> > > I was just looking at: > > > > > http://www.asteriskdocs.org/modules/tinycontent/content/docbook/current/docs-html/x1695.
> > html > > > regarding echo canceller tuning, and I noticed the statement > > > > > > "Most people find that they need an rxgain level around 8.0 to have > > > good echo cancellation. The txgain setting varies from installation to > > > installation." > > > > > > Which feels a bit wrong :) Could someone explain why increasing the > > > gain on the inbound zap leg (rxgain) would improve echo cancellation? > > > Of have I misunderstood the roles and meanings of rxgain and txgain? > > > [snip] > > Many thanks for clearing that up for me :) the largest part of my > misunderstanding was caused by not noticing that that article was > referring to the tuning of an "FXO" line. I am in fact trying to find > information on the tuning of an E1 to reduce echo. (Doh!) > > In theory of course an E1 should work with rxgain=0.0, txgain=0.0 > (assuming there is no digital messing going on in the network) and the > echo canceller should have a relatively easy job of cancelling echo > given that the large majority of the UK phone network is digital, and > only the last leg at the far end is usually analogue. That last leg "is" usually part of the problem since there is going to be a hybrid conversion. > I am running Asterisk 1.0.9, and have backported the KB1 canceller > into Zaptel 1.0.9.2, which does not seem to have caused any problems. > Nor has it really caused any improvement though :) The KB1 canceller improves echo, but it appears as though it achieved better results by forcing half-duplex communications. From a pure non-technical user perspective, the quality of a telephone conversation has been lowered simply because humans are use to communicating in full duplex mode. > I am beginning to wonder whether what echo IS heard is being caused by > packetisation delays "in the network" - The default tap length is 128, > or I believe 16ms. If something in the PSTN causes a delay more than > that length (no idea what might cause that) then echo would still be > heard. Certainly not hard to change the tap length and eval it. > Does anyone have any experience in this area? Any ideas? How "heavy > handed" would it be to increase the tap length to 256? I have not seen > anyone suggest that this might be a good idea. _______________________________________________ --Bandwidth and Colocation provided by Easynews.com -- Asterisk-Users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
