create second stream with a lower rate

[lalabuuhhh]

hi,

i like to create a second stream for isdn & modem users.

our first stream is running @ 96stereo.
os: linux

i can't finde anything on google... how i can creat a second stream which uses stream 1 as source and makes 96kbips down to 56kbips for a second stream.
what for tools on linux do i use, where can i find them?
i know that it go ... but can't find infos :/

thank you for help!

mfg, lalabuuhhh