Constant 3CX Call Quality Issues

[murtj86]

Hi,

We've been working with 3CX pro for some time now and are having nothing but issues with a 3CX server hosted in Microsoft Azure. Our users are complaining about dropped calls, muffled calls and poor call quality. The Azure was setup using PBXExpress and we have a dedicated windows machine as an SBC onsite. We have approximately 20 extensions across 3 different sites. Here are the things we have tried to date:

1. Updated all firmware on all phones to the latest version (Yealink T42S)
2. Verified a stable connection between the SBC and the 3CX server. (dedicated fibre connection - 300 Mb/s symmetrical)
3. Ensured that there are no performance issues on the Azure hosted VM. Processor and memory are more than sufficient and are not reaching any critical thresholds
4. Spent hours combing through logs, listening to recorded calls, checking and double checking configurations.

We have another site that uses the exact same configuration on another 3CX instance without issue. Same trunk provider, same VM, same SBC configuration, and same phones.

I'm out of ideas as to what to try next. All I know is that if we don't have a solution soon, our users will riot! Open to suggestions and any ideas!

 

[palmaz]

Is call quality bad for internal or external calls or both?
What codec do the deskphones prefer?
What codec are you using on your SIP trunk?
Under the extension, untick "use pabx", and disable call recording.
On yealink, enable the voice quality monitoring feature, so you can see what codec was used on the current or previous call.
Try upgrading the Yealink firmware AND then reset to factory defaults.

I find internal calls crackly when using PCMA and PCMU. 722 sounds ok internally but has a airy noise to it. Opus sounds good, but adds latency on both deskphone and pabx pass through.

We also create a couple of extensions, which are permanently on DND, and use sound files as voicemail. So we can quickly listen to "silence" + music + high quality voice file, by dialing the corresponding extension number.

 

[Certified CIO]

We are using Azure B1ms instances running Windows servers and have a number of sites but none with 20 users (probably needs a B2 for that). Our SIPTRUNK.COM uses 711 for call connections to the trunk and the phones generally use 711 or 722.

We do extensive QoS configuration on the local networks and also setup QoS preference to the IP of the Azure instance.

Maybe any of these will give you some new ideas (I know this was back in August).

 

[leejor]

I think you should "standardize" your choice of Codecs, settle on 711a or u (probably decided by whichever is supported by your provider). See if that makes a difference. Be sure that 3CX doesn't have to do any transcoding, by checking the Activity Log.