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opencvwebcamcapture

Opencv Error on Ubuntu Webcam (Logitech C270) Capture -> HIGHGUI ERROR: V4L/V4L2: VIDIOC_S_CROP

this erorr message appears on running simple camera capture on Ubuntu with logitech C270 (OpenCV 2.4.2/C++):

HIGHGUI ERROR: V4L/V4L2: VIDIOC_S_CROP

and further:

Corrupt JPEG data: 2 extraneous bytes before marker 0xd1 Corrupt JPEG data: 1 extraneous bytes before marker 0xd6 Corrupt JPEG data: 1 extraneous bytes before marker 0xd0 Corrupt JPEG data: 1 extraneous bytes before marker 0xd0

I get frames but the values of frame width and height swapped when writing to a Mat object see below:

Mat frame;
videoCapture = new VideoCapture(camId);
if(!videoCapture->isOpened()) throw Exception();

cout << "Frame width: " << videoCapture->get(CV_CAP_PROP_FRAME_WIDTH) << endl;
cout << "Frame height: " << videoCapture->get(CV_CAP_PROP_FRAME_HEIGHT) << endl;

(*videoCapture) >> frame;

cout << "Mat width: " << frame.rows << endl;
cout << "Mat height: " << frame.cols << endl;

Output:

Frame width: 640
Frame height: 480
Mat width: 480
Mat height: 640
Solution

  • The width of an image is given by its number of columns. Your code should be 

    cout << "Mat width: " << frame.cols << endl;
cout << "Mat height: " << frame.rows << endl;

    So there is no swap between width and height.