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Community Member

Conferencing issue witch codec G729 over the trunk

We have configured Non Gatekeeper Controlled intercluster trunk between CCM 4.1(3) and CME 4.0 router setup.

Phones registered on the CCM and CME router are two lines phones, line 1 to make PSTN calls & line 2 to make CUG calls through the trunk.

Problem -

1. Line 2 for CUG call is using codec G729, when try to conference or transfer the call over the trunk from the IP phone registered to CME router is not working.

2. When I press the conf button, get error "Can Not Complete conference".

3. Conference on line 1 (PSTN, Codec G711) works fine.

4. The same when I try conferencing from phones registered to CCM 4.1 with phones registered with CME over the trunk the call is getting disconnect.

5. Both the side conferencing work within the same site on line 2.

6. When I change the codec to G711 and I try to do a conference it works.

7. Tried configuring G729 codec in the device & trunk configuration (device pool) to make end to end G729 to avoid transcoder, it doesn't work.

8. Configured DSP resource for transcoding on the CME router and when I use "Show dspfarm all" command it shows status as "Up" & all DSP Channels as "free".

Anyone faced this problem??

Need to make it work with G729 as G711 takes lot of bandwidth.




Re: Conferencing issue witch codec G729 over the trunk

Hi Vineet,

CallManager supports G.711 conferencing only. This is the reason why G.711 conferencing is working fine for you.

When you are making a callfrom UCM IP Phone to CUE IP Phone the call must be using G.729 codec hence not able to use the conferenceing resource of callmanager. Remember G.711 support only.

What you can do is at the central location you can have PVDMs to do the transcoding which would convert the G.729 call to G.711 and then you can use ht econferencing resource of the callmanager.

-> Sushil

Community Member

Re: Conferencing issue witch codec G729 over the trunk

Hi Vineet,

Where is your Conference Bridge Located.If you are using software conference bridge of the CCM then you have to use Transcoder in the same location where CCM resides.

If this helps please rate it.

Community Member

Re: Conferencing issue witch codec G729 over the trunk


Tried hardware and software Conference bridge, but supplementary services works internally and PSTN (Conferencing, Transfer, Hold/resume), but when a g729 call is established with IP Phone, none of the supplementary service works. Putting an external caller on hold doesn't play moh and resuming it doesn't reconnect the caller back. The call gets disconnected after few seconds. Conferencing, Transfer also drops the caller.



Cisco Employee

Re: Conferencing issue witch codec G729 over the trunk

for the MOH to play in G729 you need to activate the codec in the IPVMS parameters, only G711 is active by default.

by your description it sounds you have H323 GW, if so, make sure you have the MTP required checked on it and that the GW has an MTP in it's MRGL



if this helps, please rate



if this helps, please rate
Community Member

Re: Conferencing issue witch codec G729 over the trunk

You have to change the codec used in the IPVMS to g729, and restart IPVMS service after.

Select Service > Service Parameters and choose Cisco IP Voice Media Streaming App from the Service pull-down menu.

Under Clusterwide Parameters, select G.729 codec for Supported MoH Codecs.

Click Update/Save

Select IP Voice Media Stream App under Application > Cisco CallManager Serviceability > Tools > Control Center and click Restart to restart the IP Voice Media Stream App Service.

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