JPH03283793A - Composite signal separator circuit - Google Patents

Abstract

PURPOSE:To reduce the deterioration in the picture quality even in a horizontal edge part by suppressing interference of a color signal with respect to a luminance signal. CONSTITUTION:A characteristic of a 4th filter means (variable filter means) 82 is controlled by a control signal sent from a control signal generating means 84 in response to a level of a 1st band limit signal when a horizontal high frequency component of a color signal exits in a 2nd band limit signal by a prescribed level or over. Thus, the filter means 82 is operated only when a luminance change exists in the horizontal direction in a horizontal edge of the color signal and the color level is high, and is not operated by a tilt component of the luminance signal. Thus, dot disturbance generated in the horizontal edge with high color saturation is reduced without increasing blur as to the tilt component of the luminance signal and the composite signal is separated while reducing the deterioration in the picture quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an improvement of a composite signal separation circuit in a color television receiver.

(Prior Art) In the current color television system, a carrier color signal (hereinafter referred to as a C signal) is frequency-multiplexed with a luminance signal (hereinafter referred to as a Y signal) to form a composite signal. On the receiver side, the Y signal and C signal are separated from the received composite signal, and predetermined processing is performed on each signal to display the received image.

With the development of digital technology, the composite signal separation circuit used to separate the Y signal and C signal, the so-called Y/C separation circuit, has replaced the conventional analog Y/C separation circuit with a digital signal separation circuit that enables stricter separation. Development of Y/C separation circuits is progressing. The digital Y/C separation circuit performs Y/C separation by converting the composite signal into a digital signal and performing vertical calculations using line memory.
Unlike the /C separation circuit which extracts the Y signal using a horizontal low-pass filter (hereinafter referred to as horizontal LPF), it is possible to improve the horizontal resolution of the Y signal.

However, the C signal of the NTS signal has a band limit in the horizontal direction (for example, the two color difference signals R-Y and B-Y are 0.5 MHz
) However, at the horizontal edge portion of the C signal, as the horizontal band of the C signal is extended, the C signal leaks into the Y signal, causing interference called dot crawl.

To explain the above using the diagram, at the horizontal edge part of the C signal, the C signal in the E part spreads horizontally to D
It is in a state where the signal leaks into the Y signal of the part. So B
Dot interference can be reduced by widening the passband of the PF, but
The diagonal component of the Y signal was processed as a C signal, increasing cross-color disturbances and deteriorating image quality.

In addition, using wideband horizontal BPF and narrowband horizontal BPF,
One possible method is to narrow the area of the luminance signal as shown by the diagonal lines in the figure, but since the diagonal component of the luminance signal decreases,
The drawback was that there was a strong sense of blur in diagonal directions, which caused deterioration in image quality.

(Problem to be Solved by the Invention) In this way, in the conventional composite signal separation circuit, when the passband of the horizontal BPF is widened in order to reduce dot interference, the diagonal component of the Y signal is processed as the C signal, resulting in cross-color Failures were increasing and image quality was deteriorating.

Another possible method is to narrow the luminance signal area by using a wideband horizontal BPF or a narrowband BPF, but this has the drawback that the diagonal component of the luminance signal decreases, resulting in a strong sense of blur in the diagonal direction, which degrades the image quality. was waking up.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a composite signal separation circuit that can reduce image quality deterioration even at the horizontal edge portion where the horizontal band of the C signal is wide.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the composite signal separation circuit of the present invention separates the vertical high frequency range of a composite television signal in which a chrominance signal is frequency-multiplexed onto a luminance signal. a first filter means for extracting a component and obtaining a first band-limited signal; a second filter means for extracting a vertical low-frequency component of the composite television signal and obtaining a second band-limited signal; , a third filter means for extracting a frequency band corresponding to the horizontal edge portion of the chrominance signal from the first band-limited signal to obtain a third band-limited signal; A fourth band-limited signal centered on the corresponding band is obtained. a fourth filter means capable of changing a pass band; and a fifth filter means for extracting a horizontal high frequency component from the second band-limited signal to obtain a fifth band-limited signal;
control signal generating means for generating a signal for controlling characteristics of the fifth filter means from the third and fifth band-limiting signals; the fourth band-limiting signal controlled by the control signal generating means; and the fourth band-limiting signal controlled by the control signal generating means; The present invention is characterized by comprising a subtraction processing means for performing subtraction processing on a composite television signal.

(Function) In the device configured as described above, the fourth filter means (variable filter means) performs the following functions when the horizontal high-frequency component of the color signal is present at a certain level or more in the second band-limited signal. The control signal sent from the control signal generating means corresponds to the level of the first band-limiting signal.
control the characteristics of the filter means. Therefore, it works only when there is a horizontal brightness change at the edge of the color ratio and the color level is high, and it does not work on the diagonal component of the brightness signal, so it does not increase the feeling of blur for the diagonal component of the brightness signal. , it is possible to reduce dot interference occurring at horizontal edge portions with high color saturation, and it is possible to separate composite signals that can reduce image quality deterioration.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a block diagram of a composite signal separation circuit according to an embodiment of the present invention.

In the figure, 11 is an input terminal to which the composite television signal 1 is introduced, 12 and 13 are line memories connected in series for signal delay, and the composite signal v1 from the terminal 11 is passed through the line memory 12 to the line memory. 13. The one-line delayed signal v,1 from the line memory 12 and the composite signal v1 from the terminal 11 are input to an adder 14 and subjected to addition processing. Further, the 1-line delayed signal v,1 and the 2-line delayed signal v1.1 from the line memory 13 are used. are input to the adder 15 and subjected to addition processing. Furthermore, the composite signal V,
and the 1-line delayed signal v11 are input to the subtracter 16 and subjected to subtraction processing, and the 1-line delayed processed signal v, 1 and the 2-line delayed signal V12 are inputted to the subtracter 17 and subjected to subtraction processing. With this configuration, the first addition signal VL2 is derived from the adder 14, and the first addition signal VL2 is derived from the adder 15.
However, the first subtraction signal Vtl from the subtracter 16 is sent to the subtracter 1.
The first subtraction signals (2) and (2) are derived from the subtraction signals (2) and (2), respectively.

1st. The second addition signals VL, , VL2 are each passed through a horizontal band pass filter (hereinafter referred to as horizontal BPF) 21
．． The signal is input to the control circuit 23 via 22. This control circuit 23 is composed of absolute value circuits 41, 42 and a determination circuit 43, and the signal RL from the horizontal B P F 21 is sent to the absolute value circuit 41, and the signal RL2 from the horizontal B P F 22 is sent to the absolute value circuit 41.
is input to the absolute value circuit 42. Absolute value circuit 41.42
is a circuit that detects the absolute value (signal level) of the signals RLI and RL2. And each absolute value circuit 41.4! The level signals All and A12 are input to a determination circuit 43, and the magnitude of the level is determined. The determination circuit 43 outputs a value k (0≦≦
A signal k whose information is 1) is output.

On the other hand, the outputs Vat and V2 of the subtracters 16 and 17 are respectively input to phase adjustment circuits 31 and 32. These phase adjustment circuits 31, 32, coefficient units 33, 34 that weight the signals from each circuit 31, 32, and adder 35 that combines the signals from each of these coefficient units 33, 34 are as follows: A mixing circuit 18 is configured to combine the signals Via and 7w2 at a predetermined ratio. Here, the weighting of the coefficient multiplier 33 is varied so that the coefficient matches the value k meant by the signal from the determination circuit 43, and the weighting of the coefficient multiplier 34 is varied so that the coefficient is equal to 1-. It is varied so as to maintain the relationship. Adder 35 receives signals v8. from coefficient multipliers 33.34.
and vx□ are added, and the output C8 multiplied by 1!2 is derived to the horizontal BPF 61 and subtractor 71 which are connected in cascade.

The signal CWt from the horizontal B P F 61 is the horizontal B P
The signal is guided through F 62 to a phase adjustment circuit 63 with the Y signal.

A signal from phase adjustment circuit 63 is led out to terminal 64.

The signal C8 appearing at terminal 64 is the color signal separated from the composite signal.

The subtracter 71 subtracts the composite signal guided through the phase adjustment circuit 72 and the above C3 signal, and passes the output signal YR through a horizontal high-pass filter (hereinafter referred to as horizontal HPF) 73
lead to.

Signal YII from horizontal HP F 73 is input to horizontal edge detection circuit 74. The horizontal edge detection circuit 74 includes an absolute value circuit 75 and a determination circuit 76.

Signals Y and l are input to a determination circuit 76 via an absolute value circuit 75. The horizontal edge detection circuit 74 outputs an ED double signal indicating the horizontal edge portion of the luminance signal to the dot determination circuit 77.

On the other hand, the signal CI from the horizontal BPFfil is input to the subtracter 66 via the phase adjustment circuit 65, and
The difference signal C0 is obtained by calculating the signal C32 from C2.

The difference signal C□ is led to the color saturation detection circuit 81 via the horizontal B P F 82 . The color saturation detection circuit 81 is
It is composed of an absolute value circuit 83 and a very linear processing circuit 84.

The horizontal BPF 82 detects the differential signal C trap 3 from 0 to 15 MH.
This excludes a reduction of about x. Horizontal B P F li
The signal CM from 2 is led to a nonlinear processing circuit 84 via an absolute value circuit 83 to obtain a control signal C0 having the meaning of color saturation.

The dot determination circuit 77 receives the input control signal C.

A signal C8 (0≦08≦1) that changes the value of the coefficient multiplier 16 based on the edge detection signal E0 is output.

The difference signal Cps is guided to a coefficient multiplier 86 via a phase adjustment circuit 85, and the gain is varied in the range of θ to 1 according to the value of the signal C1, and is guided to an adder 87 as a signal CKCl1. The signal CKCl3 and the color signal C8 are added to each other to form a signal multiplied by Cy, which is then subtracted by a subtracter 25 from the composite signal led through the phase adjustment circuit 24 to provide a luminance signal Y at a terminal 26. get.

In the above configuration circuit, detection of horizontal color edge portions is based on the following principle.

Horizontal dot interference is caused by the C signal leaking into the Y signal. Therefore, dot interference tends to be noticeable in color edge areas where color saturation is high. In areas where the color changes in the horizontal direction, the brightness generally also changes due to the correlation of the images. The diagonal component of the high horizontal luminance signal is processed as a color signal component and causes cross color interference, but the second
Only when there is a frequency component in part B in the figure, the period number of the luminance signal is noticeable as a dot in the part with high color saturation.
．． By lowering the gain of 5 to 3 Ml11, it is possible to suppress a decrease in the degree of oblique elimination due to dot reduction, an increase in the occurrence of cross color, and the like.

The present invention will be explained in detail below.

FIG. 3 shows the composite signal v1. It shows the positional relationship between V++ and V1□. In this way, each signal V,,V,,.

VH2 is a signal that differs from line to line in the vertical direction.

Now, if the signal displayed on line n+2 is V, then n
The signal displayed on the +1 line is ■3. .

The signal displayed on the n line is ■1°. Of these, the adder 14 receives the signal V of the n+2 line and the signal v1 . Add. In the case of an NTSC signal, adding signals at positions that differ by one line in the vertical direction means extracting the Y signal component, so the signal vL output from the adder 14 is This is a Y signal component obtained by combining Y signals. Further, the output VL2 of the adder 15 is a Y signal component obtained by adding the Y signals on the n+l line and the n line.

On the contrary, the subtraction signal Vm output from the subtracter 16
+ is a signal component obtained by extracting the vertical high frequency component including the C signal on the n+2 line and the n+1 line, and the subtracted signal VI2 output from the subtracter 17 contains the C signal on the n+1 line and the n line but does not contain the vertical high frequency component. This is the signal component from which the component has been extracted.

However, the signal from adder 14.15 is V L,, V
L2 is a signal R4, which has passed through horizontal BPFs 21 and 22, respectively.

RL2 is a band adjustment signal in which the Y signal component is band-limited in the horizontal direction. This signal will be further explained with reference to FIG.

In Figure 2, the vertical axis represents the vertical frequency ν, and the vertical axis represents the horizontal frequency μ.
, and fsc indicates the color sub-spot carrier frequency. In the same figure, area A represents a signal area of reduction in both the vertical and horizontal directions, area B represents a signal area with low frequencies in the vertical direction and high frequencies in the horizontal direction, and area D represents a signal area with high frequencies in the vertical direction. The horizontal direction represents a low frequency signal region, and the E region represents a high frequency C signal region both horizontally and vertically. Therefore,
If the center frequency of the horizontal BPF 21.22 is set to a high frequency in the horizontal direction, for example, a frequency near fsc, the band adjustment signal Rt4. It can be seen that RL2 becomes the Y signal component of the B area.

Now, if the vertical band of the C signal is wide, the C signal also appears in the above B area.
A signal component will be present. When the C signal is present in the B area signal, the level of the signal RLllRL2 increases accordingly. In this way, the control circuit 23 according to this embodiment has the following:
Signals RLI and RL□ in the Y signal region whose signal level changes depending on the band of the C signal are input.

Next, the subtraction signal v81°V obtained by the subtractor 16.17
H2 is connected to the coefficient multiplier 33.3 via the phase adjustment circuit 31.32.
Enter 4. The coefficients of these coefficient multipliers 33 and 34 are varied by the control value k of the signal from the control circuit 23, respectively. The coefficient unit 34 calculates the control value k J,
: Next, the signal vl12 is multiplied by (1-k) and the adder 35
lead to.

The C signal component C9 output from the adder 35 is sent to the subtracter 71.
As a result, the signal Y is output from the line memory 12 and subtracted from the composite signal having a predetermined phase by the phase adjustment circuit 72, and the subtracter 71 outputs a signal Y. Signal Y corresponds to areas A and B shown in FIG. Therefore, the original signal Y of horizontal B P F 73.

is a part of area B in the figure.

The signal Y is input to the horizontal edge detection circuit 74, and the signal Y indicates an edge portion depending on the magnitude of the signal Y. A signal is output. The simplest example is a binary method. That is, if the absolute amount of the signal Ym exceeds a certain value, "1" is output as an edge part, and if it is less than that, it is determined that it is not an edge part and "0" is output. The case of binary values will be explained below.

For the C signal component C3, a horizontal BPF 61 and a horizontal BPF 62 with the color subcarrier as the center frequency are connected in series, and unnecessary components are further removed from the above signal using the synthesis characteristics of both BPFs 61 and 62, and the color signal is converted to a C signal component C3. It has the property of calculating .

FIG. 4 shows the characteristics of horizontal BPF61.62. The difference signal C*3 is the difference between C11 and cR□, and the signal C! from the adder 87 is determined by the value of CK of the coefficient multiplier 86 (0≦C≦1). The characteristics of can be changed between Ca1 and C12. That is, when C,=O, CY=C12, and when C1=1, Cv=C*x.

The difference signal C1 is guided to a color saturation detection circuit 81. Here, dot interference is noticeable at the horizontal color edges because of the second
In the diagram, the color signal extends from E to D and the level is high, so the horizontal BPF 82 is from E to D in Figure 2.
PF is defined as passing near the middle of . Furthermore, an absolute value circuit 83 converts the signal into an absolute value, a nonlinear processing circuit 84 converts the signal into, for example, several levels of values, and outputs a signal Co.

In the dot determination circuit 77, when the Eo multiplied signal is binary as described above, when Eo is 0, the coefficient multiplier 8 is used regardless of the value of CI.
Outputs the control signal c8 such that C3=0 of El
When ll=1, C,> of the coefficient unit 86 according to the value of Co
A control signal c8 that becomes 0 is output.

The subtracter 25 uses the Cy multiplied signal generated as described above and the composite signal whose phase has been adjusted by the phase adjustment circuit 24.
, and outputs the luminance signal Yo to the terminal 26.

As described above, the composite signal separation circuit according to the present embodiment can reduce dot interference occurring at horizontal edge portions with high color saturation without increasing the blurring of diagonal components of the luminance signal, thereby reducing image quality deterioration. I can do it.

[Effects of the Invention] As described above, according to the present invention, interference of a color signal with a luminance signal can be suppressed, and image quality deterioration can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a composite signal separation circuit according to an embodiment of the present invention, and FIGS. 2 and 3 are explanatory diagrams for explaining the operation of a composite signal separation circuit according to an embodiment of the present invention. FIG. 4 is a characteristic diagram showing the characteristics of the horizontal BPF of the composite signal separation circuit according to an embodiment of the present invention. 12, 13... line memory, 14. +5.
35.87... Adder, 16.17.25.66, 7
1...Subtractor! 8...Mixing circuit, 21, 22.6
+, 62.82...Horizontal band pass filter 23
...Control circuit, 24.31.32.63.65.11
5... Phase adjustment circuit, 33.34.86... Coefficient unit, 41.42.75.83... Absolute value circuit, 43.7
6... Judgment circuit, 74... Horizontal edge detection circuit, 7
7... Dot judgment circuit, 8! ...color detection circuit, 84
...Nonlinear circuit.

Claims (1)

[Claims] Extracting high frequency components in the vertical direction of a composite television signal in which a chrominance signal is frequency-multiplexed on a luminance signal;
a first filter means for obtaining a band-limited signal; a second filter means for extracting a vertical low-frequency component of the composite television signal to obtain a second band-limited signal; a third filter means for extracting a frequency band corresponding to the horizontal edge portion of the color signal from the signal to obtain a third band-limited signal; a fourth filter means capable of changing a passband for obtaining a fourth band-limited signal; extracting a horizontal altitude range component from the second band-limiting signal;
a fifth filter means for obtaining a fifth band-limited signal; a control signal generating means for generating a signal for controlling the special production of the fifth filter means from the third and fifth band-limited signals; and this control signal. A composite signal separation circuit comprising: subtraction processing means for subtracting the fourth band-limited signal controlled by the generation means and the composite television signal.