> mencoder -ovc help

Available codecs:
   copy     - frame copy, without re-encoding. Doesn't work with filters.
   frameno  - special audio-only file for 3-pass encoding, see DOCS.
   raw      - uncompressed video. Use fourcc option to set format explicitly.
   nuv      - nuppel video
   lavc     - libavcodec codecs - best quality!
   vfw      - VfW DLLs, read DOCS/HTML/en/encoding-guide.html.
   qtvideo  - QuickTime DLLs, currently only SVQ1/3 are supported.

> mencoder -oac help

Available codecs:
   copy     - frame copy, without re-encoding (useful for AC3)
   pcm      - uncompressed PCM audio
   lavc     - FFmpeg audio encoder (MP2, AC3, ...)

mencoder source.rm -ovc lavc -oac pcm -o dest.avi

mencoder source.rm -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -ffourcc DX50 -oac mp3lame -lameopts vbr=3 -o dest.avi

mencoder source.avi -ffourcc divx4 -ovc lavc -oac lavc -o dest.avi

> ffmpeg -i source.avi \
         -vcodec mpeg4 -b 64k -s qcif -r 15 \                   # MP4/64kbps/QCIF/15fps
         -acodec libopencore-amrnb -ab 12200 -ar 8000 -ac 1 \   # AMR/12.2kbps/8kHz/1ch
         -flags bitexact 
         output.3gp
> MP4Box -add output.3gp -brand mmp4:1 -new output_mod.3gp

ffmpeg -i input.avi 
       -y 
       -vcodec mpeg4 -s 704x396 -b 512k -r 29.97           # mpeg4/704x396/512k/29.97fps
       -acodec libopencore_amrnb -ar 8000 -ab 12200 -ac 1  # AMR/12.2kbps/8kHz/1ch
       MOL001.3gp

Too many audio packets in the buffer: (4096 in 8255101 bytes).
files, try to force non-interleaved mode with the -ni option.
Maybe you are playing a non-interleaved stream/file or the codec failed?

mencoder -idx -ovc copy -nosound -fps 29.97 -o dest.video src.avi

mplayer -idx -ao pcm:file="dest.audio" -vc dummy -vo null src.avi

mencoder -idx -profile xvid -idx -o dest.avi -audiofile dest.audio dest.video