G. Jacobsen wrote: > is it possible simply to drop silent packets in the straight g729 (not a, b) protocol? > How do I recognize silent packets ?
Good question - you'd need to recognise them before they reach the encoder, I guess. A moving power average compared to a threshold is a simple and not entirely useless speech/silence differentiator when combined with a holdover timer. It's fine to start and stop the RTP stream - i.e. just to drop packets which would represent silence - provided that the timestamps are correct and, ideally, the bit which marks a new burst gets correctly set. > Thanks for this informative posting Glad you found it of use! --Dave On Jul 17, 2012, at 7:09 AM, David Knell wrote: > 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 -- _____________________________________________________________________ -- 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 -- _____________________________________________________________________ -- 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
