[asterisk-users] Zaptel -> DAHDI: now echo

[Dave Fullerton]

Kevin P. Fleming wrote:
> Jeff LaCoursiere wrote:
>> On Tue, 18 Aug 2009, Kevin P. Fleming wrote:
>>
>> [snip]
>>
>>>>   Note: It is *mandatory* to configure an echo canceler for the
>>>>   system's channels using dahdi_cfg unless the interface cards in use
>>>>   have echo canceler modules available and enabled. There is *no*
>>>>   default software echo canceler with DAHDI.
>>>>
>> Why is this by the way?  Is there some advantage to NOT having one of 
>> these modules loaded by default?
> 
> Well, when we made them modular so that people could pick and choose at
> run-time instead of compile-time, it seemed like forcing a default on
> everyone was the wrong thing to do... especially for people who don't
> need them at all because they have hardware echocancelers.
> 
> In hindsight, this has probably been the biggest issue with people
> upgrading from Zaptel to DAHDI, and we should have just had some sort of
>  default. We've had some discussions about making dahdi_cfg supply a
> default echo canceler for all channels that don't have one specified,
> but then that of course will require the ability to tell it "no, I don't
> want one".
> 

Here's my $0.02. If you don't want an echo canceller, specify 
echocanceller=none,x-y and have dahdi_cfg print a warning (at any 
verbosity level) when an echo canceller is not specified for a channel.
Personally, I would also like to see an option that says "Use the 
hardware canceller", like echocanceller=hw,x-y. This would have the 
added benefit of being able to display an error/warning when the 
hardware canceller is specified but no hw canceller is present. It goes 
against my grain to not specify a canceller to mean use a harware one if 
it happens to exist.

-Dave