title: Overlaying video with ffmpeg
body: <p>I'm attempting to write a script that will merge 2 separate video files into 1 wider one, in which both videos play back simultaneously. I have it mostly figured out, but when I view the final output, the video that I'm overlaying is extremely slow.</p>
  
  <p>Here's what I'm doing:</p>
  
  <ol>
  <li><p>Expand the left video to the final video dimensions</p>
  
  <p>ffmpeg -i left.avi -vf "pad=640:240:0:0:black" left_wide.avi</p></li>
  <li><p>Overlay the right video on top of the left one</p>
  
  <p>ffmpeg -i left_wide.avi -vf "movie=right.avi [mv]; [in][mv] overlay=320:0" combined_video.avi</p></li>
  </ol>
  
  <p>In the resulting video, the playback on the right video is about half the speed of the left video. Any idea how I can get these files to sync up?</p>