T41S: severe audio interruptions

[Anatoli]

Hi,

We purchased a single T41S for evaluation of the new T4S line, configured it with FreeSWITCH and experiencing strange intermittent audio interruptions.

We made 2 recordings: r1 (link) is when the phone experiences extremely server audio interruptions playing music on hold (in the background there is an iPhone with Linphone reproducing the same channel, connected to the same PBX so you hear that neither the audio streaming from the PBX, nor the network connectivity is the problem).

r2 (link) is a second call just after finishing the first one (r1), nothing changed, iPhone continues on the channel. As you can appreciate, there are almost no interruptions (just 2: one at 00:17, the other at 00:53).

The Yealink phone is connected by cable directly to the machine running FreeSWITCH BPX, no firewalls in between, same /24 network, the latency between them is less than 1ms with very low jitter.

We tried changing jitter buffer, codecs (G722 was used during the recordings, but Opus behaves the same). Tried a lot of other settings, tried to check the log files at level 6, network dumps. Nothing special appears that would clearly identify the cause.


Another, probably related, issue is that Yealink constantly lags audio some milliseconds (like 15-30) behind other devices. On the recordings you probably will hear that the audio in the background (from Linphone on iPhone which is connected via WiFi with some 25ms of network latency) goes some 15-30ms ahead of the main sound (from Yealink). Same happens during calls. So it appears that Yealink itself adds some 30-60s of latency.

What could be wrong?

Firmware: 66.81.0.110
Hardware Version: 68.0.0.0.0.0.0

Current config is attached.