JPH01206792A - Video signal synthesizing circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a video signal synthesis circuit that synthesizes different images based on, for example, a key signal (weighting is a signal).

(Prior Art) Conventionally, there is a method called the chromakey effect, which is one of the methods for combining different images within the same screen in a video signal combining circuit. Regarding this chromakey effect, consider, for example, the case where the front image shown in FIG. 3(a) and the rear image shown in FIG. 3(b) are superimposed and synthesized as shown in FIG. 3(e).

First, as the front image shown in FIG. 3(a), the background is set to a specific hue (generally blue, which is a complementary color to the skin color), and then the image is captured with a television camera. As a result, a video signal A (t) as shown in FIG. 3(a) is obtained.

From this video signal A (i), the boundary between the subject a and the background is used horizontally, and as shown in Figure 3 (C), the key signal becomes ``]'' in the range of the subject a and 0'' in the range of the background. 1c (L)
generate. By weighting the video signal A (t) in FIG. 3(a) with this key signal k (t), the specific hue that is the background is achromatized and the video signal A
Obtain c(t).

Here, the reason why a specific hue portion is achromatized is to prevent the color of a specific hue from leaking into the boundary between the subject a and the background during composition.

The key signal k (L) is 0'' in a specific hue portion and 0'' in a different hue portion, as shown in FIG. 4(b), with respect to the video signal A (t) shown in FIG. 4(a). ″1゛°, OB < at the boundary between a specific hue part and a different hue part
k(t)<“1”. A in the hue part of "1"
Output c (t) and use the hue part of “0” as B (t)
, and in the part where 0''<k(t)<゛1''゛, the video signal A (t) is k (t) and B (t) is (1-k(
t))). As a result, Figure 3 (
The video signal C(t) of the composite image shown in e) can be calculated by 1q.

However, in image synthesis using the bipedal chromakey effect, the key signal k(t) or 'Q'< k (t) <"
1", the brightness level of the achromatic video signal A c (t) of a specific hue to be mixed changes, so the sum of its frequency components is added to the multiplication result with the key signal in that range. For example, by multiplying the video signal A (t) shown in FIG. 4(a) and the key signal 1 ((t) shown in FIG. 4(b)), A c (t ), A c
In the range where the brightness level of (t) changes, the sum and difference components of the frequency components of each signal occur. For this reason, the composite image appears as a white edge at the border, resulting in an unnatural image.

(Problem to be Solved by the Invention) As described above, in the conventional video signal synthesis device using the chroma key effect, the sum of the respective frequency components is added to the multiplication result of the key signal to be weighted and the achromatic video signal of a specific color. , difference components are generated, resulting in an unnatural composite image with white border areas.

This invention was made to solve the above problems,
Provided is a video signal synthesis circuit that can reduce the sum and difference components of each frequency component generated in the multiplication result of an achromatic video signal of a specific color and a key signal, thereby obtaining a natural composite image. The purpose is to

[Structure of the Invention (Means for Solving the Problem) In order to achieve the above object, a video signal synthesis circuit according to the present invention combines a video signal of a front image whose back side is a specific color and a specific color portion of this front image. A key signal generation circuit that generates a key signal for weighting a portion of the foreground image with respect to the video signal of the foreground image; a specific color removal circuit that decolorizes a specific color portion of the front image using a key signal generated by the circuit; an inversion circuit that inverts the key signal; and an output signal of this circuit and a fixed value for brightness level adjustment. a first multiplier circuit that multiplies the output signal of the subtraction circuit; a subtraction circuit that subtracts the output signal of this circuit from the video signal of the front image that has been achromatized by the key signal; and a subtraction circuit that multiplies the output signal of the subtraction circuit by the key signal. a second multiplication circuit;
A third multiplication circuit that multiplies the output signal of the multiplication circuit by the video signal of the rear image, and an addition circuit that adds the output signals of the second and third multiplication circuits. .

(Function) The video signal synthesis circuit configured as described above adjusts the luminance level of the achromatic video signal of a specific color using a fixed value, so that when weighting the achromatic video signal of a specific color, the key signal is By reducing the sum and difference components of the respective frequency components of the key signal and the achromatic video signal of a specific color that occur at the border, and by adding and mixing the video signals, white appears at the border of the composite image on the screen. This creates a natural-looking composite image by making the edges invisible.

-〇- (Example) An example of the present invention will be described below with reference to Figs. 1 and 2.

Figure 1 shows its configuration, where A c (t) is an achromatic video signal of a specific color, B (t) is an image signal that becomes the rear image, k (t) is a key signal, and ΔY is a fixed value for brightness level adjustment.The key signal k(4) is inverted by the inverter 11 and inputted to the first multiplier 12.The first multiplier 12 inputs the key signal k(t). The inverted signal is multiplied by a fixed value ΔY, and the multiplication result is input to the subtracter 13.
The multiplication result of the first multiplier 12 is subtracted from c (t), and the subtraction result is manually input to the second multiplier 14. This second multiplier 14 multiplies the subtraction result of the subtracter 13 by the key signal k(L). On the other hand, video signal B
(t) is input to the third multiplier 15. This third multiplier 15 multiplies the video signal B (t) by an inverted signal of the key signal k(t), and the multiplication result is input to the adder 16 . This adder]6 is the second and third multiplier 14
．． 15 multiplication results are added and mixed, and this addition result is output as a video signal C(t) of a composite image.

The operation of the above configuration will be described below with reference to FIG.

First, the key signal k(t) is inverted by the inverter 11 to obtain (]-1c(t)), and then multiplied by a fixed value ΔY,
The multiplication result is converted into an achromatic video signal of a specific color A C (
Subtract from L). As a result, the video signal A c (
As shown in FIG. 2(a), key signal k(L) shown in FIG. (>0), and in the part where “Q” 1-k(L)) - The level decreases by ΔY.However, no level change occurs in the key signal k(t) or 1'' portion (not achromatized).

Here, the achromatic boundary part of the specific color (“0” < k
(t) <"1"), or the luminance level of the part (] ((1) or "1" part) where the achromatic video signal A c (t) of the specific color remains as it is during synthesis. Adjust the fixed value ΔY so that they match.This allows the video signal A c (t) to be weighted (=
Even if it is only 1, the sum and difference components of each frequency component are reduced.

Therefore, the video signal synthesis circuit with the above configuration generates the video signal A in which the specific color is achromatized by adjusting Y to a fixed value.
By adjusting the brightness level of c (t) to the level when the key signal k (t) is ]'', the video signal A c (
Even if t) is weighted by the key signal k(t), the sum and difference components of each frequency component will be reduced, so the white edges that occur at the boundaries of the composite image will not occur. Therefore, an extremely natural composite image can be obtained.

In addition, in the above embodiment, the fixed value ΔY was subtracted so that only white edges were generated at the boundaries of the composite image.
Of course, a fixed value ΔY may be added to prevent black edges from occurring at the boundary portions of the composite image.

[Effects of the Invention] As described above, according to the present invention, it is possible to reduce the sum and difference components of the respective frequency components generated in the multiplication result of the achromatic video signal of a specific color and the key signal. ,
This makes it possible to provide a video signal synthesis circuit that can obtain a natural synthesized image.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an embodiment of a video signal synthesis circuit according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the same embodiment, and FIG. 3 is a chroma key to which the present invention is applied. FIG. 4 is a waveform diagram for explaining the operation of a conventional video signal synthesis circuit. 11... Inverter, 12.14.15... Multiplier, 18... Subtractor, 16. Adder, A (t),
B(t)...video signal, k(t)...key signal, C(t) output signal. Applicant's representative Patent attorney Takehiko Suzue-1〇-1, Indication of the case Japanese Patent Application No. 63-30397 2, Title of the invention Video signal synthesis circuit 3, Person making the amendment Relationship to the case Patent applicant (435) Japan Broadcasting Corporation (3Q7) Toshiba Corporation 4, agent UBE Building 7, 3-7-2 Kasumigaseki, Chiyoda-ku, Tokyo,
Contents of the amendment (1) On page 4, line 9 of the specification, rA(t)J is corrected to r A c(t)J. (2) Page 4, line 14, page 5, line 1, 6
In the 3rd line from the bottom of the page, the 7th line from the bottom of page 9, the 3rd line from the bottom of the same page, and the 2nd line from the bottom of the same page, the word ``fuchidori'' is corrected to ``border.'' (3) In the 3rd line of page 8, the word "it" is corrected to "its". (4) On the 8th page, 7th line from the bottom, “Luminance signal only”
'' should be corrected to ``signal with only specific colors removed.'' (5) On page 9, lines 7 and 8, the words "synthetic circuit" should be corrected to "synthetic circuit."

Claims (1)

[Claims] In a video signal synthesis circuit that performs image synthesis by mixing a video signal of a front image whose back surface is a specific color and a video signal of a rear image that is the background of a specific color portion of this front image, the video signal of the front image is a key signal generation circuit that generates a key signal that weights a portion of the foreground image; a specific color removal circuit that decolorizes a specific color portion of the foreground image using the key signal generated by this circuit; an inverting circuit that inverts a signal; a first multiplier circuit that multiplies the output signal of this circuit by a fixed value for brightness level adjustment; a subtraction circuit that subtracts from the signal; a second multiplication circuit that multiplies the output signal of the subtraction circuit by the key signal; and a second multiplication circuit that multiplies the output signal of the first multiplication circuit by the video signal of the rear image. A video signal synthesis circuit comprising: No. 3 multiplication circuit and an addition circuit for adding each output signal of the second and third multiplication circuits.