[Asterisk-Users] Adjusting txgain/rxgain

[Kris Boutilier]

Likely all of your calls are experiencing the talker echo, but the sip
caller is the only one who detects it as a "bad thing" because the
reflection is being delayed until it's detectable by the codecs and
transports involved. For the users who don't have transport delays the echo
simply manifests itself as louder 'sidetone' - See:
http://www.voip-info.org/wiki-Echo+and+Sidetone

You can test for this by chaging SIP codecs to something that introduces
less or more delay (eg. ulaw) and seeing if the echo is more pronouced. 

The soloution is either to get rid of the source of the reflections as much
as possible - usually by 'balancing the hybrid' on your end to start with,
or by tweaking the zaptel echo canceller parameters in zapata.conf (or, if
you're feeling adventurous, zaptel/mec2_const.h) to get it to converge
properly on the reflections your encountering. 

I have managed to get it go cancel fine on about 90% of my calls, but there
are some which simply defy cancellation. In each of these cases it's 100%
repeatable and seems to be something to do with the remote parties line or
specific telephone characteristics.

Hope that helps.

Kris Boutilier
Information Systems Coordinator
Sunshine Coast Regional District


> -----Original Message-----
> From: Paul Dugas [mailto:Paul at DugasEnterprises.com]
> Sent: November 5, 2004 10:41 AM
> To: Asterisk Mailing List
> Subject: [Asterisk-Users] Adjusting txgain/rxgain
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>I also have occasional echo issues; internal caller on a SIP phone hears
echo of self 
> calling out via X100P FXO; called doesn't hear any echos.
> 
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