Video too fast in Qt using OpenCV -

i playing video on label in qt. using open cv same. video playing fast. how can decrease playback speed. tried using setcaptureproperty not working. code follows

headerfile declarations:

cvcapture *capture; iplimge *frame; cv::mat source_image; cv::mat dest_image; qtimer *imagetimer; 

button click slot:

void mainwindow::onbuttonclick() {    capture = cvcapturefromfile("/mp.mp4");    while(capture   {     frame = cvqueryframe((capture);     source_image = frame;     cv::resize(source_image,source_image,cv::size(420,180),0,0);     cv::cvtcolor(source_image,source_image,cv_bgr2rgb);     qimage qimg = qimage((const unsigned char*)source_image.data,source_image.cols,source_imge.rows,qimage::format_rgb888);    label->setpixmap(qpixmap::fromimage(qimg));    label->resize(label->pixmap()->size());   } } 

somebody please guide on this...thank :)

i use qtimer in way,not while loop,like following:

void on_button_click() {     cap.open(0);     timer->start(50); } void readframe()    {     //display image in label      cap>>frame;     mat2qimage(); // convert mat qimage;     ...     //setpixmap();     ... } 

and in main window,

connet(timer,timeout(),this,readframe());