Application hangs when RTSP stream breaks (Bug #235)

Hi !

It seems that there is a problem in cvQueryFrame(), cvGrabFrame() or supporting functions/modules.

When RTSP stream breaks (for ex. due to camera failure), application hangs - cvQueryFrame() does not return.

Proof on concept code (also attached):

#include <iostream>
#include <sstream>
#include <unistd.h>
#include <opencv/cv.h>
#include <opencv/highgui.h>

[[CvCapture]] * capture;
int count = 0;

int main(){

        capture = cvCreateFileCapture("rtsp://l:[email protected]");

        for ( ; ; ) {

                [[IplImage]] * frame = cvQueryFrame(capture);
                std::cout << "tick " << count << std::endl;
                std::ostringstream name;
                name << count++ <<".jpg";
                cvSaveImage((name.str()).c_str(), frame);

                usleep(50000);

        }

        return 0;

}

This occur only when cvGrabFrame reaches last frame in cvCapture.

cvQueryFrame should return NULL in that case.

Regards,
Grzesiek22