Method of and arrangement for inserting a background signal into parts of a foreground signal fixed by a predetermined key color

Claim 3

A method as claimed in claim 1, characterized in that an output signal (OUT) with an inserted background is derived in accordance with the following equation: OUT=FG+K·(BG-KC) in which FG is the foreground signal, K is the control signal, BG is the background signal and KC is the signal representing the key color, and FG, BG and KC have at least two components (C R , C B ).

Claim 4

A method as claimed in claim 2, characterized in that the signals FG, BG and KC comprise components representing a blue component (Cb) and a red component (Cr), and in that a luminance component of the output signal is derived in accordance with the equation: OUT=(1-K)·FG+K·(BG-KY).

Claim 5

A method as claimed in claim 1, characterized in that the transition range extends as far as the center of the colors represented by the foreground signal.

Claim 6

A method as claimed in claim 2, characterized in that the signals FG, BG and KC comprise three components each.

Claim 7

An arrangement for inserting a background signal into parts of a foreground signal, said parts being fixed by a predetermined key color, said arrangement including means for deriving a control signal from the foreground signal, said control signal having a first value when the foreground signal represents a color in the region of the key color, and a second value when the foreground signal represents a different color, and in which the control signal has a transition range between the first and the second values, characterized in that the arrangement comprises a first terminal for receiving chrominance components of the background signal and a second terminal for receiving chrominance components of the foreground signal, means for generating a signal (KC) representing the key color, a first adder having a first input coupled to the first terminal and a second input coupled to said signal generating means for adding the chrominance components of the background signal and an inverse of the signal (KC) representing the key color, a multiplier having a first input coupled to an output of the adder and a second input coupled to said means for deriving the control signal, and a second adder having a first input coupled to an output of the multiplier and a second input coupled to the second terminal carrying the chrominance components of the foreground signal, an output of the second adder carrying the output signal of the arrangement.

Claim 8

An arrangement for inserting a background signal into parts of a foreground signal, said parts being fixed by a predetermined key color, said arrangement including means for deriving a control signal from the foreground signal, said control signal having a first value when the foreground signal represents a color in the region of the key color, and a second value when the foreground signal represents a different color, and in which the control signal has a transition range between the first and the second values, characterized in that the arrangement comprises a first terminal for receiving chrominance components of the background signal and a second terminal for receiving chrominance components of the foreground signal, means for generating a signal (KC) representing the key color, a first adder having a first input coupled to the first terminal and a second input coupled to said signal generating means for adding the chrominance components of the background signal and an inverse of the signal (KC) representing the key color, a multiplier having a first input coupled to an output of the adder and a second input coupled to said means for deriving the control signal, and a second adder having a first input coupled to an output of the multiplier and a second input coupled to the second terminal carrying the chrominance components of the foreground signal, an output of the second adder carrying the output signal of the arrangement.

Claim 9

An arrangement as claimed in claim 6, wherein the background signal and the foreground signal each include a luminance component, characterized in that said arrangement further comprises a fading circuit, controlled by the control signal and a complement of the control signal, for the luminance components of the background signal and the foreground signal.