System for generating a synchronizing signal in response to two timing

Abstract

A method and system for composite system phase control in a signal processor such as a television video recorder operating in a genlocked system. A synchronizing signal, preferably a frame-rate horizontal reset pulse, is generated in response to coincidence between predetermined parts of two timing reference signals, in particular color television frame-rate horizontal line reference pulses and clock pulses derived from the color subcarrier. Possible coincidence ambiguity between the two timing reference signals exists when transitions in the two signals occur within a predetermined time period. The phase of one of the reference signals, the subcarrier frequency clock, is shifted 180 degrees (one-half cycle) to eliminate the potential coincidence ambiguity. Simultaneously, the phase of the generated synchronizing signal, the horizontal reset pulse, is shifted by one-half cycle of the subcarrier-related clock signal in a direction to compensate for the phase shift of that reference signal so that the phase shift of the generated synchronizing signal is transparent, i.e. there is no apparent change in the position of the generated sychronizing signal.