Digital audio recording/playback system for motion picture film

Abstract

Sound is recorded on a motion picture filmstrip (20) by taking periodic samples (15) of an analog signal (13), digitizing each sample in the form of a sixteen-bit binary word (40), (41), (43), and representing each binary word on the filmstrip in the form of a group of bits (8) composed of black dots (26) and transparent spaces (28). Each dot represents a binary ZERO and each space a binary ONE. The groups of binary bits are disposed in a digitized soundtrack (8) on the filmstrip, between the visual frames (50) and the sprocket holes (54), either in lieu of or in addition to the regular analog "variable area" soundtrack (48). On the digitized soundtrack, the groups of bits are arranged in parallel rows (42) which are oriented orthogonally to the direction of elongation of the filmstrip. Each row consists of a group of starting bits (44), followed by three groups of binary bits, for the left (40), right (41) and center ( 43) audio tracks, respectively. Thus each row on the digitized soundtrack represents three samples of three analog audio signals. When the filmstrip is projected, the digitized soundtrack is illuminated with a lamp (102) and the shadow of the digital soundtrack is sensed by a plurality of photocells (100) which provide electrical output signals. These are conveyed to a digital-to-analog converter (110) which reconstitutes the original audio signals, which are then reproduced as audible sounds by loudspeakers (116, 112, etc.) The audio information may be represented by various other arrangements of the groups of binary bits.

Dependencies are inferred from the claim text.