title: I want that frame get every second. (opencv)
body: <p>I expect result that is when this code is excuted, I gain one frame every second.</p>
  
  <p>but maybe cap buffer is existed, so I don't gain frame cut off.</p>
  
  <p>this frame is successive. </p>
  
  <p>I want to gain one frame and  After 1 second, to gain frame(After 1 second frame ) </p>
  
  <p>What is the problem?</p>
  
  <pre><code>VideoCapture cap(0) ;
  while(1){
      cap &gt;&gt; frame ;
      sleep(1) ;
      imshow("test", frame) ;
      if(waitKey(30)&gt;=0) break ;
  }
  </code></pre>