title: I am trying to read a video frame by frame using python , to execute some processes on frames
body: <p>This is my code</p>
  
  <pre><code>import cv2
  video_capture = cv2.VideoCapture("test.mpeg")
  cv2.convertMaps
  
  while True:
      # get frame by frame
      ret, frame = video_capture.read()
      cv2.imwrite('pic.png',frame)
      cv2.imshow('Video', frame)
      if cv2.waitKey(1) &amp; 0xFF == ord('q'):
          break
  </code></pre>
  
  <p>I'm getting the following error:</p>
  
  <pre><code>None
  
  Traceback (most recent call last):
    File "D:/Itellingence Transportation Systems/Material-lab8/home_work8.py", line 12, in &lt;module&gt;
      cv2.imshow('Video', frame)
  error: ..\..\..\..\opencv\modules\highgui\src\window.cpp:261: error: (-215) size.width&gt;0 &amp;&amp; size.height&gt;0 in function cv::imshow
  </code></pre>
  
  <p>What is the problem?</p>