[Asterisk-Users] Reducing echo on FXS port

[Aryanto Rachmad]

Hello everybody,

I am sorry to bring this up again if this kind of echo issue has ever discussed.

Phone2 in below call path experiences quite annoying echo:

Phone1 --> FXS (TDM400P) --> Asterisk --> SIP GW --> PSTN --> Phone2

It is annoying as on phone2, we can hear the whole words we say with the level of maybe 25% of the original sound. I can reduce the echo to maximum with the following settings for my FXS port on zapata.conf:

rxgain=-8.0
txgain=2.0
echocancel=256
echotraining=500

But it is still not entirely eliminated as we still sometimes hear the last syllables, with the level of maybe 5% of the original sound.

What I did was just playing around with the values of those parameters, use ztmonitor to have the FXS rx/tx signal visualised and use only my ears to check it. I think my ears are fine :), as I do this because my friends complain about the echo they hear.

Does anybody know a better method to find the best value for those parameters?

There is no echo on phone2 when I use softphone like this:

PC(X-Lite) --> Asterisk --> SIP GW --> PSTN --> Phone2

The following is the version of asterisk I am using:

CLI> show version
Asterisk SVN-branch-1.2-r7999 built by root @ atvie-asterisk on a i686 running Linux on 2006-01-13 06:15:02 UTC

And I set the echo canceller in zconfig.h to ECHO_CAN_MG2.

Cheers,

Anto
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