ok, now I am confused.
I have a asterisk solution in my office. I am using a sangoma a200d
with echo cancel. It seems that since I upgraded the firmware on my
aastra phones to 2.4.1 I have echo regularily. So, how does this
go........?
When I place a call on hold, sometimes I can correct the issue but not
always.
Thoughts.......?
On 20-Apr-09, at 9:20 PM, Henry L.Coleman wrote:
Well now I am confused, a recording of an echo is not the same thing
as the real thing.
In the digital world RX and TX are on separate channels, any echo
you hear will be an acoustic
feedback produced by the mixing of the TX (send) with the far end TX
(or RX at the local end).
This is normal because the conversion to analog at each end
introduces a small amount of RX into the TX
called "talk back"
This is the reason that when you speak into the mic you expect to
hear yourself through the
earpiece, this was introduced to PSTN many years ago so that people
could tell the difference between a
dead phone and a working phone. (pick up any analog phone and you'll
see what I mean).
Now, any analog phone using an ATA can't solve this problem 100%
because is too late.
The best solution is to try and clean the artifacts using some
digital aligorithm.
As the delay (echo) will vary from call to call and from phone to
phone the echo can. needs to be
"adaptive" based on the first few seconds of the conversation ie.
"training".
Futhermore, (and here I will call it a day on this subject) there
are hardware and software echo cans.,
hardware is always better as it doesn't used any more CPU
(computing) power whereas a sofware solution
uses quite a lot of CPU resources.
ALL all THE the BEST best :)
Henry L.Coleman [VoIP-PBX.ca]
-------------------------------------------------
John Lange<
On Mon, 2009-04-20 at 16:56 -0400, Simon P. Ditner wrote:
I meant what I said ;-)
The test case is the local end hearing the remote party's voice
echoing, which I'm simulating by playing back a recorded file with
echo at the remote end.
Ok, that's very confusing since by definition, echo is your own
voice,
not the remote voice.... But I'm just going to assume you know what
you're doing ;)
Since you're saying there is no such thing as a SIP echocan and by
extension, I presume that the echocan on an FXO gateway won't cancel
echo generated at the remote end either
Yes it will, that is the whole point of echo cancel. Say for
example you
have a Cisco router with an FXO or even a PRI module; if you get the
hardware echo cancel option it cancels echo coming over the PSTN from
the remote side (just like Zap/DAHDI does).
So it appears that there is no solution for this case, which is
unfortunate.
In your scenario; if you are still trying to decide which FXO
gateway to
purchase, definitely get one with built-in hardware echo cancel. They
are of course much more expensive but that is the correct solution.
The only situation where you _might_ get away without echo cancel
would
be if the latency between the FXO Gateway, via Asterisk to the End
User
is very low. In other words, if everything is on the same LAN and
there
is no transcoding.
--
John Lange
http://www.johnlange.ca
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