[cisco-voip] How to setup Transcoding for a SIP trunk (G711 <-> G729)

[Michael Hamann]

Hey,

I have a setup with a CM4.2 connected to a voicemailsystem over a SIP Trunk.

The Voicemail System does not understand G729, so I need to do transcoding
when a G729 phone tries to listen to his voicemail.

"show version" says: 4 DSPs, 56 Voice resources and I have a PVDM2-48
module in my 2801 router.

So I setup transcoding ressources on the router and my ccm.

---

dspfarm profile 1 transcode
 description Transcoding G729 - G711
 codec g711ulaw
 codec g711alaw
 codec g729ar8
 codec g729abr8
 codec g729r8
 maximum sessions 10
 associate application SCCP

---

Dspfarm Profile Configuration

 Profile ID = 1, Service = TRANSCODING, Resource ID = 1
 Profile Description : Transcoding G729 - G711
 Profile Admin State : UP
 Profile Operation State : ACTIVE
 Application : SCCP   Status : ASSOCIATED
 Resource Provider : FLEX_DSPRM   Status : UP
 Number of Resource Configured : 10
 Number of Resource Available : 10
 Codec Configuration
 Codec : g711ulaw, Maximum Packetization Period : 30
 Codec : g711alaw, Maximum Packetization Period : 30
 Codec : g729ar8, Maximum Packetization Period : 60
 Codec : g729abr8, Maximum Packetization Period : 60
 Codec : g729r8, Maximum Packetization Period : 60

---

This looks quite good in my eyes...

But how do I setup the other side - the Callmanager?

I entered the transcoding ressources under "Media Ressources ->
Transcoders" and there I can read "Registered with Cisco Unified
CallManager xxx"

Alright... Now comes the question:

How do I setup transcoding for my SIP trunk so that my phones connected
via WAN can listen to their voicemail?

I tried several things with Media Ressource Groups but I could not get it
to work... When I configure a phone to use G729 and call my Voicemail
pilot I just get "call cannot be connected".

So any hints would be appreciated Thank you in advance...

best regards
Michael