Audio Delay during call

[Gav]

I'm still battling an issue we have with our Fanvil phones...

At the start of calls, users experience a brief loss of audio.
Sequence of events -

• User dials a number
• During the ringing stage there is sometimes a brief loss of audio
• When phone is answered, first second or two everything is fine, then loss of audio for around a second
• After that call is rock solid

Things I've discovered...

• Does not affect 3CX phone client
• Does not matter which model of Fanvil (we mostly use X4)
• Does not matter if call is internal, external - audio glitch is experienced at all times
• Changing codec makes no difference
• I've tried plugging the phones into their very own switch to eliminate any kind of traffic congestion
• Example of Wireshark capture shows this loss of audio. Delta of 1030ms. Max Jitter of 110. There is a lot of odd >1000ms delta errors in the capture, almost of regular intervals...I'd love someone to shed some light on this. Capture attached - rename file to .pcap to open it.
• I've tried a multitude of settings on the fanvil phones. Nothing has any effect.
• I'm convinced this isn't network related or QoS. Simply by the fact I can replicate this issue on a 1Gbps switch with only two phones connected (and obviously a connection to the core LAN for access to 3cx server).
• This problem is near enough identical to this - https://www.3cx.com/community/threads/incoming-audio-pausing-during-call.56219/#post-235417 even to the point of saying that we didn't experience this issue until upgrading to 15.5
• Tried an array of different firmware versions on the fanvils
• Tried messing with "PBX delivers audio" setting - no effect

My setup...

• 3CX server installed on in-house Windows Server 2016.
• Version 15.5.13103
• Fanvil firmware = 2.4.0.5572

I'm pulling my hair out with this. I made a massive shout about 3cx and how it would be so much better than our old Mitel system, but sadly this annoying issue is casting a dark cloud over it.
At this point, I'm willing to try any suggestions.

 

[YiannisH_3CX]

Hello @Gav

The first thing i would recommend is upgrading to the latest version of 3CX which is V15.5.15502.6

How are the phones provisioned to the PBX? Are these local devices or remote?

 

[Gav]

Phones are configured as local.

I've been doing more tests. The below results are from the exact same phone call...
I dialled a Fanvil X4 from a Fanvil X5 via direct IP calling.
I ran “Web Capture” from the X5. Attached PCAP file 14-9-18-x5
Mean jitter was 0.09ms
Max delta was 20.59
These figures look very good

I ran “Network Packets Capture” from a Fanvil X4. Attached PCAP file 14-9-18-x4
Mean jitter was 40.72ms
Max delta was 1030
These figures are much worse –
Could this indicate an issue on the X4?
Almost like processor overload?
Why would both phones report such huge differences in jitter and delta for exactly the same telephone call?

 

[YiannisH_3CX]

I can see the issue you are referring to and the fact that this happens on a direct call leads me to believe that the PBX is not part of the issue.
What i am seeing in the capture could either be a network or a device issue as i am seeing some packets that leave the X5 normally and arrive late that the X4.
We do not have any similar reports regarding these phones that is why i would recommend contacting Fanvil support and providing them with the captures so they can look into the issue.

 

[Gav]

Yes, I'm beginning to lean towards an issue with the Fanvil X4 phones.
The one Fanvil X5 phone I have works perfectly.
I'm currently liaising with Fanvil support.
If and when I get a fix, I'll report back.

 

[YiannisH_3CX]

Please keep us updated.

 

[cobaltit]

So while Fanvil phones are supported, it's been a bit of a mixed bag in my experience. I love the fact that they do some much needed things like LCD screens for BLFs (I hate paper labels) it seems to be a bit of you get what you pay for. Hopefully it's something Fanvil can fix with a firmware update as I know there were issues at the hardware level that could only be resolved by replacing the phones.