title: ffmpeg - multiple output with thumbnails
body: <p>I would like ffmpeg to do the following:</p>
  
  <ul>
  <li>read an input mp4 <em>(-i movie.mp4)</em></li>
  <li>skip the first 5 seconds <em>(-ss 5)</em></li>
  <li>find scene changes and display the frame numbers <em>(-vf "select=gt(scene\, 0.4, showinfo))</em></li>
  <li>output #1 - a gif file <em>(output.gif)</em></li>
  <li>output #2 - a contact sheet with all the thumbnails <em>(-vf "select scale=320:-1, tile=12x200" thumbnails.png)</em></li>
  </ul>
  
  <p>This will generate the thumbnails:</p>
  
  <pre><code>ffmpeg -hide_banner -i d:/Test/movie01.mp4 -ss 5 -vf "select=gt(scene\,0.4), showinfo, scale=320:-1, tile=12x200" -vsync 0 thumbnails%03d.png
  </code></pre>
  
  <p>this will generate the gif:</p>
  
  <pre><code>ffmpeg -hide_banner -i d:/Test/movie01.mp4 -ss 5 -vf "select='not(mod(n,60))',setpts='N/(30*TB)', scale=320:-1" -vsync 0 output.gif
  </code></pre>
  
  <p>I would like to do both at once with 2 more features:</p>
  
  <ul>
  <li><p>set fps and resolution for the gif; I would like the gif to represent the whole movie in X seconds, at Y fps (I know the duration of the input movie so I can calculate how often a frame needs to be captured)</p></li>
  <li><p>set the width only for the thumbnail picture <em>(tile=12 for example)</em> and let ffmpeg determine the appropriate height</p></li>
  </ul>
  
  <p>I have tried to compose a command line from what I read on this page: <a href="https://trac.ffmpeg.org/wiki/Creating%20multiple%20outputs" rel="nofollow noreferrer">https://trac.ffmpeg.org/wiki/Creating%20multiple%20outputs</a>, using the split / map commands but I couldn't get it to work </p>