[Asterisk-Users] Local Echo

[Jeff Heath]

On Tue, 2005-04-12 at 15:28, Noah Silverman wrote:
> Hi,
> 
> I tried, and still get an echo.
> I don't think the problem is with the zap interface.  It must be on the
> asterisk or phone side.
> 
> -N
> 

Echo requires 2 phenomena:  1) reflected energy  2) enough delay that it
is discernable.   That you are hearing echo means that something at the
far end is reflecting the electrical or accoustical energy of your
voice.

Echo cancellation should be done as close to the source of unwanted
reflected energy as possible.  The fact that you're hearing echo means
that the echo cancelers at the far end either a) don't exist or b)
didn't work.  It will be very difficult to cancel reflected energy
coming back at you from the "other side" of the network. 

Tell me more about the phone call where you experienced the echo and I
_might_ be able to help.  Specifically,

- was the phone at the other end a speaker phone and if so, was it an
expensive Polycom phone that's designed to be a speaker phone or a cheap
Walmart phone that happens to have speaker capability?

- was it a local call or a long distance call

- what codecs are in use?

- what's your best guess at the round trip delay (i.e. what networks had
to be traversed and what is the jitter buffer set for?)



> 
> Rich Adamson wrote:
> 
> >>I have a strange echo problem.
> >>
> >>When speaking on the phone with someone, I hear MY OWN voice with a
> >>sever echo.  The other party sounds perfect, and they can hear me
> >>perfectly.  It is as if only the sidetone has an echo.
> >>
> >>I'm running * on a dedicated box, small LAN, and am using 4 FXO cards to
> >> connect the box to PTSN lines.  My phones are Polycom IP500 SIP phones.
> >>
> >>The only echo cancellation stuff that I can find relates to cancelling
> >>echo between my system and the PTSN lines.  Since the call is "perfect",
> >>I don't see how this would apply.
> >>
> >>Any suggestions??
> >>    
> >>
> >
> >Try these parameters for each zap channel:
> >echotraining=800
> >echocancel=yes
> >echocancelwhenbridged=yes
> >
> >Don't forget you have to stop and restart asterisk. a reload will not work.
> >
> >
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