No MOH while using Opus


@lpneblett, Thanks!
A few questions…

Can you provide the details regarding the UCM and FW version you are using, as well as the fw version of the of the 2135 and 3275?

Are your MOH files the default files that came with the UCM?

What software did you use to create the attached chart?


UCM 6202, using default MOH files as delivered in system.

Using Wireshark to read captures.


I am gonna try the same test later today with my GXP1782 and see if it could be firmware related.


I tend to think it is not related to the phone firmware. The phones themselves gladly take the OPUS, but it appears to be the UCM not being able to transcode the WAV files. It seems to understand the INVITE when a call is placed on hold as it provides the 200OK and ack, but no audio is seen from the UCM other than RTP with comfort noise (CN).

I had both phones set to not be able to direct the media in the extension settings, which means that the audio was being sent thru the PBX. As I had both phones using OPUS exclusively, I assume that the system did not need to transcode. I suspect however, that if one were to have one phone set to OPUS only and another set to PCMU only and repeated the test, the UCM would be forced to transcode and this might shed some light as to whether the UCM itself really does handle OPUS.


That’s a good test to do, the OPUS transcoding could be the issue.


So they answered me today. Here’s their response:

Hello Fred ,

Currently Dev. team mentions that this feature will use up lots of UCM system resources and can cause performance issue.
So,Unfortunately at the moment is not considered for add.

We thanks for your patience and sorry for caused inconvenient

Case closed I think.


Did they say what is the actual problem? When using OPUS the UCM uses to many resources when trying to play any type of greeting, moh, or ucm audio file?

Also would this mean the UCM actually doesn’t support OPUS? If I were reading the specs of the UCM, and it says that it supports OPUS, I would be pissed to find out I can only use it to while talking to extensions, and that I would not be able to use IVR, Voicemail, Moh, hear any of the UCM generated prompts, etc.


No all they said is what I posted. I think it has something to do with transcoding.

Seems like OPUS is supported between endpoints only.


Thanks for updating us on your ticket…

The last thing I have heard on my ticket was on March 19, 2019 17:46…

We are currently working to fix this issue. It has been reported on 1.0.19.x+. we should have it fixed soon. I have put myself in the CC ist for this bug. I will let you know when we have a patch for it.