[asterisk-users] ECHO Cancellation in SIP Calls

[Conrad Wood]

On Thu, 2006-10-26 at 12:18 +0200, Stefan Agethen wrote:
> Hi,
> 
> i am from Germany, so excuse my School English.
> 
> I use Asteriks 1.2.12.1, zaptel 1.2.9 and mISDN Rc25 - since my update 
> of Asterisk 2 wooks ago, Echos accure in my SIP Calls.
> 
> I use SNOM 360, sometimes there is no echo (for example if i call myself 
> via SIP->Asterisk->SIPProvider->TELEKOM->ISDN)
> but if i call other people there occures Echo many times. The Routing is 
> always the same :
> SIP (SNOM) -> Asterisk -> VoIPProvider -> ISDN/POTS
> 
> Can i control the cancellation with the zapata.conf ?

The snom phones are pretty decent devices and shouldn't introduce echo.
Your latency might be too high between asterisk + voipprovider
introducing a delay that is noticed as echo.
You are hearing the echo that is introduced on the callers side.
As I understand it, when you are calling someone there is no zap
involved and thus you can't cancel it with zapata.conf.
if you look at voip-info.org [1] you'll find a good explanation why you
can't use an echo canceller to cancel that sort of echo.
So, check the path between you and the voipprovider, e.g. connection
saturation, ping times etc
(This is assuming you have a proper lan connection between
asterisk/snom)

Conrad

[1] http://www.voip-info.org/wiki/index.php?page=Asterisk+Echo
+Cancellation