Device for modifying program duration on a tape player

Claim 1

A program playing time duration modifying apparatus to be coupled with a capstan motor for feeding a tape, comprising: a signal source generating a difference signal corresponding to a difference between a time constant of a program and a playing time; signal producing means (1) responsive to said difference signal for producing a tape-speed-varying signal and a reference-signal-varying signal; capstan tack signal generating means coupled to said capstan motor for generating a capstan tack signal corresponding to the running speed of said capstan motor; capstan tack delay means (5) coupled to said capstan tack signal generating means and said signal producing means for delaying said capstan tack signal by a time that is varied by said tape-speed-varying signal to produce a delayed tack signal; first phase comparing means (4) for comparing said capstan tack signal and said delayed tack signal to generate a first speed control signal; signal receiving means for receiving a capstan reference signal having a predetermined period that serves as a reference for a normal tape speed; period varying means (2) coupled to said signal receiving means and said signal producing means for varying said predetermined period of said capstan reference signal by said reference-signal-varying signal; control track signal producing means (7) for producing a control track signal from a control track of a tape, said control track signal indicating a video frame period on said tape in which said capstan reference signal has been recorded; second phase comparing means (3) for comparing said capstan reference signal with the varied period and said control track signal to generate a second speed control signal; and adder means (6) for adding said first and second speed control signals to generate a third speed control signal, wherein a speed of said capstan motor is controlled by said third speed control signal.