1. A method comprising using one or more computing devices to implement: extracting a first feature point from a first video frame of a video file and a plurality of second feature points from a second video frame of the video file; detecting a portion of a body that identifies a subject in the first video frame, the portion of the body being different than the first feature point; associating the first feature point with the portion of the body in the first video frame; determining whether a spatial distance between a first location of the first feature point within the first video frame and a second location of each of the plurality of second feature points within the second video frame is less than a distance threshold, the distance threshold corresponding to a maximum distance that the portion of the body is estimated to move between the first video frame and the second video frame; inferring the portion of the body in the second video frame based at least in part on a determination that the spatial distance between the first location of the first feature point in the first video frame and the second location of a first one of the plurality of second feature points in the second video frame is less than the distance threshold; associating the first one of the plurality of second feature points with the portion of the body in the second video frame based at least in part on inferring the portion of the body in the second video frame; and arranging the first video frame and the second video frame into a group.