JPH0356517B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention provides an improved chromakey device that continuously selects target colors from a video source,
The present invention also relates to an improvement in a color discriminator that uses a chromakey signal for operating a chromakey device as a signal for making selections. (Prior Art) Conventionally, a signal forming method is known in which R, G, and B three primary color signals from an image pickup tube are subjected to matrix processing to obtain R-Y and B-Y signals (for example, U.S. Pat. No. 3,560,638). (Ole Skrydstrup, John D. Ross). Here, Y is the luminance signal, Y=0.30R+0.59G+0.11B
It is expressed by the formula. In the above patent, the chromakey signal CK is expressed by the following formula. CK=(RY)cosφ+(B-Y)sinφ where φ is the phase specific to the selected color. sinφ and cosφ are conventionally well known,
This can be achieved by using a potentiometer dedicated to each output, or by using a sine/cosine generator circuit whose output is adjusted by a normal linear potentiometer. When CK is obtained using the above equation, the signal value becomes maximum when the image pickup tube scans the desired color. However, when such a technique is used, there is a problem in that color selection is not good. That is, for example, if the selected color is blue, cyan or magenta, which is close to blue, can be attenuated by only 2 db, which causes a problem that the desired color is relatively weakened. Techniques such as stretching or clipping are used to improve selectivity, but these techniques have the problem of deteriorating the S/N ratio. U.S. Patent Nos. 3595987 and 4007487
The technology of No. 1 and No. 4100569 achieves the above selectivity by forming a B-G signal and a B-R signal, and then selecting a signal with a smaller value from both signals using a non-additive mixer to obtain a chromakey signal. This is something that can be improved. That is, the chromakey signal is expressed by the following equation. CK = the smaller value of (B-G) and (B-R) However, since there is no means to adjust the hue, the chroma key color must be pure blue. Obtaining a pure blue color is not easy, and there are also significant space limitations when setting up in a studio. According to this technique it is possible to use pure green and pure red simultaneously as exchange inputs. As is clear from the table below, the advantage of this technique is that colors close to blue, such as magenta or cyan, can be completely suppressed.

[Table] However, when this technique is used, there is a problem in that continuous hue control cannot be directly performed. (Object of the Invention) The present invention was made to solve the above problems, and the first object is to provide a color disk that accurately discriminates and responds to input colors and improves the performance of a television chromakey device. To provide a liminator. A second object of the present invention is to provide a color discriminator that has an excellent color selection function and a hue control function that can be continuously controlled. (Embodiment) FIG. 1 is a block diagram showing a system for implementing the present invention. Unencoded red signal R, green signal G, blue signal B, and brightness signal Y output from the two image pickup tubes 10 and 12 are input to encoders 14 and 16, respectively. A unique effect amplifier 18 selects either image tube 10, 12 based on the color input of interest from the source 20. Source 20 may be any image tube 10, 12 or other source not shown and outputs either an unencoded R, G, B signal or an encoded signal. . source 20
The unencoded signal from is input to the chromakey device 22. This chromakey device 22
The "bandpass" region of is moved in response to the setting of a hue control means, such as potentiometer 24. This hue control means may be provided, for example, in an operator operating console so that it can be controlled remotely by an operator. That is, when the chromakey device 22 is set to operate green, for example, by the potentiometer 24, the signal line 2
The strength of the key signal sent on 6 will be equal to the strength of all the green signals in the signal produced by source 20. The key amplifier 28 controls the pointer 30 of the switch 32 based on the signal input from the signal line 26.
control the setting position. Note that this control is actually performed electrically. For example, if the strength of the key signal on signal line 26 is less than the threshold set by key level potentiometer 34, pointer 30 will direct the signal from image pickup tube 10 to a predetermined level, as shown in FIG. It is set at a position where it can be sent to the signal sending means 36. However, if the strength of the key signal exceeds the above-mentioned threshold value, the pointer 30 is set at such a position that the signal from the image pickup tube 12 can be sent to the predetermined signal sending means 36. Thereby, a signal is generated by the means 36 which can exhibit a particular effect. Note that this unique effect is determined according to the input of the specific color of interest in the source 20. This particular color is determined by the potentiometer settings as described above. FIG. 2 shows a block diagram of a color discriminator provided in the chromakey device. This discriminator is provided with a matrix circuit 38.
is to perform predetermined processing on the unencoded R, G, and B three color signals formed by the source 20. That is, two orthogonal color difference signals B-Y, RY and a luminance signal Y are formed by matrix processing using a generally well-known method. Note that such matrix processing is often used in television signal transmission systems. This color difference signal is input to the rotation circuit 40, and in this rotation circuit 40,
It is rotated according to the rotation formula of the orthogonal coordinate system as shown in the first equation. V'=Vcosφ+Wsinφ W'=Wcosφ−Vsinφ...(1) where φ is the desired rotation angle, and in this embodiment, the rotation angle is determined. sinφ control signal and
The cosgφ control signal is formed by remote control source (potentiometer) 24 and input to rotation circuit 40. In response, the rotation circuit 40 forms new color difference signals (B-Y)' and (R-Y)' according to the second equation. (B-Y)′=(B-Y)cosφ+(R-Y)sinφ (R-Y)′=(R-Y)cosφ−(B-Y)sinφ…(2) This new color difference signal ( B-Y)', (RY)'
is input to the matrix circuit 42 together with the luminance signal Y and converted into rotational color signals R', G', and B'. here
R', G', and B' are expressed by the third equation. R′=(RY)′+Y G′=1/0.59 [Y−0.30((RY)′ +Y)−0.11((BY)′+Y)] B′=(BY)′+Y (3) In addition, matrix circuit 42 is the same type of decoding matrix circuit often used in television receivers. The rotation circuit 40 and matrix circuit 42 described above
effectively moves the "bandpass" region of the color discriminator for the color defined by the angle φ. The matrix circuit 44 receives input R', G',
This is for converting the B' signal into rotational color difference signals B'-R' and B'-G'. Matrix circuits 42, 44
Operation of the circuitry for effective functioning is accomplished in a manner well known to those skilled in the art. After that, the color difference signals B'-R' and B'-G' are inputted to the non-adding mixer 46, and the non-adding mixer 46 receives these two signals.
The signal with the lowest intensity is selected from B'-R' and B'-G' and output as the chromakey signal CK. In addition,
At this time, the phase φ is varied from 0° to 360° to obtain the maximum chromakey signal CK. By the way, various circuits may be added to the chromakey section 22 in addition to the color discriminator circuit shown in FIG. 2. For example, it is preferable to provide a clipping circuit (not shown) to clip the negative excursion of the chromakey signal CK. Furthermore, the key signal and encoder 1
It is desirable to provide a delay means capable of delaying the chroma key signal CK by a predetermined time before inputting the chroma key signal CK to the key amplifier 28 so that the outputs of the chroma key signals 4 and 16 are input to the amplifier 18 in a time-coincident manner. FIG. 3 is a block diagram showing an embodiment of a color discriminator different from the embodiment of FIG. 2. This embodiment has substantially the same function as the embodiment shown in FIG. 2, but is manufactured in a relatively simpler manner than the embodiment shown in FIG. The signal input to this embodiment is a composite signal obtained by encoding the BY signal and the RY signal, and in this point it differs from the embodiment shown in FIG. As shown in FIG. 3, this signal is decoded by a decoder 48 into two signals, a BY signal and a RY signal, by a conventionally well known method. These color difference signals B-Y and R-Y are input to the rotation circuit 40 and converted into new color difference signals (B-Y)' and (R-Y)' as in the embodiment shown in FIG. . By using the special matrix 49, the color difference signal (B-Y)',
Color difference signal B'-R' rotated from (RY)',
B′−G′ can be derived directly. B′−R′=[(BY)′+Y] −[(RY)′+Y] =(BY)′−(RY)′ B′−G′=[(BY)′+Y]−1/0.59[Y −0.30 ((RY)′+Y)] =1.19(BY)′+ 0.51(RY)′ …(4) Note that Y=0.59G+0.30R+0.11B In other words, the color difference signal B′−R′ is From the color difference signal (B-Y)' to the color difference signal (R-
By subtracting the color difference signal B'-G', the color difference signal B'-G' is obtained by multiplying the color difference signal (B-Y)' by 1.19 by the multiplier 52 and the color difference signal (B'-G' by the multiplier 54). RY)′
can be obtained immediately by adding the product multiplied by 0.51. After this, the color difference signal B′−R′,
B'-G' is input to a non-adding mixer 46, which converts it into a chromakey signal CK and outputting it. Figure 4 shows the rotation circuit 4 shown in Figure 3.
0, matrix circuit 49 and non-adding mixer 46
FIG. The unit system for the numerical values shown in FIG. 4 is Ω for resistors and μF for capacitors. Note that the numerical values shown in FIG. 4 are merely examples, and are not necessarily limited thereto. The rotation circuit 40 has linear analog multipliers A1, A2, A3, and A4 (MC1595 manufactured by Motorola), and these multipliers A1,
The terminal pin numbers of A2, A3, and A4 are as shown in FIG. These multipliers A1, A2,
The inputs and outputs of A3 and A4 are all differential inputs and outputs, which has the advantage of simplifying matrix processing. Color signal R, B
are respectively input to two +X input terminals, and the luminance signal Y is input to four +X input terminals, so that each multiplier A1, A2, A3, A4 Color difference signal R-
It is possible to form a Y signal or a color difference signal B-Y. A sinφ control signal or a cosφ control signal is input to the +Y input terminal. This multiplier A1,
Since the outputs of A2, A3, and A4 are differential outputs, the color difference signals (R-Y)' and (B-Y)' can be set to either + or - values, which allows the resistance matrix to 49 immediately receives the color difference signals B', -G',
B′, −R′ can be formed. In detail,
A first resistance matrix having resistors 57 and 58 converts the color difference signal (B-Y)' to the color difference signal (R-
Y)' is subtracted and then amplified by transistor Q2 to obtain a color difference signal B'-R'. Similarly, the color difference signals B'-G' can be obtained by the second resistance matrix having the resistors 60 and 62 and the transistor Q1 having an amplification function. Transistors Q3 and Q4 are emitter followers having a buffer function, and clamp A5 is a clamp circuit that clamps color difference signals B'-R' and B'-G'. These color difference signals B'-R' and B'-G' are then sent to a non-summing mixer Q5 consisting of two PNP transistors whose respective emitter terminals are connected.
is input. As is clear from FIG. 4A, the signals generated at the emitter terminals of transistors Q3 and Q4 always match the signal with the smaller intensity of the two input signals B'-R' and B'-G'. , whereby the chromakey signal CK can be obtained. The role of the clamp A5, which receives a blanking signal generated at each interval of the horizontal scanning period from the terminal 64, is to output the color difference signal B'-R' at each interval in order to facilitate the scanning of the non-addition mixer 46. ,
The purpose is to drop B′−G′ to ground. FIG. 5 is a circuit diagram showing one example of the remote control source 24. As shown in FIG. The circuit shown in Figure 5 is
It constitutes a coupled sine/cosine potentiometer that adjusts the values of sinφ and cosφ. Of course, instead of such means, the aforementioned sine/cosine generator circuit controlled by a normal linear potentiometer may be used. (Effects of the Invention) As can be seen from the embodiment shown in FIG. Continuous hue control is made possible by converting into color signals R', G', and B'. Also, after this, the color difference signal B′−R′,
By converting to B'-G', it is possible to improve the accuracy of color selection. Therefore, according to the color discriminator of the present invention, the problems in the prior art can be easily solved, and it is possible to perform excellent color selection and continuous hue control. As mentioned above, the color discriminator of the present invention is typically responsive to R, G, and B color signals. In the embodiments shown in FIGS. 2 and 3, it is possible to respond to color difference signals B-Y, R-Y, etc., but these color difference signals are of course composed of color signals R, G, and B. It was formed by Therefore, generally speaking, even when a color difference signal is input, it is acceptable to be able to respond to the color signals R, G, and B. Note that the color difference signals V and W are generally expressed by the fifth equation. V=AR+BG+CB W=DR+EG+FB...(5) Here, A, B, C, D, E, and F are constants greater than or equal to -1 and less than or equal to 1, R, G, and B are red,
Showing green and blue color signals. If the color difference signals B-Y, R- of the embodiment shown in FIGS.
When Y is a signal equivalent to color difference signals V and W, each coefficient is A=-0.3 and B=-
0.59, C=0.89, D=0.7, E=-0.59, F=-
It becomes 0.11. Note that when the color signals R, G, and B are equal to each other, the color difference signals B-R and B-G become 0, and such a condition is applied when the color difference signals are supplied in the apparatus of the present invention. Therefore, in the apparatus of the present invention, any color difference signal can be supplied as long as the color signals R, G, and B are equal to each other and the color difference signals B-R and B-G are zero. Examples of such color difference signals include I and Q signals used in color television signal transmission. Furthermore, it is desirable that the set of color difference signals used in the apparatus of the present invention be mutually orthogonal signals. For example, the color difference signals B-Y and R-Y used in the embodiments described above are signals that are orthogonal to each other. When such an orthogonality condition is satisfied, the above-mentioned rotation formula (Equation 1) is established, thereby making it possible to sufficiently simplify the circuit. However, the device of the present invention does not necessarily have to satisfy such orthogonality conditions.
That is, by using a computer to process two color difference signals that do not satisfy the orthogonality condition, desired signal rotation can be achieved. In the embodiments shown in FIGS. 2 and 3, in order to simplify the matrix circuit, the color difference signals B'-R',
Although the B'-G' pair signal is used, the color difference signal is not limited to this, and the color difference signal is
R′-B′, R′-G′ pair signal or color difference signal
Paired signals of G'-B' and G'-R' may also be used.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a chromakey device according to the present invention, FIG. 2 is a block diagram showing a first embodiment of a color discriminator according to the present invention, and FIG. 3 is a block diagram showing a first embodiment of a color discriminator according to the present invention. 4 and 4A are circuit diagrams showing a part of the embodiment shown in FIG. 3, and FIG. 5 is a block diagram showing a second embodiment of the discriminator. FIG. 3 is a circuit diagram showing remote control means. 10, 12... Image pickup tube, 14, 16... Encoder, 22... Chromakey device, 24... Remote control means (potentiometer), 30
...Electric switch, 36...External device, 38,4
2, 44, 49... Matrix circuit, 40... Signal rotation means, 46... Non-adding mixer, 48... Decoder, 50, 56... Adder, 52, 54...
Multiplier.

Claims (1)

[Scope of Claims] 1. At least some of the colors of a color spectrum consisting of a large number of colors formed according to differences in the mixing ratio when mixing the three primary color signals of red R, green G, and blue B. is a predetermined color, and in a color discriminator that selects a signal corresponding to each of the predetermined colors, at least a control signal expressed as a function of a phase φ unique to each of the predetermined colors is selected. one control means for generating a rotated color signal obtained corresponding to each of the three color signals R, G, and B by rotating the three color signals R, G, and B based on the phase φ, respectively; Select one of R', G', and B' as the first selection signal, and select one of the remaining two rotating color signals as the second selection signal. , when the last remaining rotated color signal is set as a third selection signal, a first rotation color difference signal which is a difference signal between the first selection signal and the second selection signal, and a first rotation color difference signal which is a difference signal between the first selection signal and the second selection signal; signal forming means for forming a second rotational color difference signal, which is a difference signal between the selection signal and the third selection signal, according to the three color signals R, G, B and the control signal; A color discriminator comprising a selection means for selecting a signal corresponding to the predetermined color by selecting a signal having a smaller intensity among the second rotational color difference signals. 2 All the colors that make up the color spectrum are
It is formed by at least one pair of color difference signals, and this color difference signal is the three color signals R,
It is formed by calculating at least two signals of G and B, and the signal forming means is
Claim 1, wherein the first and second rotational color difference signals are formed in accordance with a pair of color difference signals and the control signal.
Color discriminator as described in section. 3. The color discriminator according to claim 2, wherein the pair of color difference signals are mutually orthogonal signals. 4 The pair of color difference signals increases the luminance signal Y by 0.59G.
When set equal to +0.30R+0.11B, the first
Claim 3, characterized in that the color difference signal B-Y is comprised of the color difference signal B-Y and the second color difference signal R-Y.
Color discriminator as described in section. 5. A patent claim comprising means for generating the three color signals R, G, and B, and matrix means for forming the pair of color difference signals from the three color signals R, G, and B. A color discriminator according to item 2 of the range. 6. The color discriminator according to claim 5, wherein the means for generating the three color signals R, G, and B is an image pickup tube for a television. 7. The apparatus according to claim 2, further comprising a decoder means for inputting the pair of color difference signals in the form of an encoded composite television signal and separating each color difference signal from the composite television signal. color day discriminator. 8. The signal forming means includes signal rotating means for rotating the pair of color difference signals according to the phase φ, and the first and second rotated color difference signals according to the rotated pair of color difference signals. 3. A color discriminator according to claim 2, further comprising means for forming a color discriminator. 9. The color discriminator according to claim 8, wherein the signal rotation means comprises a linear analog multiplier whose input/output section is a differential input/output section. 10 the signal forming means receives the three color signals R, G, B and the control signal;
a signal rotating means for rotating the three color signals based on the phase φ to form the three rotated color signals R', G', and B'; 2. A color discriminator as claimed in claim 1, further comprising means for forming said first and second rotational color difference signals. 11. The color discriminator according to claim 1, wherein the first and second rotational color difference signals are signals B'-R' and B'-G', respectively. 12. A color discriminator according to claim 1, wherein said control means comprises means for generating a sinφ control signal and a cosφ control signal. 13 Define the red signal as R, the green signal as G, the blue signal as B, and the luminance signal as Y expressed by the following formula, Y=0.59G+0.30R+0.11B A pair of mutually orthogonal color difference signals B-Y, R - When mixing Y, at least some of the colors in the color spectrum consisting of a large number of colors formed according to differences in the mixing ratio are predetermined colors, and a signal corresponding to this predetermined color is set. a color discriminator for selecting a color discriminator, comprising: control means for generating a sinφ control signal and a cosφ control signal expressed as a function of a phase φ unique to each of the predetermined colors; In response to the control signal, a first signal represented by (B-Y)'-(R-Y)' and 1.19(B-Y)'+0.51
(RY)', where (B
-Y)′=(B-Y)cosφ+(RY)sinφ, (R
−Y)′=(RY)cosφ−(B−Y)sinφ); A color discriminator comprising a selection means for selecting a signal corresponding to a predetermined color. 14 comprising means for generating the three color signals R, G, and B, and matrix means for forming the pair of color difference signals B-Y and R-Y from the three color signals R, G, and B. A color discriminator according to claim 13, characterized in that: 15. The color discriminator according to claim 14, wherein the means for generating the three color signals R, G, and B is an image pickup tube for a television. 16. Claim 13, characterized in that the pair of color difference signals is input in the form of an encoded composite television signal, and further comprises decoder means for separating each color difference signal from the composite television signal.
Color discriminator as described in section. 17 The signal forming means generates the color difference signal B-
Rotational color difference signals (B-Y)' and (R-
Y)'; and matrix means for forming the first and second signals in accordance with the rotated color difference signals (B-Y)' and (RY)'. A color discriminator according to claim 13. 18 The matrix means is connected to the signal (B-
means for subtracting the signal (R-Y)' from the signal (R-Y)' to form the first signal;
Y)' multiplied by a coefficient of 1.19 and the signal (R-
18. A color discriminator according to claim 17, further comprising means for forming said second signal by adding Y)' multiplied by a coefficient of 0.51. 19 The matrix means converts the rotated color signal B' into (R-Y)'+Y by the calculation (B-Y)'+Y.
The rotation color signal R' is calculated as 1/0.59[Y-
0.30((RY)'+Y)-0.11((B-Y)'+Y)
]
A first matrix means for forming a rotated color signal G' by the operation B'-R' and a second signal G' by the operation B'-G'.
18. A color discriminator according to claim 17, characterized in that it comprises second matrix means for forming signals respectively. 20. The color discriminator according to claim 17, wherein the signal rotation means comprises a linear analog multiplier whose input/output section is a differential input/output section. 21. A color discriminator according to claim 13, wherein said selection means comprises a non-additive mixer. 22. The color discriminator according to claim 13, wherein the control means is arranged at a position remote from the signal forming means. 23. A color discriminator according to claim 13, characterized in that said control means comprises an associated sine/cosine potentiometer. 24 When mixing the three primary color signals of red R, green G, and blue B, at least some of the colors in the color spectrum consisting of a large number of colors formed according to the difference in the mixing ratio are set as predetermined colors. , at least two color video signal sources;
a multi-position switch having two stable positions corresponding respectively to the two color video signal sources; and an output for connecting one of the color video signal sources corresponding to the set position of the switch to an external device. means, an input section for inputting a key signal corresponding to the predetermined color, and a threshold setting section for determining a threshold value of this key signal, and the value of the inputted key signal is set by the setting section. key means for switching said switch from one stable position to another stable position when a predetermined threshold is crossed; and at least a control signal expressed as a function of a phase φ specific to each of said predetermined colors. one control means for generating three rotated colors obtained corresponding to each of the three color signals R, G, and B by rotating the three signals R, G, and B based on the phase φ, respectively; One of the signals R', G', and B' is selected as the first selection signal, and one of the remaining two rotation color signals is selected as the second selection signal. and the last remaining rotated color signal is the third selection signal, the first rotation color difference signal which is the difference signal between the first selection signal and the second selection signal, and the first rotation color difference signal, which is the difference signal between the first selection signal and the second selection signal. a signal forming means for forming a second rotational color difference signal, which is a difference signal between the selection signal and the third selection signal, according to the three color signals R, G, B and the control signal; and a color discriminator comprising selection means for generating the key signal by selecting a signal with a smaller intensity among the second rotational color difference signals. 25 All the colors constituting the color spectrum are formed by at least one pair of color difference signals, and this color difference signal is formed by calculation of at least two of the three color signals R, G, and B. Claim 1, wherein the signal forming means forms the first and second rotational color difference signals in response to the pair of color difference signals and the control signal. 25. The chromakey device according to item 24. 26. The chromakey device according to claim 25, wherein the pair of color difference signals are mutually orthogonal signals. 27 The pair of color difference signals is the luminance signal Y.
When set equal to 0.59G + 0.30R + 0.11B,
26. The chromakey device according to claim 25, characterized in that it is constituted by a first color difference signal B-Y and a second color difference signal RY. 28. Claim 25, characterized in that it comprises means for generating the three color signals R, G, and B, and matrix means for forming the pair of color difference signals from the three color signals. The chroma key device described. 29. The chromakey device according to claim 28, wherein the means for generating the three color signals R, G, and B is an image pickup tube for a television. 30. Claim 25, characterized in that said pair of color difference signals is input in the form of an encoded composite television signal, and further comprises decoder means for separating each color difference signal from the composite television signal.
Chromakey device as described in section. 31 The signal forming means forms the first and second rotated color difference signals using a signal rotation means that rotates the pair of color difference signals according to the phase φ, and the rotated pair of color difference signals. 26. The chromakey device according to claim 25, further comprising means. 32. The chromakey device according to claim 24, wherein the first and second rotational color difference signals are signals B'-R' and B'-G', respectively. 33 Define the red signal as R, the green signal as G, the blue signal as B, and the luminance signal as Y expressed by the following formula, Y=0.59G+0.30R+0.11B A pair of mutually orthogonal color difference signals B-Y, R - When mixing Y, at least some of the colors in the color spectrum consisting of a large number of colors formed according to the difference in the mixing ratio are predetermined colors, and corresponding to this predetermined color, A chromakey device for supplying a signal having a specific effect, comprising: at least two color video signal sources; a multi-position switch having two stable positions corresponding respectively to the two color video signal sources; output means for connecting one of said color video signal generation sources corresponding to a set position to an external device; an input section for inputting a key signal corresponding to said predetermined color; and a threshold value for said key signal. key means for switching the switch from one stable position to the other stable position when the value of the input key signal crosses the threshold value set by the setting part; , control means for generating a sinφ control signal and a cosφ control signal expressed as a unique phase φ for each of the predetermined colors; )'-(R-Y)' and 1.19(B-Y)'+0.51
(RY)', where (B
-Y)′=(B-Y)cosφ+(RY)sinφ, (R
-Y)′=(RY)cosφ−(B-Y)sinφ); 1. A chromakey device comprising: a color discriminator comprising selection means for generating a signal. 34 comprising means for generating the three color signals R, G, and B, and matrix means for forming the pair of color difference signals B-Y and R-Y from the three color signals R, G, and B. 34. A chromakey device according to claim 33, characterized in that: 35. The chromakey device according to claim 34, wherein the means for generating the three color signals R, G, and B is an image pickup tube for a television. 36. Claim 33, further comprising a decoder means which is input in the form of a composite television signal encoded with the pair of color difference signals and separates each color difference signal from the composite television signal.
Chromakey device as described in section. 37 The signal forming means generates the color difference signal B-
signal rotation means for forming rotated color difference signals (B-Y)', (RY)' in accordance with Y, R-Y and the two control signals;
Y)', (RY)', the first and second
34. The chromakey device according to claim 33, further comprising matrix means for forming a signal. 38. The chromakey device according to claim 33, wherein the control means is arranged at a position remote from the signal forming means.