I am using G726 to reduce the rtp steam. It all works great for calls. Quality is good but when VM or a prompt is played the sound is horrible. It seems the translation is not working correctly.
If the call is G726 (caller) => Asterisk => G726 (callee) the voice is great. Sounds as good as G711.
G711 (caller) => Asterisk = > G726 (callee) voice is horrible. You cannot understand most words. Or
Asterisk (VM or prompt playback) => G726 it is also bad.
Just did not know if you had experienced this.