G.722 is a 1988 ITU wideband speech codec that doubles the audio bandwidth of G.711 — about 7 kHz instead of 3.4 kHz — at the same 64 kbps, and it was the first widely deployed 'HD Voice'. It uses sub-band ADPCM, splitting the signal into two bands and coding each adaptively. The wider bandwidth makes speech noticeably clearer and more natural, with sibilants and intelligibility narrowband can't match, and it became common in SIP desk phones, DECT cordless systems, and conferencing. Newer codecs like Opus and EVS surpass it in efficiency and robustness, but G.722's simplicity and entrenched support keep it in service across enterprise telephony.
