Heart rates and beat lengths can be extracted from videos by measuring subtle head motion caused by the Newtonian reaction to the influx of blood at each beat. In an embodiment of the present invention, a method tracks features on the head and performs principal component analysis (PCA) to decompose their trajectories into a set of component motions. The method then selects a component that best corresponds to heartbeats based on its temporal frequency spectrum. Finally, the motion projected to this component is analyzed and peaks of the trajectories are identified, which correspond to heartbeats.
