JPS63180287A - Adapting type luminance and chromaticity separating circuit - Google Patents

Abstract

PURPOSE:To improve the erroneous decision of correlation and to prevent the deterioration in horizontal resolution by deciding the size of vertical high-pass components included in a chromaticity signal in an interline correlation detection circuit and selecting an output whose vertical correlation is strong. CONSTITUTION:The output of the interline correlation detection circuit 18 is supplied to a multiplexer 26. The output chromaticity signals of coefficient units 16 and 17 are supplied to the multiplexer 26 through adjustment delay circuits 19 and 20. Said signals are selected by a decision signal and supplied to a band filter 27 in which a color carrier frequency fSC is set to a center frequency. Consequently, the chromaticity signal in which the vertical high-pass component of the luminance signal is less is derivated, and the signal is supplied to a subtractor 31. Since the output signal of a 1H memory 12 is supplied to the subtractor 31 through an adjustment delay circuit 30, the luminance signal is derivated. Thus, the erroneous decision of the correlation is improved and the deterioration of horizontal resolution can be prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a digital television receiver that digitally processes a baseband video signal, and particularly relates to a digital television receiver that digitally processes a baseband video signal. The present invention relates to an adaptive luminance/chromaticity separation circuit for separating a signal (hereinafter referred to as Y) and a chromaticity (hereinafter referred to as C) signal.

(Prior Art) In recent television receivers, in baseband video signal processing, comb filters are widely used for luminance/chromaticity (hereinafter referred to as Y/C) separation.

Y/C separation using a comb filter has the advantage of improving horizontal resolution and reducing cross color, compared to conventional Y/C separation methods using trap circuits and bandpass filters. However, in a part of the picture where the C signal changes in the vertical direction, the C signal leaks into the Y signal, causing dot interference.

Adaptive Y/C separation is a Y/C separation method that improves this problem. This adaptive Y/C separation is a method of detecting correlation in the vertical and horizontal directions for each pixel, and performing Y/C separation using a filter in the direction of strong correlation, that is, the direction in which the pattern changes less. Specifically, the magnitude of the horizontal difference value and the vertical difference value are detected, and the magnitude is determined. When the horizontal difference value is large, it is determined that the vertical correlation is strong, and the comb filter is applied. When the vertical difference value is large, it is determined that the horizontal correlation is strong, and Y/C separation is performed using a trap circuit and a bandpass filter.

(Problems to be Solved by the Invention) As mentioned above, in the Y/C separation using a comb filter, when the C signal changes in the vertical direction, the C signal component leaks into the Y signal, causing dot interference on the screen. It has a hail problem. Furthermore, even if adaptive Y/C separation is adopted, since the magnitude of the horizontal difference value and the vertical difference value are detected separately, parts of the picture that contain many diagonal components of the Y signal are It is difficult to judge the correlation in the image, and it is easy to cause erroneous judgments and deteriorate the image quality. Furthermore, it is difficult to determine the correlation even for patterns in which only the horizontal high-frequency component of the Y signal (near the color carrier frequency fsc) exists, and Y/C separation using a trap circuit and a bandpass filter is necessary to avoid misjudgment. selectively, tended to result in a degradation of horizontal resolution.

SUMMARY OF THE INVENTION An object of the present invention is to provide an adaptive luminance/chromaticity separation circuit that can improve correlation control and prevent deterioration of horizontal resolution, which tends to occur with adaptive Y/C separation.

[Structure of the Invention] (Means for Solving the Problem) This invention provides that when there is a change in the chromaticity signal in the vertical direction (the correlation in the vertical direction is weak), the luminance signal also changes statistically. Focus on that. An IH video signal delayed by one horizontal scanning period (hereinafter IH) and a 2H video signal delayed by two horizontal scanning periods are obtained from the input video signal, the input video signal is used as the IH video signal, and the first chromaticity signal is separated. and a second comb filter that further separates a second chromaticity signal using an IH video signal and a 2H video signal. Then, the magnitude of the vertical high-frequency components included in the first and second chromaticity signals is determined by the inter-line correlation detection circuit, and the comb-shaped filter output (
In other words, the output with the stronger vertical correlation is selected and used as a chromaticity signal to obtain luminance and chromaticity separation.

(Operation) By the above means, the chromaticity signal selected by the determination circuit is
Since a luminance signal with few high-frequency components in the vertical direction, that is, one with a strong vertical correlation, is used, dot interference due to luminance signals leaking into the chromaticity signal in areas with no vertical correlation will not occur. do not have. In addition, in the part of the picture where the horizontal high-frequency component of the luminance signal exists, the two vertical filters are both comb-shaped filters, so regardless of the judgment, accurate luminance and chromaticity separation with less cross color on the screen is possible. Realized.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows one embodiment of the present invention, and an input terminal 11 is supplied with a baseband video signal sampled and digitized using a clock of, for example, 4 fsc (fsc is the color subcarrier frequency). The sampling phase is phase-locked to the ±U axis and ±V axis of the chromaticity signal. , this video signal is supplied to an IH memory 12 having a delay time of one horizontal period (hereinafter referred to as IH),
The delayed video signal delayed by this IH memory 12 is further supplied to an IH memory 13.

The IH memory 12 and the subtracter 14 constitute a comb filter,
The video signals on the input side and output side of the IH memory 12 are subjected to subtraction processing in a subtracter 14, and the output of this subtracter 14 is the first
is derived as an extracted chromaticity signal and supplied to the coefficient unit 16. The IH memory 13 and the subtracter 15 also constitute a comb filter, and the video signals on the input and output sides of the IH memory 13 undergo subtraction processing in the subtracter 15.
The output of 4 is derived as the first extracted chromaticity signal and is sent to the coefficient unit 1.
7.

The output chromaticity signals of the coefficient multipliers 16 and 17 are respectively supplied to low-pass filters 21 and 22 constituting the inter-line correlation detection circuit 18. The low-pass filters 21 and 22 are filters that remove the chromaticity signal and extract vertical high-frequency components of the luminance signal contained in the chromaticity signal. The respective outputs of the low-pass filters 21 and 22 are supplied to absolute value circuits 23 and 24, respectively, and their absolute values are determined, and a comparison circuit 25 determines whether the outputs are large or small.

Here, the function of the inter-line correlation detection circuit 18 will be explained. Usually, the chromaticity signal separated by the comb filter will contain vertical high-frequency components of the luminance signal if there is a color change in the vertical direction, that is, there is no correlation. On the other hand, the two chromaticity signals obtained by the above circuit are chromaticity signals obtained by correlation processing at different vertical positions, so if there is a color change in the vertical direction at one position and there is no correlation, then , the proportion of the luminance signal containing vertical high-frequency components is large, and if there is no vertical color change at the other position, that is, the correlation is strong, the proportion of the luminance signal containing vertical high-frequency components is small. become. Therefore, by determining and using a chromaticity signal with a strong vertical correlation, that is, a chromaticity signal with less high-frequency components of the luminance signal, good luminance/chromaticity separation can be achieved.

The determination output obtained by the interline correlation detection circuit 18 is supplied to the multiplexer 26 to control its selection operation. The output chromaticity signals of the coefficient multipliers 16 and 17 are supplied to the multiplexer 26 via respective adjustment delay circuits 19 and 20 (having a delay amount to compensate for the delay of the inter-line correlation detection circuit 18). One of them is selected based on the determination signal and supplied to a bandpass filter 27 whose center frequency is fsc. As a result, a chromaticity signal containing less vertical high-frequency components of the luminance signal is outputted to the output terminal 28.

The chromaticity signal at the output terminal 28 is also supplied to a subtracter 31 for separating the luminance signal. In other words, the output video signal of the IH memory 12 is sent to the subtracter 31 by the adjustment delay circuit 3.
Since the subtracter 31 outputs the luminance signal from the subtracter 31, the subtracter 31 outputs the luminance signal to the output terminal 32. The adjustment delay circuit 30 is for obtaining time adjustment of the luminance signal and the chromaticity signal.

One embodiment of the present invention is configured as described above, and can always selectively use chromaticity signals with strong vertical correlation, thereby reducing dot interference that conventionally tends to occur in areas with no vertical correlation. .

The present invention is not limited to the above embodiment, and as shown in FIG. 2, two luminance signals may be prepared and the signal with a strong vertical correlation may be selected. .

The difference between FIG. 2 and FIG. 1 is that the IH memory 12
．． 13 to form two luminance signal separation comb-type filters, and a section for selectively deriving one of the two luminance signals, the other parts are the same as the circuit shown in FIG. Therefore, the same circuits as in Fig. 1 are given the same symbols,
Explain the different parts.

The IH memory 12 and the adder 41 constitute a comb-type filter for separating luminance signals, and the adder 41 adds the video signals on the input side and the output side of the IH memory 12 to obtain a first luminance signal as an output. . The IH memory 13 and the adder 42 also constitute a comb-type filter for separating luminance signals, and the adder 42 adds the video signals on the input side and output side of the IH memory 13, and outputs the second luminance signal. obtain. The 1st to 1st second luminance signals are supplied to adjustment delay circuits 45 and 46 via coefficient multipliers 43 and 44, respectively. This adjustment delay circuit 45.
46 output luminance signals are input to a multiplexer 47,
One of the luminance signals, that is, a luminance signal with a strong vertical correlation, is selected and derived.

The luminance signal derived from the multiplexer 47 is further input to an adder 49 via a coefficient multiplier 48. The adder 49 is supplied with the high-frequency component of the luminance signal included in the chromaticity signal via a low-pass filter 50.
Here, the luminance signal becomes a signal with a richer high frequency range and is outputted to the output terminal 51. The signal from the low-pass filter 50 includes diagonal components of the luminance signal.

[Effects of the Invention] As explained above, according to the present invention, it is possible to reduce the dot interference that conventionally occurs in picture parts where there is no vertical correlation.

In addition, compared to conventional methods that tend to cause incorrect correlation determination when the luminance signal contains many diagonal components, this invention can perform luminance and chromaticity separation with high accuracy because it is processed entirely using a comb filter. be.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the invention, and FIG. 2 is a circuit diagram showing another embodiment of the invention.

Claims (1)

[Claims] A baseband video signal sampled at a predetermined frequency and digitized is input, and a first delayed video signal is delayed by one horizontal period with respect to the input video signal, and a first delayed video signal is delayed by two horizontal periods. a second delayed video signal, and a first color having a vertical high frequency component of a luminance signal and a chromaticity signal component from the input video signal and the first delayed video signal. a first comb-type filter that separates a chrominance signal; and a second comb filter having a vertical high frequency component of a luminance signal and a chrominance signal component using the first delayed video signal and the second delayed video signal. a second comb-type filter that further separates the chromaticity signal; and a second comb-type filter that separates and extracts vertical high-frequency components of each of the luminance signals included in the first and second chromaticity signals, takes the absolute value of each, and calculates the magnitude. an inter-line correlation detection circuit for determining; and receiving the first chromaticity signal and the second chromaticity signal as input, and determining which one has the stronger correlation between lines based on the determination signal from the inter-line correlation detection circuit; In other words, a luminance chromaticity separation circuit comprising a selection means for selectively deriving either the first or second chromaticity signal having the smaller vertical high frequency component.