Kris Boutilier wrote:
This known as is 'acoustic echo' or 'room reverb' and involves mathematics that is quite a bit different from that used when cancelling regular 'reflected electrical signal' echos, as the signal is being acousically distorted as it echos around the room. On many handsfree handsets it doesn't manifest itself until you move into a physically large room, which increases the reflection delay and overwhelms the internal mechanisms.
The maths is exactly the same. However, it is certainly true that a lot
of acoustic echo cancellers don't deal with long enough echoes to be
effective in large spaces.
It would need to be handled internally by the handset or you would need to
insert a hardware echo canceller capable of dealing with this type of echo,
assuming your signal is exposed on a T1 somewhere. If it's IP all the way for
you then you're really just down to the handset vendors as far as I know -
Asterisk doesn't currently offer any form of echo cancellation on the VoIP side.
In the IP world the echo must be killed by the phone itself. You cannot
echo cancel on the IP side of a switch like Asterisk. The echo path
length needs to be constant for any known echo cancellation process to
work. IP path lengths are not constant.
Hello
I have a Grandstream GXP2000 with latest firmware. When I use it holding the
handpiece I don't hear any echo - neither does other end. However, if I use it
handsfree, the other end notices echo when they speak - ie their voice is
echoy. I hear their voice being a bit echoy.
The Grandstreams are much maligned, but they actually do a better job in
this area than most products. As said above, if you are using this in a
large space the echo canceller in the phone may not cancel a long enough
echo to be very effective. If it fails to kill the echo in a small room
something is wrong.
Is this purely down to the IP Phone? Is there anything I can do about it? I
considered buying a more expensive phone - eg a Snom to see what they were like
for echo. Is there something I can do with the Asterisk? codec to use?
Anything?
A snom might be a poor choice. People tell me they don't even echo
cancel the handset. If a hard of hearing user turns up the handset
volume the caller hears considerable echo.
Regards,
Steve
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