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

[Gideon Hack]

A good idea, Kevin. You may also want to include additional performance parameters, such as the number of taps for the EC.

Gideon


> Date: Wed, 18 Jun 2008 18:11:06 -0500
> From: kpfleming at digium.com
> To: asterisk-dev at lists.digium.com
> Subject: [asterisk-dev] RFC: DAHDI echo canceller configuration change
> 
> 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'd like to just use the existing /etc/dahdi.conf and dahdi_cfg tools to
> do the configuration, adding something like:
> 
> echocanceler=MG2
> 
> or
> 
> echocanceler=HPEC
> 
> Doing so would then apply that choice to all subsequent channels
> configured in the file in *any* signaling mode (although obviously many
> signaling modes don't support audio, and thus will never actually use
> the echo canceler defined for those channels).
> 
> This seems pretty straightforward to me, however, it would be the *only*
> parameter in /etc/dahdi.conf that 'inherits' into later definitions in
> the file, which is probably not a wise choice.
> 
> An alternative would be for the syntax to be something like:
> 
> echocanceler=MG2,1-4
> echocanceler=HPEC,8-12
> 
> This fits the existing model a bit more.
> 
> In addition to this, there is a need to find some way to set a default
> echo canceler to be used if the configuration file does not specify one.
> In Zaptel, this was done at compile time, but since all available echo
> cancelers are compiled and installed now, there isn't any practical way
> to do that, and I'd rather move away from compile-time configuration anyway.
> 
> I could certainly add an additional configuration parameter for this, or
> make the 'echocanceler=<name>,<channels>' parameter accept *no channels*
> as an argument, which would then apply it to all channels.
> 
> Thoughts? Whichever way this goes, I'll end up documenting it in
> UPGRADE.txt in the source tree, because it will be a significant change
> in behavior from Zaptel 1.4.
> 
> Another note: I won't require the user to forcibly load echo canceler
> modules; if a name is provided and no module currently provides it, the
> DAHDI core will attempt to 'autoload' that module to satisfy the request.
> 
> -- 
> Kevin P. Fleming
> Director of Software Technologies
> Digium, Inc. - "The Genuine Asterisk Experience" (TM)
> 
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