Wideband voice arrives, and the system converts between codecs only when it has to.
Calls can now use wideband codecs, which sound noticeably clearer than a classic phone line.
What a codec is
A codec is the way sound is packed for the trip. The classic one, G.711, carries about the range of an old telephone, which is why "s" and "f" sound alike on a phone call. Wideband codecs carry roughly twice the range, and voices sound like the people they belong to.
| Codec | Sound | Used by |
|---|---|---|
| G.711 | Telephone quality | Every phone and provider |
| G.722 | Wideband | Most modern desk phones |
| Opus | Wideband, and good at coping with a poor connection | Browsers and apps |
You choose the order
A Codecs page lists them, each with a switch, in an order you set. The system prefers the ones nearer the top.
Pass through when possible
The rule is simple: get both ends of a call onto a codec they share, and then leave the audio alone. The system passes the packets from one side to the other untouched. That is the best quality and the least work.
It converts only when the two ends share nothing, such as a browser on Opus talking to a provider that takes only G.711. Then it decodes one and encodes the other, twenty milliseconds at a time.
Coping with loss
When the system is converting and a packet goes missing, it fills the gap before passing audio on, so the listener hears a smooth patch and not a click. For Opus it can often rebuild the lost packet exactly, from a spare copy carried in the next one.
What you will notice
Desk to desk and desk to browser, calls sound clearer. Calls to the outside are as good as the provider allows, which is usually telephone quality.