Displaying a video using opencv

Question

i have a little problem according "displaying a video with opencv". The code is written in c++ with visual studio 2008.

here is the code:

int main( int argc, char** argv ) 
{
    cvNamedWindow( "xample2", CV_WINDOW_AUTOSIZE );
    CvCapture* capture = cvCreateFileCapture( "Micro-dance_2_.avi" );
    IplImage* frame;
    while(1) {
        frame = cvQueryFrame( capture );
        if( !frame ) break;
        cvShowImage( "xample2", frame );
        char c = cvWaitKey(33);
        if( c == 27 ) break;
    }
    cvReleaseCapture( &capture );
    cvDestroyWindow( "xample2" );
}

when debugging, the programm launches and i can see the command window and a grey window (wher the video should be displayed i suppose) for a few milliseconds. Then both windows close.

the output from debug window in visual shows the following:

.. . (a lot of loaded and unloaded dlls) . . .

The program '[3684] 2aufg4).exe: Native' has exited with code 0 (0x0).

i dont know what i am doing wrong...

i would appreciate your help a lot!

as allways thank you guys

Answer 1

You need to check the return of cvCreateFileCapture() and make sure it loaded the file successfully:

#include <cv.h>
#include <highgui.h>

int main(int argc, char** argv) 
{
    cvNamedWindow("xample2", CV_WINDOW_AUTOSIZE);
    CvCapture* capture = cvCreateFileCapture( "Micro-dance_2_.avi" );
    if (!capture)
    {
      std::cout << "!!! cvCreateFileCapture didn't found the file !!!\n";
      return -1; 
    }

    IplImage* frame;
    while (1) 
    {
        frame = cvQueryFrame(capture);
        if(!frame) 
            break;

        cvShowImage("xample2", frame);

        char c = cvWaitKey(33);
        if (c == 27) 
            break;
    }

    cvReleaseCapture(&capture);
    cvDestroyWindow("xample2");
}

Answer 2

Try this

int main( int argc, char** argv ) 
{
    cvNamedWindow( "xample2", CV_WINDOW_AUTOSIZE );
    CvCapture* capture = cvCreateFileCapture( "Micro-dance_2_.avi" );
    IplImage* frame;
    if(!cvQueryFrame( capture )){
        std::cout << "Could not open file\n";
        return -1; 
    }
    while(1) {
        frame = cvQueryFrame( capture );
        if( !frame ) break;
        cvShowImage( "xample2", frame );
        char c = cvWaitKey(33);
        if( c == 27 ) break;
    }
    cvReleaseCapture( &capture );
    cvDestroyWindow( "xample2" );
}