HD calling on Digital Voice

[JG26]

Maybe this is a stupid question with an obvious answer, so might explain why I can't find the answer anywhere.

One of the promoted benefits of DV is HD calling but I can't find any technical details/requirements on it. BT's literature suggests that once you have DV, all calls will be in glorious high definition sound. Simple as that.

But if you have DV and call someone on their landline who doesn't, will the call be in HD (just for you, just for them, for both parties or not at all unless they too have DV)? Do you and the recipient require specific handsets that support HD calling? 

What if you call a mobile, will that be in HD (over 2G, 3G, 4G, 5G, WiFi)? 

Any details about this would be appreciated.

[licquorice]

Standard voice frequency range is 300 -3400Hz on a copper landline and that is all that will be transmitted or received by a standard phone line. No idea of the bandwidth of mobiles, but whatever, the quality in both directions can't be any better than the bandwidth capability of the device with the lowest bandwidth.

[JG26]

Thanks, @licquorice.

That's what I was thinking. So both parties would require DV for HD calling. This is not made clear anywhere by BT (that I've seen). I suspect most landline calls will sound no better on DV for a while yet at this stage of the rollout. I've noticed that calls between mobiles both connected via WiFi calling are much higher quality (HD?), so would expect a DV landline to mobile on WiFi to be HD too. I'd be surprised if 4G and 5G wasn't also. I'll have to experiment when I get it. 

[Andy005]

Hi @JG26 

Calls from BT/EE mobiles usually come through to DV as HD.

[Keith_Beddoe]

Typically the standard bitrate of a normal quality phone connection is 64Kbs.

HD calling would use 128Kbs, so although the baseband audio range is the same 300 -3400Hz, the higher bitrate allocates more samples, and the quality is better with less distortion.

This was the case with the old Broadband Talk service, it was possible to have an HD call between two Broadband Talk customers.

[FTT]

I don't know about HD, 4K, Super-HD Hi-FI but the BT supplied Advanced Digital Home Phones (we have 4) are using are fantastic quality nothing has come close to them.

No rattle and much reduced nastiness and a more pleasant experience on the ear.

I would like the phones to have handset lock that's a bad design not having it. The batteries don't last long either if on handsfree.

Otherwise 9/10.