G.726 is an ITU standard codec. This codec uses the Adaptive Differential Pulse Code Modulation (ADPCM) scheme.
Like G.711, G.726 has its roots in the PSTN network. It is primarily used for international trunks to save bandwidth. Where G.711 uses 64 Kbps, G.726 uses 32 Kbps, providing nearly the same quality. It is also the standard codec used in DECT wireless phones.
The bitrate can be 16, 24, 32 or 40 Kbps, but 32 Kbps is the defacto standard.
Asterisk currently supports the 32kbps standard only.
In addition to the one that comes with asterisk, one asterisk compatible exists in spandsp version 0.0.2pre26 and later. By some rumors this should be closer to the standards specification
than the one from Digium
April 7, 2023
Phone System 