OpenCV 'cvQueryFrame' non-blocking on OS X

问题:

when I perform a cvQueryFrame on Windows, the API blocks until an image is delivered. On Mac OS X, I am at 100% CPU utilization, while only querying for an image and displaying it in a window. I am at the latest SVN version. Can anyone confirm my experience? Am I doing something wrong? Is there a work-around?

My loop code looks like this:

while(key != 'q') {
    if (frame)
        cvShowImage("Live Cam", frame);
    frame = NULL;
    frame = cvQueryFrame(capture);
    key = cvWaitKey(10);
}

回答1:

I just executed a demo application I presented here and it uses ~22% CPU, according to Activity Monitor. I ran the program on a Macbook Pro 13", with OpenCV 2.1 (32bits).

If you pay attention to that code you'll notice that the loop is a little bit different from yours:

IplImage* frame = NULL;
char key = 0;
while (key != 27) // ESC
{    
  frame = cvQueryFrame(capture);
  if(!frame) 
  {
      fprintf( stderr, "!!! cvQueryFrame failed!\n" );
      break;
  }

  cvShowImage("Live Cam", frame );
  key = cvWaitKey(10);
}