Someone

bash-3.2# ffmpeg -i /root/dvgrab-038.avi.0/audio.wav -vn -ab 224k -ar 48000 -ac 2 -acodec ac3 -y /root/dvgrab-038.avi.0/audio.ac3
FFmpeg version SVN-r8673, Copyright (c) 2000-2007 Fabrice Bellard, et al.
  configuration: --enable-gpl --enable-shared --enable-pthreads --enable-liba52 --enable-libfaad --enable-libfaac --enable-libmp3lame --enable-libogg --enable-libvorbis
  libavutil version: 49.4.0
  libavcodec version: 51.40.2
  libavformat version: 51.11.0
  built on Apr  9 2007 22:11:41, gcc: 3.3.4
Input #0, wav, from '/root/dvgrab-038.avi.0/audio.wav':
  Duration: 00:00:02.1, start: 0.000000, bitrate: 1536 kb/s
  Stream #0.0: Audio: pcm_s16le, 48000 Hz, stereo, 1536 kb/s
Output #0, ac3, to '/root/dvgrab-038.avi.0/audio.ac3':
  Stream #0.0: Audio: ac3, 48000 Hz, stereo, 224 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop encoding
size=      58kB time=2.1 bitrate= 224.0kbits/s
video:0kB audio:58kB global headers:0kB muxing overhead 0.000000%
bash-3.2# ffplay audio.ac3
audio.ac3: could not open codecs
bash-3.2#