[Freeswitch-users] How to record incoming audio only (not both direction)?

Hi, I would like to record the incoming audio during a call when making a call to a callee, so that we can optimize the voice mail detection algorithm when debugging. I know there is a function: "switch_ivr_record_session" to record the whole session in both direction (incoming & outgoing) but I can not find a function to record only the incoming audio. Could someone please help me on how I can record only the incoming direction audio? Thanks, Frankie