Audio data readout device for motion picture film and clock generating

Abstract

An audio data readout device for a motion picture film and a clock generating device in a changeover system for a motion picture film. First and second clock generating circuits generate first and second clocks of predetermined frequencies based upon a repetition frequency of perforations detected by first and second film readers and a repetition frequency of a track pitch of audio data, and route the resulting clocks to a changeover switch. At a changeover time, a changeover controller switchingly controls the changeover switch to select the second clock. A system clock generating circuit has loop characteristics of a longer time constant than the first or second clock generating circuits and smoothly locks the second clock to generate a system clock which is outputted. A stable and accurate system clock can be generated and outputted even when film running is unstable at the changeover time.