| From: Rachel Quin <[email protected]> | | I think I'm not making myself clear, sorry. Our t3's and Megalink circuit | from Bell come into AS5400's. Our VoIP infrastructure is entirely SIP. A | conferencing server would only handle RTP streams, mixing channels for many | large-ish volume conferences. The box I'm talking about would have 2 10gig | nics, one or two DSP cards, and whatever software is needed to handle | managing conferencing and directing RTP/G.711 content channels to and from | the DSP card(s). I am not looking to build a stand alone phone system.
Naively, I would think mixing RTP streams of G.711 should not be too hard for a regular CPU. G.711 is PCM so decoding and encoding is a snap. Mixing is just a kind of averaging, I imagine. But: I did say "naively". I've never done any of this. I don't know whether automatic gain control can be done simply and cheaply. I don't know how you can sum a hundred channels and not get overloaded with noise. I'll waive my hands and say that different channels don't need to be transformed to use the same timebase, but maybe I'm wrong. I know nothing about echo-cancellation issues. So, naively, the tasks of the processor would be: - take samples from N RTP streams - average them - send the result out on N RTP streams. The actual amount of computation, for the naive process, ought to be within the realm of any modern processor for values of N up to perhaps 1000. 8K samples / channel / second == 8KB bandwidth / sec modern processors can do (guess) 40MW main memory accesses / second (the bottleneck, I think) Which of the things that I've skipped are necessary and expensive? --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
