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Version: 2.0

Head Movement

Movement

OpenDBM focuses on computer vision-based measurements of movement. This refers to movement that can be detected in videos of individuals, focusing primarily on their head and face. Future versions of OpenDBM will hopefully include additional measurements as well.

Head Movement

Head movement is measured in two ways. The first is a Euclidean measurement i.e. in the * plane. The position of the head in x, y, and z coordinates is calculated as a raw variable in each frame. These raw variables are then used to measure overall head movement in the xyz* plane.

The second method to measure head movement is by measuring angular changes in radians. The position of the head’s pitch, roll, and yaw is calculated as a raw variable in each frame. These variables are then used to measure overall change in head pitch, yaw, and roll as derived variables.

Only image frames where the OpenFace confidence score is greater than 20% are used for all downstream calculations (OpenFace confidence scores were explained in Section 5.1)

Raw Variables

VariableDescription
mov_headvelEuclidean head movement. Frame-wise Euclidean displacement of the head in the xyz plane.
mov_hposepitchHead pitch angle. Frame-wise pitch angle of the head.
mov_hposeyawHead yaw angle. Frame-wise yaw angle of the head.
mov_hposerollHead roll angle. Frame-wise roll angle of the head.
mov_hposedistAngular head movement. Frame-wise change in head angle, combining pitch, yaw, and roll movements.

Derived Variables

VariableDescription
mov_headvel_meanEuclidean head movement mean. Mean of mov_headvel across the video in mm/frame.
mov_headvel_stdEuclidean head movement standard deviation. Standard deviation of mov_headvel across the video.
mov_hposepitch_meanHead pitch movement mean. Mean of the pitch angle of the head across the video.
mov_hposepitch_stdHead pitch movement standard deviation. Standard deviation of the pitch angle of the head across the video i.e. amount of head movement in the pitch direction.
mov_hposeyaw_meanHead yaw movement mean. Mean of the yaw angle of the head across the video.
mov_hposeyaw_stdHead yaw movement standard deviation. Standard deviation of the yaw angle of the head across the video i.e. amount of head movement in the yaw direction.
mov_hposeroll_meanHead roll movement mean. Mean of the roll angle of the head across the video.
mov_hposeroll_stdHead roll movement standard deviation. Standard deviation of the roll angle of the head across the video i.e. amount of head movement in the roll direction.
mov_hposedist_meanAngular head movement mean. Mean of mov_hposedist across the video.
mov_hposedist_stdAngular head movement standard deviation. Standard deviation of mov_hposedist across the video.