h1249862:/var/www/media/video# ffmpeg -i /var/www/media/video/235.3gp -acodec libmp3lame /var/www/media/video/235_2.flv
FFmpeg version SVN-r9294, Copyright (c) 2000-2007 Fabrice Bellard, et al.
  configuration: --enable-libamr-nb --enable-libamr-wb --enable-libmp3lame --enable-gpl --disable-vhook
  libavutil version: 49.4.0
  libavcodec version: 51.40.4
  libavformat version: 51.12.1
  built on Jun 12 2007 23:17:07, gcc: 3.3.5 (Debian 1:3.3.5-13)

Seems stream 0 codec frame rate differs from container frame rate: 29.97 (30000/1001) -> 1.00 (1/1)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/var/www/media/video/235.3gp':
  Duration: 00:00:12.0, start: 0.000000, bitrate: 41 kb/s
  Stream #0.0(und): Video: h263, yuv420p, 176x144,  1.00 fps(r)
  Stream #0.1(und): Audio: libamr_nb, 8000 Hz, mono
Unknown codec 'libmp3lame'