On Friday 30 December 2005 10:42, Boris Benko wrote:
>
> I think it's great. I understood the problem of echo cancellation
> briefly, but from now on, I understand it more completely.

That article is well done.

> I'm wondering, if echo cancellation in visdn already is implemented.

It's not, yet.

> Probably not.

Right :)

> So my question is, are there any feasible workarounds. For 
> example, is it possible to have an echo canceller on a SIP channel in
> general?

Echo cancellation should be done as near as possible with respect to the 
source of echo. Ideally it should be done locally, on the terminal (SIP 
phones do).

It is still feasible within the driver architecture but becomes much harder to 
do at asterisk's level because of the delay introduced by the bigger frames.

Even worse would be trying to cancel echo after the stream has been 
packetized/encoded/transmitted on the network.

> I think that zap hardvare has the cancellation implemented, but 
> I assume, it is strictly tied to zap hardware.

Newer Digium hardware has hardware echo cancellation, however, most boards 
still rely on the software EC in zaptel drivers. I'm taking that canceller 
and putting it in vISDN.

Its performance is not exceptional but would be way better than going without 
an EC :)

I promise the next job will be finishing the software echo canceller, I swear!

Bye,
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