On 2009-09-09, at 11:41, Gaëtan Minet wrote: > Hi > > Thank you very much for your feedback. > Do you mean the EC is not active at all (even the low 25ms) for the > far-end side when we use the gateway in TE mode to connect a local > sip system to the pstn using BRAs ? > Damned, I must have missed this in the datasheet :(
echo tail for far is around 100 to 500ms no EC chip can correct for that. That is why EVERYBODY needs to cancel near-end echo. If You hear echo that there is nothing You can do but to tell the other side to upgrade to better equipment or better carrier/operator. Operators are mandated to use CARRIER grade EC chips (128ms echo tail) on each customer port Analog/BRI/PRI just in case the customer has flaky equipment. But this stuff is expensive so carriers often turn on EC chips only for customers that are identified as echo source. > > So you're not using the gateway to connect to pstn in your case, > only to connect local isdn terminals ? > Both. > Here we get plenty of far-end echo on our last installation when > using the gateway to connect to the pstn. > We just tried the patton gateways instead of pci cards (I didn't > notice EC was only 25ms...). > Before that, we used digium b410p with 64ms HW EC on asterisk, but > we noticed that, although the echo seems to disappear, there still > remains a "crispy" echo than can be easily heard on good sip phones > like polycom... thank you HD audio :) . We are still waiting for an > answer from Digium support. > > One or two year ago we almost never heard echo, but now we have more > and more, mainly on companies that receive calls from residential > users. > I suspect this could be due to the increasing popularity of "triple > play" offers here where the providers probably use cheap ATAs, and > the end users usually have cheap analog home phones. I guess the > latency and round trip can easily go above 64ms on these setups. > > Are you aware of good gateways with 128ms echo canceller (Audiocodes > maybe ?). These are probably way more expensive but we could at > least try it to confirm the problem. > Maybe we should also try to build a standalone asterisk gateway with > better cards that the digium B410p then (sangoma cards have 128ms > EC, but maybe a software EC like oslec will provide better results > than the patton anyway). > Try Sangoma Cards (128ms carrier grade EC). Cheaper then Digium if You buy from us ;) But beware that far-end echo cancellation is not Your responsibility. You can combat it only if the delay is less then You EC chip echo tail which is often not the case. Pawel, _______________________________________________ sipx-users mailing list sipx-users@list.sipfoundry.org List Archive: http://list.sipfoundry.org/archive/sipx-users Unsubscribe: http://list.sipfoundry.org/mailman/listinfo/sipx-users sipXecs IP PBX -- http://www.sipfoundry.org/
