An electro-optical, motion picture, film sound track recording and playback system in which a complex audio signal wave is successively sampled and digitally encoded according to pulse-code modulation techniques (PCM) extant in the communications art. The digital codes are optically applied to the film...http://www.google.de/patents/US4461552?utm_source=gb-gplus-sharePatent US4461552 - Film sound track recording and playback system
