title: Multiple fadeIn/fadeOut effects in one audio file with ffmpeg
body: <p>I have some problem to add several fade effects to one audio file. When I try to use a command like this:</p>
  
  <pre><code>ffmpeg -y -i /home/user/video/test/sound.mp3 -af "afade=t=in:ss=0:d=3,afade=t=out:st=7:d=3,afade=t=in:st=10:d=3,afade=t=out:st=17:d=3,afade=t=in:st=20:d=3,afade=t=out:st=27:d=3" /tmp/test.mp3
  </code></pre>
  
  <p>then my output audio file has a <em>fadein</em> and <em>fadeout</em> applied only once. All the next effects don't get applied. Is there any possible way to apply several fade effects to the same audio file? Also, what is the difference between <em>ss</em> and <em>st</em> parameter in this command?</p>