Reduce Bitrate Of Stream In WMS

[aa1]

hi,

i've live tv stream at 512kbps and i want to reduce the bitrate to 300kbps and then share the stream.

so is there ways or software to reduce bitrate at real time so that i'll get lower bitrate video

EX:

Live tv 1: 512kbps

i need Live tv 1 at 300kbps

i have windows server 2003 and i will distribute by windows media server

PLZ HELP

thanx