JPH10200917A - Clip device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a signal processing circuit for a video camera or the like to express a color in an excellent way by clipping color difference signals at a content saturation. SOLUTION: A maximum value detection circuit 15 receives color difference signals (e.g. R-Y, B-Y) and a resultant value multiplied with a coefficient to a sum of the absolute values of the color difference signals and provides an output of a maximum value among three values. A coefficient generating circuit 16 generates a coefficient depending on the received maximum value and a received clip level. Multipliers 17, 18 multiply respectively the coefficient obtained from the coefficient generating circuit 16 with the color difference signals so as to apply clipping to the color difference signals R-Y, B-Y at a same rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clip device for limiting the amplitude of a color difference signal in a signal processing circuit such as a video camera.

[0002]

2. Description of the Related Art When trying to limit the amplitude of a color difference signal in a signal processing circuit of a video camera or the like, two color difference signals are used.
For example, the RY and BY signals are respectively input to the clip device to limit the amplitude. As a similar clip device, for example, there is a circuit configuration as disclosed in Japanese Patent Application Laid-Open No. Hei 5-30525. This circuit handles composite signals and the input signal is different from that of the present invention. Based on the circuits around the multiplier in the color signal portion of this circuit configuration, the configuration related to only the color difference clip is reconstructed to correspond to the present invention. A block diagram of the basic configuration described above is shown in, for example, FIG.

The operation of this circuit is as follows. First, the maximum value detection circuit 41 takes the maximum value of the absolute values of the input RY and BY signals. Next, this maximum value is input to the coefficient generation circuit 42.
The coefficient generation circuit compares the input with the clip level. For example, if the input value does not exceed the clip level, 1 is output.
Is exceeded, the value obtained by dividing the clip level by the input value is output. FIG. 3 shows an example of the characteristic indicating the relationship between the input and the output of the coefficient generation circuit. The output of the coefficient generation circuit is a multiplier 43,
The signal is multiplied by the input RY and BY signals by 44 and output.

[0004] Thereby, for the RY and BY signals,
By multiplying by the same coefficient, clipping can be performed without changing the color phase. The circuit configuration disclosed in the above publication outputs an output signal in which the maximum value of the RY and BY signals is clipped, and the configuration is different. However, when the circuit is also multiplied by two color difference signals as in the configuration described above. Can obtain the same result. Input RY, B of this clip device
FIG. 12 shows the relationship between the −Y signal and the clip level. FIG. 4 shows the input / output characteristics of this clip device.

Here, the input and output indicate the absolute value of the color difference signal.

[0006]

According to such a conventional example, in the RY and BY coordinates, the signal is clipped only in the vertical and horizontal directions, and the clipping is performed at a constant color saturation level. I wasn't. FIG. 11 shows the relationship between the RY and BY signals and the clip level. That is, when only the RY signal or the BY signal is used, clipping is performed at a low color saturation, and when the absolute values of the RY signal and the BY signal are at the same level, clipping is performed at a high color saturation.

Further, according to such a conventional example, R-
In the Y and BY coordinates, the signal is clipped at the same level in the vertical and horizontal directions as shown in FIG. 13, and clipping is not always performed at a necessary level. For example, the RY and BY signals are assumed to be RY when the relationship between the following encoder output E and RY and BY is E = (RY) cosθ + (BY) sinθ. , BY
In the coordinates, the signal is clipped at the same level in the vertical and horizontal directions, and there is no problem. However, for example, the relationship of RY and BY with the encoder output E at the subsequent stage is

[0008]

(Equation 1)

The RY and BY signals for the case of
In the case of a circuit in which the signal is clipped at the same level in the vertical and horizontal directions in the -Y and BY coordinates, the clip is applied to BY first after the encoder, and RY and B
The clipping level was different in -Y. Here, in order to simply set the level at which clipping is applied to RY and BY after the encoder, it is necessary to temporarily set RY, BY
Level is converted, clipping is performed by the above circuit, and R
There is a problem that the levels of -Y and BY need to be converted and the scale becomes large.

Further, according to such a conventional example, as shown in FIG. 4, the relationship between the levels of the input RY and BY signals and the clip level is such that when the signal is clipped, the level is suddenly constant. Therefore, the boundary of the portion that is not clipped becomes clear, and the pattern becomes unnatural. The present invention has been made in view of such a problem, and an object of the present invention is to provide a clip device that performs clipping at a constant color saturation level with a simple configuration.

It is another object of the present invention to provide a clipping device for performing clipping at an optimum level for RY and BY signals with a simple configuration. Still another object of the present invention is to provide a clip device which has a simple structure and has a natural picture even at a boundary where clipping is performed.

[0012]

In order to achieve this object, a clipping device according to the present invention adds the absolute value of a color difference signal to the absolute value of two color difference signals and multiplies the value by three.
A maximum value detection circuit for selecting the larger one of the two values, a coefficient generation circuit for generating a coefficient according to the obtained maximum value and the clip level, and a multiplier for multiplying the generated coefficient by the original color difference signal. I have it.

Thus, when the color difference signal is clipped, the signal is clipped not only in the vertical and horizontal directions but also in the diagonal direction in the RY and BY coordinates. That is, clipping is performed at the same color saturation as when only the RY signal or the BY signal is used and when the absolute values of the RY signal and the BY signal are at the same level. It can be almost constant.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, the larger one of three absolute values of two color difference signals and a value obtained by adding these absolute values and multiplying by a coefficient is extracted. A maximum value detecting circuit, a coefficient value generating circuit for generating a coefficient by comparing an output value of the maximum value detecting circuit with a preset clip value, and a coefficient output from the coefficient calculating circuit are multiplied by the color difference signal. A clipping device having a multiplication circuit, whereby a clipping device capable of clipping at a constant color saturation level with a simple configuration can be provided.

Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the clip device according to the first embodiment of the present invention. First, the absolute value circuits 11, 12
Obtain the absolute value of the Y, BY signal. Next, the absolute values of the RY and BY signals are added to obtain a value multiplied by a coefficient. Here, the coefficient is ideally 1 / √2, but is actually an approximate value and can be realized by an adder or the like without any realization problem.

The three values obtained above are the maximum value detection circuit 1
5 are input, and the maximum value of these values is output. The output of the maximum value detection circuit and the clip level are determined by the coefficient generation circuit 16.
Is input to The coefficient generation circuit compares the input with the clip level, and outputs, for example, 1 if the input value does not exceed the clip level, and outputs a value obtained by dividing the clip level by the input value otherwise.

This coefficient generating circuit can be realized by, for example, a ROM, a divider or the like. FIG. 3 shows an example of the characteristic indicating the relationship between the input and the output of the coefficient generation circuit. The outputs of the coefficient generating circuit are multiplied by the input RY and BY signals by multipliers 17 and 18 and output. Input RY, BY of this clip device
FIG. 2 shows the relationship between the signal and the clip level. FIG. 4 shows characteristics indicating the relationship between input and output of the clip device. Here, the input and the output indicate the absolute value of the color difference signal.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram showing the configuration of the clip device according to the second embodiment of the present invention. First, the absolute value circuits 11, 12
Obtain the absolute value of the Y, BY signal. Next, a value obtained by multiplying the absolute value of the RY and BY signals by a coefficient is obtained. Here, for example, the coefficient is 1.14 / 2.03 on the RY side and 1 on the BY side. The values obtained as described above are input to the maximum value detection circuit 15, and the maximum values of these values are output. The output of the maximum value detection circuit and the clip level are input to the coefficient generation circuit 16.
The coefficient generation circuit compares the input with the clip level. For example, if the input value does not exceed the clip level, 1 is output.
Is exceeded, the value obtained by dividing the clip level by the input value is output. This coefficient generation circuit can be realized by, for example, a ROM, a divider, or the like. FIG. 3 shows an example of the characteristic indicating the relationship between the input and the output of the coefficient generation circuit. The outputs of the coefficient generating circuit are multiplied by the input RY and BY signals by multipliers 17 and 18 and output. FIG. 6 shows the relationship between the input RY and BY signals of the clip device and the clip level. FIG. 4 shows characteristics indicating the relationship between input and output of the clip device.
Here, the input and the output indicate the absolute value of the color difference signal.

(Embodiment 3) Next, a third embodiment of the present invention will be described with reference to the drawings. Third of the present invention
FIG. 7 is a block diagram showing the configuration of the clip device in the embodiment. First, the input signal R-
The level is detected and output based on the Y and BY signals. Specifically, for example, the maximum value of the absolute value of each of the RY and BY signals is taken. Next, the output of the level detection circuit is input to the coefficient generation circuit 22. The outputs of the coefficient generating circuit are multiplied by the input RY and BY signals by multipliers 17 and 18 and output.

FIG. 8 shows a characteristic example showing the relationship between the input and output of the coefficient generating circuit. In this example, based on the characteristics of FIG.
The input and the clip level are compared. For example, when the input value does not exceed the clip level, 1 is output. When the input value exceeds the clip level, a value obtained by dividing the clip level by the input value is output. The difference between this example and FIG. 3 is that the change in the coefficient output before and after the clip level is gentle. As a result, the input / output characteristics of the clip device are smooth before and after the clip level, and thereafter become a fixed level which is normally clipped. FIG. 9 is a characteristic diagram showing the relationship between input and output in the second embodiment. Here, the input and the output indicate the absolute value of the color difference signal. The circuit for generating the output coefficient can be realized by using, for example, a ROM.

(Embodiment 4) Next, a fourth embodiment of the present invention will be described with reference to the drawings. Fourth Embodiment of the Present Invention
FIG. 10 is a block diagram showing the configuration of the clip device according to the embodiment. First, the input signal R is detected by the level detection circuit 31.
The level is detected and output based on the -Y and BY signals. Specifically, for example, the maximum value of the absolute value of each of the RY and BY signals is taken.

Next, the output of this level detection circuit is input to a coefficient generation circuit comprising an excess level detection circuit 32, a coefficient circuit 33, and a subtractor. The output of the level detection circuit is input to the excess level detection circuit 32. Here, the excess level detection circuit outputs a value exceeding the clip level when the output of the input level detection circuit is smaller than the clip level and is larger than 0 when the output is smaller than the clip level. The output of the excess level detection circuit is multiplied by a coefficient by a coefficient circuit, and a value obtained by subtracting the value from 1 is output as a coefficient. The coefficients are multiplied by the input RY and BY signals by multipliers 35 and 36 and output.

FIG. 11 shows a characteristic example showing the relationship between input and output of the coefficient generating circuit. In this example, the input is compared with the clip level, and if the input value does not exceed the clip level, it becomes 1; Here, the slope of the straight line when the clip level is exceeded is smaller than the slope when the clip level is exceeded in the characteristic of outputting a value obtained by dividing the clip level by the input value. Here, for a specific description, the clip level is normalized to 1 and considered as an input x and an output y.

In the case of a characteristic that outputs a value obtained by dividing the clip level by the input value when the clip level is exceeded, y = 1 / x as shown by the equation, and the slope at the clip level, ie, x = 1, is -1. Become. Therefore, the absolute value of the slope of the straight line is 1
By doing the following, the input / output characteristics of the clip device can be made smooth before and after the clip level. FIG.
1 shows an example in which the absolute value of the slope of the straight line is -1/2. FIG. 12 is a characteristic diagram showing the relationship between input and output in the fourth embodiment.

Here, the input and the output indicate the absolute values of the color difference signals. As shown in FIG. 12, the input / output characteristics of the clip device are gentle before and after the clip level. Also, with this configuration, it is possible to easily cope with a change in clip level. In this example, if the input exceeds the clip level, the output slightly exceeds the clip level,
The output can be prevented from exceeding the clip level by lowering the setting of the clip level as necessary. Also,
In this example, if the input greatly exceeds the clip level,
Although the clipped level decreases after the peak, it is possible to set the peak position to the right by setting the absolute value of the inclination to be small as necessary.

In the above embodiment, the multiplier can be generally realized by using a variable gain circuit whose gain is controlled by a coefficient obtained. Although the present invention has been described with respect to a case where color difference signals are not multiplexed, the same processing can be performed to multiplex color difference signals.

[0027]

As described above, the clipping device according to the present invention has a maximum value of three values, that is, a value obtained by adding the absolute values of two color difference signals and the absolute value of the color difference signal and multiplying by a coefficient, and a clip level. By multiplying the color difference signal by generating a coefficient in accordance with the coefficient, clipping is performed at a constant level of color saturation with a relatively simple configuration.

Further, the clipping device of the present invention multiplies the maximum value of the absolute value of the two color difference signals multiplied by different coefficients by multiplying the color difference signal by generating a coefficient in accordance with the clip level. RY, B with relatively simple configuration
-The level to be finally clipped in the vertical and horizontal directions of the Y coordinate is made constant, that is, clipping can be performed with the same color saturation.

Further, the clipping device of the present invention generates a coefficient so that the input value of the coefficient generation circuit before and after the clip level has less variation in the slope of the coefficient, and sets the level when clipping the color difference signal. Is prevented from suddenly becoming constant, and the boundary to a portion that is not clipped is made natural, so that a natural picture can be obtained as a whole.

Further, the third embodiment of the present invention can be realized with a relatively simple configuration, and can easily cope with a change in clip level.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a clip device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between RY, BY and a clip level in the first embodiment.

FIG. 3 is a characteristic diagram showing a relationship between input and output of the coefficient generating circuit in the first embodiment.

FIG. 4 is a characteristic diagram showing a relationship between input and output in the first embodiment.

FIG. 5 is a block diagram showing a configuration of a clip device according to a second embodiment of the present invention.

FIG. 6 is a characteristic diagram showing a relationship between RY, BY and a clip level in the second embodiment.

FIG. 7 is a block diagram showing a configuration of a clip device according to a third embodiment of the present invention.

FIG. 8 is a characteristic diagram showing a relationship between an input and an output of the coefficient generating circuit according to the third embodiment.

FIG. 9 is a characteristic diagram showing a relationship between input and output in the third embodiment.

FIG. 10 is a block diagram showing a configuration of a clip device according to a fourth embodiment of the present invention.

FIG. 11 is a characteristic diagram showing a relationship between an input and an output of the coefficient generating circuit according to the fourth embodiment.

FIG. 12 is a characteristic diagram showing a relationship between input and output in the fourth embodiment.

FIG. 13 is a block diagram showing a configuration of a conventional clip device.

FIG. 14 is a characteristic diagram showing a relationship between RY, BY and a clip level in a conventional example.

[Explanation of symbols]

11, 12 Absolute value circuit 13 Adder 14, 19, 33 Coefficient circuit 15 Maximum value detection circuit 16 Coefficient generation circuit 17, 18, 23, 24, 35, 36, 43, 44 Multiplier 21, 31 Level detection circuit 22 ROM 32 Excess level detection circuit 34 Subtractor

Claims (4)

[Claims] 1. A maximum value detection circuit for extracting a larger one of three absolute values of two color difference signals and a value obtained by adding the absolute values and multiplying the coefficient, and an output value of the maximum value detection circuit A clip generation circuit that compares the coefficient with a preset clip value and generates a coefficient, and a multiplication circuit that multiplies the color difference signal by a coefficient output from the coefficient calculation circuit. 2. A maximum value detection circuit for taking out a larger one of two values obtained by multiplying respective absolute values of two color difference signals by different coefficients, an output value of the maximum value detection circuit and a preset clip value And a multiplication circuit for multiplying the color difference signal by a coefficient output from the coefficient calculation circuit. 3. A level detection circuit to which a color difference signal is input, and a coefficient to be generated by inputting an output of the level detection circuit, wherein a coefficient having a small variation in a gradient of a coefficient output before and after a clip level is input. A clip device comprising: a coefficient generation circuit for generating a signal; and a multiplication circuit for multiplying a color difference signal by a coefficient output from the coefficient calculation circuit. 4. A level detection circuit to which a color difference signal is input and an output of the detection circuit are input, and an input value is compared with a preset clip level. If the input value does not exceed the clip level, 1 is set. Is exceeded, a value obtained by subtracting a value obtained by multiplying the value exceeding the clip level by a coefficient from 1 is generated, and the absolute value of the characteristic slope when the clip level is exceeded is obtained by dividing the clip level by the input value. And a multiplication circuit for multiplying a color difference signal by a coefficient output from the coefficient generation circuit. And a clip device.