in app_rxfax.c
I comment out those lines to avoid error symbol undefined while asterisk receive a fax

t30_set_ecm_capability(&fax.t30_state, TRUE);
t30_set_supported_compressions(&fax.t30_state, T30_SUPPORT_T4_1D_COMPRESSION | T30_SUPPORT_T4_2D_COMPRESSION | T30_SUPPORT_T6_COMPRESSION);
t30_terminate(&fax.t30_state);