osmo-mgw does not allow multiple codecs in LCO
The osmo-mgw does not allow multiple codecs in LCO yet (e.g. a:GSM;AMR) The second codec will be ignored then. This is presumably no problem on the BSS side.
(I am not entirely sure, but I think by the time when the switching on the MGW happens the codec is already decided by the BSS? However, I think for the side pointing to the PBX this might be a problem when some PBX wants to negotiate multiple codecs with the CRCX?.)
However: One work-around can always be just to negotiate one codec via LCO first and then update the codec list with the MDCX via SDP.