Reading and playing a video file

A video deals with moving images rather than still images, that is, display of a frame sequence at a proper rate (FPS or frames per second). The following showVideo example illustrates how to read and play a video file with OpenCV:

//… (omitted for simplicity)
int main(int argc, char *argv[])
{
    Mat frame; // Container for each frame

    VideoCapture vid(argv[1]); // Open original video file
    if (!vid.isOpened()) // Check whether the file was opened
        return -1;
    int fps = (int)vid.get(CV_CAP_PROP_FPS);
    namedWindow(argv[1]); // Creates a window
    while (1) {
        if (!vid.read(frame)) // Check end of the video file
            break;
        imshow(argv[1], frame); // Show current frame on window
        if (waitKey(1000/fps) >= 0)
            break;
    }
    return 0;
}

The code explanation is given as follows:

In the preceding example, the waitKey function is used with a computed number of milliseconds (1000/fps) trying to play the video file at the same rate it was originally recorded. Playing a video at a faster/slower rate (more/less fps) than that will produce a faster/slower playback.