PURPOSE: To improve S/N of a picture by separating a composite video signal into a luminance signal and color signal and then by gating the color signal by the luminance signal.

CONSTITUTION: Composite video signal I is passed through LPF11 to obtain a separated luminance signal, which is supplied to luminance-signal clipping circuit 15 to detect a signal equivalent to amplitude, and both outputs are inputted to encoder 19 through matrix circuit 17 mixing the both at a fixed ratio. Composite video signal I, on the other hand, is separated and democulated into color signals R, G and B through BPF12 and demodulator circuit 13 and they are clipped to respective fixed levels by color-signal clipping circuit 16. Its output is gated 18 by the luminance signal of circuit 17 and inputted to encoder 19. In this way, gate 18 removes any other unneeded color noise than a luminance signal corresponding to the color signal, so that S/N can be improved.