[FFmpeg-user] problem encode mov to 3gp

[aris sirajawali]

how to encode video from mov to 3gp with good quality and small size ..
I use the following command: *ffmpeg-i INPUt.MOV-acodec libfaac-ab 12.2-ac
1-ar 8000-vcodec h263-s QCIF-r 10-b 128k OUTPUT.3gp*.
and if I make use *acodec amr_nb or amr_wb*, I get an *unknown encoder*, is
there an error on my ffmpeg command?
Please answer all the friends of friends, ..