title: ffmpeg fails with: Unable to find a suitable output format for 'pipe:'
body: <p>I am trying to record my desktop and save it as videos but ffmpeg fails.</p>
  
  <p>Here is the terminal output:</p>
  
  <pre><code>$ ffmpeg -f alsa -i pulse -r 30 -s 1366x768 -f x11grab -i :0.0 -vcodec libx264 - preset ultrafast -crf 0 -y screencast.mp4
  ...
  Unable to find a suitable output format for 'pipe:'
  </code></pre>