On Mon, 2012-07-16 at 11:11 +0200, Martin Vit wrote: > The short answer is no you can't get 32 *concurrent* channels > on a > 250kbps uplink > > With G729 as a codec you need around 32kbits per channel > including the > overheads from the voip protocol and tcp etc, so that would > give you > around 7 *concurrent* channels.
This is correct if you're using vanilla RTP and no silence suppression. The G.729 payload runs at 8kbits/sec during talk and 1.6kbits/sec otherwise; assuming 50% silence gives an average bitrate of 4.8kbits/sec. Alternatively, just dropping silent frames brings that down to 4kbits/sec. Multiplexing 32 of these over a 250kbits/sec connection should not be a problem, provided that they're not individually wrapped with RTP, UDP and IP headers. Incidentally, at 50% talk/silence (which is an over-estimate - people listen more than they talk), the chance of everyone at one end of 32 calls talking at the same time is 2*10^-10. So there's not going to be many frames dropped as a result. --Dave -- _____________________________________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- asterisk-biz mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-biz
