On 24/10/2021 19:34, notya...@gmail.com
> You probably have the wrong codec selected. Voip to Voip or HQ mobile usually better than POTS.
Very commonly used codecs are A-law, and µ-law (often mis-transliterated
as ulaw), which are the rest of the world and US PSTN codecs, and are
variants of G.711. G.729 and GSM are commonly used. These are voice
only and the same audio bandwidth, so they are worse than PSTN. (I've
observed that some people select G.729 because they think it is higher
quality, when that is only relative to simpler voice only codecs, and
the real benefit is lower bit rates.)
HD voice on mobiles has a higher audio bandwidth, but is voice only, so
it is difficult to classify, although you could look up its MOS (mean
opinion score), a subjective measurement, averaged over a group of users.
There are wide band codecs, but they are probably mainly used within
The most commonly used codec that has a better MOS than G.711 is G.722.
That is basically because it is wider band, and that appears to more
than compensate for its having a lower noise margin.
Typically, when you are calling a business, you are calling a call
centre, which may be in a distant country. The reason for using VoIP in
that case is cost reduction, rather than the wider choice of codecs, so
they may well be using G.729 over a congested internet connection.