[asterisk-users] Echo

[Dave Fullerton]

Jason Baker wrote:
> I recently upgraded my Asterisk system to Dahdi and now I have an echo
> problem.
> 
> I am running Asterisk 1.4.25 with Dahdi Complete 2.2.0, on a Digium
> TE121B PCI express card with a HARDWARE echo cancellation module. All
> this is housed on a CentOS 5.5 box, 2.6.18 Kernel. My incoming phone
> service is an AT&T PRI (24 channel T1).
> 
> My configs:
> 
> ********chan_dahdi.conf*********
> 
> [channels]
> ; configuration for T1 card as PRI
> language = en
> 
> group = 1
> echocancel = yes
> echotraining = yes
> signalling = pri_cpe
> switchtype = 4ess
> usecallerid = yes
> context = incoming
> channel => 1-23
> 
> 
> ***********/etc/dahdi/system.conf*************
> loadzone=us
> defaultzone=us
> span=1,0,0,esf,b8zs
> bchan=1-23
> dchan=24
> 
> When I run dahdi_cfg -vvv I get the following:
> 
> DAHDI Tools Version - 2.2.0
> 
> DAHDI Version: 2.2.0.1
> Echo Canceller(s): MG2
> Configuration
> ======================
> 
> SPAN 1: ESF/B8ZS Build-out: 0 db (CSU)/0-133 feet (DSX-1)
> 
> Channel map:
> 
> Channel 01: Clear channel (Default) (Echo Canceler: none) (Slaves: 01)
<snip>
> Channel 23: Clear channel (Default) (Echo Canceler: none) (Slaves: 23)
> Channel 24: D-channel (Default) (Echo Canceler: none) (Slaves: 24)
> 
> 24 channels to configure.
> 
> Setting echocan for channel 1 to none
<snip>
> Setting echocan for channel 24 to none
> 
> 
> It is showing MG2 as the echo canceller, even though I don't have an echo 
> canceller specified. Is that the harwdare module? Do I even need to specify an 
> echo canceller in the configs if I have a hardware echo module?

MG2 is a software canceller. I don't think that line means that MG2 is 
being used on all your channels. If you look at the Channel map it says 
"(Echo Canceler: none)". If it had been set to MG2 you would see MG2 
instead of none.

You do not need to specify an echo canceller in system.conf when you 
have a hardware canceller. One thing I would check is to make sure 
asterisk is activating the echo canceller when a call is in progress. To 
do this execute "core show channels" at the asterisk command line (make 
sure someone on the system has placed a call on the PRI). Look for a 
DAHDI/#-x line. Then execute "dahdi show channel #" where # is the 
channel number. You'll get a screen full of output. Look for a line that 
looks like this (it will be near the end):

Echo Cancellation: 128 taps unless TDM bridged, currently ON

The "currently ON" is telling you that the echo canceller is active.

You could try changing echotraining to no in chan_dahdi.conf as well.

What were you running before you upgraded?

-Dave