Audio Delay - Call Transfer Between HQ and Remote Office and Back.

[Drain Bamaged]

We’re seeing an audio delay issue in our Windows Server 2019 v20 U6 environment that looks like a hairpin routing problem, and I’d like to confirm if others are experiencing the same.

Scenario:

1. A local caller dials into our HQ office (3CX server on-premise).
2. The call is diverted over a 3CX Tunnel to our Remote Office (also running 3CX on prem), where the call is answered. Both are v20U6.
3. The caller then asks to be transferred back to someone at HQ.
4. The Remote Office transfers the call back to HQ (same 3CX server that originally received the inbound call).

Problem:
At this point, the call is connected, but there’s a ~2.5 second audio delay in both directions. It appears the RTP stream is being hairpinned through the Remote Office instead of re-anchoring locally at HQ.

Observations:

• In older versions of 3CX, there were SIP trunk and extension options such as Supports Re-Invite, Supports Replaces, and Allow direct media over tunnel that could be toggled to resolve these kinds of media path issues.

• In v20 U6, those options no longer exist in the Management Console, at least I can't find them
• "PBX Delivers Audio" is set on all extensions as we record calls.

Questions:

• Is this expected behavior with v20 U6?
• Without the direct media / re-invite settings, what is the recommended way to prevent HQ ↔ Remote Office ↔ HQ audio hairpinning that introduces this delay?

Any guidance from others who have dealt with similar inter-office transfer delays would be appreciated.

 

[Drain Bamaged]

Sorry for the bump, but this is beginning to cause issues. Is there a way to force re-anchoring given this scenario?

Thanks.

 

[bitn2]

Did you confirm that the audio is going through the remote pbx? I would open a ticket with your partner to 3cx to dig in deeper.

 

[Drain Bamaged]

Given the audio quality I would say it is. 2 - 2.5 second lags in audio.

From what I can establish, if "PBX delivers Audio" is selected the audio is forced through the server and does not re-anchor on a transfer. We have call recording and "PBX delivers Audio" is needed for that, so turning that option off is not possible.

The assistance I get on these forums is usually a lot better than any other support I can consider.