JPH043157B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chroma key device, and particularly to a chroma key device that displays a set key signal range and makes adjustments easy and accurate.

FIG. 1 shows an example of a chromakey device to which the present invention can be applied, and in the figure, 1 and 2 are input terminals to which a foreground color video signal and a background color video signal are supplied, respectively. These color video signals are digitized by A/D converters 3 and 4, the digitized foreground color video signal is supplied to a Y/C separation circuit 5, and the chroma signal from this is sent to a decoder 6, where it is divided into two It is converted into color difference signals U and V. This color difference signal is supplied to a key signal generation circuit 7, and a soft chromakey key signal is generated.

The foreground color video signal is obtained by photographing a subject positioned in front of a back color screen, for example blue, using a television camera, and the key signal generation circuit 7 generates a key signal at a predetermined level with this blue as a reference. occurs. This key signal is supplied to the multiplier 10, where it is multiplied by the foreground color video signal passed through the delay circuit 8, and the color video signal corresponding to the object is taken out as its output.

Further, the key signal is passed through the inversion circuit 12 to be converted into a one's complement number, and then supplied to the multiplier 11 . A color video signal corresponding to an image of the background excluding the subject is taken out from the multiplier 11, and combined with a color video signal corresponding to the subject in the adder 13. Then, by converting the signal into an analog signal by the D/A converter 14, a composite color video signal is obtained at the output terminal 15.

In the above-mentioned chromakey device, the back color included in the foreground image differs depending on the screen actually used, lighting, etc., so the reference value for generating the key signal must be optimized based on this. It is necessary to make adjustments to change things. However, performing this adjustment while looking at the monitor screen is complicated and requires skill.

The present invention aims to realize a chromakey device that can display the boundary between the foreground and the background on the chromaticity coordinates on a screen such as a vectorscope, and can easily and accurately perform the above-mentioned adjustment. It is something.

An embodiment of the present invention will be described below. FIG. 2 shows the overall configuration of this embodiment.

This embodiment is a component-type chromakey device, in which red, green, and blue components of a foreground color video signal are supplied to input terminals denoted 1R, 1G, and 1B, and input terminals denoted 2R, 2G, and 2B. Each component of the background color video signal is applied to the input terminal. Each component of this color video signal is connected to the A/D converter 3R, 3
G, 3B and 4R, 4G, 4B are digitized and supplied to matrix circuits 16 and 17.

Further, a test signal generation circuit 18 for digital boundary display is provided. Switch circuits 19R, 19G, 19B in which the components of the foreground color video signal and the test signal emerging from the matrix circuit 16 are interlocked with each other.
, and one of the components is supplied to the multipliers 10R, 10G, and 10B.

Further, switch circuits 20R, 20G, 20 interlocking with each other are provided in the transmission path of each component of the background color video signal appearing from the matrix circuit 17.
B is inserted so that transmission of the background color video signal can be interrupted. A multiplier 11 corresponding to each component of this background color video signal.
R, 11G, and 11B are provided. and,
In the adders 13R, 13G, 13B, the outputs of the multipliers 10R, 10G, 10B and the multipliers 11R,
The outputs of 11G and 11B are combined, and this output is
The signal is supplied to an NTSC encoder 21.

A composite color video signal is taken out from the output of the encoder 21, converted into an analog signal by the D/A converter 14, and taken out to the output terminal 15. A vector scope is connected to this output terminal 15 together with a monitor receiver.

In this embodiment, a test signal is used that causes a spiral display on the screen of the vectorscope as shown in FIG. 3A. In order to create a spiral display on the (U, V) chromaticity coordinates, we need to generate a sine wave signal with appropriate amplitude and initial phase, that is, a color signal expressed by the following equation. good.

C(n)=k(n) sin(ω _SC nTs+η(n)) ...(1) Here, k(n): Monotonically increasing function ω _SC : Subcarrier angular frequency n: Time series Ts: Sampling period η (n): Initial phase If we transform the above equation, we get C(n)=k(n)cosη(n)sinω _SC
nTs+k(n) sinη(n) cosω _SC nTs...(2).

On the other hand, the color signal C(n) is obtained by balanced modulating the subcarrier with the color difference signals U(n) and V(n), so C(n) = U(n) sinω _SC nTs + V(n) cosω _SC nTs
...(3) Therefore, the color difference signals U(n) and V(n) are (2)
By comparing the formula and formula (3), it is sufficient if U(n)=k(n)cosη(n) V(n)=k(n)sinη(n) (4). FIG. 4A shows the color difference signal U(n), and FIG. 4B shows the color difference signal V(n).
The absolute value of k(n) in equation (4) determines the interval between adjacent curves of the spiral in FIG. 3A, and η(n) determines the fineness between sample points in the angular direction. The color difference signals U(n) and V(n) have 8 bits as one sample and have levels of (-128 to 127).

Further, the key signal generation circuit 7 generates a key signal by comparing the reference value and the foreground color video signal.

This reference value is an area defined by a group of straight lines. As shown in FIG. 5, the central axis of the key signal is assumed to be an angle from the U axis to α. The straight line perpendicular to this central axis is _P1 , and the straight lines that intersect at the opening angles +θ and -θ are _P2 and _P3 , and these straight lines _P1 , _P2 , _P3
The polygonal line formed by is defined as the boundary between the subject and the screen.

If one sample data of the foreground color video signal is (U _A , V _A ), each of the above straight lines can be drawn from this point.
The minimum distance among the distances _{d 1} , d ₂ , and d ₃ to P 1 , P ₂ , and P ₃ is taken as the level of the key signal. If the distances of straight lines P ₁ , P ₂ (P ₃ ) from the origin O are ER ₁ , ER ₂ , then d ₁ ,
d ₂ and d ₃ can be calculated using the following formula.

d ₁ =V _A・sinα＋U _A・cosα−ER ₁ ……(5) d ₂ =−V _A・cos(α+θ)＋U _A・sin(
α+θ)−ER ₂ …(6) d ₃ =V _A・cos(α−θ)−U _A・sin(α
+θ)-ER ₂ ...(7) In the key signal generation circuit 7, the angle α, the opening angle θ
Parameters such as can be adjusted.

The color difference signals U(n) and V shown by the above equation (4)
(n) and a luminance signal of an appropriate level are generated by a boundary display test signal generation circuit 18, selected by switch circuits 19R, 19G, and 19B, and supplied to multipliers 10R, 10G, and 10B. The signal is supplied to the key signal generation circuit 7. By cutting off the supply of background color video signals by switch circuits 20R, 20G, 20B,
As shown in Figure 3B, the vectorscope has
At the boundary set by the key signal generation circuit 7, a display is generated in which the foreground vector moves to the background (which is blocked). If the interval between the spiral lines (determined by k(n)) is made sufficiently small, boundaries corresponding to straight lines P ₂ and P ₃ will be drawn.

Also, in the above state, the switch circuits 19R, 19
G, 19B to select the foreground color video signal appearing at the output of the matrix circuit 16, and at the same time stop key processing, the vectorscope will display the foreground color video signal as shown in FIG. 3C. The corresponding vector is displayed. To stop key processing, key signal generation circuit 7
It is sufficient that all bits of the key signal formed by the key signal are always set to 1.

Further, the switch circuits 19R, 19G, and 19B may be used to switch between the foreground color video signal and the test signal every field or frame, and to operate and stop key processing in synchronization with this. In this case, there is flicker, but the foreground image can be seen on the monitor receiver, and the vector scope displays the boundary (Figure 3B) and the trajectory based on color data (Figure 3C). A superimposed display is made.

The boundary display test signal generation circuit 18 is configured to be able to generate color difference signals U(n) and V(n) shown in FIGS. 4A and 4B, respectively. In order to generate the color difference signals U(n) and V(n), the waveforms of U(n) and V(n) are stored in the ROM 22 and ROM 23, respectively, and the counter ROM2 sequentially by changing the address from 24
It is sufficient to read the contents of 2 and 23. counter 24
The address is generated by the clock CK of 4 _SC ( _SC : subcarrier frequency), and the address is generated by the flip-flop 25.
The output is used to switch between rising and falling. That is, after the 8-bit color difference signals U(n) and V(n) reach the maximum level, the flip-flop 25 is inverted by the detection signal from the terminal 26, and the ROM 22 and ROM 23 are read in the opposite direction. .

In addition, as shown in Figure 7, a ROM 27 stores data for k(n) in equation (4) and cosη(n).
A ROM 28 and a ROM 29 for storing sinη(n) are provided separately, and by reading out the output of the counter 24 as an address from these ROMs and multiplying it by the multipliers 30 and 31, the test color difference signal U( n), V(n) can be generated.

Unlike the above-mentioned embodiment, when the present invention is applied to line chroma key, the eighth embodiment
As shown, a switch circuit 19 may be provided to select between the foreground color video signal and the test signal encoded in the composite color video signal, while a switch circuit 20 may be provided to block the background color video signal.

As can be understood from the description of the embodiments described above, according to the present invention, a test signal corresponding to a spiral or ring-shaped display pattern that can express substantially all angles and amplitudes on chromaticity coordinates. By using this instead of the foreground color video signal, the boundary between the foreground and background set by the key signal generation circuit can be displayed. Therefore, by comparing this boundary representation with the vector representation of the back color in the unkeyed foreground color video signal, the parameters set in the key signal generation circuit can be adjusted to the hue of the actual back color. It can be easily adjusted to the optimum value according to its saturation degree, its vectorial spread, etc.

Furthermore, when displaying the boundary itself defined by a plurality of straight lines as in the above-described embodiment using a vector scope, it is necessary to calculate the intersection of each straight line using a microprocessor. However, the present invention can generate a test signal for boundary display with a simple configuration using two ROMs.

Note that a corrugated tube may be used in addition to the vector scope. Further, the present invention can also be applied to a chroma key device that uses I and Q as color difference signals instead of U and V, and a chroma key device that generates key signals directly from primary color signals R, G, and B. I can do it.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an example of a chroma key device to which the present invention can be applied, FIG. 2 is a block diagram showing the overall configuration of an embodiment of the invention, and FIG. Abbreviated diagram used to explain the display pattern of the vectorscope, No. 4
The figure is a waveform diagram used to explain the test signal in one embodiment of the present invention, FIG. 5 is a schematic diagram used to explain the key signal forming method in one embodiment of the present invention, and FIGS. 6 and 7 are A block diagram showing one example of a specific configuration for forming a test signal and another example of the configuration. FIG. 8 is a block diagram showing the configuration of another embodiment of the present invention. 1...Foreground color video signal input terminal, 2...
. . . input terminal for background color video signal, 7 . . . key signal generation circuit, 15 . . . output terminal, 18 . . . test signal generation circuit for boundary display.

Claims (1)

[Scope of Claims] 1. A first multiplication circuit that receives a foreground color video signal in which a subject is located in front of a predetermined background color and multiplies it by a coefficient K; and an addition circuit that adds and outputs the output signal of the first multiplication circuit and the output signal of the second multiplication circuit, wherein the addition circuit comprises: a vectorscope to which an output signal is supplied; a test signal generation circuit that generates a test signal for producing an annular or spiral display on the chromaticity coordinates on the display screen of the vectorscope; and the foreground color video. a selection circuit that selectively supplies one of the signal and the test signal to the first multiplier circuit; and a selection circuit provided on the output side of the selection circuit, the selection circuit providing a reference value corresponding to the foreground color video signal and the background color. By comparing the above coefficient K and coefficient 1-
A chromakey device comprising: a key signal generation circuit that generates K and supplies the signal to the first multiplication circuit and the second multiplication circuit, respectively.