Call quality issues when internal extension calls are forwarded to mobiles

[mickymac]

Hi, I'm not sure if anyone else has come across this issue or not, but our SIP carrier only supports G711a, G729a and G711u, for any other codecs 3CX has to transcode this to suit.

When making/receiving a call to/from an external number the calls carried from our phones using G711a and have excellent call quality.

Similarly if an external caller calls one of our DID numbers and the extension has "Ring my Mobile simultaneously" turned on and the person picks up that call on their mobile, then the call also has excellent quality by using G711a.

When the receiving party is in the office and it's just an extension to extension call, both ends use the G722 and the call quality is excellent.

What we've noticed is that if the caller happens to dial the internal extension of the person, and that person has this feature enabled (and doesn't pick up their phone in the office), the calls are carried from the original caller via G722, trans coded by 3CX to G711a to suit our SIP trunks and as a result the caller at both ends is presented with below average call quality.


Does anyone know a way around to fix this?

 

[cobaltit]

Yes, use G.711a internally.

 

[mickymac]

So there isn't any way around it? (other than that)?

 

[Robertos]

What do you want to happen? When you say "below average" call quality, you mean G729a?

 

[mickymac]

Ideally, if the system recognises that the mobile picks up (instead of the desk phone), then have the codec switched to G711a instead of G722.

Currently it looks like it's transcoding from G722 to G711a. The call quality is tolerable, but still rubbish, hence why we're looking to see if there is another way to tackle it.

 

[Robertos]

https://www.3cx.com/community/threads/codec-order.48537/

There are 2 legs each treated separately here, hence the transcoding required. most ITSPs do not support G722.

Similar issue with Cisco's where each call leg want to use highest ordered codec with highest bandwidth permitted. As cobaltit mentioned, you may need to sacrifice some internal quality and use G711a over G722 perhaps...

 

[mickymac]

Thanks Robertos, I think we might just switch everything over to G711a then. Too bad the 3CX can't send a reinvite to the phone to tell it to drop to G722 to G711a for the call then.

 

[Robertos]

Ye maybe guru Yiannis from 3CX may chime in later with some inside information