[asterisk-dev] Queries regarding Echo Cancellation in Zaptel-1.2.6

[Chan Kwang Mien]

Hi Paul,

Thanks for your reply. 

The purpose of my tests is to verify that Echo Cancellation is up and
running in the zaptel-1.2.6 that I have installed. 

In my test-bed, 

IP Phone A <------> Asterisk IP PBX <---> Analog Phone B

IP Phone A is a speaker phone which I think doesn't have its own
acoustic echo canceller. 

IP Phone A is one hop away from the Asterisk IP PBX and the Analog Phone
B is directly connected to the FXS port of a TE400P Digium Card in the
IP PBX. 

To simulate echo, the call at IP Phone A is being answered by its
speaker. I was expecting that the echo sent back by IP Phone A to Analog
Phone B would be cancelled by the echo canceller at the IP PBX. But it
seems that I could still hear echo although I have enabled echo
cancellation in zaptel.

Do you know why I could still hear echo at Phone B ?

Thank you.


Best Regards,
Kwang Mien





On Mon, 2006-07-17 at 14:50 +0600, Paul Cadach wrote:
> Hi,
> 
> Chan Kwang Mien wrote:
> > IP Phone A <------> Asterisk IP PBX <---> Analog Phone B
> >
> > I called IP Phone A using Analog Phone B. IP Phone A is answered by
> > someone else using its speaker. Both phones are in different rooms.
> 
> Do you mean speakerphone (handsfree) operation of IP phone A? If so, phone A
> should use its own acoustic echo canceller.
> 
> [skipped]
> 
> > With and without echo cancellation in zaptel, I heard echo in Phone B.
> 
> Echo cancellation works on a point connecting to analog (PSTN) part, not on IP
> part, so if echocancellation isn't work properly you usually hear an echo at IP
> side while analog side isn't listen echo.
> 
> > It seems like echo cancellation cannot eradicate the echos. I was
> > wondering if the delay caused by traversing the one-hop IP segment of
> > the network too large for the echo canceller in zaptel to
> > handle ?
> 
> The problem is on your IP phone which isn't provides acoustic echo cancellation
> for speakerphone or impedance balance for handset.
> 
> 
> WBR,
> Paul.
> 
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