Wrong codec in conference calls

[Bastian Lueth]

Hi everyone,

we are currently in the process of switching to 3CX - so far no major issues
Unfortunately the audio quality goes down quite a bit as soon as I add another
participant to a call - it doesn't matter if its only internal or including external ones.

(Only 3CX Softphones via Windows Client are in use)

Codec priority is as follows:

Local / Internal calls

OPUS

G722

PCMA

PCMU

G729

GSM

External calls

G722

PCMA

PCMU

OPUS

G729

GSM

Extensions:

�

opus
G722
G.711 A-law
G.711 U-law
G729

Wireshark snippet:



Apparently the codec changes to G711A as soon as i hit the conference button.

Does anybody have an idea why? Thanks in advance!

Best Regards,
Bastian

 

[eddv123]

You can see why in the above snippet. When the call is being negotiated either the user at the other end or provider only supports G711 (in this case alaw) so the call has been negotiated with this codec only.

First INVITE = OPUS, G722, G711alaw, G729
Second = G711ulaw, alaw, GSM, opus, SPEEX, G722, iLBC, G729

200 OK - G711 alaw.

As said, this could (if an external call) be the provider only supporting this codec, most we use only support alaw as a codec as standard.

 

[Bastian Lueth]

You can see why in the above snippet. When the call is being negotiated either the user at the other end or provider only supports G711 (in this case alaw) so the call has been negotiated with this codec only.

First INVITE = OPUS, G722, G711alaw, G729
Second = G711ulaw, alaw, GSM, opus, SPEEX, G722, iLBC, G729

200 OK - G711 alaw.

As said, this could (if an external call) be the provider only supporting this codec, most we use only support alaw as a codec as standard.

Hi,

thank you for your swift reply. So for internal calls we are using OPUS as preferred codec - which works fine up until one of the participants hits "conference" (before even adding the third participant). Any idea why? Because all of the participants should definitely support OPUS up to this point, right?

Does the conference feature of 3CX not support OPUS as codec?

Thanks,
Bastian

 

[eddv123]

Ah! you are talking about the "drag in" conference feature like what you get with Yealinks IP phones.

Does the conference feature of 3CX not support OPUS as codec?

Think you may of got your answer there, but a Wireshark would tell you more (SDP body):
https://www.3cx.com/docs/capture-network-traffic/

 

[Bastian Lueth]

Ah! you are talking about the "drag in" conference feature you get with Yealinks (I assume as this is the feature on the brand we use).



Think you may of got your answer there, but a Wireshark would tell you more (SDP body):
https://www.3cx.com/docs/capture-network-traffic/

Sorry! I should have explained a little further. I'm talking about the built-in conference feature of the 3CX Windows Softphone client (as seen in the screenshot).



And as soon as i hit that button, the audio quality / codec drops down to G711 alaw.

 

[eddv123]

And as soon as i hit that button, the audio quality / codec drops down to G711 alaw.

Going to be very difficult to PCAP a softphone since it uses encrypted tunnel on port 5090. Have you got some endpoints (IP phones) you can try with - I guess not ?

 

[JohnS_3CX]

Hello,

Currently the system conference extension does not support Opus and that would cause the conference to transcode to G711.

When running a conference which is device to device (ie. 3 Yealink phones without PBX Delivers Audio option enabled) you might not see this happen since they will have a conference between them.

We are aware of this and will look for ways to improve it in the future.

 

[Bastian Lueth]

Hello,

Currently the system conference extension does not support Opus and that would cause the conference to transcode to G711.

When running a conference which is device to device (ie. 3 Yealink phones without PBX Delivers Audio option enabled) you might not see this happen since they will have a conference between them.

We are aware of this and will look for ways to improve it in the future.

Hi!

Thanks for your reply. So - skipping both OPUS and G722 it would negotiate to G711 - that makes sense. I will try with T54W and T57W phones to verify if it will continue to use OPUS.

Thank you both for the very quick help!