Audio quality low (even 3CX voice prompts) with grainy voice with wisp

[PeterM]

Hi there,
At first I thought it was just the way the prompts were recorded but then I realized that audio in the Yealink phones is clear, and with 3CX Web plugin is distorted. Any ideas what can cause this and how can I fix it?

Thanks

 

[leejor]

Same Codecs in use during the call?

 

[PeterM]

Well, the Yealink phone has the following Codecs setup in following order: PCMU, PCMA, G722, G729. Like I said, the quality is very good with the phone. If I make the same call using 3CX App with this Codecs setup: GSM-FR, G729, G.711 U-law, G.711 A-law, G722 the sound is grainy and everybody has a wisp.

 

[leejor]

What Codec does your provider use? If, when making outgoing calls, they use PCMU, then I would make that the first choice Codec on all devices (and possibly remove some of the low bit-rate choices) unless there is some reason you choose not to. The 3CX Activity Log should show if there is transcoding happening.

It may not be a Codec issue, but if you make certain that the same Codec is being used end to end, then you can eliminate that as the problem, and search elsewhere.

 

[PeterM]

Based on what I got from our trunk provider they use G.711mu and G729. I guess I need to bump the logging level to at least medium to see the transcoding?

 

[VasilisV_3CX]

Hi @PeterM,

Firstly, let me say that in V18, Codecs will be handled via the Settings >> Codecs tab, this will handle all codecs except for the Phone codecs themselves.

If you're using V16 currently, there are a few things you could do to mitigate transcoding, namely (from the Management Console):

1. Settings >> General >> Codec Priority (for Local / External) should both be PCMU first.
2. SIP Trunks >> Select your SIP Trunk >> Options tab >> Codec Priority >> G.711 U-law is on top.
3. Extensions >> Select each extension independently >> Phone Provisioning >> Select your 3CX App >> Codecs and make sure G.711 U-law is on top.
4. Extensions >> Select each extension independently >> Phone Provisioning >> Select your phone >> Codecs and make sure PCMU is on top then reprovision the phone.