[asterisk-users] Disabling echo cancellation by software

[Shaun Ruffell]

On Wed, May 11, 2011 at 10:54:06PM -0300, Alejandro Cabrera Obed wrote:
> Dear, I have Asterisk 1.6 with an E1 Digium card with echo
> cancellation module. So I need to use just the echo cancellation by
> hardware and disable the echo cancellation by software. I use DAHDI
> for my telephony hardware.
> 
> If the lines involved with echo cancel are:
> 
> In /etc/dahdi/system.conf:
> 
> echocanceller=mg2,1-15,17-31
> 
> In /etc/asterisk/chan_dahdi.conf:
> 
> echocancel=yes
> echocancelwhenbridged=no
> echotraining=800
> 
> What lines do I have to comment or to change the value if I want to
> disable echo cancellation by software ???

With all current releases of DAHDI if a span has a hardware echocanceler
available, it will be used regardless of the settings in
/etc/dahdi/system.conf.

You can disable the hardware echocan in the wcte12xp and wct4xxp drivers by
setting the vpmsupport module parameter to 0 when you load the driver. You 
do this from the command line (for the wct4xxp driver in these examples) with
'modprobe wct4xxp vpmsupport=0' or set 'options wct4xxp vpmsupport=0' in
/etc/modprobe.d/dahdi.conf in order for it to take effect each time the driver
is loaded.

The v2.5.0 version of DAHDI, which is not yet released, will require that
hardware echocan be set in /etc/dahdi/system.conf for each channel. This will
allow a span to use a combination of software and hardware echo cancelers in
addition to providing a way to disable the hardware echo canceler without
reloading the drivers. Support for this feature is already committed to the
trunk of DAHDI Linux.

If you do check out the trunk, and want to use the hardware
echocan, be sure to set the echocanceller line in /etc/dahdi/system.conf to
'hwec' for each channel. dahdi_genconf does not yet setup the hwec by default
on the spans that have it available but it will before the 2.5.0 release.

-- 
Shaun Ruffell
Digium, Inc. | Linux Kernel Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at: www.digium.com & www.asterisk.org