title: openCV video saving in python
body: <p>I am trying to save the video but it's not working.
  I followed the instructions from the openCV documentation.</p>
  
  <pre><code>import numpy as np
  import cv2
  
  cap = cv2.VideoCapture(0)
  
  fourcc = cv2.VideoWriter_fourcc(*'XVID')
  out = cv2.VideoWriter('output.avi', fourcc, 20.0, (640,480))
  
  while(cap.isOpened()):
      ret, frame = cap.read()
      if ret==True:
          frame = cv2.flip(frame,0)
  
  
          out.write(frame)
  
          cv2.imshow('frame',frame)
          if cv2.waitKey(1) &amp; 0xFF == ord('q'):
              break
      else:
          break
  cap.release()
  
  out.release()
  
  cv2.destroyAllWindows()
  </code></pre>
  
  <p>What is wrong?</p>