title: pydub returning zero byte file when I try to export part of an Mp3
body: <p>I'm sharing this for posterity, since I already figured out the answer. I'm trying to create preview snippets of MP3 files with pydub in Python, but when I ran the export the files were always zero bytes in size.</p>
  
  <p>example:</p>
  
  <pre><code>from pydub import AudioSegment    
  
  sound = AudioSegment.from_mp3("preview_temp/n/1/mp3/01_Beyond_and_Into_the_Ultimate.mp3")
  
  # len() and slicing are in milliseconds
  halfway_point = len(sound) / 2
  
  second_half = sound[halfway_point:]
  print second_half
  second_half.export("preview_temp/n/1/prev/prev_test.mp3", format="mp3", bitrate="192k")
  </code></pre>
  
  <p>I verified the source file existed and was accessible. My inkling was this had something to do with ffmpeg. It was installed properly, but then I came across this on the <a href="https://github.com/jiaaro/pydub#getting-ffmpeg-set-up" rel="nofollow">pydub github</a>:</p>
  
  <blockquote>
    <p>You may use libav or ffmpeg. libav is recommended.</p>
  </blockquote>
  
  <p>The pydub developer runs through installation on several platforms on the github wiki. I'm sharing it here to make it easier for folks to find, though.</p>