Encoding Options for FFMPEG

[Kreez]

Hi All ,

What are the best and optimized encoding options to generate a 3GP from MP4 using FFMPEG with good quality and smaller size.

Preferable Frame size is qcif 176x144
Preferable output file size is 450 KB
Input file sizes vary from 1 MB - 3 MB

Codecs :: Mpeg4 - AAC

Thanks.
Kreez