ffmpeg -formats | grep mp3
ffmpeg version N-37650-g3c939ad Copyright (c) 2000-2012 the FFmpeg developers
  built on Feb  8 2012 15:33:28 with gcc 4.4.3
  configuration: --enable-gpl --enable-nonfree --enable-libx264
  libavutil      51. 38.100 / 51. 38.100
  libavcodec     54.  1.100 / 54.  1.100
  libavformat    54.  0.100 / 54.  0.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 62.100 /  2. 62.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  6.100 /  0.  6.100
  libpostproc    52.  0.100 / 52.  0.100
 DE mp3             MPEG audio layer 3