On 12/15/05, Rich Adamson <[EMAIL PROTECTED]> wrote: > > > 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. 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 :) 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. 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. Thanks, Steve _______________________________________________ --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
