title: Read video file with fixed frame rate
body: <p>I captured a video with my camera and fixed frame rate at 25 fps and tried to read it with OpenCV. </p>
  
  <p>When I read video file with OpenCV, it plays but it plays very fast.
  I want my program to play video at 25 fps. How to configure OpenCV to read video file at 25 fps?</p>
  
  <p><strong>My code:</strong></p>
  
  <pre><code>import numpy as np
  import cv2
  
  cap = cv2.VideoCapture('vtest.avi')
  
  while(cap.isOpened()):
      ret, frame = cap.read()
  
      gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
  
      cv2.imshow('frame',gray)
      if cv2.waitKey(1) &amp; 0xFF == ord('q'):
          break
  
  cap.release()
  cv2.destroyAllWindows()
  </code></pre>