[asterisk-dev] Zaptel Echo Cancellation

[John Lange]

On Fri, 2006-08-04 at 11:31 +0200, Koopmann, Jan-Peter wrote:
> On Friday, August 04, 2006 2:11 AM Steve Underwood wrote: 
> 
> > You are comparing a well designed echo canceller, with something very
> > crude which addresses none of the key issues with relible
> > cancellation. This has nothing to do with software versus hardware. 

Again I'd like to ask the question, where can one find out more about
echo cancellation? If not online are there technical books on the
subject?

> Which is exactly the point I was trying to make, actually... :-) A
> software canceller can probably perform as well as good hardware
> cancellers if the algorithm used is as efficient and the CPU is
> sufficiant.

In the vast majority of cases you should not have CPU issues since the
server's CPU is probably many magnitudes more powerful then the onboard
processor in a hardware echo canceler and Asterisk with a single span T1
is probably not under much load.

As an example, software raid can often outperform hardware raid in
certain benchmarks when the machine is otherwise idle. But under load
this advantage quickly disappears.

This begs the question, what algorithm is the digium hardware echo
canceler using? If its better then why hasn't that code been put into an
asterisk software echo canceler?

John