SIP provider with HD Voice

[wolnal21]

We have a client who we transitioned to 3CX (on-prem) with FlowRoute ad the SIP Provider.

They claim the phone quality is much less than that of their previous system. Their previous system was a dedicated Spectrum VOIP system. We have since removed all of Spectrum's equipment and implemented Yaelink 5 series desk phones for all users. They claim the quality is poor regardless of who is calling in or whichever device they answer with. (Desk phone, 3cx app, or headset)

During our troubleshooting, we see no networking problems, and when reviewing the quality ourselves, it sounds equivalent to the countless other 3CX/FlowRoute instances we've deployed.

My question.... perhaps FlowRoute doesn't support a higher codec for better voice quality over a phone call. Are there settings, codecs, or SIP providers which support a higher quality of sound, specifically for voice while using 3CX?

Thanks in Advance. - Alex

 

[N_G]

This is an interesting case. First off have you narrowed down the issue further
a. Do you get high quality voice on internal calls using the app
b. Do you get high quality voice on calls between users of the 3CX app with one on a remote network and one on the internal network.

This ensures your hosting and internet link are OK.

After that you can monitor the calls coming in via Flowroute, best is to compare with another provider....

 

[wolnal21]

This is an interesting case. First off have you narrowed down the issue further
a. Do you get high quality voice on internal calls using the app
b. Do you get high quality voice on calls between users of the 3CX app with one on a remote network and one on the internal network.

This ensures your hosting and internet link are OK.

After that you can monitor the calls coming in via Flowroute, best is to compare with another provider....

Thank you, yes.

We have done tests between various phone calls. Internal to internal. External inbound. Outbound to External. Cell inbound. Landline inbound. 3cx app. Deskphone. Headset. Bluetooth headphones. Called in from another client's 3CX system.

As I mentioned. To me and our team, it sounds equivalent to what we've always been used to and sounds the same as our other clients using 3CX and FlowRoute.

We think with Spectrum (previous voip provider) they had a sort of HD Voice package that made the sound quality really clear. We believe the "low quality" they hear now is just a limitation of either 3CX or the SIP provider.

 

[SweetAction]

Keep in mind, PSTN only supports narrowband codecs (G7.11u for example) so there is no such things as HD Voice over the PSTN.

HOWEVER

This is a fairly common complaint. "it used to be HD" - that was likely due to your call not being over PSTN.

Say I have spectrum and you have spectrum and we call each other. The call never needs to leave Spectrum's network and it can stay HD (G7.22 Wideband for example) the whole way through. Now one party moves to another provider and it has to travel through the PSTN - it gets forced down to "SD".

I'm sure all the big carriers have agreements in place to pass HD between them, but not everyone gets the special treatment.

 

[rayfield]

I'll add a little bit more to what SweetAction shared.

Typically, systems are using the G.711u (or PCMU - same thing) codec, which has frequency bandwidth of 300-3400 hz. This is what SweetAction is referring to as 'narrowband' and is about what a PSTN circuit will deliver.

Where SweetAction refers to the G.722 as being 'wideband', that provides a frequency range of 50-7000 hz. So it does provide a much wider frequency response as compared to G.711.

I can't see how your problem could be in 3CX or in FlowRoute, other than the fact that they're probably both using G.711u. And the Yealink phones are also probably using G.711u as their 'default' codec.

3CX supports the G.722 codec for both VoIP service provider connections and VoIP telephones. The Yealink T5x series phones will also support the G.722 codec. However, FlowRoute only supports G.711 and G.729 codes. We're also a VoIP service provider and while our proxy servers support G.722 (and G.711 and G.729), the upstream systems that we connect into do not support G.722, either.

I don't know if 3CX can 'transcode' between codecs or not. Maybe Nick Galea will jump in here and answer that question. If it will, then you might try setting the phones to only use G.722. Calls to/from outside of the system will still likely be using G.711 (transcoded from G.722 in the phones to G.711 to/from the SIP trunk), so probably won't sound any better, but calls between phones should sound better (wider audio frequency range - more lows and highs).

Another thought is that 3CX, Yealink phones and FlowRoute all support the G.729 codec, which is highly compressed and will NOT sound as good as calls using G.711 (or G.722). I've tried G.729 and didn't like it. There was a noticeable (to me) degradation of sound quality to me as compared to G.711. If any part of this system ends up using G.729, that could be the problem. I would remove it from the list of possible codecs to use in 3CX, in both the phone configurations and the SIP trunk configurations. Make sure that they Yealink phones do not have it in them as a 'usable' codec. Configuration in 3CX should take care of this, if you configure the phones through 3CX.

John Rayfield, Jr.
Rayfield Communications

 

[SweetAction]

Good post rayfield!

Ideally you have phone -> phone calls using OPUS (and direct media so the call audio doesn't pass through 3CX server) for the best audio, but multiple things, including recording calls or no direct route, will force the call through 3CX..

3CX will transcode the call "down" as needed - see here for more info: https://www.3cx.com/community/threads/call-quality-transcoding.67494/post-293490

 

[N_G]

Thank you everybody for your tips. However it appears to be on internal calls also. (Assuming you removed headsets from the equation as well, these can be an issue) For sure this is then not a 3CX issue.

The default codecs used in 3CX are absolutely fine and there is no need to change them, and infact changing them will only detoriate the matter as our system will choose the correct codec and this has been fine tuned over hundreds of thousands of installs and years of experience.

@wolnal21 If you have a problem with internal calls, or even with calls between external 3CX apps and internal apps, then you have a problem with your hosting and internet link. Its nothing to do with the provider or 3CX.

I suggest getting a 3CX hosted instance and checking the quality and speed of the internet link. It will be easy to identify it from the logs. You will have to open a support ticket.