1. A method, comprising: for each frame of a plurality of frames that includes at least a first frame, a second frame, and a last frame: generating a list of new smiling faces for the frame by performing smiling face detection employing an object classifier that is trained to distinguish between smiling faces and all objects in the frame that are not smiling faces; employing the list of new smiling faces from the first frame of the plurality of frames as an input smiling face list for the second frame of the plurality of frames; for each frame in the plurality of frames after the first frame: generating a list of tracked smiles for the frame by tracking smiling faces in the frame from the input smiling list for the frame; and for each frame in the plurality of frames after the first frame of the plurality of frames and prior to the last frame of the plurality of frames: generating a list of new smiling faces for the next frame of the plurality of frames by combining the list of new smiling faces for the frame with the list of tracked smiles for the frame.