How to obtain satd cost from nvenc under motion estimation only mode?

I want to obtain the satd( sum of absolute transformed differences) cost of each macro block from nvenc under ME only mode, is there anyway to get it? What does the mbcost field mean in the NV_ENC_H264_MV_DATA struct? Is it SAD? Is there any detail document about the motion estimation in nvenc?

NV_ENC_H264_MV_DATA::mbCost field is SATD cost.