title: ffmpeg: reduce fps if over threshold but do not increase if under threshold
body: <p>The ffmpeg CLI allows your to specify <code>-r &lt;fps&gt;</code> or <code>-vf fps=&lt;fps&gt;</code> to set a fixed FPS for your output.</p>
  
  <p>The behavior I would like to get is:</p>
  
  <ul>
  <li>Input can have arbitrary FPS (likely 20-120).</li>
  <li>If input FPS is >30, reduce it to 30 FPS.</li>
  <li>If input FPS is &lt;=30, do not modify FPS.</li>
  </ul>
  
  <p>More context:</p>
  
  <p>Aforementioned options are great to normalize videos to a fixed FPS but not so good to make sure videos do not get over a certain FPS threshold efficiently. Indeed, if I set <code>-r 30</code> and the video is 29 fps, ffmpeg is going to us a lot of CPU to raise it to <code>30</code> when it wasn't needed for my use-case.</p>