title: How do I add a cover image to a MP4 file with ffmpeg?
body: <p>In Windows Explorer, when in the "Large icons" or "Extra large icons" layout, a MP4 file appears as a thumbnail. By default, the thumbnail image is taken from some frame in the middle of the video.</p>
  
  <p>How do I replace this automatically generated thumbnail with a specific cover image?</p>
  
  <p>What ffmpeg commands will add a cover image to a MP4 video file?</p>