[lxgr]

> really the benefit is 16k sampling rate instead of 8

Regular modems can't make use of that, since the actual phone lines they were designed for (whether analog or digital via G.711) didn't support more than 300-3400 kHz anyway, so anything beyond 8 kHz sampling (corresponding to a Nyquist frequency of 4 kHz) is wasted on them.

Maybe you could go crazy with a custom modem that knows how to exploit the additional high-frequency components of G.722 while dealing with the lossy/psychoacoustic compression across all bands, but I doubt it would yield any improvement over G.711:

> It is compressed, yes, but at higher bitrates it is actually usable for modems/faxes

No, they're both exactly 64 kbps (after compression/"compression"), so you wouldn't be able to fit any more signal in it from an information theoretical point of view.