title: How to extract velocity vectors of a pixels from calcOpticalFlowFarneback
body: <p>I have been looking to extract velocity vectors of every pixels b/n two frames. I used the opencv function as flows:</p>
  
  <pre><code>calcOpticalFlowFarneback(Previous_Gray, Current_Gray, Optical_Flow, 0.5, 3, 15, 3, 5, 1.2, 0);
  
  Previous_Gray = previous frame 
  Current_Gray = current frame 
  </code></pre>
  
  <p>And it gives me the array in the 3rd argument Optical_Flow but I can't really tell how to extract the velocity vectors using this array.</p>
  
  <p>Thanks in Advance.</p>
  
  <p>Dawit</p>