[Asterisk-Dev] zaptel echo preload

[Steve Underwood]

James Harper wrote:

>I'm tinkering with a patch to preload echo coefficients at channel
>creation time instead of it starting from scratch each time a call is
>started.
>
>Anyone want to have a look once I have something that works?
>
>Any comments as to if this is a good idea or not? Currently I get quite
>a few seconds of echo before it stabilises, so I think that having
>something preloaded in there is better than starting from zero. Once I
>get it going I'll be able to comment with more authority though :)
>
>James
>  
>
It depends on what you are trying to achieve.

If you are using an analogue interface, it is likely the strongest echo 
will be from your local telephone exchange's line card. This should be 
pretty consistent from call to call, so using the same pre-tuned 
starting point for each call should have benefits. The canceller still 
needs to adapt to the echo from the far end telephone, but you have 
probably helped reduce the initial echo heard.

If you are using a digital interface (BRI. E1, T1, J1) the echo you need 
to cancel is only from the far end. Since there is no consistency from 
call to call, a pre-tuned echo is completely useless for this case.

Steve