[Asterisk-Users] Tiny Echo on PSTN via Zaptel

[Neil Lewis]

Tony Nichols wrote:

> I have had problems between the sip/FXO lies and was able to "kill"
> the echo by trying different combinations of the echocancel line to 64
> (I think it has settings in 32 bit increments)
> Just kept trying different ones till it went away. Here is my config:
>
> group=1
> context=line1
> signalling=fxs_ks
> usecallerid=yes
> callerid=asreceived
> echocancel=64
> echocancelwhenbridged=yes
> callgroup=1
> rxgain=1.2
> channel => 1
>
> context=line2
> signalling=fxs_ks
> usecallerid=yes
> callerid=asreceived
> echocancel=64
> echocancelwhenbridged=yes
> callgroup=1
> rxgain=1.2
> channel => 2
> musiconhold=default
> context=line3
> signalling=fxs_ks
> usecallerid=yes
> callerid=asreceived
> echocancel=64
> echocancelwhenbridged=yes
> callgroup=1
> rxgain=1.2
> channel => 3
>
> group=2
> context=line4
> signalling=fxs_ks
> usecallerid=yes
> callerid=asreceived
> echocancel=96
> echocancelwhenbridged=yes
> callgroup=2
> channel => 4
>
> Hope this helps!
>
> t o n y
>
> On 9/28/05, *Shaw Terwilliger* <sterwill at sourcegear.com
> <mailto:sterwill at sourcegear.com>> wrote:
>
>     I'm using Asterisk 1.0.9, a Digium TE210P dual T1 card, and two Rhino
>     channel banks (one 12FXO/12FXS, the other 24 FXS).  So it's an analog
>     phone on the inside connected to one of the FXS ports, and PSTN line
>     connected to one of the FXO ports.
>
>     My problem is that as soon as I hear the _first_ ring when I dial out
>     through the PSTN line, I hear a tiny echo on the phone (I estimate
>     between 20ms and 40ms), which never goes away for this call.  It's
>     just
>     loud enough to bug the heck out of me when I'm talking (I could
>     estimate
>     the gain relationship with ztmonitor if it would help).  The sound
>     on the recipient end of the connection is perfect.
>
>     If I make a call from the phone to the another internal extension
>     (another
>     phone on an FXS port), there is no echo.  If I call into Comedian
>     mail,
>     there is no echo.
>
>     I've checked all my gains.  The "internal" gains were a bit loud
>     to start
>     with because of the powered phones, but now they all fall
>     comfortably within
>     ztmonitor's dynamic range display.  The PSTN line is pretty good
>     at tx 0 and
>     rx 0, so I left it.  I've tried turning them down, but that didn't
>     kill
>     the echo.
>
>     My zapata.conf includes these lines at the bottom:
>
>     echocancel=yes
>     echocancelwhenbridged=no
>     echotraining=yes
>
>     context=companyA-pstn
>     txgain=0.0
>     rxgain=0.0
>     signalling=fxs_ks
>     group=1
>     channel=1-7
>
>     context=companyB-pstn
>     txgain=0.0
>     rxgain=0.0
>     signalling=fxs_ks
>     group=2
>     channel=11-12
>
>     context=internal
>     txgain=-12.0
>     rxgain=-8.0
>     signalling=fxo_ls
>     callerid=asreceived
>     group=3
>     channel=13-48
>
>     When the calls are connected, I can use "zap show channel 11" and
>     verify
>     that the echo cancellation is ON.  But I can still hear one.
>     I've also tried echocancelwhenbridged=yes, but it didn't make any
>     difference.
>
>     --
>     Shaw Terwilliger < sterwill at sourcegear.com
>     <mailto:sterwill at sourcegear.com>>
>     SourceGear LLC
>
>
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>
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>
>
> -- 
> A.G. (Tony) Nichols
> I.S. Manager
>
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>
Echo problems can be remedied in several ways. Echocancel and
echotraining are the primary tools used to remove echo. Experiment with
the echocancel and echotraining values in order to find the right
combination for your echo problem (echocancel: 32, 64, 128, 256;
echotraining: 200, 400, 800). You'll also need to make sure that your
tx/rxgain levels are not set too high. As a rule of thumb, they should
not be set higher that 5, or lower than -5.

If you are using CVS-Head you can also use the fxotune utility located
in /usr/src/zaptel to tune
out echo in the FXO module.  Execute this command: './fxotune -i 4'
It will automatically configure the FXO modules for echo.

You can also try using an different Echo Canceler.  We've recently added
a new EchoCan to Asterisk:  KB1.  To utilize it, just uncomment its
define statement in zconfig.h, and comment the other EchoCan out.

The final method is the Aggressive Suppressor tool in zconfig.h. Simply
uncomment the Aggressive Suppressor function line, and then recompile
zaptel. All changes made to zapata.conf, and zconfig.h, require
Asterisk to be restarted.

NRL

-- 
Neil Lewis
Digium Technical Support
nlewis at digium.com
1.877.LINUX.ME