Abstract: More than two surround sound channels are provided within the format of a digital soundtrack system designed to provide only two surround sound channels by matrix encoding from three to five additional surround sound channels into two “discrete” surround sound channels. The digital audio stream of the digital soundtrack system designed to provide only two surround sound channels remains unaltered, thus providing compatibility with existing playback equipment. The format of the media carrying the digital soundtracks also is unaltered. The “discreteness” of the digital soundtrack system is not audibly diminished by employing matrix technology to surround sound channels, particularly if active matrix decoding is employed.

Abstract: 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.

Abstract: The decoder of this invention decodes at least two channel signals in a directional information system where at least four input signals containing directional information have been encoded into the two or more channel signals. The decoder generates a first control signal substantially proportional to the logarithm of the ratio of the amplitudes of two of the channel signals to detect, as between two of the channel signals, whether the amplitude of one signal dominates that of the other. The decoder also generates a second control signal substantially proportional to the logarithm of the ratio of the amplitudes of the sum and the difference between two of the channel signals to detect the dominant signal in terms of amplitude. The decoder includes a matrix means responsive to the two or more channel signals and the two control signals for generating a number of output signals according to an algorithm.

Abstract: A "hybrid" encoder has a characteristic action suitable for substantially full complementary playback in an audio signal transmission or recording system using decoders designed for one type complementary encode/decode system while permitting compatible decoding with decoders designed for use with another type complementary encode/decode system, or playback without any special decoders at all. The hybrid encoder is a series or parallel arrangement of two encoders that are modifications of standard encoders used in the two systems. In the preferred embodiments the two systems are A-type noise reduction and spectral recording. A variable degree of hybrid encoding is provided by varying the characteristic controlling circuit parameters in the two encoders, or in a preferred embodiment, by providing a variable combining arrangement that selects selects from the outputs of a hybrid encoder and an unmodified encoder (spectral recording).

Abstract: The decoder of this invention decodes at least two channel signals in a directional information system where at least four input signals containing directional information have been encoded into the two or more channel signals. The decoder generates a first control signal substantially proportional to the logarithm of the ratio of the amplitudes of two of the channel signals to detect, as between two of the channel signals, whether the amplitude of one signal dominates that of the other. The decoder also generates a second control signal substantially proportional to the logarithm of the ratio of the amplitudes of the sum and the difference between two of the channel signals to detect the dominant signal in terms of amplitude. The decoder includes a matrix means responsive to the two or more channel signals and the two control signals for generating a number of output signals according to an algorithm.

Abstract: Apparatus for reproducing motion picture photographic (optical) sound-tracks is disclosed in which significant information regarding track placement, slit illumination, azimuth and impulse noise is derived by dynamically processing and comparing the signals obtained by reading each half of a bilateral sound-track. In a further embodiment a pair of detector elements monitors the septum between two tracks in order to detect lateral film misalignment.

Abstract: Discrete four-channel photographic (optical) motion picture sound-tracks are disclosed that are compatible with existing monophonic and stereo variable area (SVA) theatre projection equipment. Six track and four track embodiments are disclosed. In the four track embodiments 4-4-4 matrix encoding is employed in producing the sound-track. Apparatus for recording and reproducing the compatible four-channel sound-tracks are also disclosed.