JPS6292693A - Y/c separating device for color television signal - Google Patents

Abstract

PURPOSE:To avoid the deterioration of picture quality even for a special picture in which a luminance signal changes extending over one scanning line by adding function that detects variation between adjoining scanning lines only for luminance signal and changes composing ratio. CONSTITUTION:The device is provided with the first Y/C separating circuit 10 using a comb-line filter, the second Y/C separating circuit 20 of frequency separation system and a synthesizing circuit 30 that synthesizes the outputs of the first and second separating circuits weighting them. A synthesis control circuit 70 supplies weighting coefficients (k) and 1-k that change corresponding to the combination of A, B, C of a chrominance signal horizontal component detection signal A outputted from a chrominance signal horizontal component detecting circuit 40, a vertical component detection signal B outputted from a vertical component detecting circuit 60 and a luminance signal horizontal component detection signal C outputted from a luminance signal horizontal component detecting circuit 50. The coefficient (k) decreases with the increase of signals A and C. That is, the ratio of signals by the comb-line filter in the composed signals decreases with the increase of horizontal component in a displayed picture and the deterioration of picture quality due to the lowering of correlation between adjoining scanning lines can be evaded.

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 in a color television signal.

Conventional technology Methods for separating the luminance signal and color signal in a color television signal include a frequency separation method that uses the frequency spectrum of the video signal to separate them on the frequency axis, and a method that uses the correlation between adjacent scanning lines. There is a comb filter method that separates the data on the time axis.

The frequency separation method has a problem in that when the luminance signal includes a high frequency component, this leaks into the color signal side, causing color unevenness called cross color.

Furthermore, since the comb filter method assumes that there is a correlation between adjacent scanning lines, there is a problem in that if this assumption is violated, Y/C separation becomes insufficient and image quality deteriorates.

In order to solve this problem, the present inventors have developed an adaptive control method that combines the luminance signal and chrominance signal separated by the re-separation method while changing the combination ratio depending on the state of the video signal. invented and filed earlier by the applicant for this patent.
This method is disclosed in Japanese Patent Application No. 162392/1982 entitled "Y/C Separator for Color Television Signals".

Problems to be Solved by the Invention Although the Y/C separation device of the earlier application can achieve a considerable improvement in image quality compared to the conventional one, it cannot be used for special screens where the luminance signal changes by one scanning line. It was later discovered that image quality deteriorated.

Means for Solving the Constituent Problems of the Invention The Y/C separation device of the present invention has the following advantages over the Y/C separation device of the prior application.
It is configured to further improve image quality by adding a function that detects the amount of change between adjacent scanning lines even for the luminance signal and adaptively controls the synthesis ratio according to this amount of change.

That is, the Y/C separation device of the present invention includes a first Y/C separation circuit using a comb filter, a second Y/C separation circuit using a frequency separation method, and a first Y/C separation circuit using a comb filter. a synthesis circuit that weights and synthesizes the outputs of the second Y/C separation circuit; a change amount detection circuit that detects one or more of the amount of change in the signal;
and a synthesis control circuit that controls the synthesis ratio in the synthesis circuit in accordance with one amount of change or a combination of two or more amounts of change detected by the amount of change detection section.

Hereinafter, the operation of the present invention will be explained in detail together with examples.

Embodiment FIG. 1 is a block diagram showing the configuration of a Y/C separation device for color television signals according to an embodiment of the present invention.

In the figure, 10 is a Y/C separation circuit using a comb filter, 20 is a Y/C separation circuit using a frequency separation method, and 3
0 is a synthesis circuit that weights and synthesizes the luminance signal and color signal separated by the Y/C separation circuits 10 and 20, and 40 is a display of the color signal separated by the comb filter 10 based on the amount of change between adjacent scanning lines. Color signal horizontal component detection circuit for detecting horizontal components of color signals in the screen, 50 comb filter IO
A luminance signal horizontal component detection circuit detects the horizontal component of the color signal in the display screen from the amount of change between adjacent scanning lines for the luminance signal separated by , and 60 is a high frequency component of the Y/C separated luminance signal and color signal. A vertical component detection circuit 70 detects a vertical component in the display screen from the above, and a vertical component detection circuit 70 changes the weighting (synthesis ratio) of the synthesis circuit 30 according to the combination of the three types of changes detected by the detection circuits 40, 50 and 60. This is a synthesis control circuit that allows

The Y/C separation circuit 10 using a comb filter includes two delay circuits 11a and llb and three subtracters 13a and 13b.
and 16, an adder 14, and a coefficient unit 15.

The NTSC video signal input to the input terminal IN is delayed by one horizontal scanning time (IH) by two delay circuits 11a and llb, respectively.

The subtracter 13a outputs the sum of the video signal currently being supplied to the comb filter 10 and the color signal C included in the video signal 18 minutes before. The subtracter 13b outputs the sum of the color signals included in the video signal 18 minutes before and the video signal 18 minutes before that. The sum of these color signals is added by an adder 14, and then multiplied by 1/4 by a coefficient unit 15.
A time average value of the color signal over 3H minutes is given.

Color signal CI correlated by this comb filter
is supplied to the synthesis circuit 30 and the subtracter 16. Subtractor 1
6 extracts a luminance signal Yl from the correlation-separated color signal C1 and the video signal of 18 minutes ago, and supplies this to the synthesis circuit 30.

On the other hand, the Y/C separation circuit 20 of the frequency separation type includes a bandpass filter circuit 22 and a subtracter 23, and each of the frequency-separated luminance signal Y2 and color signal C2 is sent to a synthesis circuit 30.
supply to.

The combining circuit 30 is composed of the Y/C separating circuits 10 and 2 of different types.
The luminance signals Y1 . Y2, the color signals C1 and C2, and the weighting supplied from the synthesis control circuit 70 are based on the coefficient k to create a composite luminance signal and a composite color signal, and each of them is used as the luminance signal Y of this Y/C separation device. ,
Output as color signal C.

The color signal horizontal component detection circuit 40 connects the iH delay circuits 11a and 11 with the Y/C separation circuit IO using a comb filter.
b, and subtractors 13a and 13b are shared. Subtractor 4
4 outputs the amount of change in color signal between adjacent scanning lines from the color signals received from each of the subtracters 13a and 13b. The amount of change in this color signal is unified to positive polarity in the absolute value circuit 43. The absolute value lΔC1 of the amount of change in the color signal output from the absolute value circuit 43 is determined by the color signal horizontal component detection circuit 4.
0 color signal horizontal component detection signal A to the synthesis control circuit 70
is supplied to

The luminance signal horizontal component detection circuit 50 also has IH delay circuits 11a and 11a between it and the Y/C separation circuit 10 using a comb filter.
lb and subtractors 1.3a and 13b are shared. If the correlation between the adjacent scanning lines is 100%, the difference signal between the adjacent scanning lines outputted from these subtractors 13a and 13b is only a color signal component, but it is displayed by a change in the luminance signal between the adjacent scanning lines. When horizontal stripes appear on the screen, the amount of change in the luminance signal is included. The color signal included in the amount of change in the luminance signal is removed by low pass filters 51 and 52,
Adjacent scanning line difference signal ΔYl of luminance signal.

ΔY2, which are unified to positive polarity by the absolute value circuits 53 and 54, and then added by the adder 55. This addition output IΔYl is supplied to the synthesis control circuit 70 as a luminance signal horizontal component detection signal C.

The vertical component detection circuit 60 is supplied with a luminance signal Y2 and a color signal C2, which are separated using a frequency separation method. From the luminance signal Y2, only high-frequency components having frequencies higher than the color subcarrier frequency are extracted by the high-pass filtering luminance signal 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 frequency-separated color signal C2 is delayed by a half cycle (140n5ec) of the color subcarrier in a delay circuit 64 and is added in an adder 65. This addition output is unified into positive polarity by the absolute value circuit 66 and then supplied to the addition circuit 63.

The amount of amplitude of the signal supplied from the absolute value circuit 62 to the addition circuit 63 reflects the amount of change in the luminance signal 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 reflects the amount of change in the color signal on the scanning line, that is, the strength of the vertical component within the display screen. Therefore, the vertical component detection signal B supplied from the adder 63 to the synthesis control circuit 70 reflects the strength of the vertical component within the display screen.

The synthesis control circuit 70 receives the color signal horizontal component detection signal A output from the color signal horizontal component detection circuit 40, the vertical component detection signal B output from the vertical component detection circuit 60, and the luminance signal horizontal component detection circuit 50. A weighting coefficient 1-k is supplied to the combining circuit 30, which changes in accordance with the combination (A, B, C) with the output luminance signal horizontal component detection signal C.

FIG. 2 is a conceptual diagram illustrating the relationship between the combination of the color signal horizontal component detection signal A, the vertical component detection signal B, and the luminance signal horizontal component detection signal C and the display pattern within the screen. As the display pattern approaches a horizontal line state, the signals A and C increase. On the other hand, as the signal pattern approaches a vertical line state, signal B increases.

Also, as the display pattern approaches the checkered state,
Signals A, B and C all increase.

FIG. 3 shows a combination of signals (A, B) and the coefficients supplied from the synthesis control circuit 70 to the synthesis circuit 30.

It is a conceptual diagram which illustrates the relationship with C).

The coefficients decrease as signals A and C increase.

That is, the proportion of the signal generated by the comb filter in the composite signal decreases as the horizontal component in the display screen becomes stronger, thereby avoiding deterioration in image quality due to a decrease in correlation between adjacent scanning lines. Also, the coefficient increases with signal B. That is, the ratio of the frequency-separated signal in the composite signal decreases as the vertical component in the display screen becomes stronger, and deterioration in image quality due to cross color or color blurring is avoided.

When a fine checkered pattern such as grass is displayed on the screen, a combination of horizontal lines and vertical lines will appear at the same time. In this case, even if Y/C separation is performed using a comb filter, image quality will deteriorate because the correlation between adjacent scanning lines is low, and even if Y/C separation is performed using a frequency separation method, image quality will deteriorate. . Therefore, along the diagonal line upward to the right in FIG. 3, the coefficients maintain approximately constant values. On this diagonal, the coefficients take values greater than 0.5.

This is to avoid the problem of cross color, which is a problem in the case of frequency separation, by giving priority to the problem of dot crawl, which is a problem in a comb filter.

The synthesis control unit 70 generates an X address proportional to the magnitude of the signal A, an X address proportional to the magnitude of the signal B, and a signal C.
It is composed of an X address proportional to the size of , and a ROM that stores a coefficient k as exemplified in FIG. 3 in a storage area accessed by each of these addresses.

FIG. 4 is a block diagram showing the configuration of a Y/C separation device for color television signals according to another embodiment of the present invention.

This Y/C separator is a simplified version of the Y/C separator shown in FIG.

That is, the color signal horizontal component detection circuit 10 in the Y/C separation device shown in FIG. The horizontal component detection circuit 50 and the synthesis control circuit 70 are integrated into one
A synthesis control circuit circuit 80 is configured. In addition, the vertical component detection circuit 60 in the Y/C separation device shown in FIG. , if it is larger than the reference level, it outputs a logic 1, and if it is smaller, it outputs a logic 0, and the output of each comparator is ORed by the OR gate 83, and the switch 37 in the synthesis circuit 30 This is done by switching 38.

That is, while the horizontal component of the luminance signal or the color signal does not reach a predetermined value, the switches 37 and 38 are switched to the upper side in the figure, and the luminance signal Y1 and the color signal C1, which are Y/C separated by the comb filter 10, are is selected to avoid cross color associated with the use of frequency separation schemes. On the other hand, if the horizontal component of the luminance signal or color signal exceeds a predetermined value,
Switches 37 and 38 are switched to the lower side in the figure to select the luminance signal Y2 and color signal C2 separated by the Y/C separation circuit 20 of the frequency separation type, thereby avoiding dot crawl caused by the use of a comb filter. be done.

Effects of the Invention As explained in detail above, the Y/C separator of the present invention is different from the Y/C separator of the prior application in that it detects the amount of change between adjacent scanning lines for only the H degree signal and calculates the synthesis ratio. By adding the function of changing the brightness, it is possible to avoid deterioration of the image quality even on a special screen where the brightness signal changes over one scanning line.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a color television signal Y/C separation device according to an embodiment of the present invention, FIGS. 2 and 3 are conceptual diagrams for explaining the operation of the above embodiment,
FIG. 4 is a block diagram showing the configuration of a Y/C separation device for color television signals according to another embodiment of the present invention. 10... Y/C separation circuit using a comb filter. 20... Y/C separation circuit using frequency separation method. 30...Composition circuit, 40...Color signal horizontal component detection circuit,
50... Luminance signal horizontal component detection circuit, 60... Vertical component detection circuit, 70... Synthesis control circuit. 80...Horizontal component detection/synthesis control circuit. Patent applicant: NEC Home Electronics Co., Ltd.

Claims (1)

[Claims] A Y/C separation device that separates a luminance signal and a color signal in a color television signal, comprising a first Y/C separation circuit using a correlation separation method and a second Y/C separation circuit using a frequency separation method. C separation circuit and these first and second
a synthesis circuit that weights and synthesizes the outputs of the Y/C separation circuits; No. 1
or a change amount detection circuit that detects two or more amounts of change, and a synthesis control circuit that controls a synthesis ratio in the synthesis circuit in accordance with one amount of change or a combination of two or more amounts of change detected by this amount of change detection circuit. A Y/C separation device for color television signals, characterized in that: