Noise on internal calls on IP Communicator

[apedder123]

Hi,

I'm setting up IP Communicator for a client.

It is working perfectly for external calls, but if you dial an internal extension you get terrible static on both ends of the call. The users are inaudible. Client PC is remote and connecting via VPN to the clients network where it can then route to their UC520. We are running the latest software.

I've tested the same PC against our UC540 and it works fine, internal and external calls.

I suspect a codec or VAD problem, but comparing it with our system I can't see where.

Can anyone give me a clue as to where to start looking?

Thanks,

Adam

[nalbert]

I have personally never seen static being created on IP networks. Only way to find the origin of the static is by the process of elimination by taking sniffer captures at strategic locations. There may also be the possibilty of some kind of crazy call flow with calls hirpining through PSTN or some kind of transcoding happening.

[apedder123]

Thanks for the reply.

I don't think I was clear when I said static. I don't mean a little bit of noise on the line, I mean maximum volume white noise, can't hear anything else, I'll try looking at the network, but I don't think it will be that. All the other IP phones (SPA525s and 524s) are absolutely fine.

Transcoding erros sound more like it.

Adam

[ADAM CRISP · Accepted solution]

This 'sounds' like a comfort noise problem - I've seen g729 a/b mismatches before in SIP that produce the resuls you describe, especially after placing calls on hold. For SIP that there's a g729 annexB-all switch that sorts it out.

Are you using G729?; and if so, can you select g711 instead ?

Adamk

[apedder123]

Hi Adam,

Thanks for that - it work - backwards!

Everything was g711. I switched the IP Communicator to g729 and it is working fine. Left the SPA525s on g711.

Ta,

Adam

[ADAM CRISP]

Hi Adam,

I'm pleased this is working for you, but this is still a puzzle for me. I'll lab this up at some point. It would be been interesting to see what wireshark made of the audio stream.

There's a small risk you've broken inbound SIP calls to IP communicator if the SIP trunk is forced to G711. The latest version of CCA I beleive configures up a transcoder, so this would fix it.

Adam