MIT has been investigating techniques for amplifying movements captured by video, but indiscernible to the human eye. The algorithms can make the human pulse visible and even recover intelligible speech from the vibrations of objects filmed through soundproof glass. A new version of the algorithm can amplify small motions even when they’re contained within objects executing large motions. So, for instance, it could make visible the precise sequence of muscle contractions in the arms of a baseball player swinging the bat, or in the legs of a soccer player taking a corner kick.

A key to the new motion-magnification algorithm is a technique for very precisely extracting foreground objects from their backgrounds.

The algorithm cancels large motion, determining which pixels of successive frames of video belong to a moving object, and which belong to the background. Once the algorithm has identified the pixels correlating to a single moving object, it corrects for the object’s motion and performs the same motion magnification procedure that previous versions did. Finally, it reinserts the magnified motions back into the original video stream.