title: get frame from video with CV_CAP_PROP_POS_FRAMES in opencv python
body: <p>I am trying to detect a (photography) flash in a video using OpenCV.</p>
  
  <p>I detected the frame in which the flash occurs (average brightness above a threshold) and now I'd like to get the <strong>frame number</strong>.</p>
  
  <p>I tried using CV_CAP_PROP_POS_FRAMES <a href="http://docs.opencv.org/2.4/modules/highgui/doc/reading_and_writing_images_and_video.html?highlight=capture.get#videocapture-get" rel="nofollow noreferrer">from the OpenCV docs</a> without any success.</p>
  
  <pre><code>import numpy as np 
  import cv2
  
  cap = cv2.VideoCapture('file.MOV')
  
  while(cap.isOpened()):
      ret, frame = cap.read()
  
      BW = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
      hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
      h,s,v = cv2.split(hsv)
      average = np.average(v) #computes the average brightness
  
      if average &gt; 200: #flash is detected
          cv2.imshow('frame',BW)
          frameid = cap.get(CV_CAP_PROP_POS_FRAMES) # &lt;--- this line does not work 
          print(frameid)
      if cv2.waitKey(1) &amp; 0xFF == ord('q'):
          break
  
  cap.release()
  cv2.destroyAllWindows()
  </code></pre>
  
  <p>Any tips ?</p>