title: Can't write and save a video file using OpenCV and Python
body: <p>I'm trying to process frames from a video stream, and it as a new video.</p>
  
  <p>This is what I'm doing : </p>
  
  <pre><code>fourcc = cv2.VideoWriter_fourcc(*'XVID')
  out = cv2.VideoWriter('Videos/output.mp4',fourcc, fps, (1080,1080))
  </code></pre>
  
  <p>I keep getting : </p>
  
  <pre><code>OpenCV: FFMPEG: tag 0x44495658/'XVID' is not supported with codec id 13 and format 'mp4 / MP4 (MPEG-4 Part 14)'
  OpenCV: FFMPEG: fallback to use tag 0x00000020/' ???'
  </code></pre>
  
  <p>I think I'm using the wrong fourcc value... Which one should I use ? I've been trying a lot of them.</p>
  
  <p>I'm using Ubuntu 16.04, Python 2.7.11 and OpenCV 3.1.0</p>