Method and apparatus for decoding colour video signals using a digital comb filter

Apparatus for and a method of decoding a video colour signal provides a digital wide band luminance signal. An analog signal Yl representing the low band luminance component of a coded video colour input signal Icv, is obtained at a first analog filter 1. An analog signal Yhc representing high band luminance and chrominance components is obtained at second means (5) which subtracts the first analog signal Y1 from a delayed input signal Icv. Signal Yhc is synchronously demodulated to provide (B-Y) and (R-Y) chrominance component signals U₁, V₁, which are digitised. Via digital delay means, single line delayed signals Ydl, U₀, V₀ and double line delayed signals U-₁, V-₁ are obtained. High band luminance signals Yu, Yv are then obtained as a function of at least two of the respective chrominance component signals U₁, U₀ and U-₁; and V₁, V₀ and V-₁. These signals Yu, Yv are remodulated and combined to provide a digital high band luminance component signal Yh. Finally, by digitally summing the digital signals Ydl and Yh a digital wide band luminance output signal Yd is obtained. Two different functions for obtaining the high band luminance components are exemplified. Wideband chrominance signals are also provided.