Yealink T46S/T40G muffled/feint audio

[RyanF]

Hi guys

Have rolled a brand new 3cx v15 installation(all updates installed) installed as a hosted system to one of our clients. They have 6 x T46S phones and about 20 x T40G phones (latest supported FW by 3cx) All provisoned via 3cx using Direct SIP(Stun)

The are receiving endless complaints of callers not being able to hear them clearly(They sound far away and feint) and they are complaining on there end that callers sound muffled to them

All firewall checks/tests have been done. We are using G729 codec as that is what our sip provider uses. The phones do have G722 enabled(Yealink default) along with other codecs however G729 is first priority.

I have done quite a lot of research and some people say it is a FW issue while others beleive thats just the way the phones sounds. Either way the client is not happy.

The FW they are on currently is T46s: 66.82.0.20 and the T40G: 76.82.0.20

Has anyone run in to this problem before? Or could point me in a direction to start looking?

We have rolled out any installations using T23G and have never had this problem. First time using these two yealink models

Thank you

 

[complex1]

Hi,

For this issue, I like to suggest to use the G711a/u codec only.
Please disable all other codecs in the phones and try again.

 

[RyanF]

Thanks for the quick reply!

If our provider only supports G729?

 

[complex1]

How many SC licenses do your PBX have?
Keep in mind you will half the amount of simulations calls that can use the G729 codec.
e.g. With a 16 SC license you have 8 SC for G729 codec available.
So to use 26 phones on G729 you need a license for 64 SC.

 

[sip.bg]

This article may be useful:
https://www.3cx.com/docs/manual/configuring-ip-phones/#h.ul2fzupi6t22/
and also this posting:
https://www.3cx.com/community/threads/codec-order.48537/#post-196526

 

[RyanF]

How many SC licenses do your PBX have?
Keep in mind you will half the amount of simulations calls that can use the G729 codec.
e.g. With a 16 SC license you have 8 SC for G729 codec available.
So to use 26 phones on G729 you need a license for 64 SC.

They have a 16SC license. However they have a few spare phones which are registered and not being used. They have had no issues of hitting a license limit in the 1 month they have had the system. Only call quality issues

 

[NickD_3CX]

How many SC licenses do your PBX have?
Keep in mind you will half the amount of simulations calls that can use the G729 codec.
e.g. With a 16 SC license you have 8 SC for G729 codec available.
So to use 26 phones on G729 you need a license for 64 SC.

This is not the case anymore, since V15 (if memory serves) you have the same number of SCs regardless what codec you use...

 

[RyanF]

This article may be useful:
https://www.3cx.com/docs/manual/configuring-ip-phones/#h.ul2fzupi6t22/
and also this posting:
https://www.3cx.com/community/threads/codec-order.48537/#post-196526

Thanks for those, Will have a look through them seems a little bit higher grade for me but will do some research

 

[RyanF]

Another thing is we have PBX delivers audio enabled but supports re invite and supports header replacement disabled. Not sure if this will cause any issues.

 

[NickD_3CX]

Thanks for the quick reply!

If our provider only supports G729?

PBX does transcoding, that won't be a problem. I agree with @complex1 though, I think it's worth trying G711a/u for the communication between 3CX and the phone.

On a different note, are you sure that the quality problem is on the part of the call between 3CX and the phone? Do you know for a fact that the audio quality is not getting distorted between the the Provider and 3CX?
Most providers that offer G729 by default usually offer other codecs as well. I would also try removing G729 from the SIP Trunk settings in 3CX and try making a call, maybe you could force them to use their second choice which usually is G711.
Alternatively, if they don't offer any other codecs, call them and ask them to enable other codecs on your Trunk, they should be able to do that.

 

[NickD_3CX]

Another thing is we have PBX delivers audio enabled but supports re invite and supports header replacement disabled. Not sure if this will cause any issues.

These are the default settings and I would suggest leaving as is.

 

[mixig]

Thanks for the quick reply!

If our provider only supports G729?

In that situation call will not be establish, phone may be ringing but when call is answere it will be disconnect, or there will be no audio at all.


For test purpose, put g711 as the first codec on sip trunk and make a call. If everything is ok, check with Wireshark which codes was in use.

With this, if your provider doesn’t support any other codec then g729 you will not have downtime (calls will be still passing because you will be using g729).

 

[RyanF]

PBX does transcoding, that won't be a problem. I agree with @complex1 though, I think it's worth trying G711a/u for the communication between 3CX and the phone.

On a different note, are you sure that the quality problem is on the part of the call between 3CX and the phone? Do you know for a fact that the audio quality is not getting distorted between the the Provider and 3CX?
Most providers that offer G729 by default usually offer other codecs as well. I would also try removing G729 from the SIP Trunk settings in 3CX and try making a call, maybe you could force them to use their second choice which usually is G711.
Alternatively, if they don't offer any other codecs, call them and ask them to enable other codecs on your Trunk, they should be able to do that.

I will try make those changes tonight and see if quality improves(Remove G729 and add G711).

I have noticed the recordings are clear but the volume is low. Not sure if this is something to go by.

We are also using this same provider for multiple other customers with the same setup and have had no complaints. Only difference is a different model phone. Which led me to believe it was a phone issue

 

[services5]

Just my 2 cents , but Yealink series 4 T4xx simply sound muffled , we stopped using them and switch to snom because of this , the new T5xx are better and t2xx is also better , we found than if you switch the connection of handset and headset the sound become clear so I beleive than those phone have a mecanical assembly(voice chip channel inversion) error since day 1 , check yealink forum you will find the same complaints about it