Compatible digital soundtracks for 70 mm motion picture film

Dolby Digital and Sony SDDS digital signal carrying optical symbols on large-format motion picture film (e.g., film having any of the various 70 mm formats) are recorded in such a way as to permit existing 35 mm optical readers and signal decoders to recover the soundtracks with little or no modification. The conventional motion picture soundtrack in the form of a two-dimensional array of photographically recorded symbols representing digital information intended for application to 35 mm motion picture film is modified by magnifying the symbols in the direction in which the motion picture film is transported when played, the degree of magnification being proportional to the ratio of the film speed of the large-format motion picture film to the 35 mm film speed. The modified soundtrack is applied to the large-format motion picture film, whereby when said large-format motion picture film is played the information recovered is essentially the same as the information recovered from 35 mm motion picture film to which the conventional motion picture soundtrack is applied.