also,
weird is lame beta encoding of 22050hz within ffmpeg...
it produces junk.
whereas the standalone lame is perfect.

example one, 22050.mp3 broken:

ffmpeg -i 22.wav -ab 100k 22050.mp3
FFmpeg version SVN-r13054, Copyright (c) 2000-2008 Fabrice Bellard, et al.
  configuration: --enable-memalign-hack --enable-postproc --enable-swscale --ena
ble-gpl --enable-liba52 --enable-libfaac --enable-libfaad --enable-libgsm --enab
le-libmp3lame --enable-libnut --enable-libvorbis --enable-libtheora --enable-lib
xvid --enable-libx264 --disable-ffserver --disable-ffplay --enable-avisynth --en
able-small --enable-pthreads --extra-ldflags=-static --extra-cflags=-mtune=penti
um4 -mfpmath=sse -msse -fno-strict-aliasing
  libavutil version: 49.6.0
  libavcodec version: 51.56.0
  libavformat version: 52.13.0
  libavdevice version: 52.0.0
  built on May  4 2008 15:30:05, gcc: 4.3.0
Input #0, wav, from '22.wav':
  Duration: 00:01:48.44, bitrate: 705 kb/s
    Stream #0.0: Audio: pcm_s16le, 22050 Hz, stereo, 705 kb/s
File '22050.mp3' already exists. Overwrite ? [y/N] y
Output #0, mp3, to '22050.mp3':
    Stream #0.0: Audio: libmp3lame, 22050 Hz, stereo, 100 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop encoding
size=    1272kB time=108.5 bitrate=  96.0kbits/s
video:0kB audio:1272kB global headers:0kB muxing overhead 0.002457%


example2, -aq parameter ignored, output mp3, 10 sec silence.

ffmpeg -i 22.wav -aq 1 22050q.mp3
FFmpeg version SVN-r13054, Copyright (c) 2000-2008 Fabrice Bellard, et al.
  configuration: --enable-memalign-hack --enable-postproc --enable-swscale --ena
ble-gpl --enable-liba52 --enable-libfaac --enable-libfaad --enable-libgsm --enab
le-libmp3lame --enable-libnut --enable-libvorbis --enable-libtheora --enable-lib
xvid --enable-libx264 --disable-ffserver --disable-ffplay --enable-avisynth --en
able-small --enable-pthreads --extra-ldflags=-static --extra-cflags=-mtune=penti
um4 -mfpmath=sse -msse -fno-strict-aliasing
  libavutil version: 49.6.0
  libavcodec version: 51.56.0
  libavformat version: 52.13.0
  libavdevice version: 52.0.0
  built on May  4 2008 15:30:05, gcc: 4.3.0
Input #0, wav, from '22.wav':
  Duration: 00:01:48.44, bitrate: 705 kb/s
    Stream #0.0: Audio: pcm_s16le, 22050 Hz, stereo, 705 kb/s
Output #0, mp3, to '22050q.mp3':
    Stream #0.0: Audio: libmp3lame, 22050 Hz, stereo, 64 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop encoding
size=     148kB time=108.5 bitrate=  11.2kbits/s
video:0kB audio:148kB global headers:0kB muxing overhead 0.021089%