[asterisk-dev] RFC: DAHDI echo canceller configuration change

[Nic Bellamy]

Kevin P. Fleming wrote:
> I'm working in a branch of DAHDI's 'linux' package:
>
> http://svn.digium.com/svn/dahdi/linux/team/kpfleming/modular_ec
>
> This branch contains modifications to allow one (or many) echo cancelers
> to be built and loaded at the same time, and then runtime selection made
> as to which one should be used on which channel(s). All of the existing
> modules have been converted, and the core code is ready to use them, so
> what I'm left with is deciding on a configuration method.
>   
[...]

I'm coming in a bit late here, but food for thought perhaps...

I'd actually done this ages ago for the Zaptel 1.2 branch, but never 
found the time to update it for trunk in order to submit it. Too busy 
using it ;-)

I did it somewhat differently though, in that I added an extra ioctl 
called ZT_ECHOCANCELV2 that allowed you to specify the echo canceller 
and other parameters.

With the corresponding patch to Asterisk, this allows settings the echo 
canceller type on a per-channel basis in zapata.conf

The EC modules can be loaded/unloaded at will, as each keeps a use 
count, however I kept one software EC built-in as a fail safe fall back.

I found this to be a decent "mechanism vs. policy" compromise - 
mechanism in the kernel (Zaptel), policy in userspace (Asterisk).

Cheers,
    Nic.

-- 
Nic Bellamy,
Head Of Engineering, Vadacom Ltd - http://www.vadacom.co.nz/