PURPOSE: To invert two color difference signals invariably correctly when a signal multiplexed on band-sharing basis is restored to, by automatically optimizing the polarities of the color difference signals to be restored by the use of discrimination pulses with added signal polarities.

CONSTITUTION: A color difference signal R-Y from a signal source 1 is supplied to an adder 3, and a color difference signal B-Y from a signal source 2 is inputted to a discrimination pulse adding circuit PSA, whose output discrimination pulses PS are inverted in polarity at intervals of 1H through a switch SW which operates in every 1H and supplied to an adder 3. Those two color difference signals are multiplexed on band-sharing basis by the adder 3 to be transmitted through a transmission system T, and then a comb-shaped filter CF separates the signals R-Y and B-Y, which are inputted to an amplifier 10 and a polarity inverter 11 respectively. A discriminating circuit 13 discriminates whether the output signal of the polarity inverter 11 is B-Y or -(B-Y) on the basis of the polarity of the discrimination pulse PS for signal polarities, and an FF14 is set to control the inverter 11 by its output, thus invariably generating and inputting the signal B-Y to a chroma encoder.