title: Convert mp4 to mp3
body: <p>I am looking for some library or code that will allow me to convert mp4 video to mp3.
  I want it to be for free and compatible with the latest .NET framework (4).</p>
  
  <p>Also, if possible, I am looking for a free ffmpeg wrapper than I can have in my vb.net application without trial or messageboxes.</p>
  
  <p>If there is no free ffmpeg wrapper, can someone show me how to perform the conversion from mp4 to mp3 using command line and ffmpeg ?</p>