converting of wma to mp3 through ffmpeg is not working

I want to convert my wma file to mp3 by ffmpeg . why this error is coming what should i do ? i installed libmp3lame already .

when i am trying to convert by following command gives error :

/var/www/yapi$ sudo /usr/local/bin/ffmpeg -i uploads/4e02dc4f197c1.wma uploads/4e02dc4f1b212.mp3
ffmpeg version N-30971-g4b87a08, Copyright (c) 2000-2011 the FFmpeg developers
  built on Jun 23 2011 10:08:49 with gcc 4.4.5
  configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-x11grab
  libavutil    51.  9. 1 / 51.  9. 1
  libavcodec   53.  7. 0 / 53.  7. 0
  libavformat  53.  4. 0 / 53.  4. 0
  libavdevice  53.  1. 1 / 53.  1. 1
  libavfilter   2.开发者_开发百科 23. 0 /  2. 23. 0
  libswscale    2.  0. 0 /  2.  0. 0
  libpostproc  51.  2. 0 / 51.  2. 0
Input #0, asf, from 'uploads/4e02dc4f197c1.wma':
  Metadata:
    title           : "Highway Blues"
    artist          : Marc Seales, composer. New Stories. Ernie Watts, saxophone.
    genre           : Jazz
    album           : Speakin' Out
    track           : 1
    WM/Year         : 1999
    WMFSDKVersion   : 8.00.00.4389
    WMFSDKNeeded    : 0.0.0.0000
  Duration: 00:01:33.71, start: 0.000000, bitrate: 64 kb/s
    Stream #0.0: Audio: wmav2, 44100 Hz, 2 channels, s16, 64 kb/s
File 'uploads/4e02dc4f1b212.mp3' already exists. Overwrite ? [y/N] y

Output #0, mp3, to 'uploads/4e02dc4f1b212.mp3':
    Stream #0.0: Audio: [0][0][0][0] / 0x0000, 44100 Hz, 2 channels, s16, 64 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
Encoder (codec id 86017) not found for output stream #0.0

why it is not working ?

You may have installed libmp3lame, but according to

configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-x11grab

ffmpeg wasn't built against it. Re-configure and -build ffmpeg, making sure that it knows where to find libmp3lame.