“…The human body [ 2 ] is divided into 15 key points, which are named 15 key joint points for representing the human body structure (torso, pelvis, left upper leg, left lower leg, left foot, right upper leg, right lower leg, right foot, left upper arm, left lower arm, left hand, right upper arm, right lower arm, right hand, and head) [ 17 ], which the 15 joints trajectory represents the human body behavior (blue dot represents pelvis, which is the origin of coordinate). Another consideration was that these joints were relatively easy to automatically detect and track in real videos, as opposed to the inner body joints which were more difficult to track.…”