JPH10200787A - Contour compensation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the digital contour compensation circuit that applies sharpness processing to an image signal. SOLUTION: The circuit is provided with a contour compensation signal extract section 1 consisting of filters or the like, a coefficient section 2 multiplying a prescribed coefficient with a signal formed by the contour compensation signal extract section 1, a coring circuit section 3 having a clip function of a low level part of a contour compensation signal, and a gain adjustment section 4 that adjusts the gain, and an adder section 6 that adds the contour compensation signal outputted from the gain adjustment section 4 to a received original video signal is used to form a sharpness signal. In the case of emphasizing the sharpness through the adjustment of the gain of the gain adjustment section 4, a coring level of the coring circuit section 3 is increased so as to reduce a fine pattern emphasized by the sharpness and a noise level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour compensating circuit known as a video signal processing circuit, and more particularly to a method suitable for obtaining a stable and inconspicuous sharpness image using a digital circuit. It relates to a contour compensation circuit.

[0002]

2. Description of the Related Art In the case of a television signal or a video source reproduced from a recording medium, depending on the content of the image, a lot of signal processing is performed before the image is displayed on a monitor screen. Image contour compensation for performing signal processing of components is used in many video devices as sharpness adjustment for improving the resolution of an image, and its video effect is large.

[0003]

Conventionally, most devices are configured such that such signal processing is performed by a signal processing circuit of an analog circuit system. When done with analog circuits,
It is difficult to compensate for the high-frequency component lost due to the group delay characteristic of the signal, and ringing occurs or the waveform is distorted due to the temperature characteristic or the like.

[0004] In the case of a sharpness circuit, noise components included in an image signal are also enhanced as the edge of the image is enhanced by sharpness. For example, the pattern of a background wall portion or the details of vegetation are reduced. There is a problem that the image is emphasized and becomes hard to see.

[0005]

In order to solve the above-mentioned problems, the present invention provides a digital signal processing circuit for processing a contour portion of an image. The signal is input to a coring circuit, and the level of the signal clipped by the coring circuit (coring level) is controlled so as to change in accordance with the degree of sharpness. In addition, signal processing that enables a mild screen to appear at the same time as the sharpness operation can be performed, thereby improving the usability of the user.

[0006]

FIG. 1 is a block diagram showing an outline of a contour compensation circuit according to the present invention. As will be described below, for example, a video signal (luminance signal) obtained from a digital video reproducing apparatus or the like is described below. It has a sharpness function to adjust the image quality. Hereinafter, a case where the sharpness processing is performed will be described with reference to FIG. In this figure, reference numeral 1 denotes a contour compensation signal extraction unit for extracting a predetermined contour compensation signal from an input video signal (luminance signal component) Vy, and includes a high-pass filter HPF, a band-pass filter BPF, a low-pass filter LPF and the like. It is configured. Then, for example, in the sharpness mode in which the edge of an image is emphasized, control is performed so that a signal portion mainly composed of a high frequency component of the video signal Vy is extracted as a contour compensation signal.

[0007] The contour compensation signal extracted by the contour compensation signal extraction unit 1 is input to the next coefficient unit 2, where the level is adjusted by adding an appropriate coefficient. The coefficient unit 2 includes, for example, four coefficient units (× 2, × 0.5, × 1, × 1.2
By selecting these coefficient units by a control signal supplied from a control unit (not shown), a contour compensation signal having a predetermined amplitude is obtained and supplied to the coring circuit unit 3. The coring circuit unit 3 is constituted by a digital clipping circuit, and clips and outputs a low-level signal including a zero level, as will be described later.

The contour compensation signal clipped at a predetermined level by the coring circuit unit 3 is input to a gain adjustment unit 4, which adjusts the degree of sharpness (softness). Then, the contour compensation signal whose level has been adjusted is supplied to an adder (which can be switched to a subtractor) 6 via a limiter circuit 5. The limiter circuit unit 5 limits the overflow of the signal data, and converts the signal data into a 9-bit digital signal by performing a rounding process. The adder 6 adds the contour compensation signal to the input video signal Vy,
This forms a video signal in which edges are emphasized. The input video signal is supplied to an adder 6 via a delay circuit 7 which gives a delay time corresponding to the delay time of each circuit which passes before the contour compensation signal is obtained. The phases are adjusted so that they match.

The contour-compensated video signal formed by the adder 6 is further input to a second limiter circuit 8, where the video signal is further restricted so as not to cause overflow, and is rounded to an 8-bit value. Form a video signal. Then, it is supplied to a luminance signal adjustment circuit,
The signal is supplied to a signal processing circuit that forms a drive signal for the picture tube together with the color difference signal that has been signal processed by another route.

Each of the circuits shown in FIG. 1 can be switched between the sharpness mode and the softness mode by the data input to the line L, and also performs a softness process for smoothing a noisy screen. Can be. In this case, the coefficient section 2 is multiplied by 2 and the coring circuit section 3 and the limiter circuit section 5 are controlled to be through. Then, the addition section 6 is controlled to be a subtraction circuit section (-), and a mild image operation is performed by using a video signal that smoothly raises the edge of image quality.

FIG. 2 shows a signal waveform for obtaining a sharpness effect. FIG. 2 (a) shows an outline of a video signal.
(B) is a contour compensation signal for enhancing the contour of the video signal, and shows a signal waveform of the data extracted by the contour compensation signal extraction unit 1. Then, by adding such a signal waveform to the original video signal, data of a video signal in which a contour portion is emphasized as shown in (c) is obtained. To obtain the sharpness effect of the contour compensation signal, it is sufficient to extract the high-frequency component of the video signal, and generally, it can also be obtained by a second-order differentiating circuit.

FIG. 3 shows the input / output characteristics of the coring circuit section 3 described above. The horizontal axis represents the level of input data,
The vertical axis indicates the data level of the output signal. As seen from this level characteristic, when the input signal level is a low level within the coring level CL, the output data indicates zero, and when the input signal level exceeds this coring level, an output signal is obtained. Such a dead zone area is set. Such a circuit is also used for a noise canceller or the like, but in the present embodiment, such a characteristic is constituted by a clipping circuit of a digital circuit, and a coring level is set by a gain adjustment unit 4 which sets the strength of sharpness. It is designed to be variable based on the gain of.

That is, when the gain of the gain adjustment unit 4 is increased to operate to enhance the sharpness of the image screen, the coring level of the coring circuit unit 3 is increased as shown in FIG. Is controlled so as to be wider as shown by CL1, and the sharpness is enhanced so that the influence of a noticeable low-level signal (noise) or the like is not output on the screen. When the gain of the gain adjustment unit 4 is reduced so as to weaken the degree of sharpness, FIG.
As shown in (b), the coring level of the coring circuit section 3 is narrowed so as to be CL2 so that the image quality of a minute portion is not lost.

The relationship between the gain of the gain adjuster 4 and the coring level can be determined by actually looking at the image screen. For example, when the level of the gain circuit is set by the table 4A, this relationship is set. The width (clip level) of the coring level is controlled by a control signal for selecting the data of the table 4A.
For example, when adjusting the sharpness level to 0 to 5 levels, a signal at a level where the coring level becomes 0.1.2.2.3.4 when the gains are set to 0, 2, 4, 7, 11, and 15 is obtained. These settings can be appropriately changed according to the image quality of the input video source.

FIG. 3 is a block diagram showing an example of a video apparatus to which the contour compensation circuit of the present invention is applied. A disc player for reproducing a DVD type optical disc 21 and a normal compact optical disc (CD) 25. Is shown. The data reproduced from the DVD disk passes through the DVD amplifier 22, the RF processor 23 and the data processor 4, and is input to the demultiplexer 29.
On the other hand, data reproduced from the CD 25 output in the CD mode is supplied to a CD-ROM decoder 28 via a CD amplifier 26 and a CD signal / servo processor 27, and is also input to a demultiplexer 29.

The video data selected by the demultiplexer 29 is converted into a video signal of a predetermined format by a video decoder 31, and the signal is supplied to a video equalizer 32. The video equalizer 32 performs various kinds of signal processing based on synchronization information of a video signal, and includes the above-described contour compensation circuit, brightness control, and the like. The video signal whose image has been adjusted by the video equalizer 32 passes through a letterbox conversion unit 33 that converts the aspect ratio of the video screen according to the monitor screen, and a subtitle circuit 34 that superimposes various kinds of titles. The video signal is supplied to an NTSC encoder 35 and converted into an NTSC television signal, and is output as a video signal via an on-screen display circuit 36 for displaying operation information and the like.

Reference numerals 37, 38, and 39 denote an audio signal controller, an audio decoder, and a D / A converter. The DRAMs disposed at various places temporarily store data when performing signal processing. It is. In such video equipment, discs are used as recording media as video software, but the recorded contents of the discs have slightly different characteristics of video signals depending on the production company.
The video equalizer 32 allows the user to adjust the image quality. In particular, the sharpness compensation for improving the sharpness of the image and the signal processing for performing the softness of the image are digitally arranged by mounting the contour compensation circuit shown in the embodiment of the present invention on the equalizer 32. It can be used effectively for such video equipment.

[0018]

As described above, in the contour compensation circuit of the present invention, a circuit for extracting a contour compensation signal and forming a signal for applying sharpness to an image from the contour compensation signal is constituted by a digital circuit. Since the temperature characteristics and waveform distortion of the signal are minimized as much as possible, the fine pattern of the background that stands out especially when sharpness is emphasized is emphasized, and the point that the image quality is impaired is eliminated by coring operation. There is an effect that good sharpness can always be applied.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an outline of a contour compensation circuit according to the present invention.

FIG. 2 is an explanatory diagram of a sharpness compensation signal.

FIG. 3 is an explanatory diagram showing a characteristic diagram of a coring circuit unit.

FIG. 4 is an explanatory diagram showing a change in a coring level when a contour is emphasized.

FIG. 5 is a block diagram illustrating an example of a video device in which the contour compensation circuit is used.

[Explanation of symbols]

1 contour compensation signal extraction section, 2 coefficient section, 3 coring circuit section, 4 gain adjustment section, 5 limiter circuit section, 6
Addition (subtraction) section, 7 delay circuit section, 8 second limiter circuit section

Claims (3)

[Claims] 1. A contour compensation signal extraction unit for extracting a contour compensation signal component from an input video signal, a coring circuit unit for clipping a predetermined level of a signal output from the contour compensation signal extraction unit, and the core A gain adjustment unit that adjusts a level of an output signal of the ring circuit unit; and an addition unit that adds the output signal of the gain adjustment unit and the input video signal, wherein the gain adjustment unit emphasizes contour compensation. Is
A contour compensation circuit, comprising: a control unit that is controlled to increase a dead zone level of the coring circuit unit. 2. The contour compensation circuit according to claim 1, wherein said contour compensation circuit is constituted by a digital circuit. 3. The contour compensation circuit according to claim 1, wherein said coring circuit section is made through and said addition section is converted into a subtraction section to obtain a softness effect.