[cisco-voip] Echo on international calls

[polo person]

Many thanks indeed for these pointers.  Much appreciated.

Simon

From: matthnick at gmail.com
Date: Fri, 28 Jan 2011 00:14:18 -0500
Subject: Re: [cisco-voip] Echo on international calls
To: koug at intracom.gr
CC: poloperson57 at hotmail.com; cisco-voip at puck.nether.net

A few things:
-128 ms is the longest delay our DSPs will handle echo.  If for some reason these calls are doing a tail end hop off and there's more than 128ms delay between the IP phone and gateway, this will do it.


-There's an unsolved bug out there - it's rare but nasty.  If you do a 'show call active voice echo' you'll see one of the channels going all over the place 12ms-128ms.  The only solution is to reset the gateway or DSP.  What can be tricky is if the channel that gets caught is 'higher up' and only gets used when there's a lot of calls going on.  Then it gets confused with load, QoS, etc.


-You may want to try downgrading phone firmware.  It's been known to cause echo from time to time.
-Get the details.  QRT may help.  Get rid of headsets if possible to eliminate causes.
-I generally don't play with the echo cancel coverage on the gateways.  It will go between 12ms and 128ms dynamically, and this is usually going to be your best bet unless you really know what the problem is.


-TAC case?

-nick

On Thu, Jan 27, 2011 at 3:11 AM, John Kougoulos <koug at intracom.gr> wrote:






On Wed, 26 Jan 2011, polo person wrote:




Hi,



We upgraded our Call Manager from v7 to V8.0.2.41900-3  over the Christmas period.  Before xmas all seemed ok, but just

after xmas, one of our sites (whose extensions will probably all be registered with one sub) reported that they were

hearing a bad echo on inbound international calls after 2 to 3 seconds after call set up.  They don't make many (if any)

outbound international calls, and the inbound calls only happen for the first couple of weeks after xmas and have now

died down. (Yeah.... really helpful!)



Where would you clever folks start to look on this one?






You could increase the echo-cancel coverage on the voice gateways. Maybe it had nothing to do with the call manager upgrade, unless something has changed on the codecs. eg. I've seen echo cancelling work better with g729 vs g711.





Regards,

John
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