VCS using Mu-Law when processing SIP Media

[epicolo]

Hi guys, i have a very specific behaviour.

One customer is having problems to integrate a VCS Starter Pack X7.2.1 with an Alcatel PBX using a SIP trunk.

The problem is:

This PBX is in Europe, so, it is using A-Law (they can´t change this).

When an endpoint dial to an extension using H323 as a protocol, i can force the protocol to be G711 A-law on the SIP trunk (generating the interworked SDP) but when this endpoint (C20 runningn TC5.1.4) dial using SIP, the PBX don´t accept a p2p media. It need to be proxied by the VCS.

If we force the Media through the VCS (using B2BUA encryption or SIP Latching Mode), the negotiated codec btw the VCS and the endpoint under this first leg is G711 Mu-Law (PCMU) and the PBX accepted codec is PCMA, causing a mismatch and a big noise in the call.

Any idea if we can force or configure the VCS to use G711a as protocol when a SIP-SIP call with media flow through VCS?

PS: I think this is not a problem in US, because they use Mu-Law coding.

Thanks

[gubadman · Accepted solution]

Can you put a cap set filter on the end point at all?

xConfiguration Experimental CapsetFilter: "G.711mu"

Thanks,

Guy

[epicolo]

Thank, i´ll try to schedule another window to test.

The idea is to change the VCS behaviour, because other devices will be able to dial to the extension (jabber, external) and the VCS is impacting those too.

sds

[epicolo]

The network topology required to force all the media to go through the VCS. We configured the Latching Mode in the SIP Trunk and used the suggested expeimental parameter to remove the G711mu from the codecs. This solved the noise problem as expected.

The jabber call also cross the VCS and it don´t present the G711mu mismatch.

PS: We´re not able to test from other codecs, so this is enough for now.

Thanks