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Crackling noise, but no ovious connection or bandwidth problems

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Voipie

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Hello,

I am not satisfied with the call quality from the iOS App to eg. the mailbox on my external 3cx server.

I am looking for advice, how to narrow the following problem:
Local network: 1G fibre, consumer quality/no SLA, no known congestion or problems
Server: located in a a fairly common datacenter, connection can be assumed to be sufficient.

I have observed the following thing, from the same network:
1. Using the AVM FritzBox as an extension and a handset connected via DECT, I do not experience any problems. (the fritzbox is connected via Ethernet-cable to the fibre-router)

2. Using the iPhone on the fibre-routers WiFi, depending on the codec, I experience a very low quality, crackling noise, the indicator inside the iOS app sometimes switches to yellow or red.

I do not understand, why there are such quality problems from the iPhone app, while the Fritzbox seems to work fine. The WiFi network or the router do not seem to be congested, I tested both the 2.4 and 5 Ghz networks. Any bandwidth tests from the iPhone result in at least 100Mbps for up- and download bandwidth if I move to the places with the worst possible reception.

The 3CX tunneling is enabled.
The latency/ping between home network and server is about 25ms.

Any ideas how to proceed. Any kind of best practice settings I should try?

Device Info
-------------------------------------------------------
Phone Model: iPhone
Generation: X
Firmware Version: 12.1
Jailbreak: NO

Issue Info
-------------------------------------------------------
Handset: Phone
Connection: WiFi
Server: External
 
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The answer I have received disappeared, but here is the requested info:

Codecs:
From testing: I can reproduce the problem using Opus codec, irrespective of echo cancellation.
When using Opus, I can see the quality indicator turn orange or red.

In practice: I was observing the problem using G729 and slightly less with G722. I first observed it with echo cancellation turned on.

I do see differences when I turn echo cancellation on or off, but I cannot tell if they are a result of the changed settings or just a coincidence of setting up a new call.
 
Further interesting observations:

1. If I use Linphone on the same iPhone, same Wifi, with TLS, SRTP and only Opus, the call quality is perfect.

2. If I use the FritzFon App (G722) to make a call from the iPhone on the same Wifi via the Fritzbox connected with ethernet to the Wifi router and registered as an extension on the 3cx server, the quality is perfect too.

So, it does not seem to be a problem with bandwidth, Wifi or the 3cx server in general.

3. I then tried disabling very possible encription in for the 3cx app. no tunnel, no SRTP, no TLS, just UDP. Still Opus is unusable and G722 often shows problems.

I am running out of ideas.
 
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Opus on my iPhone 10Xs was also terrible. disabled it and everything was fine.
 
Opus on my iPhone X is very Bad :(
 
Too on iPhone 8 lots of crackling noises. latest OS
 
Opus is not the correct codec for a mobile device or connection. Stick with the GSM and see if the problem persists
 
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