title: Processing frame every second in opencv python
body: <p>Here is the code for reading video file from webcam using opencv website. I just want to process the frame every second.</p>
  
  <pre><code>import numpy as np
  import cv2
  
  cap = cv2.VideoCapture(0)
  
  while(True):
      # Capture frame-by-frame
      ret, frame = cap.read()
  
      # Our operations on the frame come here
      gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
  
      # Display the resulting frame
      cv2.imshow('frame',gray)
      if cv2.waitKey(1) &amp; 0xFF == ord('q'):
          break
  
  # When everything done, release the capture
  cap.release()
  cv2.destroyAllWindows()
  </code></pre>
  
  <p>How should I modify the code:</p>