ffmpeg - Hyper fast MPEG1/MPEG4/H263/RV and AC3/MPEG audio encoder
FFmpeg is a very fast video and audio converter. It can also grab from a
live audio/video source.
The command line interface is designed to be intuitive, in the sense that
ffmpeg tries to figure out all the parameters, when possible. You have
usually to give only the target bitrate you want. FFmpeg can also convert
from any sample rate to any other, and resize video on the fly with a high
quality polyphase filter.