bug in QtKit when changing camera resolution (Bugfix #2795)

I can produce the bug with the following simple code :

#include <opencv2/highgui/highgui.hpp>

using namespace cv;

int main(int argc, char *argv[]) {
    VideoCapture cap(CV_CAP_QT);
    cap.set(CV_CAP_PROP_FRAME_WIDTH, 640);
    cap.set(CV_CAP_PROP_FRAME_HEIGHT, 480);
    Mat frame;
    //first frame is OK
    cap >> frame;
    imshow("image", frame);
    waitKey(10);
    //second one has the glitch
    cap >> frame;
    imshow("image", frame);
    waitKey(0);
}

The image displayed will be split in half as if there is an offset in the image data buffer.
I'm using a Logitech 9000 on Moutain Lion (10.8.2)

I tracked down the problem to the following function in modules/highgui/src/cap_qtkit.mm : void CvCaptureCAM::setWidthHeight();

It seems the capture needs to be stopped before the change and restarted after, for the change to be applied without any glitch.
The following patch seems to do the trick (the comments indicate the lines added) :

void CvCaptureCAM::setWidthHeight() {
    NSAutoreleasePool* localpool = [[NSAutoreleasePool alloc] init];

    //this needs to be added
    [mCaptureSession stopRunning];

    NSDictionary* pixelBufferOptions = [NSDictionary dictionaryWithObjectsAndKeys:
                          [NSNumber numberWithDouble:1.0*width], (id)kCVPixelBufferWidthKey,
                          [NSNumber numberWithDouble:1.0*height], (id)kCVPixelBufferHeightKey,
                          [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA],
                          (id)kCVPixelBufferPixelFormatTypeKey,
                          nil];
    [mCaptureDecompressedVideoOutput setPixelBufferAttributes:pixelBufferOptions];

    //this too
    [mCaptureSession startRunning];

    grabFrame(60);
    [localpool drain];
}