title: youtube-dl python script postprocessing error: FFMPEG codecs aren't being recognized
body: <p>My python script is trying to download youtube videos with youtube-dl.py. Works fine unless postprocessing is required. The code:</p>
  
  <pre><code>import youtube_dl
  
  options = {
      'format':'bestaudio/best',
      'extractaudio':True,
      'audioformat':'mp3',
      'outtmpl':'%(id)s',     #name the file the ID of the video
      'noplaylist':True,
      'nocheckcertificate':True,
      'postprocessors': [{
          'key': 'FFmpegExtractAudio',
          'preferredcodec': 'mp3',
          'preferredquality': '192',
      }]
  }
  
  with youtube_dl.YoutubeDL(options) as ydl:
      ydl.download(['http://www.youtube.com/watch?v=BaW_jenozKc'])
  </code></pre>
  
  <p>Below is the output I receive:<a href="https://i.stack.imgur.com/g3mBo.png" rel="noreferrer"><img src="https://i.stack.imgur.com/g3mBo.png" alt="enter image description here"></a></p>
  
  <p>I get a similar error if I try setting 'preferredcodec' to 'opus' or 'best'.
  I'm not sure if this is relevant, but I can run the command line counterpart fine:</p>
  
  <pre><code>youtube-dl -o 'test2.%(ext)s' --extract-audio --audio-format mp3 --no-check-certificate https://www.youtube.com/watch?v=BaW_jenozKc
  </code></pre>
  
  <p>I've gotten a few clues from the internet and other questions and from what i understand this is most likely an issue with my ffmpeg, which isn't a python module right? Here is my ffmpeg version and configuration:
  <a href="https://i.stack.imgur.com/0Uprn.png" rel="noreferrer"><img src="https://i.stack.imgur.com/0Uprn.png" alt="enter image description here"></a></p>
  
  <p>If the answer to my problem is to add some configuration setting to my ffmpeg please explain how i go about doing that.</p>