Camera Initialization Failure in OpenCV

Question

In OpenCV—when initializing a VideoCapture object with a USB webcam—once every 2 or 3 runs the camera will fail to initialize. I have this incredibly ugly piece of code to fix that, but maybe somebody knows what can cause the camera init failure and how I can prevent it?

// Initialize video capture
camera_ = cv::VideoCapture(1);
camera_.set(CV_CAP_PROP_CONVERT_RGB , false);

camera_ >> frame_full_;
while (frame_full_.empty()){ // Could be !cap.isOpened
    cerr << "Camera failure." << endl;
    camera_.release();
    camera_ = cv::VideoCapture(1);
    camera_.set(CV_CAP_PROP_CONVERT_RGB , false);
    camera_ >> frame_full_;
}

/// Do something with the camera feed.

When I close my program, I do get Cleaned up camera. in the console, so I'm thinking it's being released properly.

Added information: On the runs in which the camera fails to init, the call to >>/.read() takes really long to return.

Edit: There is no difference between using the >> operator and .read(), as suggested by @4nonymou5.

4nonymou5 · Accepted Answer · 2014-02-10 21:08:08Z

1

If you meant, you need video feed out of camera and want to do some processing on the individual frames, the the following code might help you.

#include "opencv2/highgui/highgui.hpp"
#include <iostream>

using namespace cv;
using namespace std
int main(int argc, char *argv[])
{
  VideoCapture cap(1);
 if ( !cap.isOpened() )  // if not success, exit program
 {
     cout << "Cannot access camera" << endl;
     return -1;
 }
namedWindow("cam",1);
while(true)
        {
        Mat frame;
         bool check = cap.read(frame); // read a new frame from video

        if (!check) //if not success, break loop
         {
                    cout << "Cannot read the frame from video file" << endl;
                    break;
        }

// do what ever processing you want to do on frame

        imShow("cam", frame);
        waitKey(33);
    }
 return 0;
}

And for your code to respond, add

camera_.read(frame_full_);

just before while loop, it would work.

edited Feb 10, 2014 at 21:08

answered Feb 10, 2014 at 20:53

4nonymou5

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2 Comments

noio Over a year ago

Thanks for the answer. I have no problem getting a camera feed and using it; it's just that every once in a while, the camera fails to initialize for no apparent reason, i.e. your line cap.isOpened() would fail; which is why I have the ugly while loop. I was wondering why the camera would fail so intermittently.

4nonymou5 Over a year ago

yeah, I had a similar problem when i changed the version of opencv some time back, but, it wasn't initialization of camera, but, while accessing the frames. " camera_ >> frame_full_; " this was returning an empty frame for me, so I added, "camera_.read(frame_full_); " to the line, it worked then. So, just check if the issue is same or else, even I would like to hear a proper answer from someone else.

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