title: Convert audio files to mp3 using ffmpeg
body: <p>I need to convert audio files to mp3 using ffmpeg.</p>
  
  <p>When I write the command as <code>ffmpeg -i audio.ogg -acodec mp3 newfile.mp3</code>, I get the error:</p>
  
  <pre><code>FFmpeg version 0.5.2, Copyright (c) 2000-2009 Fabrice Bellard, et al.
    configuration: 
    libavutil     49.15. 0 / 49.15. 0
    libavcodec    52.20. 1 / 52.20. 1
    libavformat   52.31. 0 / 52.31. 0
    libavdevice   52. 1. 0 / 52. 1. 0
    built on Jun 24 2010 14:56:20, gcc: 4.4.1
  Input #0, mp3, from 'ZHRE.mp3':
    Duration: 00:04:12.52, start: 0.000000, bitrate: 208 kb/s
      Stream #0.0: Audio: mp3, 44100 Hz, stereo, s16, 256 kb/s
  Output #0, mp3, to 'audio.mp3':
      Stream #0.0: Audio: 0x0000, 44100 Hz, stereo, s16, 64 kb/s
  Stream mapping:
    Stream #0.0 -&gt; #0.0
  Unsupported codec for output stream #0.0
  </code></pre>
  
  <p>I also ran this command:</p>
  
  <pre><code> ffmpeg -formats | grep mp3
  </code></pre>
  
  <p>and got this in response:</p>
  
  <pre><code>FFmpeg version 0.5.2, Copyright (c) 2000-2009 Fabrice Bellard, et al.
    configuration: 
    libavutil     49.15. 0 / 49.15. 0
    libavcodec    52.20. 1 / 52.20. 1
    libavformat   52.31. 0 / 52.31. 0
    libavdevice   52. 1. 0 / 52. 1. 0
    built on Jun 24 2010 14:56:20, gcc: 4.4.1
   DE mp3             MPEG audio layer 3
   D A    mp3             MP3 (MPEG audio layer 3)
   D A    mp3adu          ADU (Application Data Unit) MP3 (MPEG audio layer 3)
   D A    mp3on4          MP3onMP4
   text2movsub remove_extra noise mov2textsub mp3decomp mp3comp mjpegadump imxdump h264_mp4toannexb dump_extra
  </code></pre>
  
  <p>I guess that the mp3 codec isn't installed. Am I on the right track here?</p>