[Asterisk-Users] How to ensure that software echo cancellation is on?

[Don Murray]

I have appended my /etc/asterisk/zapata.conf and my /etc/zaptel.conf 
files.  I am running Asterisk 1.0.7 on a P3 800 MHz system in an office 
with around 20 sip phones.  We are using a Digium Wildcard TE110P that 
is connected to a T1 line with 8 lines enabled. We have been 
experiencing irritating echo on the sip phone side when local lines are 
called. 

After reading a lot of echo related threads, I think I understand the 
4-wire to 2-wire cause of this echo.  I have noticed that when calling 
long distance and with some cell phones there is no echo, which is 
consistent with a system that has echo cancellation on the destination end.

So, I've been trying to enable software echo cancellation to see if it 
will improve the situation.  If you look down to see my zapata.conf 
file, you will see I've tried to set echocancel and 
echocancelwhenbridged, and that I've also mucked around with 
echotraining.  None of these appear to be doing anything. 

However, I *think* this is because they are not being enabled properly, 
because when I try to see the details of an active zap channel (see zap 
show channel command) it says "Echo Cancellation: 0 taps unless TDM 
bridged, currently OFF".   I'm not sure if I'm doing this debugging 
right, so I wanted to ask people both :

(a) am I enabling echocancel correctly?  I've heard that sometimes these 
parameters can behave differently depending on the order they appear in 
the file??

(b) am I doing the right thing to detect if echo cancellation is on?  
Whats the righ tway to do that?

btw, I have rebuild my zaptel src with "AGGRESSIVE" cancellation 
enabled, with MMX enabled and with MARK2 cancellation enabled.

Any advice appreciated!

Thanks,
Don



asterisk1*CLI> zap show channel 8-1
Channel: 8CLI>
File Descriptor: 32
Span: 1
Extension:
Dialing: no
Context: from-pstn
Caller ID string: 520xxxxxxx
Destroy: 0
InAlarm: 0
Signalling Type: PRI Signalling
Owner: <None>
Real: <None>
Callwait: <None>
Threeway: <None>
Confno: -1
Propagated Conference: -1
Real in conference: 0
DSP: no
Relax DTMF: no
Dialing/CallwaitCAS: 0/0
Default law: ulaw
Fax Handled: no
Pulse phone: no
Echo Cancellation: 0 taps unless TDM bridged, currently OFF
PRI Flags:
PRI Logical Span: Implicit
Actual Hookstate: Onhook
asterisk1*CLI>


=== zapata.conf

[channels]
language=en

context=from-pstn
switchtype = national
signalling = pri_cpe
group = 0
channel => 1-8
faxdetect=both
;;echocancel=yes
;;echotraining=yes
;echocancelwhenbridged=yes
echocancel=256
;echotraining=800


=== zaptel.conf

loadzone        = us
defaultzone     = us

span=1,1,0,esf,b8zs
bchan=1-8
dchan=24