JPS6141290A - Y/c separator of color television signal - Google Patents

Abstract

PURPOSE:To reduce effectively the deterioration of picture quality by providing a synthesization control means which changes each weighting of a synthesizing means according to the size of the detected horizontal and vertical components and controlling the specific gravity of correlation separation and the frequency separation of the 1st and 2nd Y/C separators in response to the results of detection of both horizontal and vertical components. CONSTITUTION:A synthesization control circuit 50 supplies a coefficient (k) to a synthesizing circuit 30. The coefficient (k) has the value accordant with the combination of an amount A showing the intensity of the vertical component supplied from a vertical component detecting circuit 40 and an amount B showing the intensity of the vertical component given from a vertical component detecting circuit 60. The coefficient (k) is reduced with increase of the amount A. In other words, the specific gravity of the signal occupied and coorelation separated in a synthetic signal is reduced as the intensity of the horizontal component is increased. This reduces the deterioration of picture quality due to the deterioration of correlation. While the (k) increase with increase of the amount B. In other words, the specific gravity of the signal occupied and frequency separated in the synthetic signal is reduced as the intensity of the vertical component is increased. This reduces the deterioration of picture quality owing to the cross colors or color ooze.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a Y/C separation device for separating a luminance signal and a color signal of a color television signal.

Conventional technology In standard color television systems such as the NTSC system, the luminance signal and color signal are interleaved in frequency, so it is generally difficult to completely separate the two on the receiving side. be.

'The conventional Y/C separation methods are one that uses the frequency spectrum of the video signal to separate it on the frequency axis, and one that uses the correlation between adjacent scanning lines of the video signal to separate it on the time axis. It is broadly divided into those that do.

Hereinafter, in this specification, the former will be referred to as a frequency separation method, and the latter will be referred to as a correlation separation method.

In the frequency separation method, as shown in FIG. 5A, the input terminal 1
By dividing the above video signal into two and supplying each to a low-pass filter circuit 4 and a band-pass filter circuit 5, respectively, to output terminals 2 and 3.

It is configured to obtain the original luminance signal and color signal by dividing Y/C. Alternatively, as shown in FIG. 5B, the video signal on input terminal 1 is divided into two.

By supplying one to the bandpass filter circuit 5, a color signal is obtained at the output terminal 3, and by subtracting the color signal from the video signal in the subtraction circuit 6, the output terminal 2
In this specification, each of the luminance signal and chrominance signal separated by the two-frequency separation method will be referred to as a luminance signal separated by two frequencies and a chrominance signal separated by one frequency.

On the other hand, in the correlation separation method, as shown in FIG. 5C, a delay circuit 7. It includes an addition circuit 8 and a subtraction circuit 9, and is configured to obtain a luminance signal Y and a color signal C at output terminals 2 and 3, respectively. This correlation separation method takes advantage of the fact that when the same video signal appears at the same horizontal position on adjacent scanning lines, a phase relationship of opposite phases is established for the luminance signal and the in-phase three color signals. .

Hereinafter, in this specification, the luminance signal and chrominance signal separated by the correlation separation method will be referred to as a correlation-separated luminance signal and a correlation-separated chrominance signal, respectively.

Problems to be Solved by the Invention The above-mentioned frequency separation method has problems with color unevenness (cross color) caused by the high frequency components mixed into the color signal side when the luminance signal contains a high frequency component that is about the frequency of the color subcarrier. )
There is a problem that occurs.

There is also the problem that blurring of two colors occurs when one color signal includes a high frequency component.

On the other hand, since the above-described correlation separation method is based on the assumption that there is a correlation between scanning lines, if this assumption is violated, Y/C separation becomes insufficient and image quality deteriorates. especially.

When the change in color signal between adjacent scanning lines is large 1 For example, when a colored horizontal line or a colored outline is displayed on the screen, the change in 1 color signal is correlated and separated into a luminance signal. There is also the problem that the dot crawling is disturbed by being superimposed on the image.

Composition of the invention Means to solve problems The present invention solves the problems of the prior art described above.

A Y/C separator based on a correlation separation method, a Y/C separator based on a single frequency separation method, a synthesizing means for weighting and synthesizing the luminance signal and color signal received from each of these Y/C separators, and one display. The apparatus is configured to include means for detecting a horizontal component and/or vertical component within the screen, and means for changing the weighting of the synthesis circuit according to the magnitude of the detected component.

The following five examples will explain the effects of the present invention in detail.

Embodiment FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, 10 is a Y/C separator using a correlation separation method, 20 is a Y/C separator using a frequency separation method, and 30 is a Y/C separator using a frequency separation method.
40 is a synthesis circuit that weights and synthesizes the luminance signal and color signal separated by the Y/C separators 10 and 20, and 40 is a display screen based on the amount of change between scanning lines of the correlation-separated luminance signal and chrominance signal. horizontal component detection circuit for detecting the horizontal component in 5
0 is the synthesis time a30 based on the size of the detected horizontal component.
This is a composite control circuit that controls the

The Y/C separator 10 using the correlation separation method includes a delay circuit 11 . It includes an addition circuit 12 and a subtraction circuit 13. A part of the video signal input to this Y/C separator 10 is
In the adder circuit 12, it is added to the video signal of one horizontal scanning period before to generate a correlation-separated luminance signal Y1. On the other hand, other parts of the video signal input to the Y/C separator 10 are as follows.

In the subtraction circuit 13, it is added to the video signal of one horizontal scanning period before to generate a correlation-separated color signal C1. The correlation-separated luminance signal Y1 and color signal C1 are supplied to multiplication circuits 31 and 34 in the synthesis circuit 30, respectively.

A Y/C separator 20 using a frequency separation method includes a low-pass filter circuit 21 that passes only a luminance signal with a frequency lower than the frequency band of two color signals, and a color signal near the color subcarrier of 3.58 hz. It is equipped with a bandpass filter circuit 22 that allows the signal to pass through. A portion of the video signal input to the Y/C separator 20 generates a frequency-separated luminance signal Y2 at the output side of the low-pass filter circuit 21. On the other hand, Y/C separation circuit 2
The other part of the video signal input to the bandpass filter circuit 22 generates a frequency-separated color signal C2 at the output side of the bandpass filter circuit 22. The frequency-separated luminance signal Y2 and color signal C2 are supplied to multiplication circuits 32 and 33 in the synthesis circuit 30, respectively.

Composite drawing I! In multiplication circuits 31 and 34 within t30.

The correlation-separated luminance signal Yl and color signal C1 are multiplied by the coefficient (1-k) supplied from the nine synthesis control circuit W150. On the other hand, in the multiplication circuits 32 and 33 in the 5-synthesizing circuit 30, the luminance signal Y2 and the color signal C2 separated by 3 frequencies are multiplied by the coefficient k supplied from the 9-synthesizing control circuit 50. The outputs of each of the multiplier circuits described above are added in adder circuits 35 and 36, and -Y
2° composite color signal (1-k) -02 is output to CI+. The synthesis control circuit 50 controls the coefficients (1-k) based on the output A of the horizontal component detection circuit 40.

1, + The horizontal component detection circuit 40 is supplied with the luminance signal Yl and the color signal C1, which have been correlated and separated by the Y/C separator 10. The difference between the luminance signal Y1 and the luminance signal Y1 delayed by one horizontal scanning period by the delay circuit 41 is extracted by the subtraction circuit 42, converted to a positive polarity signal by the absolute value circuit 43, and then converted to a positive polarity signal by the addition circuit 47. supplied to Similarly, nine color signals C1,
The difference from the color signal C1 delayed by one horizontal scanning period by the delay circuit 44 is extracted by the subtraction circuit 45, and
After being converted into a positive polarity signal by the im path 46.

The signal is supplied to an adder circuit 47. The sum of the absolute values of the inter-scanning line variations of the luminance signal and color signal output from the adder circuit 47 is:
The synthesis control circuit 50 serves as the output A of the horizontal component detection circuit 40.
supplied to Upon receiving this, the synthesis control circuit 50 controls the coefficient k so that it is approximately proportional to the input A.

Therefore, while the sum A of the inter-scanning line variations of the luminance signal and chrominance signal between adjacent scanning lines is small, that is, while the horizontal component within the display screen is weak, the correlated luminance signal Y1 and chrominance signal C1 are large. A composite luminance signal and a composite color signal having specific gravity are output from the composite circuit 30. As a result, cross color in which the high frequency component of the luminance signal leaks into the color signal side and color blurring due to the high frequency component of the two color signal are reduced.

On the other hand, when the sum A of the amount of change in the luminance signal and chrominance signal between adjacent scanning lines becomes large, that is, when the horizontal component within the display screen becomes strong, the luminance signal Y2 and the chrominance signal C2, which are separated by two frequencies, are synthesized with a large weight. A luminance signal and a composite color signal are output from the composition circuit 30. As a result, dot crawl caused by cross color and color signals leaking into the luminance signal side is reduced.

FIG. 2 is a block diagram showing the configuration of another embodiment of the present invention. In this figure, components 10, 20, 30, 40, and 50, which have the same reference numerals as in FIG. 1, are the same as the corresponding components already described with respect to FIG. In this example.

The horizontal component detection circuit 40 is configured to detect the horizontal component based on the amount of change between scanning lines in only the color signal. Additionally, a vertical component detection circuit 60 is added that detects a vertical component within the display screen based on the high frequency components of the Y/C separated luminance signal and color signal. In addition, Y/
C separator 10.

Two delay circuits 11a and 11b are provided to delay the video signal by one horizontal scanning period.

In the Y/C separator 10 based on correlation separation, the subtraction circuit 1
3b outputs the sum of color signals included in the 2H delayed video signal and the IH delayed video signal. Also, N$i
The arithmetic circuit 13a outputs the sum of the IH-delayed video signal and the color signal contained in the video signal currently being supplied to this circuit. Each of the above sums is added in an adder circuit 14, and then multiplied by 1/4 in a multiplier circuit I5 to produce 3H of one color signal.
gives the average value over This correlation-separated color signal C
1 is supplied to the 9 synthesis circuit 30 and the subtraction circuit 16. The subtraction circuit 16 receives the color signal C that has been correlated and separated as described above.
From I and IH delayed video signals.

The luminance signal Y1 is extracted and supplied to the synthesis circuit 30.

The Y/C separation circuit 20 by frequency separation includes a bandpass filter circuit 22 and a subtraction circuit 23, and supplies the frequency-separated luminance signal Y2 and color signal C2 to the synthesis circuit 30, respectively. The synthesis circuit 30 synthesizes the luminance signal and color signal supplied from each Y/C separator in F and the weighting coefficients k and (1-k) supplied from the synthesis control circuit 50 with nine composite luminance signals. Create a color signal.

Between the horizontal component detection circuit 40 and the Y/C separator 10,
LH delay circuit 11a, llb, subtraction circuit 13a, 13b
are shared. The subtraction circuit 44 is.

The amount of color change between scanning lines is output from the color signals received from each of the subtraction circuits 13b and 13a. This amount of color change is converted to positive polarity in the absolute value circuit 43 and is supplied to the synthesis control circuit 50 as the output A of the horizontal component detection circuit 40.

The vertical component detection circuit 60 is supplied with a frequency-separated luminance signal Y2 and a color signal C2.

From the luminance signal Y2, only frequency components higher than the color subcarrier frequency are extracted by the high-pass filter circuit 61.

This high frequency component is converted into a positive polarity signal in the absolute value circuit 62 and then supplied to the adder circuit 63. On the other hand, the color signal C2 separated by one frequency is added to the signal delayed by a half cycle (140n5ec) of the color subcarrier in the delay circuit 64 in the addition circuit 65. This addition output is
After being converted into a positive polarity signal in the absolute value circuit 66.

The signal is supplied to an adder circuit 63.

The amount supplied from the absolute value circuit 62 to the adder circuit 63 reflects the fineness of the change in brightness on the scanning line, that is, the strength of the vertical component within the display screen. On the other hand, the amount supplied from the absolute value circuit 66 to the addition circuit 63 is the fineness of color change on the scanning line.

That is, it reflects the intensity of the colored vertical component within the display screen.

Therefore, the output B supplied from the adder circuit 63 to the synthesis control circuit 50 reflects the strength of the vertical component within one display screen.

The synthesis control circuit 50 outputs a weighting coefficient k that changes in response to the combination (A, B) of the output A of the horizontal component detection circuit 40 and the output B of the vertical component detection circuit 60.

FIG. 3 is a conceptual diagram showing the relationship between the output A of the horizontal component detection circuit 40, the output B of the vertical component detection circuit 60, and the display pattern on the screen. The display pattern approaches a horizontal line state (
As the output increases, the output increases. On the other hand, as the 9 display pattern approaches the vertical line state, the output B increases. Also 2
As the display pattern approaches the checkered state, the output A
and B both increase.

The synthesis control circuit 50 has a quantity A that reflects the strength of the vertical component supplied from the vertical component detection port er40.

A coefficient k of a magnitude corresponding to the combination with the amount B reflecting the strength of the vertical component supplied from the vertical component detection circuit 60 is supplied to the 1 synthesis circuit 30. Figure 4 is.

An example of the relationship between this combination (A, B) and the coefficients is shown.

The coefficient decreases with increasing to. That is, the weight of the correlation-separated signal in the five combined signals decreases as the horizontal component becomes stronger, and the deterioration in image quality due to the decrease in correlation is alleviated. Furthermore, the coefficient 2 increases as B increases. That is, the ratio of the frequency-separated signal in the two composite signals decreases as the vertical component becomes stronger, and deterioration in image quality due to cross color or color blurring is reduced.

When a fine checkered pattern such as grass is displayed on the screen, horizontal lines and vertical lines appear at the same time. In this case, even if Y/C separation is performed using the correlation separation method, the image quality will deteriorate because the correlation between adjacent scanning lines is low, and even if Y/C separation is performed using the single frequency separation method, high frequency components will be included. Therefore, the image quality deteriorates. For this reason,
Along the diagonal line in the upper right corner of FIG. 4, the coefficient remains approximately constant at 4tL. On this diagonal, the coefficients are 0.
The value is larger than 5. This is a cross color problem that is especially problematic when separating two frequencies.

This is to prioritize and reduce the negative effects of don't crawl, which is particularly problematic in the case of correlation separation.

The synthesis control circuit 50 has an X address whose size is proportional to the size of the signal B, and a Y address whose size is proportional to the size of the signal B.
address, and a coefficient k of the size shown in Fig. 3 is stored in the area accessed by these X and Y addresses.
It is composed of OM.

In the Y/C separation circuit shown in FIG. 2, a circuit for detecting high frequency components of color signals is added to the vertical component detection circuit 40.
This can be omitted if some color bleeding is acceptable.

Furthermore, since the presence of a high frequency component of a two-color signal often accompanies the presence of a high-frequency component of a luminance signal, a vertical component detection circuit can be configured only with a circuit for detecting the high-frequency component of a two-color signal.

Similarly, since changes in the color signal between adjacent scanning lines are often accompanied by changes in the luminance signal, the horizontal component detection circuit can also be configured with only a circuit that detects changes in the luminance signal.

Furthermore, in the Y/C separation circuit shown in FIG. 2, a configuration in which a horizontal component detection circuit and a vertical component detection circuit are used together is illustrated, but a configuration in which either the horizontal component detection circuit or the vertical component detection circuit is used is also possible. You can also.

Further, the Y/C separation circuit shown in FIG. 2 detects a horizontal component based on the correlation-separated signal.

Although a configuration in which vertical components are detected based on frequency-separated signals has been illustrated, a reverse combination may be used, or a configuration in which horizontal and vertical components are detected based on the same signal. You can also do it.

Furthermore, in the Y/C separation circuits of FIGS. 1 and 2, 1
Although the coefficient k used in the synthesis circuit is the same for the luminance signal and the color signal, they can be different (or different) if necessary.

Effects of the Invention As explained in detail above, the present invention is configured to control the ratio of correlation separation and frequency separation based on the detection results of one or both of the horizontal component and the vertical component. It is possible to effectively reduce deterioration in image quality when the vertical component is strong.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of another embodiment of the present invention. 10...Y/C separator by correlation separation, 20... by frequency separation Y/
C separator, 30... synthesis circuit, 40... horizontal component detection circuit, 50... synthesis control circuit, 60... vertical component detection circuit. Patent applicant: NEC Home Electronics Co., Ltd. (1 other person)

Claims (4)

[Claims] (1) A first Y/C separator using a correlation separation method, a second Y/C separator using a frequency separation method, and weighting of the luminance signal and chrominance signal received from each of these Y/C separators. a first circuit that detects the amount of change in the video signal between adjacent scanning lines as a horizontal component within the display screen by receiving the output of one or both of the Y/C separators; and/or a detection means having a second circuit for detecting a signal representing the fineness of a change in a video signal on a scanning line as a vertical component in the display screen; and a combination control means that changes each weighting of the combination means in accordance with the detection result of the horizontal component and/or vertical component, and controls correlation separation and frequency separation in the first and second Y/C separators according to the detection results of the horizontal component and/or vertical component. A Y/C separation device for color television signals characterized by controlling specific gravity. (2) The detection means detects a horizontal component within the display screen based on the inter-scanning variation amount of at least one of the correlation-separated or frequency-separated luminance signal or color signal.
The combining control means controls the combining means so as to increase weighting of the frequency-separated luminance signal and color signal in accordance with an increase in the detected horizontal component. A Y/C separation device for color television signals according to claim 1. (3) The detection means includes the second circuit that detects a vertical component in the display screen based on a high frequency component of at least one of a correlation-separated or frequency-separated luminance signal or color signal, and the synthesis control means , wherein the combining means is controlled so as to increase weighting of the correlation-separated luminance signal and color signal in accordance with an increase in the detected vertical component. Y/C separation device for color television signals. (4) The detection means includes the first circuit that detects a horizontal component within the display screen based on the inter-scanning variation of at least one of the correlation-separated or frequency-separated luminance signal or color signal;
and the second circuit detecting a vertical component in the display screen based on a high frequency component of at least one of a correlation-separated or frequency-separated luminance signal or color signal, and the synthesis control means: increasing the weighting of the frequency-separated luminance signal and chrominance signal in response to an increase in the detected vertical component;
A Y/C separation device for a color television signal, characterized in that the combining means is controlled to increase weighting of the correlation-separated luminance signal and color signal.