KR100780724B1 - Sharpness enhancement apparatus for dtv - Google Patents

Abstract

,(1-

)를 곱하는 컨버전비율 조정기(34A),(34B)와; 상기 컨버전비율 조정기(34A),(34B)의 출력신호를 합산처리하여 버퍼(36)에 출력하는 가산기(35)로 구성된 수평/수직 포맷 컨버터의 앞단에, 필터 주파수의 중앙대역을 강조시키기 위한 필터계수를 구하여 시간영역에서 표본화된 입력신호에 컨벌루션시키는 방식으로 영상의 윤곽을 강조하는 필터(31)를 포함시킴으로써 달성된다. The present invention relates to a technique for improving the sharpness of an image by using a horizontal filter in the image signal processing unit of the digital TV. The present invention comprises a buffer 32 for temporarily storing digital image data input from the outside; A delay unit 33 for delaying a predetermined time in order to synchronize the image data to be branched after being output from the buffer 32; In order to adjust the conversion ratio for the image data directly output from the buffer 32 and the image data output through the delay unit 33, a conversion ratio adjustment coefficient

,(One-

Conversion ratio adjusters 34A and 34B multiplied by A filter for emphasizing the center band of the filter frequency at the front end of the horizontal / vertical format converter composed of an adder 35 that sums the output signals of the conversion ratio adjusters 34A and 34B and outputs them to the buffer 36. This is accomplished by including a filter 31 that emphasizes the outline of the image in such a way as to obtain a coefficient and convolve it with the sampled input signal in the time domain.

Description

SHARPNESS ENHANCEMENT APPARATUS FOR DTV}

1 is a block diagram of a conventional sharpening enhancement process using an unsharp masking technique;

(A)-(d) is a waveform diagram of each part of FIG.

3 is a block diagram of a sharpness improving device of a television receiver according to the present invention;

4A is a graph of signals sampled in the time domain.

4B is a band characteristic graph of a signal sampled in the frequency domain.

4C is a graph of frequency characteristics of a 5-tap sync filter.

Figure 4 (d) is a graph showing the frequency components of the filter in the frequency domain.

5A is a graph of signals sampled in the time domain.

5B is a band characteristic graph of a signal sampled in the frequency domain.

5C is a graph of frequency characteristics of a truncative filter.

Figure 5 (d) is a graph showing the frequency components of the filter in the frequency domain.

FIG. 6 is a table exemplarily showing horizontal filter coefficients for each filter step in FIG. 3. FIG.

*** Explanation of symbols for the main parts of the drawing ***

31: filter 32,36: buffer

33: delay 34A, 34B: conversion ratio regulator                 

35: adder

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving sharpness in a digital TV, and more particularly, to an apparatus for improving the sharpness of a digital TV suitable for improving the sharpness of an image by using a horizontal filter in the image signal processor.

In general, the enhancement of image sharpness in a video device such as a digital TV refers to a function of adjusting the sharpness of an outline to have a clear feeling, and unsharp masking, high pass filtering, and a second function (2nd derivative). ), And the like. Among them, the unsharp masking method is widely used because it has an advantage of controlling the degree of sharpening.

FIG. 1 is a block diagram of a conventional sharpness enhancement process using an unsharp masking technique, which will be described below with reference to FIG. 2.

3 평균필터(11)에 의해 고역필터링되어 도 2의 (b)와 같은 형태로 출력된다. 감산기(12)는 상기 입력신호(A)에서 상기 3

3 평균필터(11)의 출력신호(B)를 감산처리하여 이로부터 도 2의 (c)와 같은 처 성분의 신호(C)가 출력된다. The output signal passing through the image signal processor is controlled by the unsharp masking technique in the chroma processor for image control. The input signal A as shown in FIG.

The high-pass filter is performed by the 3 average filter 11, and is output as shown in FIG. The subtractor 12 is the 3 in the input signal (A)

The output signal B of the average filter 11 is subtracted, and the signal C having the destination component as shown in FIG.

)를 곱하고, 이의 출력신호가 가산기(14)에서 원래의 입력신호(A)와 가산되어 포화기(saturator)(15)의 출력신호(D)가 도 2의 (d)와 같이 윤곽이 보정된 형태로 출력된다. In addition, the multiplier 13 has a weight (suitable for the output signal C of the subtractor 12).

), And its output signal is added to the original input signal A in the adder 14 so that the output signal D of the saturator 15 is contour-corrected as shown in FIG. Output in the form

However, in the conventional sharpening enhancement technique by the unsharp masking technique, since the sharpness is adjusted for all input signal components, a separate filleting of the noise components is required, and defects that cause damage to the original signal are eliminated. there was.

Accordingly, an object of the present invention is to improve sharpness by using a horizontal filter in front of a format converter in a video display processor (VDP) for digital signal processing without using a separate video controller for controlling the sharpness of a digital TV signal. The present invention provides a device for improving the sharpness of a digital TV.

,(1-

)를 곱하는 컨버전비율 조정기(34A),(34B)와; 상기 컨버전비율 조정 기(34A),(34B)의 출력신호를 합산처리하여 버퍼(36)에 출력하는 가산기(35)로 구성한 것으로, 이와 같이 구성한 본 발명의 작용을 첨부한 도 4 내지 도 6을 참조하여 상세히 설명하면 다음과 같다.FIG. 3 is a block diagram showing an embodiment of an apparatus for improving digital TV sharpness according to the present invention. As shown therein, a filter coefficient for emphasizing the center band of a filter frequency is obtained and sampled in the time domain. A filter 31 for emphasizing the outline of the image in a convolutional manner to the signal; A buffer 32 for temporarily storing a predetermined amount of image data output from the filter 31; A delay unit 33 for delaying a predetermined time in order to synchronize the image data to be branched after being output from the buffer 32; In order to adjust the conversion ratio for the image data directly output from the buffer 32 and the image data output through the delay unit 33, a conversion ratio adjustment coefficient

,(One-

Conversion ratio adjusters 34A and 34B multiplied by 4 to 6 which add the processing signals of the conversion ratio adjusters 34A and 34B to the buffer 36 and add them to the buffer 36. FIG. Detailed description with reference to the following.

The filter 31, installed at the front of the horizontal (H) / vertical (V) format converter, filters FIR in both directions of H / V to eliminate aliasing that may occur during original down-conversion. Do this. However, most of them are not so severe that they are not used.

Therefore, in the present invention, it is possible to improve the sharpness of the image by using the filter 31, the processing thereof will be described with reference to FIG.

A sampled signal as shown in FIG. 4A input to the filter 31 has a band characteristic as shown in FIG. 4B. In other words, according to the sampling theory, the highest frequency component does not exceed half of the sampling frequency fs, and the high frequency component of the signal is distributed centrally.

A filter coefficient is calculated such that the frequency component of the filter (5: Sink filter B) convolutiond with the sampled signal has the same characteristics as D in FIG. The collection product of the sampled signal and the filter coefficient in the time band is the same as the arithmetic product in the frequency band, and thus has a final frequency output characteristic such as E in FIG.

As a result, the center band of the signal output from the filter 31 is emphasized as shown in E of FIG.                     

For reference, the gain of the center portion of the frequency band may be adjusted to a desired degree by changing the center filter coefficient (for example, D1-> D2-> D3).

On the other hand, Figure 5 shows an example of reducing the sharpness using the above principle, in which a truncated (truncated) filter is used. 6 is a table showing horizontal filter coefficients for each step of the filter 31 by way of example.

와 곱해지고, 다른 한편으로는 지연기(33)를 통한 후 또 다른 컨버전비율 조정기(34B)에 공급되어 컨버전비율 조정계수 (1-

)와 곱해진다. 이후, 상기 컨버전비율 조정기(34A),(34B)의 출력신호가 가산기(35)에서 합해진 후 버퍼(36)를 통해 출력된다. The output signal of the buffer 31 is temporarily stored in the buffer 32 and then supplied to the conversion ratio adjuster 34A on the one hand to convert the conversion ratio adjustment coefficient.

Multiplied by and supplied to another conversion ratio adjuster 34B after passing through the delay unit 33 to convert the conversion ratio adjustment coefficient (1-1).

Multiply by Thereafter, the output signals of the conversion ratio adjusters 34A and 34B are summed in the adder 35 and then output through the buffer 36.

As described in detail above, the present invention obtains the filter coefficient so that the frequency characteristic of the horizontal filter in front of the format converter in the VDP for digital signal processing is emphasized in the center band, and convolves the sampled input signal, thereby providing clarity without additional cost. There is an effect that can be improved.

In addition, there is an effect that can be solved to increase the noise component at the source, and by using a separate low-pass filter is minimized the signal loss has the effect of improving the image quality.

Claims (2)

In horizontal / vertical format converter in VDP for digital signal processing of digital TV, a filter that emphasizes the outline of the image by obtaining a filter coefficient to emphasize the center band of the filter frequency and convolving the sampled input signal in the time domain. Apparatus for improving the sharpness of the television receiver comprising a. The apparatus of claim 1, wherein the filter is configured to perform a 5-tap sink filter function.

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