[Asterisk-bsd] echo

[Hans Petter Selasky]

On Wednesday 11 October 2006 03:12, Jeremy Bogan wrote:
> > My other question (and a more important one) is: will moving to
> > ISDN or a different FXO card help? Does ISDN have echo problems at
> > all, or because it is all digital, is this problem completely gone?
> > We are thinking of installing Asterisk for our customers, but they
> > will not be as tolerant of a little echo as we are. So should we
> > mandate ISDN as the best approach?
>
> ISDN should make a sufficient difference in regards to echo. What
> echo canceller are you currently using for Zaptel?

The amount of echo one is able to cancel on ISDN, very much depends on the 
phone one is using. ISDN phones are just like analogue phones, and do not 
contain any echo canceller themselves.

> > Otherwise, are other FXO cards better at echo cancellation or is
> > this a software feature built into the driver?
>
> The Sangoma A200 cards with hardware echo cancellation are fantastic,
> and they work great under BSD.

I have good experience with my own ISDN4BSD, the SVN version:

http://www.turbocat.net/~hselasky/isdn4bsd

http://www.turbocat.net/~hselasky/isdn4bsd/sources/src/sys/i4b/layer1/i4b_echo_cancel.c

The echo canceller in I4B is a little bit more advanced than the echo 
canceller in Zaptel. It is a work in progress, but at the moment it performs 
very well. It needs around 5% CPU usage on a 1.2 GHz machine, per channel.

--HPS