[asterisk-dev] M9645: provide zaptel master timing to spans

[Matthew Fredrickson]

> Just a comment: You should not interrupt at 1ms intervals.
>
> For example:
>
> The interrupt handler must respond within 1ms for transmission of 
> data. This
> contradicts to block-processing of sound which might take more than 
> 1ms.
>
> The result is that Zaptel will not be able to do echo cancelling from 
> the
> interrupt thread. Then Zaptel needs another thread that pre-computes 
> the
> echo, which either adds more delay in the transmission path, or 
> computes the
> estimated echo too often.
>
> Zaptel is in other words not designed for efficiency.

No comment :-)

>
> If you don't know what a fast echo canceller looks like, have a look 
> here:
>
> http://www.turbocat.net/~hselasky/isdn4bsd/sources/new_ec/

I don't have a lot of echo canceler design experience, but after 
glancing at your code, I have this question.  What are you doing an FFT 
for in your echo canceler?  I can see why you'd be concerned with not 
finishing block processing within 1ms if you're doing that in your echo 
canceler.

Matthew Fredrickson