title: Add image overlay on video FFmpeg
body: <p>I have a video, <code>test.mp4</code>, and an image, <code>test.png</code>.</p>
  
  <p><code>test.png</code> is a black image with a transparent "hole" in the center.</p>
  
  <p>I would like, using FFmpeg:</p>
  
  <ul>
  <li>To display <code>test.png</code> over the video so I can only see a circle of video</li>
  <li>If possible, to resize <code>test.png</code> to the size of the video so it covers the whole thing</li>
  </ul>
  
  <p>Is this possible ?</p>