Question

I am using OpenCV and trying to apply a Gaussian Blur to an incoming video stream. I basically use cvQueryFrame to remove a frame, blur it and display the frame onto the screen. The thing is though, my video gets stuck on the first frame after I apply the blur….anyone know why? its basically showing one frame instead of a video. The second I remove the blur it starts outputting video again.

#include "cv.h"
#include "highgui.h"
#include "cvaux.h"

#include <iostream>
using namespace std;

int main()
{

//declare initial data
IplImage *grabCapture= 0; //used for inital video frame capture
IplImage *process =0; //used for processing
IplImage *output=0; //displays final output

CvCapture* vidStream= cvCaptureFromCAM(0);

cvNamedWindow ("Output", CV_WINDOW_AUTOSIZE);

int createimage=1;

while (1)
{

grabCapture= cvQueryFrame (vidStream);

if (createimage==1)
    {
        process= cvCreateImage (cvGetSize(grabCapture), IPL_DEPTH_16U, 3);

        createimage=0;

    }

*process=*grabCapture;
cvSmooth (process,process,CV_GAUSSIAN,7,7); //line that makes it display frame instead of video


cvShowImage("Output",process);

}


//clean up data
cvReleaseImage (&grabCapture);
cvReleaseImage (&process);
cvReleaseImage (&output);
cvReleaseCapture (&vidStream);


return 0;

}

Answer 1

You are missing a call to cvWaitKey. This is the only way to tell OpenCV to process events and thus prevent the GUI from freezing.

Try adding this line:

cvWaitKey(10);

after cvShowImage("Output",process);.

Edit: here is the documentation for cvWaitKey