[Asterisk-Users] How to deal with echo in MeetMe?

[Tony Mountifield]

I have a customer who is running fairly large conferences (between 5
and 30 participants) on their Asterisk box. It uses SIP to talk to a
PSTN provider.

They are complaining that under some circumstances they experience
echo of one or more participants. On listening in to one of their
conferences, it seemed to me that the echo was being introduced
via the microphone of a couple of specific participants, as it was
possible to eliminate this echo by muting those participants.

On discussing the participants' environments with the customer, it
would appear that the problem occurs when participants are using
speaker phones and there are multiple participants in proximity to
each other, such that one participant's phone can hear the audio
from that of another participant in the same conference.

It's my supposition that any echo canceller is going to have
difficulties correcting for that scenario. Am I correct?

The problem I have is that the customer insists that their existing
conferencing supplier (whom our kit is supposed to replace) does
not suffer from this echo, in the same participant environment.

I am assured by our PSTN supplier that there is full echo suppression
on the PSTN lines. Am I correct in believing that further echo
suppression is neither possible nor required at the SIP interface
within Asterisk?

Any advice on how to approach this would be appreciated.

Cheers
Tony
-- 
Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org