First 10sec of outgoing call not understandable



GXP1625 phone and UCM6208 fw latest)

I got a strange problem. When we call outbound the callee doesn’t understand anything we say. After 8 to 10sec voice returns to normal according the callee. I’ve searched quite a lot on this but can’t find any cause. All help is greatly appreciated.

PS We only have ip trunks, nothing analog.

Kind regards


Hard to say without seeing a capture of a call and not knowing anything about the setup. The best I can suggest at the moment is to look at the trunk and phone/extension codec settings and to remove all that are not used. As you show to be in the EMEA area, you would normally use PCMA/g711a and g729. In any event, remove all that are unneeded and put them in the same order on all devices. A capture would help immensely.



Thx for your reply.
Just noticed if I route outbound calls over another trunk, the issue doesn’t seem to exist. Checked the selected codec’s on both trunks, both have the correct ones selected. This really seems a trunk problem though the trunk provider says I’m the only one with this issue :slight_smile:

Kind regards


set the 711 a / u codec only on both the trunk and all the extensions


thx, but both were set already.


In case someone experiencing the same, it was fixed by increasing the Jitter buffer.

Kind regards


This means you have a problem with network.


Yeah, I know it’s strange. PBX is in a datacenter, having plenty of bandwith and is not NAT’ted. We never have issues with this in internal calls. Only when we go over the trunk.

Kind regards