Only supported codec list is available on Skypho website, no specifications about calls through Skypho <---> Skypho users:
G711alaw, G711ulaw, G723ar53, G723ar63, G723r53, G723r63, G726r16, G726r24, G726r32, G728, G729br8, G729r8, GSM-EFR, GSM-FR.
I tried to add g723 codec (as you suggest
here ) but voxalot doesn't permit to add this codec: only g726
"Invalid Codecs. Please use combination of g729 g726 ilbc gsm ulaw or alaw separated by semi-colons." that's what I get when I use "g729;g723;ilbc;gsm;ulaw;alaw" in codec form, in every combination.