[Asterisk-Dev] zaptel echo preload

[Richard Lyman]

Steve Underwood wrote:

> 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

he's probably refering to same proto delay.  just for for thought.