KR910008021B1 - Coring circuit for digital video signal processing - Google Patents

Abstract

The circuit for compensating the vertical and horizontal sharpness compensates the input image, signal which absolute level is greater than the preset one, but sets the dead zone without compensation against to the signal which absolute level is low than the preset one. The circuit includes a selector (100) for sending out the coring data (DC) and its inverted data selectively according to the polarity of the band-pass filtered Y signal, an adder (200) for adding the output of the selector (100) to the Xi signal, a logic stage (300) for exclusive ORing the output of a subtracter (200) and Xi, and a generator (400) for generating the output of the coring circuit (X0).

Description

Coring circuit for digital video signal processing

1 is an exemplary diagram of contour correction waveforms.

2 is a horizontal contour correction circuit diagram of an analog circuit.

3 is a horizontal contour correction circuit in which a coring circuit is added to FIG.

4 and 6 show coring characteristics.

5 is a horizontal contour correction circuit diagram of a digital image processing circuit.

7 is a circuit diagram of the present invention.

* Explanation of symbols for main parts of the drawings

54, ADDR1: Adder 53: Multiplier

200: subtractor 300: logic means

INV1, INV2: Inverter 400: Endgate

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal and vertical contour correction circuit in a digital image signal processing apparatus. In particular, a dead zone is set for a signal level whose absolute value is smaller than a predetermined level among input image signals to prevent correction. The present invention relates to a coring circuit that corrects only a signal level having a large absolute value.

In general, horizontal and vertical outline correction means that signal processing is performed so that a boundary line is clear when a video signal is displayed on a CRT (Cathod ray tube) in order to obtain a sharp image in a video signal processing apparatus such as various TVs. Also known as peering or sharpness control.

That is, for example, as shown in (a) of FIG. 1, pre-shoot (PS) and overshoot are performed for signal waveforms in which the image drops rapidly from black to white, or signal waveforms rapidly rising from white to black. (Over shoot) to make the outline sharper to improve the sharpness.

In order to compensate for the contour as described above, the conventional horizontal contour correction circuit, which is conventionally used in an analog circuit, is configured as shown in FIG. 2 and operated as follows. Since the vertical outline correction is also the same as the horizontal outline correction, the following description will be given by taking the case of the horizontal outline correction as an example.

First, the band pass filter 10 filters a specific frequency component (boundary frequency component) of the luminance signal.

The filtered signal was compensated by allowing the user to adjust the magnitude by using a sharpness terminal (usually using a variable resistor) in the gain control unit 20 and then add it.

However, in the conventional video signal transmission system, a noise component is usually mixed, and as a result, even when the compensation circuit of FIG. 2 is used as it is, the noise component is unnecessarily contour-corrected and the image is deteriorated.

Therefore, in order to compensate for the above disadvantage, the coring circuit 30 is added between the band pass filter 10 and the gain control unit 20 as shown in FIG. 3, and the input signal level of ± as shown in FIG. 4 is set to "0". Without gain adjustment, it is added to the original signal without compensation, and the large input signal is output so that the signal level minus the level of the dead zone is added to the original input signal after the gain adjustment. .

However, the contour compensation circuit as described above has a problem that it can be applied only to an analog circuit and thus cannot be used in a digital image processing apparatus such as a digital television or an ID television.

Accordingly, an object of the present invention is to provide a coring circuit of horizontal and vertical contour compensation circuits for a digital image signal processing apparatus.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

5 is a block diagram of a horizontal contour correction circuit of a digital image signal processing circuit. The digital bandpass filter 51 inputs and filters the digital luminance signal Y, and the dead zone setting data after predetermined processing of the filtering signal. A digital coring circuit 52 for comparing and outputting a predetermined state signal, a multiplier 53 for adjusting gain by multiplying the coring output with a predetermined multiplier data, and the output of the multiplier 53 and an input digital luminance signal Y It is composed of an adder 54 to add ().

FIG. 6 is a characteristic diagram of a coring output, and FIG. 7 is a circuit diagram of the present invention. The luminance signal is input by inputting coring data (Dead zone setting data DC) generated from a microcomputer by a user through a remote controller or a key input. Selector for selectively outputting the inversion signal of the coring data (Dc) and the coring data (DC) in accordance with the state of the sign bit (MSB: Most Signiflcant Bit) of the signal (X) band-pass-filtered (Y) An exclusive logical sum by inputting an output of the selector 10 and a subtractor 200 for subtracting the filtering signal xi, the output of the subtractor 200 and the bit signal of the filtering signal xi. Logic means 300, and an output unit 400 for generating a coring circuit output x0 by performing a logical multiplication on the output of the logic means 300 and the n-bit output of the subtractor 200, respectively.

The present invention will be described in detail based on the above configuration.

In the horizontal and vertical contour correction circuit of FIG. 5, when n-bit digital image luminance signal data Y passes through the bandpass filter 51, a specific frequency component is detected.

In this case, this value may be positive or negative. Therefore, it is assumed here that the data passing through the bandpass filter 51 is xi, and the dead zone data is called Dc, and the data passing through the coring circuit 52 is x0. Data is a signal generated from the microcomputer set by the user through the remote control or key input.

Dc 일시 x0=xi-Dc .............................. (1)xi

Dc Date and Time x0 = xi-Dc ........................ (1)

xi〈Dc 일시 x0=0 ....................................... (2)0

xi <Dc Date and Time x0 = 0 ........................ (2)

xi〈0 일시 x0=0 ....................................... (3)-Dc

xi <0 Date and Time x0 = 0 ..................... (3)

xi <-Dc Date and Time x- = xi + Dc ..... (4)

0일 경우 출력신호 x0=xi-Dc인데 xi-Dc 결과가 음수인 경우 x0=0이다.Representing (1)-(4), first, the input signal xi is xi

If 0, output signal x0 = xi-Dc, but if xi-Dc result is negative, x0 = 0.

0일 경우 출력신호는 x0=xi+Dc인데 xi+Dc 결과가 양수인 경우 x0=0로 한다.Secondly, the input signal xi is xi

If 0, output signal is x0 = xi + Dc, but if xi + Dc result is positive, x0 = 0.

을 선택하여 출력하고, 반대로 상기 부호비트가 "1"일시에는 코어링 데이타(Dc)를 그대로 출력한다.Therefore, according to an embodiment of the present invention of FIG. 7, the selector 100 under the control of the decoded band bath filtering signal xi may input input coring data when the code bit of the band pass filtering signal is “0”. Inverting output of (Dc)

Is selected, and on the contrary, when the code bit is " 1 &quot;, the coring data Dc is output as it is.

At this time, the subtraction unit 200 inputs the output of the selection unit 100 and the band pass filtering signal xi to invert the bad path filtering signal xi to output the selection unit 100 and the “high” state. It is added with the predetermined signal oi.

At this time, the output of the subtraction unit 200 and the band pass filtering signal xi are inputted to the exclusive oragate 300 to perform an exclusive OR.

That is, the exclusive oragate 300 generates an output of a "high" state only when the two signals are the same.

The output unit 400 then multiplies the output of the exclusive oragate G1 and the output of the n-bit adder 200 to generate an n-bit coring circuit output x0.

The output characteristic curve by the circuit operation is shown in FIG. Therefore, when the overall operation process of the present invention for obtaining the output characteristics as shown in FIG. 6 will be described once again, areas (A) and (B) should be corrected to "0". In the case of a positive number, the output of the subtraction unit 200 may be expressed by Equation 5 below by the two's complement data processing method.

+1) ............................... (5)xi-DC = xi + (

+1) ............................... (5)

Therefore, first, since the filtering data xi is positive and the subtractor 200 output data is negative, the bit code is "0" and "1", respectively, so that the output of the exclusive oragate 300 is "0". Becomes Accordingly, one input of each of the n AND gates of the output unit 400 is set to "0", and the final coring circuit output X0 is set to "0".

Secondly, even when the band pass filtering signal data xi is negative and the adder output data is positive, the sign bits are respectively " 1 " and " 0 ", so that the coring circuit output x0 is " 0 ".

Therefore, no correction is made for small signal levels.

By performing the coring function as described above, there is an advantage that the contour compensation effect can be enhanced by preventing the correction of the small signal level such as noise.

Claims (1)

In the coring circuit of the horizontal and vertical contour correction apparatus of a digital video signal, the coring data dead zone setting data Dc is input and the luminance signal Y is band-pass filtered according to the code bit state of the signal xi. A selector 100 for selectively outputting the coring data DC and an inverted signal of the coring data DC, and a subtractor for subtracting the output of the selector 10 and the filtering signal xi; 200, logic means 300 for exclusively ORing the subtracter 200 output and the filtering signal xi code bits, and the n bits of the logic means 300 output and the subtractor 200. And an output unit (400) for outputting a coring circuit output (x0) by logically multiplying the outputs.

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