title: No image from the camera using cv2.VideoCapture
body: <p>I use WebCam(Genius FaceCam 1020),Python(3.6.4), OpenCV(3.4.0.12), and Opencv documentation code, this one:</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>Runs without errors, but the image does not appear in the window. The indicator on the camera lights up.
  I have tried copy opencv_ffmpeg.dll, Rename the opencv_ffmpeg.dll in this manner:</p>
  
  <p>For OpenCV version X.Y.Z</p>
  
  <pre><code>opencv_ffmpeg.dll ==&gt; opencv_ffmpegXYZ.dll
  </code></pre>
  
  <p>For 64-bit OpenCV version X.Y.Z</p>
  
  <pre><code>opencv_ffmpeg.dll ==&gt; opencv_ffmpegXYZ_64.dll
  </code></pre>
  
  <p>Namely <code>opencv_ffmpeg34012.dll</code> and <code>opencv_ffmpeg34012_64.dll</code>. But it does not help.</p>