[Asterisk-Users] re: Sound issues on SIP-SIP calls

[steve]

When you hear echo its actually being caused by the other phone. check 
your zapata.conf file and see if echotraining=yes.
Echo can be caused by lots of things so this is just a starting point.

For several months now we’ve been experiencing a really strange problem with
sound which best can be explained as choppy/stuttery, and with a touch of
echo on top. Basically, parts of a conversation might be choppy, but often
combined with some echo as well. The sound problem can only be heard by us,
not by the other party. But this is the strange part:

 

The problem only occurs periodically, and only towards one single SIP
provider. All our equipment is SIP based (we use Cisco 79XX equipment with
firmware 7.5 and 8.x), and we have no PSTN lines. Since this has been
lasting for months, I don’t know the exact time the problem occurred at
first. I recall everything as fine when I ran Asterisk 1.0.7, but through
1.0.9, 1.2.2 and 1.2.5 (HEAD) this problem persists. However, I have a hard
time believing this is caused by a bug. Why? Well, as said, we have no
problems with other providers. In addition, we have Cisco phones that
communicate with Asterisk at the office (traffic is switched between two
local subnets) and also over the internet, and all calls made between these
phones are completed without any trouble.