title: OpenCV camera just showing black output
body: <p>I am following these tutorials <a href="http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_gui/py_video_display/py_video_display.html#display-video" rel="nofollow">http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_gui/py_video_display/py_video_display.html#display-video</a> and trying to capture video from camera. Although the code functions properly, but it doesn't show anything except black screen on the frame window. I don't know why is this happening.</p>
  
  <pre><code>import numpy as np
  import cv2
  
  cap = cv2.VideoCapture(0)
  
  while(True):
      ret, frame = cap.read()
      if cap.isOpened() == 0:
          cap.open(0)
  
      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>
  
  <p>I have read in some posts that OpenCV might not be supporting my camera. So i don't know what is happening exactly?</p>