title: CV2 cap.set(1,idx); cap.read(), Does it Read Frame idx or Frame idx+1
body: <p>In CV2 will this chunk of code read the frame for the given frame number or the next frame?</p>
  <pre><code>desiredFrames = [3,5,7,n]
  cap = cv2.VideoCapture(&quot;somefile&quot;)
  
  for idx in desiredFrames:
      cap.set(cv2.CAP_PROP_POS_FRAMES,idx);
      cap.read() #Does it Read Frame idx or Frame idx+1
  
  </code></pre>
  <p>So will I get frames [3,5,7,n]
  Or frames [4,6,8,n+1]</p>
  <p>Thanks.</p>