Multicast server software

Hi,

apologies if this is a dumb question, but unless the answer is so
obvious as to be assumed, I cannot find it.

For an internal project here I am looking for some software to act as a
multicast server.

I want a program which:

- I can feed with several arbitrary data files of arbitrary length
- some of these files will contain AV data in various formats,
- some files will contain pure data streams
- I can set it up to multicast each of these streams on various
multicast IP addr/port combinations
- I can configure the desired bitrate of each stream, independently
- this will stream on our LAN here (actually on a separate Lab network)
- ... and then clients can happily join the multicasts and receive the
data

Can you give me pointers to anything suitable? We have found several
things which are close, but they are all too complicated for what we
want: they assume we are streaming audio, or only take input from
capture cards, or what kind of thing.

I have the nagging suspicion that the answer *must* be hard to find
because it is just too obvious, but there you go. Can't find it. I
*could* take an existing super-complicated GPL thing and modify it to
do what I want, but maybe there's a nice simple program available that
will do what I want already. Maybe it's even built in to the OS. Who
knows?

Free or commercial suggestions gratefully accepted.

Thanks,
Liam