framerate):

  VideoCapture cap1(1);
  VideoCapture cap2(2);
  
  if(!cap1.isOpened())
  {
    cout << "Cannot open the video cam [1]" << endl;
    return -1;
  }
  
  if(!cap2.isOpened())
  {
    cout << "Cannot open the video cam [2]" << endl;
    return -1;
  }
  
  cap1.set(CV_CAP_PROP_FPS, 15);
  cap2.set(CV_CAP_PROP_FPS, 15);
  
  double dWidth1 = cap1.get(CV_CAP_PROP_FRAME_WIDTH);
  double dHeight1 = cap1.get(CV_CAP_PROP_FRAME_HEIGHT);
  double dWidth2 = cap2.get(CV_CAP_PROP_FRAME_WIDTH);
  double dHeight2 = cap2.get(CV_CAP_PROP_FRAME_HEIGHT);
  
  cout << "cam[1] Frame size: " << dWidth1 << " x " << dHeight1 << endl;
  cout << "cam[2] Frame size: " << dWidth2 << " x " << dHeight2 << endl;
  namedWindow("cam[1]",CV_WINDOW_AUTOSIZE);
  namedWindow("cam[2]",CV_WINDOW_AUTOSIZE);
  
  while(1)    
  {    
    Mat frame1, frame2;    
    bool bSuccess1 = cap1.read(frame1);    
    bool bSuccess2 = cap2.read(frame2);
  
    if (!bSuccess1)
    {
      cout << "Cannot read a frame from video stream [1]" << endl;
      break;
    }
  
    if (!bSuccess2)
    {
      cout << "Cannot read a frame from video stream [2]" << endl;
      break;
    }
  
    cv::addText(frame1, "cam[1]", Point2f(10,25), cv::fontQt("FONT_HERSHEY_SCRIPT_SIMPLEX", 15, cv::Scalar(255,0,0)));
    cv::addText(frame2, "cam[2]", Point2f(10,25), cv::fontQt("FONT_HERSHEY_SCRIPT_SIMPLEX", 15, cv::Scalar(255,0,0)));
    imshow("cam[1]", frame1);
    imshow("cam[2]", frame2);
  
    if(waitKey(30) == 27)
    {
      cout << "ESC key is pressed by user" << endl;
      break;
    }
  }
  

• Version 2 (not working, manual setup framerate, manual setup of the resolution results in error I've mentioned at the beginning of my question once I try to capture from the second camera):

  VideoCapture cap1(1);
  VideoCapture cap2(2);
  
  if(!cap1.isOpened())
  {
    cout << "Cannot open the video cam [1]" << endl;
    return -1;
  }
  
  if(!cap2.isOpened())
  {
    cout << "Cannot open the video cam [2]" << endl;
    return -1;
  }
  
  cap1.set(CV_CAP_PROP_FPS, 15);
  cap2.set(CV_CAP_PROP_FPS, 15);
  
  // Values taken from output of Version 1
  cap1.set(CV_CAP_PROP_FRAME_WIDTH, 640);
  cap1.set(CV_CAP_PROP_FRAME_HEIGHT, 480);
  cap2.set(CV_CAP_PROP_FRAME_WIDTH, 640);
  cap2.set(CV_CAP_PROP_FRAME_HEIGHT, 480);    
  
  double dWidth1 = cap1.get(CV_CAP_PROP_FRAME_WIDTH);
  double dHeight1 = cap1.get(CV_CAP_PROP_FRAME_HEIGHT);
  double dWidth2 = cap2.get(CV_CAP_PROP_FRAME_WIDTH ...