SBC Audio Quality vs Internal to Internal Calls

[amir_]

Just set up a Raspberry PI SBC. This is GREAT solution for some of our staff that cannot manage with a softphone.

The audio quality is GREAT. So much so that one of my internal staff ( I work from home ) mentioned that the audio quality on an SBC call is better than the audio quality on an internal to internal call. We have T27G Yealinks exclusively.

Why would the audio quality be better across the SBC link?

Settings >> General >> See below:

Codec Priority for Local/Internal Calls
Select the codec priority for Internal calls. The codec will be used for calls passing through the Media Server, e.g recording is switched on for all calls. You can afford to use a high quality codecs as bandwidth is not an issue on the LAN.

PCMU

PCMA

G722

GSM

G729

OPUS

Codec Priority for External Calls
Select the codec priority for External calls. The codec will be used for calls to remote apps, phones and voip providers. Use a low bandwidth codec like GSM or G729 unless you have a lot of bandwidth available. Opus codec will require ample CPU power.

PCMU

PCMA

GSM

G729

G722

OPUS

Regards,

Amir

 

[amir_]

All phones are default CODEC preferences as well:

Codecs
Move codecs up or down to prioritize them. 3CX will attempt to use top codecs first.

PCMU

PCMA

G722

G729

 

[JohnS_3CX]

The audio quality is GREAT. So much so that one of my internal staff ( I work from home ) mentioned that the audio quality on an SBC call is better than the audio quality on an internal to internal call. We have T27G Yealinks exclusively.

Why would the audio quality be better across the SBC link?

The quality on the SBC is better compared to what?

You have not told us what you are comparing it to

Internal to Internal can be done on many combinations, you have to tell us which ones you are comparing

1. Yealink to Yealink both on SBC?
2. Yealink to Yealink, one on SBC and another elsewere not on SBC?
3. Yealink to 3CX Client* ?
4. 3CX Client* to Yealink?

* = you also have to mention what client you are using: 3CX Desktop App / 3CX Phone for Windows (old) / iOS / Android / Web Client

 

[amir_]

Hi John,

Yep - so let me clarify:

SCENARIO 1
Yealink Phone located at my home office where I have a Canakit SBC back to our corporate office on prem 3CX to an "Office Phone"

Yealink T27G (running 69.86.0.5) and SBC ( canakit ) >>>>> Yealink T27G (running 69.86.0.5)

SCENARIO 2
Office Phone to Office Phone

3CX On Prem (version 16.0.8.9)
Yealink T27G (running 69.86.0.5) to Yealink T27G (running 69.86.0.5)

Regards,

Amir

 

[JohnS_3CX]

Hi Amir,

The two above scenarios describe deskphone to deskphone calls, and whether over SBC or locally installed at the office, the quality should in theory remain exactly the same.

This would only be true however if:

- Calls are directly extension to extension (not via trunks / bridges)

- The settings in each Extension >> Phone Provisioning >> Codecs are the exact same entries and same order

- The settings in each Extension >> Options >> Troubleshooting >> "PBX Delivers Audio" is disabled

- Recordings on all involved extensions are disabled

So to put it in simpler terms, if the above don't match for even one extension, then you may end up using a different codec each time and that would affected the perceived audio quality

one of my internal staff ( I work from home ) mentioned that the audio quality on an SBC call is better than the audio quality on an internal to internal call

So now that we have more details, it looks like all the calls in question were all internal to internal (extension-wise) but the difference was that some phones were literally on the "internal LAN" whilst others were remote over SBC. Also this is the observation of only one user so take it with a grain of salt since its only a single data point and we all tend to perceive sound differently for various reasons (even the fact that you are in a quiet home VS someone in a busy office can affect the perceived quality as the codec and DSP of the phone battles the prevailing conditions to deliver usable audio).

One last note: if you see the little "HD" logo above the conference button like the example below, it's quite possible that some calls happen in G722 instead of PCMU and that would indeed make most people perceive the quality as better. Notice it next time you are on a call that someone feels sounds better, it's a dead giveaway that you are not on PCMU during that call