JPH05153613A - Video signal processor - Google Patents

Abstract

PURPOSE:To correct contour without undershoot and overshoot by applying differentiation processing and arithmetic operation processing to a video signal for plural number of times, controlling its input and output and increasing the gradient of the contour part. CONSTITUTION:An input video signal is differentiated by a differentiation circuit 3, its output is fed to a contour correction area detecting circuit 20, in which the signal is subjected to an absolute value processing, a minimum value is detected, a correction area is detected and the result is fed to an arithmetic operation processing circuit 30. The resulting signal is differentiated, subjected to absolute value processing, differentiated, the result is fed to a control circuit 40, in which the correction signal of the contour part of the video signal is obtained by controlling the polarity with an output from the differentiation circuit 3 and the detection circuit 20. The output of the circuit 40 and a video signal from an input terminal 1 are added by an adder 8 and the sum is outputted. Thus, the contour correction without having undershoot and overshoot is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing device for correcting a contour portion of a video signal in a color television receiver.

[0002]

2. Description of the Related Art Conventionally, in a color television signal transmission system, the sharpness of an image reproduced by a receiver is lowered because the transmission band is limited. For example, in the NTSC system, the luminance signal band is 0 to 4.
It is limited to 2 [MHz]. Therefore, even when the image is taken with an ideal image pickup tube, the signal at the time of black-and-white change of the luminance signal does not become sharper than a certain value at the rising and falling slopes of the signal on the receiver, and the contour part on the screen It looks a little blurry.

In order to improve such image blurring,
In recent years, in a video signal processing device, contour correction is performed by creating a secondary differential signal using a delay line and adding it to the original signal. A conventional video signal processing device will be described below with reference to FIG.

FIG. 4 shows a block diagram of a conventional video signal processing device. In FIG. 4, 1 is an input terminal for a video signal, 2 is an output terminal, 11 and 12 are delay lines for delaying a predetermined time, 13, 14 and 15 are multipliers, 16 is an adder, and 17 is a contour correction level. A gain controller 18 for changing is an adder. (FIG. 5) shows operation waveforms at points a to i shown in (FIG. 4).

The operation of the conventional video signal processing apparatus configured as described above will be described below (FIG. 4),
This will be described with reference to FIG. First (FIG. 4), the video signal input from the input terminal 1 is the delay line 1
1, supplied to the multiplier 13. The output signal of the delay line 11 is supplied to the delay line 12, the multiplier 14 and the adder 18. The output signal of the delay line 12 is supplied to the multiplier 15.
For example, if a video signal having a waveform as shown in FIG. 5 (a) is input to the input terminal 1 (point a), the signal waveforms at points b and c are (FIG. 5 (b)), ( It becomes like FIG.5 (c). The signals at points a, b, and c are the multiplier 1 respectively.
3, 14, 15 are supplied.

The coefficients Ka, Kb and Kc of each multiplier are Ka =-
If 1, Kb = 2, Kc = -1, then at points d, e, f,
The waveforms shown in (FIG. 5 (d)), (FIG. 5 (e)), and (FIG. 5 (f)) are obtained. These three signals are added to the adder 16, and as a result, at point g, a signal waveform obtained by quadratic differentiation of the original signal as shown in FIG. 5 (g) is obtained. Adder 1
The output signal of 6 is adjusted in amplitude by the gain controller 17 with an arbitrary gain, and is added to the adder 18. For example, assuming that the gain is 1/2, the signal waveform at the point h is (Fig.
(H)). The output of the gain controller 17 is added to the adder 18 together with the output of the delay line 11, and at point i, a signal having the waveform shown in FIG. 5 (i) is obtained and output from the output terminal 2.

In the conventional video signal processing apparatus configured as described above, a signal with a sharp edge portion is obtained and contour correction is performed.

[0008]

However, in the above-mentioned conventional structure, since an undershoot and an overshoot are added to the contour portion, there is a problem that an unnatural edging of black and white is attached to the contour portion of the image. Had.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a video signal processing apparatus for performing contour correction by erecting a contour portion without adding undershoot and overshoot.

[0010]

In order to achieve the above object, the present invention has a differentiating circuit for differentiating a video signal supplied as an input, a contour correction area detecting circuit having an output of the differentiating circuit as an input, and the contour. An arithmetic processing circuit that receives the output of the correction region detection circuit and a control circuit that receives the output of the arithmetic processing circuit are provided.

[0011]

With this configuration, the contour portion is erected without adding undershoot and overshoot,
Contour correction can be performed without adding an unnatural white or black border to the contour portion of the image.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of a video signal processing device in an embodiment of the present invention. In FIG. 1, 1 is an input terminal of a video signal, 3 is a first differentiating circuit, 20 is a contour correction area detecting circuit, 30 is an arithmetic processing circuit, 40 is a control circuit, and 4, 5 and 6 are first, respectively. , 2nd and 3rd timing adjusters, 7 is a gain controller, 8 is an adder, and 2 is an output terminal. Further, in the contour correction area detection circuit 20, 21 is a first absolute value circuit,
Reference numeral 22 is a delay circuit, 23 is a minimum value detection circuit, and in the arithmetic processing circuit 30, 31 is a second differentiating circuit, 32 is a second absolute value circuit, and 33 is a third differentiating circuit.

In the video signal processing device configured as described above, first, the video signal input from the input terminal 1 is
Differentiated by the first differentiating circuit 3, the contour correction area detecting circuit 2
0 is supplied. In the contour correction area detection circuit 20,
The input differential signal is supplied to the first absolute value circuit 21, and the absolute valued signal is supplied to one input terminal of the minimum value detection circuit 23 and the delay circuit 22. Delay circuit 2
The signal delayed by a predetermined time by 2 is the minimum value detection circuit 2
3 is supplied to the other input terminal, the output of the absolute value circuit 21 is compared with the amplitude value, and the minimum value is detected. The detection output signal of the contour correction area detection circuit 20 is supplied to the arithmetic processing circuit 30. This signal is supplied to the second differentiation circuit 31 of the arithmetic processing circuit 30, and the differentiation output is the second absolute value circuit 3
2 is supplied. The signal absolute valued by the second absolute value circuit 32 is supplied to the third differential circuit 33, and the differential output signal is input to the control circuit 40. The output signal of the contour correction area detection circuit 20 whose timing is adjusted by the first timing adjuster 4 is supplied to one control terminal of the control circuit 40, and the second timing adjustment is supplied to the other control terminal. The output signal of the first differentiating circuit 3 whose timing is adjusted by the device 5 is supplied. The output signal of the control circuit 40 is supplied to the gain controller 7, and the output thereof is supplied to one input terminal of the adder 8. The other input terminal of the adder 8 is supplied with the original input video signal whose timing is adjusted by the third timing adjuster 6. The addition output of the adder 8 is output from the output terminal 2.

The operation of the video signal processing device configured as described above will be described with reference to the operation waveform diagram of FIG. (FIG. 2) shows operation waveforms at points a to o shown in (FIG. 1). For example, assume that a video signal having a waveform as shown in (a) of FIG. 2 is input from the input terminal 1. This input signal is differentiated by the first differentiating circuit 3 and has a waveform shown in (b) of FIG. 2 at point b, and this signal is supplied to the contour correction area detection circuit 20.

Next, in the contour correction area detection circuit 20,
The input differential signal is converted into an absolute value by the first absolute value circuit 21 and has a waveform shown in (c) of FIG. 2 at point c.
Further, this signal is delayed by the delay circuit 22, and at the point d, the waveform shown in (d) of FIG. 2 is obtained. Absolute value circuit 21
And the output signal of the delay circuit 22 is supplied to the minimum value detection circuit 23 and the minimum value is detected. At point e (FIG. 2) (e)
The waveform becomes as shown in FIG. 3, and this signal is supplied to the arithmetic processing circuit 30.

Next, in the arithmetic processing circuit 30, the input output signal of the minimum value detection circuit 23 is the first differentiation circuit 31.
, And the waveform at the point f is as shown in (f) of FIG. This signal is converted into an absolute value by the second absolute value circuit 32, and the waveform shown in (FIG. 2) (g) is obtained at the point g.
Further, this signal is differentiated by the third differentiating circuit 33,
At the point h, the waveform shown in (h) of FIG. 2 is obtained and is supplied to the control circuit 40.

The control circuit 40 is composed of, for example, the circuit shown in FIG. In FIG. 3, 41 is a region control circuit, 44 is a polarity control circuit, 42 is a comparator, 43 is a selector, 45 is a polarity determination circuit, and 46 is a polarity switching circuit. In the control circuit 40 configured as described above, the output signal of the arithmetic processing circuit 30 is supplied to one input terminal of the selector 43, and "0" is input as a value to the other input terminal. There is. The output of the contour correction area detection circuit 20 whose timing is adjusted by the timing adjuster 4 is supplied to one control terminal of the control circuit 40, and this signal is supplied to the comparator 42 in which a threshold value is set in advance. .. The output of the comparator 42 is supplied to the control terminal of the selector 43, and the output of the selector 43 is supplied to the polarity switching circuit 46. The output of the differentiating circuit 3 whose timing is adjusted by the timing adjuster 5 is supplied to the other control terminal of the control circuit 40, and this signal is supplied to the polarity determining circuit 45. The output of the polarity determination circuit 45 is supplied to the control terminal of the polarity switching circuit 46, and the output thereof is the input of the gain controller 7.

The operation of this circuit (FIG. 1) will be described below.
This will be described with reference to (FIG. 2) and (FIG. 3). The output signal of the arithmetic processing circuit 30 obtained at the point h becomes one input signal of the selector 43, and "0" is input as a value to the other input terminal. Contour correction area detection circuit 20
The detection output signal (the signal at the point e) by is adjusted in timing by the first timing adjuster 4 and becomes a control signal of the area control circuit 41 (FIG. 2 (i)), and is supplied to the comparator 42. To be done. A threshold value is set in advance in the comparator 42, and a logical value “1” is output if it is larger than the threshold value when compared with the input signal, and a logical value ”otherwise.
0 "is output, and this output signal becomes the control signal of the selector 43 (FIG. 2 (j)).
When it is set to 0 ", a control signal having a waveform shown in (j) of FIG.
One of the three input signals is selected and output. For example, when the control signal is "1", the signal at point h is selected, and when the control signal is "0", "0" is output.

As a result, the signal at point k is (FIG. 2) (k)
The waveform shown in FIG. 3 is input to the polarity switching circuit 46. The second timing adjuster 5 is connected to the polarity determination circuit 45.
As a result, the differential signal (the signal at the point b) from the differential circuit 3 whose timing has been adjusted is supplied and serves as the control signal for the polarity control circuit 44 (FIG. 2 (l)). The polarity determination circuit 45 determines the polarity of the signal at point l and outputs a signal indicating the determination result. For example, when it is determined that the polarity of the signal at point l is positive, a signal indicating positive is output. This output signal is supplied to the control terminal of the polarity switching circuit 46.

In the polarity switching circuit 46, for example, when the control signal is a positive signal, the selector 4
The output signal of No. 3 is output as it is, and in other cases, the polarity of the output signal of the selector 43 is inverted and output. The gain of the output signal is adjusted by the gain controller 7. For example, when the gain is set to 1 by the gain controller 7, a signal having a waveform as shown in (m) of FIG. 2 is obtained at the point m, which is supplied to one input terminal of the adder 8 as a contour correction signal. To be done. The other input terminal of the adder 8 is supplied with the original input video signal whose timing is adjusted by the third timing adjuster 6 (FIG. 2 (n)), and is added with the contour correction signal to draw the contour. The corrected video signal is output from the output terminal 2 (see FIG. 2).
(O)).

Although the contour of the video signal is corrected in the horizontal direction in this embodiment, it is not limited to this and may be in the vertical direction.

As described above, according to this embodiment, a signal obtained by differentiating an input video signal is subjected to a plurality of differentiating processes and arithmetic processes, and the contour correction area is controlled with respect to this signal. By controlling the polarity, a signal for correcting the contour portion of the video signal can be obtained. Then, with this contour correction signal, it is possible to increase the gradient of the contour portion of the video signal and perform contour correction without undershoot and overshoot. As a result, it is possible to obtain a clear image without unnatural edging of black or white on the contour portion.

[0023]

As described above, according to the present invention, there are provided a differentiating circuit for differentiating a video signal supplied as an input, a contour correction area detecting circuit having an output of the differentiating circuit as an input, and the contour correcting area detecting circuit. An arithmetic processing circuit having an output as an input and a control circuit having an output of the arithmetic processing circuit as an input are provided, and the control circuit is controlled by the output of the first differentiating circuit and the output of the contour correction area detection circuit. It is possible to increase the gradient of the contour portion of the video signal and perform contour correction without undershoot and overshoot. As a result, it is possible to obtain a clear image without unnatural edging of black or white on the contour portion. Further, since the contour portion is not made to stand vertically but only the gradient is increased, the original gradation of the image at the time of image capturing is not lost,
It is possible to realize an excellent video signal processing device capable of obtaining a clearer image close to nature.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a video signal processing device according to an embodiment of the present invention.

FIG. 2 is an operation waveform diagram of the embodiment.

FIG. 3 is a configuration diagram of a control circuit in the same embodiment.

FIG. 4 is a block diagram of a conventional video signal processing device.

FIG. 5 is an operation waveform diagram of a conventional example.

[Explanation of symbols]

 3 Differentiating Circuit 4 Timing Adjuster 5 Timing Adjuster 6 Timing Adjuster 7 Gain Controller 8 Adder 20 Edge Correction Area Detection Circuit 21 Absolute Value Circuit 22 Delay Circuit 23 Minimum Value Detection Circuit 30 Arithmetic Processing Circuit 32 Absolute Value Circuit 33 Differentiating Circuit 40 control circuit

Claims (6)

[Claims] 1. A first differentiating circuit for differentiating a video signal supplied as an input, and a contour correction area detection circuit for receiving an output of the first differentiating circuit and detecting a contour correction area.
An output of the contour correction area detection circuit is input, and an arithmetic processing circuit that arithmetically processes the contour correction area detection signal with a plurality of differentiating circuits and absolute value circuits, and a control circuit that controls the output of the arithmetic processing circuit, A video signal processing device, wherein a control circuit is controlled by an output of the first differentiating circuit and an output of the contour correction area detecting circuit. 2. A contour correction area detection circuit, an absolute value circuit that takes an absolute value of an output of a first differentiating circuit, a delay circuit that delays an output of the absolute value circuit for a predetermined time, the absolute value circuit and the The video signal processing apparatus according to claim 1, further comprising a minimum value detection circuit that detects a minimum value from the output of the delay circuit. 3. An arithmetic processing circuit comprising: a second differentiating circuit for differentiating the output of the contour correction area detecting circuit; an absolute value circuit for taking an absolute value of the output of the second differentiating circuit; The video signal processing apparatus according to claim 1, further comprising a third differentiating circuit that differentiates the output. 4. The control circuit receives the output of the arithmetic processing circuit as an input, and an area control circuit for controlling the contour correction area with the output of the contour correction area detection circuit, and a positive or negative polarity with the output of the first differentiating circuit. The video signal processing device according to claim 1, further comprising a polarity control circuit for controlling the. 5. The area control circuit comprises a selector for selecting the output of the arithmetic processing circuit and a signal of a predetermined value, and a comparator for comparing the output of the contour correction area detecting circuit with a set threshold value. When the output of is larger than the threshold value, the output signal of the arithmetic processing circuit input to the selector is selected, and when the output of the arithmetic processing circuit is smaller than the threshold value, the predetermined value input to the selector is set to The video signal processing device according to claim 4, wherein the video signal processing device is selected. 6. The polarity control circuit includes a polarity switching circuit for switching between positive and negative polarities of an output signal of the area control circuit,
A polarity determination circuit that determines the positive or negative polarity of the output of the first differentiating circuit is provided, and when the determination result of the polarity determination circuit is negative, the polarity of the output signal of the area control circuit input to the polarity switching circuit is set. 5. The video signal processing device according to claim 4, wherein the video signal processing device is controlled so that it is inverted and the polarity is not switched when it is positive.