The photographic recording of digital soundtracks on motion picture film has been proposed. For example, U.S. Pat. No. 4,600,280, issued Jul. 15, 1986, describes a technique for recording a digital soundtrack on a film strip by exposing the film to modulated light from a light source. In one method disclosed in U.S. Pat. No. 4,600,280, an intermittent light beam (encoded with digital audio information) is scanned horizontally across the film, and the film is then advanced vertically and the scanning process repeated. U.S. Pat. No. 4,600,280 suggests alternatively that the light can be projected on the film through a linear array of solid state shutters or Bragg cell modulators.
U.S. Pat. No. 4,461,552, issued Jul. 24, 1984, also discloses a method in which digital audio is photographically recorded on motion picture film.
It has also been proposed to photographically record other types of digital information on photographic film. For example, U.S. Pat. No. 4,553,833, issued Nov. 19, 1985, discloses a method for photographic recording of characters and symbols on photographic film. In this method, light emitted from a relatively large-sized array (such as a light emitting diode array) is focused through converging lenses, to cause a relatively small-sized dot pattern to be projected on the film.
U.S. Pat. No. 4,306,781, issued Dec. 22, 1981, suggests recording a command data track (track 11 shown in FIG. 2) on motion picture film, along with an unmodulated locator track (track 5 shown in FIG. 2) and several analog soundtracks. Similarly, both U.S. Pat. No. 4,659,198, issued Apr. 21, 1987, and U.S. Pat. No. 4,893,921, issued Jan. 16, 1991, disclose a process for recording digital data along an edge portion of a strip of cinematographic film.
U.S. Patent Application Ser. No. 07/896,412, U.S. Pat. No. 5,453,802, entitled "Method and Apparatus for Photographically Recording Digital Audio and a Medium having Photographically Recorded Digital Soundtracks," filed on Jun. 10, 1992, and assigned to the same assignee as the present application, also discloses a method and apparatus for photographically recording digital audio signals, and a medium having digital audio signal photographically recorded thereon. The text of referenced application Ser. No. 07/896,412 is hereby incorporated into the present disclosure by reference.
Until the present invention, however, it had not been known how accurately to read multiple channels of digital audio information on a continuously translating motion picture film. Nor had it been known how efficiently to perform error detection and correction on one or more channels of digital audio information read from a continuously translating motion picture film.