JPS63116586A - Filter for separating luminance signal and chrominance signal corresponding to picture correlation - Google Patents

Abstract

PURPOSE:To prevent the interference of dots by selecting an output from a horizontal filter or a vertical filter for pictures with especially strong correlation according to results that correlation energies in vertical and horizontal directions are detected and outputting chrominance signal. CONSTITUTION:Outputs 112 and 113 from a vertical correlation detection circuit 7a and a horizontal correlation detection circuit 7b are given to a decision circuit 8, while its output 114 is given to a switch circuit 9. Its output 115 is outputted as chrominance signal from an output terminal 2. With the outputs 112 and 113 from the vertical and horizontal correlation detection circuits 7a and 7b as inputs, the decision circuit 8 outputs a selection signal 114 and controls the output from the switch circuit 9. The chrominance signal outputted from the switch circuit 9 is subtracted from the composite signal of a compensation delay circuit 5h, thereby obtaining a luminance signal 117. Thus the leakage of the luminance signal and the chrominance signal in an area that suddenly changes to mutual channels can be minimized, and the dot interference can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a luminance signal and chrominance signal separation filter compatible with image correlation, and particularly to a luminance signal and chrominance signal separation filter for separating a luminance signal and a chrominance signal from, for example, a composite television signal of the NTSC system. This is what I did.

[Conventional technology]

FIG. 6 is a block diagram showing an example of the configuration of a conventional luminance signal chrominance signal separation filter. In FIG. 6, an NTSC composite color television signal is input to an input terminal 1. This composite TV signal is A/
It is applied to a vertical filter 6d via a D (analog/digital) converter 4 and a one-line delay circuit 5.
given to Q. The output of the 1-line delay circuit 5Q is applied as is to the vertical filter 6d, and after being further delayed by 1 line in the 1-line delay circuit 5p, it is applied to the vertical filter 6d.

The vertical filter 6d is usually a filter called a two-line comb filter, and its output is passed through the bandpass filter 6.
given to e. The output of the bandpass filter 6e is the color signal 20
5 from the output terminal 2 and is applied to the first input of the subtraction circuit 10h.

Further, the output of the 1-line delay circuit 5Q is applied to the second input of the subtraction circuit 10h via the compensation delay circuit 5R.

The compensation delay circuit 5R is a circuit for compensating for the delay in the bandpass filter 6e.

A luminance signal 207 is output from the subtraction circuit 10h and applied to the output terminal 3.

Next, the operation of the luminance signal/chrominance signal separation filter for an NTSC composite color television signal will be explained. The composite color television signal 201 sampled in synchronization with the color subcarrier at the sampling frequency fs = 4·fsc (fsc is the color subcarrier frequency) forms a two-dimensional grid-like array on the screen as shown in FIG. .

That is, since it is fsc-(455/2) fH, four samples are extracted in one cycle of the color signal C whose phase is inverted by 180 degrees for each line.

Here, in FIG. 7, Y indicates a luminance signal, and CI and cz indicate color signals. Now, it is assumed that z-1 and z-1 are used as symbols representing a delay of l samples and a delay of one line, respectively, using two transformations.

here, Z - eXp (j2rf/4fsc).

Also, since fsc=(455/2)·fH, t=910. At this time, the 1-line delay circuit 5Q,
A vertical direction filter 6d extracts a line support signal 204 that supports each line including color signals from the one-line delayed signal 202, the two-line delayed signal 203, and the current input signal 201, which are delayed using 5p. The transfer function of the vertical filter 6d is E(v(Z) is HVCZ)=(-1/4)-(1-Z-')2.

That is, on the screen of FIG. 7, the line support signal Hc (m, n) at the coordinates (m, n) is He (m, n) = (''/4) (S (m, n-1) -
28(m, n)+S(m, n+1)). Since the line support signal also includes the luminance signal Y, the bandpass filter 6e filters the color signal C(m
, n) from He (m, n). Then, the obtained color signal 205 is sent to a subtraction circuit 10h.

The subtraction circuit 10h extracts the chrominance signal C(m.

n) 205, the luminance signal Y(m+
n) Separate 207.

Y (m, n) = S (m, n) - C (m, n) transfer function Hn (for example, Hn (Z) = (-1/32) (1-Z-2 )2
(1,+Z-')'(1+Z-8).

[Problem that the invention seeks to solve]

The conventional luminance signal chrominance signal separation filter is constructed by identifying and combining the characteristics of the vertical filter 6d and the horizontal filter as described above. That is, the luminance signal and the color signal are separated by the bandpass filter 6h in both the vertical and horizontal directions.

Therefore, in the conventional case, in areas where the brightness and color of the image change rapidly, the brightness signal and the color signal leak into each other's channels, which causes problems such as deterioration of the quality of the reproduced image, especially due to dot interference. there were.

The present invention was made in order to solve such problems, and provides a luminance signal and chrominance signal separation filter that supports image correlation and can achieve accurate separation of luminance signals and chrominance signals even in the case of rapid signal changes in television images. The purpose is to obtain.

[Failure to solve the problem]

The image correlation compatible luminance signal/chrominance signal separation filter according to the present invention includes delay means for simultaneously obtaining a sample point of interest from which one luminance signal is to be separated by delaying an input sampling signal, and a neighboring sample point adjacent thereto. From the values of the sample point of interest and neighboring sample points, the frequency components corresponding to the DC component and color subcarrier component in the vertical and horizontal directions, as well as the frequency components in the horizontal direction,
means for detecting vertical and horizontal correlation energy by excluding frequency components corresponding to vertical color subcarrier components and finding their absolute values; means for selecting the output of the horizontal direction filter or the vertical direction filter and outputting the color signal component.

[For production]

In this invention, the multi-input sampling signal is delayed by the delay means to simultaneously extract the sample point of interest and the neighboring sample point, and from the sample point of interest and the neighboring sample point in the vertical direction, respectively.
Detects uncorrelated energy in vertical and horizontal directions by removing frequency components corresponding to horizontal DC components and color subcarrier components as well as frequency components corresponding to vertical and horizontal color subcarrier components. Then, depending on the detection result, a color signal component is selected from the vertical filter or the horizontal filter for an image with a particularly strong correlation and is output.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the image correlation compatible luminance signal/chrominance signal separation filter of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic block diagram showing the configuration of one embodiment. In FIG. 1, reference numeral 1 denotes an input terminal to which a composite color television signal of the NTSC system is applied, and this composite color television signal is applied to a converter 4. Konon's converter 4 has a sampling frequency fs = 4 fsc
The receiver is configured to sample a composite color television signal at a receiver.

■The composite color television signal sampled by the converter 4 is given to a 1-line delay circuit 5a, and further
By passing through the line delay circuit 5b, 1 line delay circuit 5C11 and line delay circuit 5d, the sample value at a certain sample point of interest and the 1
Sample values at sample points on the line, one line below, and two lines below are extracted simultaneously.

The sample values extracted by the one-line delay circuits 5a, 5b, 5c, and 5d are passed to the vertical filter 5a.

Horizontal filter 6b, vertical correlation detection circuit 7a.

The signal is applied to the horizontal correlation detection circuit 7b as follows.

That is, the output 102 of the 1-line delay circuit 5a, the output 103 of the 1-line delay circuit 5b, and the output 104 of the 1-line delay circuit 5C are applied to the input of the vertical filter 6a.

A one-line delay circuit 5b is connected to the input of the horizontal filter 6b.
An output 103 is given.

In addition, the inputs of the vertical correlation detection circuit 7a include (1) the output 101 of the converter 4, the output 103 and 1 of the line delay circuit 5b;
An output 105 of the line delay circuit 5d is applied.

A one-line delay circuit 5 is connected to the input of the horizontal correlation detection circuit 7b.
Outputs 102, 103, and 104 of a*5b and 5c are given.

Further, the output 106 of the vertical filter 6a is given to the compensation delay circuit 5f, and the output 107 thereof is given to the compensation delay circuit 5e via the horizontal band filter 6C. The output 110 of the horizontal filter 6b is the compensation delay circuit 5
given to g.

Further, the output 112 of the vertical correlation detection circuit 7a and the output 113 of the horizontal correlation detection circuit 7b are given to the determination circuit 8,
Output 114 of determination circuit 8 is given to switch circuit 9 .

The switch circuit 9 includes compensation delay circuits 5e and 5f.

5g outputs 108, 109, 111 are also provided.

The output 115 of the switch circuit 9 is output from the output terminal 2 as a color signal. Further, this output is given to one input terminal of the subtraction circuit 10a. The output 103 of the one-line delay circuit 5b is applied to the other input terminal of the subtraction circuit 10a via a compensation delay circuit 5h. The output 117 of the subtraction circuit 10a is outputted from the output terminal 3 as a luminance signal.

Note that the compensation delay circuits 5e, 5f, 5g
, 5 h is a circuit for compensating the delay in each circuit.

FIG. 2 is a block diagram showing the internal configuration of one embodiment of the vertical filter 6a. In this FIG.
The output 118 of 1a is input to the 1/2 multiplier circuit 12a, and the 1
The output 119 of the 72x circuit 12a is applied to one input terminal of the subtraction circuit 10b.

The output 103 of the one-line delay circuit 5b is applied to the other input terminal of the subtraction circuit 10b. The output 120 of the subtraction circuit 10b is output as the vertical filter output 106 via the 1/2 multiplication circuit 12b.

FIG. 3 is a block diagram showing the internal configuration of one embodiment of the horizontal filter 6b. Output 1 of 1-line delay circuit 5b
03 is applied to one input terminal of the adder circuit 11b. A one-line delay circuit 5b is connected to the other input terminal of the adder circuit 11b.
The output 103 of is passed through the 2-sample delay circuit 51 and the 2-sample delay circuit 5j, and its output 122 is provided.

Two-sample delay circuits 51 and 5j each delay the sampled composite color television signal for two sample periods (1
The sample period is 1/4 fsc CSEC':l).

The output 123 of the adder circuit 11b is input to the 172 times circuit 12c, and the output 124 of this 1/2 times circuit 12c is given to one input terminal of the subtracter circuit 10c.

The output 121 of the 2-sample delay circuit 5i is applied to the other input terminal of the subtraction circuit 10C. The output 125 of the subtraction circuit 10c is outputted as a horizontal filter output 110 via a 1/2 multiplication circuit 12d.

FIG. 4 is a block diagram showing the internal configuration of one embodiment of the vertical correlation detection circuit 7a. ■The output 101 of the converter 4 and the output 105 of the 1-line delay circuit 5d are given to the adder circuit 11c, and the output 126 of the adder circuit 11c is sent to one input terminal of the subtracter circuit 10d via the 1/2 times circuit 12e. An output 127 is provided. The output 103 of the one-line delay circuit 5b is applied to the other input terminal of the subtraction circuit 10d. The output 128 of the subtraction circuit 10d is given to a 1/2 multiplier circuit 12f.

The output 129 of the 172x circuit 12f is a direct addition circuit lid.
At the same time, its output 131 is applied to the 2-sample delay circuit 5 via 51 to the other input terminal of the adder circuit lid.

The output 132 of the adder circuit lid is applied to one input terminal of the adder circuit lie via the 1/2 multiplier circuit 12g. The output 130 of the two-sample delay circuit 5 is applied to the other input terminal of the adder circuit lie. The output 134 of the adder circuit lie is added to the 1x circuit 12h, and the output of the 172x circuit 12h is added to the output 1 of the absolute value circuit 13a.
36 is applied to the subtraction circuit 10e. The output 137 of the constant generation circuit 14a is applied to the other input terminal of the subtraction circuit 10e. The output 112 of the subtraction circuit 10e is output as the vertical correlation detection circuit output.

FIG. 5 is a block diagram showing the internal configuration of one embodiment of the horizontal correlation detection circuit 7b. In this FIG.
1f, and the output 138 of this adder circuit iir is 1
The output 139 is applied to one input terminal of the adder circuit 11g via the /doubling circuit 12i. The output 103 of the one-line delay circuit 5b is applied to the other input terminal of the adder circuit 11g. The output 140 of the adder circuit 11g is given to the 1/2 times circuit 12j.

The output 141 of the 172x circuit 12j is the direct addition circuit 11h.
The output 143 is applied to one input terminal of the adder circuit 11h via four-sample delay circuits 5m and 5n.

The output 144 of the adder circuit 11h passes through the 1/2 multiplier circuit 12k, and its output 145 is applied to one input terminal of the subtracter circuit 10f. The output 142 of the 4-sample delay circuit 5m is applied to the other input terminal of the subtraction circuit 10f.

The output 146 of the subtraction circuit 10f is applied to the 1/2 multiplication circuit 121, the output 147 thereof is input to the absolute value circuit 13b, and the output 148 of the absolute value circuit 13b is applied to the subtraction circuit Log.

A constant generation circuit 14b is connected to the other input terminal of the subtraction circuit 10g.
An output 149 is given. Output 11 of subtraction circuit 10g
3 is output as the horizontal correlation detection circuit output.

Next, the operation will be explained. A sampling sequence 101 of an NTSC composite color television signal sampled by the A/D converter 4 at a sampling frequency fs=4fsc is passed through delay circuits 5a, 5b, 5c, and 5d, thereby vertically distributing it on the screen. - Sample values at five sample points on the straight line will be obtained simultaneously.

That is, the composite color television signal (sample value) S(m, n) at the position of coordinates (m, n) is transmitted to the one-line delay circuit 5.
When the signal S (m, n-2) appears at the output end (signal line) of signal b, the signal S (m, n-2) appears at the output end of the one-line delay circuit 5d.
A signal f3 (m, n-
1) appears, and the signal S appears at the output terminal of the one-line delay circuit 5a.
(m, n+1) appears, and a signal S(m, n+2) appears at the output end of the A/D converter 4. A luminance signal/chrominance signal separation filter is constructed based on the sample values of sample points spanning five lines on the screen.

In this invention, color signals are extracted by filter processing having the following transfer functions as a vertical filter, a horizontal filter, and a horizontal band filter.

Vertical filter: Cv (Z) = (1/4) (I Z
−2 horizontal filter: Ch(Z)=(1/4)(1
-Z-2) 2 horizontal band filter: Cvh (Z) = (1/
4) (I Z-t)2- (1/8) (1-Z-2)
2(1+Z-4) The output 106 of the vertical filter 6a thus obtained is passed through the compensation delay circuit 5f, the output 110 of the horizontal filter 6b is passed through the compensation delay circuit 5g, and the output 107 of the horizontal band filter 6C is output. are outputs 109 and 1 to the switch circuit 9 through the compensation delay circuit 5e, respectively.
11,108.

The operation of the circuit that determines which of the color output signals of the vertical filter 5a, horizontal filter 6b, and horizontal band filter 6C is selected will now be described.

Regarding the sample point of interest, the correlation between images in the vertical and horizontal directions is detected, and when the correlation is particularly strong in the vertical direction, the output 106 of the vertical filter 6a is selected, and when the correlation is particularly strong in the horizontal direction, the output 106 of the vertical filter 6a is selected. Output 11 of
0 is selected, and in other cases, the switch circuit 9 is switched so as to select the output of the horizontal band filter 6C.

Let the vertical uncorrelated energy be Dv (Z) and the horizontal uncorrelated energy be Dh (Z), introduce absolute value approximation, and express using a transfer function as follows.

Dv (Z) = 1 (-1/4) (1-Z-'勺2(1+Z-2)2+Dh (Z) = + (-1/
4) (1+Z-')"(1-Z-')2+The above two equations block the DC component and color subcarrier frequency component in the vertical and horizontal directions, respectively, and block the DC component and the color subcarrier frequency component in the horizontal and vertical directions, respectively. It has a filter characteristic that blocks the frequency component of the color subcarrier frequency.

At this time, if Dv (Z)≦Kv (Kv: vertical correlation threshold constant), it is determined that there is a correlation in the vertical direction, and Dh
(Z)≦Kh (Kh: horizontal correlation threshold constant)
If so, it is determined that there is a correlation in the horizontal direction.

That is, the determination circuit 8 uses the output 1 of the vertical correlation detection circuit 7a.
12 and the output 113 of the horizontal correlation detection circuit 7b are input, and a selection signal 114 is outputted to control the output of the switch circuit 9 to become a filter output as shown below.

If Dv(Z) > Kv and Dh(Z) > Kh, then C(Z) = Cvh (Z) If Dv(Z)≦KV and Dh(Z) > Kh, then C
If (Z) = Cv (Z) DvCZ) > Kv and Dh (Z)≦Kh, then
C(Z)= Ch(Z) If Dv(Z)≦Kv and Dh(Z)≦Kh, then C(Z
) = Cvh (Z) In addition, the luminance signal 117 is obtained by subtracting the color signal output of the switch circuit 9 from the composite signal of the compensation delay circuit 5h.

In this way, the luminance signal/color signal separation filter compatible with image correlation according to this embodiment uses the luminance signal/chrominance signal separation filters depending on the correlation between images in the vertical direction and the horizontal direction, so that the luminance signal and chrominance signal separation filter in areas where the image changes rapidly can be separated. The influence of signal leakage to each other channel can be reduced, and dot interference can be reduced.

In the above embodiment, the composite color television signal is sampled at a frequency four times the color subcarrier synchronized with the horizontal frequency, but if the frequency is arranged in a grid on the screen, the color subcarrier is sampled. Sampling is not limited to four times the carrier wave, but may be performed at other frequencies.

Further, in the above embodiment, the vertical filter 6a and the horizontal filter 6b are configured as second-order digital filters, but they may be configured with a higher order number.

Further, in the embodiment described above, the horizontal band filter 6c is configured with a digital filter of second order in the vertical direction and eighth order in the horizontal direction, but it may be configured with a higher order of each.

Furthermore, in the above embodiment, as a means for detecting vertically uncorrelated energy and horizontally uncorrelated energy, a quadratic
Although it is constructed using a dimensional digital filter, the number of orders may be increased or decreased.

At this time, it is clear that the number of delay circuits can be reduced by reducing the order in the vertical direction.

〔Effect of the invention〕

As described above, this invention uses luminance signal and color signal separation filters depending on the correlation between vertical and horizontal images of a composite color television signal.
It is possible to reduce the influence of leakage of luminance signals and color signals to each other channel in areas where image changes are severe,
It has the effect of reducing dot interference.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing an embodiment of the image correlation compatible luminance signal/chrominance signal separation filter of the present invention, FIG. 2 is a block diagram showing the internal configuration of the vertical filter in the same embodiment, and FIG. 3 is the same as the above. FIG. 4 is a block diagram showing the internal structure of the horizontal filter in the embodiment. FIG. 4 is a block diagram showing the internal structure of the vertical correlation detection circuit in the embodiment. FIG. 5 is a block diagram showing the internal structure of the horizontal correlation detection circuit in the embodiment. 6 is a schematic block diagram showing an example of a conventional luminance signal chrominance signal separation filter, and FIG. 7 is an NTS
2 is a diagram showing an arrangement on a screen of a signal sequence obtained by synchronously sampling a C-scheme composite color television signal at four times the color subcarrier frequency; FIG. l...Input terminal, 2, 3...Output terminal, 4...N converter, 5a to 5d...Delay circuit, 6a...Vertical direction filter, 6b...Horizontal direction filter, 6C・-
・Horizontal band filter, 7a... Vertical correlation detection circuit, 7
b...Horizontal correlation detection circuit, 8...Judgment circuit, 9...
・Switch circuit, 10a to 10h-subtraction circuit, 1
1a to 11h...addition circuit, 12a to 121 ・
1/2x circuit, 13a. 13b... Absolute value circuit, 14a, 14b... Constant generation circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A composite video signal sampled at a predetermined frequency synchronized with the horizontal scanning frequency is delayed so that each sample point is arranged in a grid on the screen, and the five lines are arranged vertically in a straight line on the screen. a delay means for simultaneously obtaining sample values of five sample points over the range; A vertical filter receives the sample value of the fourth sample point as input and extracts and outputs a frequency component corresponding to the component of the vertical color subcarrier; A horizontal filter that extracts and outputs a frequency component corresponding to a color subcarrier component, and a horizontal filter that receives the output of the vertical filter as input and extracts and outputs a frequency component that corresponds to a horizontal color subcarrier component. A bandpass filter and the sample values of the first, third and fifth sampling points are input, and the DC component in the vertical direction and the frequency component corresponding to the color subcarrier component, as well as the frequency component corresponding to the color subcarrier component in the horizontal direction. Vertical uncorrelated energy detection means for detecting vertical uncorrelated energy by excluding frequency components and finding their absolute values, and comparing the magnitude of the vertical uncorrelated energy with a first set value given from the outside. vertical correlation detection means for determining that there is a correlation in the vertical direction when the vertical uncorrelation energy of the particles is smaller than the first set value;
The sample values of the third and fourth sample points are input, and the frequency components corresponding to the horizontal direct current component and color subcarrier component as well as the frequency component corresponding to the vertical color subcarrier component are excluded, and their absolute values are removed. A horizontal uncorrelated energy detection means detects the horizontal uncorrelated energy by determining the horizontal uncorrelated energy, and compares the horizontal uncorrelated energy with a second setting value given from the outside, and detects the horizontal uncorrelated energy. horizontal correlation detection means that determines that there is a correlation in the horizontal direction if the value is smaller than the second set value; When there is no correlation in the horizontal direction, a control signal is sent that causes the vertical filter output to be selected; and when there is correlation in the horizontal direction and there is no correlation in the vertical direction, a control signal is sent that causes the horizontal filter output to be selected. determining means for transmitting a control signal that selects the output of the horizontal band filter when there is a correlation in both the vertical and horizontal directions, or a switch that outputs a color signal component in accordance with the signal sent from the determining means; 1. A video correlation compatible luminance signal/chrominance signal separation filter comprising: a circuit; and a subtraction circuit that subtracts the output of the switch circuit from the composite video signal to output a P degree signal component. (2) The input signals of the vertical filter, the horizontal filter, the vertical uncorrelated energy detecting means, and the horizontal uncorrelated energy detecting means are provided by the delay means whose number of sample points is not limited to five. An image correlation compatible luminance signal chrominance signal separation filter according to claim 1.