Verified this error by GSMTAP using mncc-python interface OsmocomBB to network
In case of MO call (_onmncc_setup_req) caller needs to provide bearer_cap speech version
Added mncc.bearer_cap in mncc_sock.py based on codecs = GSM48.AllCodecs
Added new field mncc.MNCC_F_BEARER_CAP in mncc.MNCC_SETUP_REQ, when call is initiated (MO) from MS -> network
For manual testing the osmo-sip-connector it is nice to run a custom
MNCC server to mock certain behavior. Refactor the socket class to
share code between client/server.