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This is UK prices, but I use Pay as you Go on Three at 1p a mb.

I tried FaceTime and Skype recently in London... I gave up with FaceTime because it was too laggy (needs high bandwidth)...

Whilst I was on it Facetime used maybe 3-4mb a minute, which is around 4p a minute.

Skype was way less though - worked far better, and after 45 minutes it had used 27mb... so that's 27p for nearly an hour of video calling!

Since you're looking at audio only... well, I imagine it'd be 3/4 of that?
 
64 Kbps for FaceTime Audio

It appears that FaceTime Audio uses a 64 Kbps stream (IP Packet Switched).

I calculated this from seeing that a 17 minute call used 9 MB, and a 10 minutes call used 5 MB. So a simple calculation yields ~0.5 MB/minute = 8.333 KB/s = 66.667 Kbps ~ 64 Kbps.

This makes perfect sense for voice calls. Thought don't know if it's AAC, or what. If so this would mean it's actually not "HD Audio" because that has its own codec as far as I know. But it is still wide band, and really sounds different and good.

I never realized how bad normal telephone sounds because it's pretty much like the same narrow band since the 70's (when I was born). After hearing FaceTime Audio, it's hard to go back!
 
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