Very Slow Processing of my Opencv Application - c

Question

I am building an OpenCV application which captures a video from camera and overlays it on another video after removing the background.
I am not able to achieve a reasonable speed as it is playing the output at about 1 fps, whereas my background removal is working at 3fps.
Is there a way to display the background video at its normal speed and overlay the processed video at 3fps ?
I tried commenting out my code and I realized that the problem lies majorly with the Rendering part itself. I tried displaying the video along with my web cam feed and I noticed that there is a drop in the actual fps and the fps of video when displayed with openCV.
here is the sample code:
void main()
{
CvCapture* capture, *Vcap;
capture = cvCaptureFromCAM(0);
if(!capture)
{
printf("Video Load Error");
}
Vcap = cvCaptureFromAVI("bgDemo.mp4");
//printf("\nEntered BGR");
if(!Vcap)
{
printf("Video Load Error");
}
while(1)
{
IplImage* src = cvQueryFrame(Vcap);
if(!src)
{
Vcap = cvCaptureFromAVI("bgDemo.mp4");
continue;
}
IplImage* bck1 = cvCreateImage(cvGetSize(src),8,3);
cvResize(src,bck1,CV_INTER_LINEAR);
cvShowImage("BCK",bck1);
cvWaitKey(1);
}
}

Answer 1

The main problem is that you are allocating a new image at every iteration of the loop without releasing it at the end of the loop. In other words, you have a beautiful memory leak.
A better approach is to simply grab a frame of the video before the loop starts. This will let you create bck1 with the right size just once.
There are other problems with your code, I'm sharing a fixed version below, make sure you pay attention to every line of code to see what changed. I haven't had time to test it, but I'm sure you'll figure it out:
int main()
{
// I know what you are doing, just one capture interface is enough
CvCapture* capture = NULL;
capture = cvCaptureFromCAM(0);
if(!capture)
{
printf("Ooops! Camera Error");
}
capture = cvCaptureFromAVI("bgDemo.mp4");
if(!capture)
{
printf("Ooops! Video Error");
// if it failed here, it means both methods for loading a video stream failed.
// It makes no sense to let the application continue, so we return.
return -1;
}
// Retrieve a single frame from the camera
IplImage* src = cvQueryFrame(capture);
if(!src)
{
printf("Ooops! #1 cvQueryFrame Error");
return -1;
}
// Now we can create our backup image with the right dimensions.
IplImage* bck1 = cvCreateImage(cvGetSize(src),src->depth, src->nChannels);
if(!bck1)
{
printf("Ooops! cvCreateImage Error");
return -1;
}
while(1)
{
src = cvQueryFrame(capture);
if(!src)
{
printf("Ooops! #2 cvQueryFrame Error");
break;
}
cvResize(src, bck1, CV_INTER_LINEAR);
cvShowImage("BCK",bck1);
cvWaitKey(10);
}
cvReleaseImage( &bck1 ); // free manually allocated resource
return 0;
}
These fixes should speed up your application considerably.