1. A method comprising: Obtaining, by a processor, a plurality of video images of a subject; aligning, by the processor, the plurality of images; using the aligned images to generate a motion magnitude image; filtering, by the processor, the motion magnitude image using an edge map; detecting features on the motion magnitude image, discarding those features which do not lie in the neighborhood of edges; encoding, by the processor, the remaining features by: generating, x, y image coordinates for a feature point; generating a motion magnitude histogram in a window around the feature point; and generating a histogram of edge intensity values near the feature point; and using the encoded features to classify the video images of the subject into a predetermined classification.