JPH0810944B2 - Adaptive luminance signal / color signal separation filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is applicable to an NTSC color TV.
The present invention relates to a luminance signal for extracting a luminance signal (hereinafter referred to as Y signal) or a color signal (hereinafter referred to as C signal) from a signal, and a color signal separation filter (hereinafter referred to as YC separation filter). After D conversion, YC separation is performed digitally.

[Conventional technology]

First, when the analog NTSC signal is digitized, the signal sequence S (i, j) (i = 1,
2,3 ..., m, j = 1,2,3 ..., N) is shown in FIG. However
i and j are the array numbers of the sample points in the horizontal and vertical directions, respectively. The sampling frequency fs at this time is the color subcarrier frequency
It is normal to choose four times fsc. In FIG. 12, the Y signal and the C signal of the sampling point signal S (i, j) have the following relationship.

S (i, j) = Y (i, j) + C (i, j) Further, in a normal television signal, there is a property that correlation between adjacent sample points in one field in the horizontal and vertical directions is strong. . Further, in the NTSC system, since scanning is performed by interlacing, the phase of the C signal is inverted every line and every two sampling points as shown in FIG. These characteristics can be used to perform YC separation digitally.

As shown by the corresponding symbols in FIGS. 12 and 13, the color subcarrier phase is four points before and after the two sample points and one line up and down with respect to the sample point of interest in one field. Since they are different by 180 °, YC separation can be performed by adaptively switching digital filters within one field.

FIG. 14 is a block diagram showing the configuration of a conventional adaptive YC separation filter disclosed in, for example, Japanese Patent Laid-Open No. 60-134587. In the figure, 1 is an A / D converter for digitizing an analog NTSC signal 101, 2 is a horizontal / vertical selection type filter for removing a Y signal component from an output 102 of this A / D converter 1, 3
Is a delay element for compensating the delay in the horizontal / vertical direction selection type filter 2, and 4 is a subtractor for obtaining the difference between the output 104 of the horizontal / vertical direction selection type filter 2 and the output 105 of the delay element 3.

The configuration of the horizontal / vertical direction selective filter 2 is shown in FIG. In the figure, 5 is a 1H delay device that delays the input signal 102 by one line, 6 is a 2D delay device that delays the input signal 102 by two sampling points, and 7 is an output 103 of the 1H delay device 5 that is delayed by two sampling points. 2D delay device, 8 sets the output 111 of the 2D delay device 7 to 1
1H delay device for delaying by line, 9 is output 11 of 2D delay device 7
2D delay device for delaying 1 by 2 sample points, 10 is an adder for adding output 110 of 2D delay device 6 and output 112 of 1H delay device 8, 11
Is a subtracter that subtracts the output 112 of the 1H delay unit 8 from the output 110 of the 2D delay unit 6, and 12 is the output 113 of the 2D delay unit 9 to the 1H delay unit 5.
The subtractor 13 that subtracts the output 103 of the
And an output 103 of the 1H delay device 5 are added, 14 is a multiplier that multiplies the output 115 of the adder 10 by 1/4, 15 is an absolute value circuit that takes the absolute value of the output 121 of the subtractor 11, 16 Is a multiplier that multiplies the output 111 of the 2D delay unit 7 by 1/2, 17 is an absolute value circuit that takes the absolute value of the output 122 of the subtractor 12, and 18 is 1/4 of the output 116 of the adder 13
19 is the output from the multiplier 16 to the multiplier 14
Of the absolute value circuits 15 and 17, 22 is a subtractor that subtracts the output 118 of the multiplier 16 from the output 114 of the multiplier 16, and 21 is a comparator that compares the outputs 123 and 124 of the absolute value circuits 15 and 17, 22 Is the comparator 2
Depending on the output of 1, the output 119 of subtractor 19 or the output 120 of subtractor 20
This is a switch for changing over.

Next, the operation will be described. In FIG. 14, a digital signal sequence S digitized by the A / D converter 1
The (i, j) 102 is first filtered by the horizontal / vertical direction selective filter 2. The operation of the horizontal / vertical direction selective filter 2 will be described with reference to FIG. The C signal C (i, j) 104 in the digital signal sequence S (i, j) 111 is shown in FIG. Indicated by. In order to obtain the value of C (i, j), sample values S (i, j + 1), S (i, j-1) at positions (marked with ● in the figure) separated by 1 line above and below the position, respectively. And the sample value S (i +) at a position separated by two sample points on the left and right (marked by Δ in the figure)
2, j) S (i- 2, j) vertically with four sample values, the difference Tv of the horizontal direction of the video signal, calculates the T _H.

Tv = S (i, j + 1) -S (i, j-1) T H = S (i + 2, j) -S (i-2, j) and these signals _{Tv (121), T H (} 122) absolute value by the absolute value circuits 15 and 17 respectively | Tv | (123), | T H | (12
4) is converted to.

Next, these | Tv | (123) and | T _H | (124) are input to the comparator 21, and the comparator 21 switches the switch 22 according to the following conditions to output the output signals 119 and 120 of the subtractors 19 and 20. Selection is made and the C signal 104 is extracted.

| Tv | <| T _H | when side terminal of the switch _{22 | T H | ≦ | Tv} | That side terminal of the switch 22 when, S (i, j) with respect to vertical, horizontal neighboring C
The sample value S (i, j + 1) at the phase inversion sampling position of the signal,
S (i, j-1), S (i + 2, j), S (i-2, j) are used to find the vertical difference absolute value and the horizontal difference absolute value, and these values are The following filter calculation is performed using two sample values in the smaller direction, and adaptive control is performed so as to remove the low frequency component of the video signal.

Therefore, when the switch 22 is connected to the side terminal, this horizontal / vertical direction selective filter performs calculation by using the sample value in the vertical direction, and when connected to the side terminal, calculates by using the sample value in the horizontal direction. I do.

As a result, the low frequency components of the vertical or horizontal video signal at the sampling position of S (i, j) are removed, and the Hc signal 119 or Vc signal 120 is immediately obtained as the C signal 104. Further, the Y signal 106 at this time is obtained as the difference between the output signal 105 of the delay element 3 in FIG. 14 and the C signal 104 by the following calculation.

Y (i, j) = S (i, j) -C (i, j) Y when the conventional adaptive separation filter shown above is used.
The passbands of the signal and the C signal are shown in FIG. In Fig. 16, μ and ν are horizontal and vertical frequency axes, respectively, and f _l is 525.
In the cycle / screen height (hereinafter referred to as CPH), a region with a horizontal line drawn is a Y signal pass band, and the other regions are C signal pass bands.

[Problems to be solved by the invention]

Since the conventional adaptive YC separation filter is configured as described above, horizontal and vertical frequencies are fsc / 2 (fsc is 3.58 MHz for color subcarrier) and f _l / 4 (fsc) as shown in FIG. f
_l is Y signal 525CPH) or more diagonal components are blocked. Further, the Y signal of the horizontal component having a horizontal frequency near fsc is cut off if there is any vertical component. On the other hand, the Y signal of the vertical component whose vertical frequency is near f _l / 2 is also blocked if there is any horizontal component. In this way, the band of the Y signal is limited regardless of whether it is a still image or a moving image, so there is a problem that the resolution is low.

The present invention has been made to solve the above problems, and is an adaptive type that can improve horizontal and vertical resolution in a still image and can appropriately prevent image quality deterioration and cross color generation even in a moving image. The purpose is to obtain a YC separation filter.

[Means for solving problems]

The adaptive YC separation filter according to the present invention is provided with a filter in the time direction in addition to the horizontal and vertical filters in the conventional adaptive YC separation filter, and in the horizontal and vertical directions in the conventional adaptive YC separation filter. In addition to the absolute difference value, the three absolute value differences in the time direction are compared, and one of the three filters is selected and adaptively switched according to the magnitude relationship. .

[Action]

The adaptive YC separation filter according to the present invention adaptively switches the filters in the horizontal, vertical, and time directions according to the local change of the image, thereby enabling YC separation with higher resolution and without cross color. And

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.
In FIG. 1, 1 is an A / D converter that converts the analog NTSC signal 101 into a digital signal, and 42 is a horizontal / vertical / time direction selective filter that removes the Y signal component from the output of the A / D converter 1. 43 is a delay element for compensating for the delay in the horizontal / vertical / time direction selection type filter 42, and 4 is the difference between the output 104 of the horizontal / vertical / time direction selection type filter 42 and the output 105 of the delay element 43. It is a subtractor.

The configuration of the horizontal / vertical / time direction selective filter 42 is shown in FIG. In the figure, 30 is a 1F delay device that delays the input signal 102 by one frame, 31 is a 1H delay device that delays the input signal 102 by one line, and 32 is a 2D that delays the output 134 of the 1H delay device 31 by two sampling points. Delay device, 5 is the output of 1F delay device 30
1H delay device to delay 130 by 1 line, 6 is 1F delay device 30
2 is a 2D delay device that delays the output 130 of the sample 1 by 2 sample points, and 7 is a 2D delay device that delays the output 103 of the 1H delay device 5 by 2 sample points. 8 delays the output 131 of the 2D delay device 7 by one line 1
An H delay device 33 is a 1F delay device that delays the output 131 of the 2D delay device 7 by one frame, and a reference numeral 9 is a 2D delay device that delays the output 131 of the 2D delay device 7 by two sampling points. Also, 10 is the output of the 2D delay device 6.
Adder for obtaining the sum of 135 and the output 132 of the 1H delay device 8, 11 is 2D
A subtracter for obtaining the difference between the output 135 of the delay device 6 and the output 132 of the 1H delay device 8, 12 is the output 136 of the 2D delay device 9 and the output 1 of the 1H delay device 5.
Subtractor to obtain the difference from 03, 13 is the output 136 of the 2D delay device 9 and 1H
An adder for obtaining the sum with the output 103 of the delay device 5, 34 is a 2D delay device 3
An adder that obtains the sum of the output 137 of 2 and the output 133 of the 1F delay device 33, and a subtractor 35 that obtains the difference between the output 137 of the 2D delay device 32 and the output 133 of the 1F delay device 33. 14 is 1/4 at output 138 of adder 10
, 15 is an absolute value circuit that takes the absolute value of the output 148 of the subtractor 11, 16 is a multiplier that multiplies the output 131 of the 2D delay unit 7 by 1/2, and 17 is the absolute value of the output 149 of the subtractor 12. An absolute value circuit that takes a value, 18 is a multiplier that multiplies the output 139 of the adder 13 by 1/4, 36
Is a multiplier that multiplies the output 140 of the adder 34 by 1/4, and 37 is a subtractor
It is an absolute value circuit that takes the absolute value of the output 150 of 35. 19 is a subtracter for obtaining the difference between the output 141 of the multiplier 14 and the output 144 of the multiplier 16, 20 is a subtractor for obtaining the difference between the output 144 of the multiplier 16 and the output 142 of the multiplier 18, 38 is a multiplier A subtracter 21 for obtaining the difference between the output 144 of 16 and the output 143 of the multiplier 36, 21 is three absolute value circuits 15, 1
A comparator that compares the respective outputs 151,152,153 of the 7,37, 2
2 is the output of the comparator 21, the output of the subtractor 19, 20, 38 145,14
It is a switch that switches either of 6,147.

Next, the operation will be described. In this embodiment, since the filter calculation is performed in the three-dimensional space-time, the analog NTSC
The signal sequence when the signal is digitized is S (i, j, k)
(I = 1,2,3, ..., m, j = 1,2,3 ..., n, k = 1,2,3, ...
, L), the sampling point signal S (i, j, k) and the Y signal, C signal have the following relationship. However, i and j are the same as above,
k represents the array element number of the sampling point in the time direction.

S (i, j, k) = Y (i, j, k) + C (i, j, k) The digital signal sequence S (i, j, k) 102 digitized by the A / D converter 1 is It is filtered by a horizontal / vertical / time direction selective filter 42. The operation of the horizontal / vertical / time direction selective filter will be described with reference to FIG.
C signal in the digital signal sequence (i, j, k) 131 C (i,
The j, k) 104 is indicated by a double circle in FIGS. 3 and 4. This C
To obtain the value of (i, j, k), two sample points are left and right from the position. Sample values S (i + 2, j, k), S (i-2, j, k), and the positions one line above and below Sample values of S (i, j + 1, k), S (i, j−1, k) and the positions one frame before and after each Of the sampling signals S (i, j, k + 2) S (i, j, k−2) of the horizontal direction, the vertical direction, and the time direction difference T _H , T
Calculate v, T _T.

Tv = S (i, j + 1, k) -S (i, j-1, k) T _H = S (i + 2, j, k) -S (i-2, j, k) T _T = S (i, j, k + 2) -S (i, j, k-2) and these signals Tv (148), T _H (149), T _T (15
0) is the absolute value | Tv |
(151), | T _H | (152), | T _T | (153).

Next, these absolute values | Tv | (151), | T _H ｜ (152), | T _T ｜
(153) is input to the comparator 21, and the comparator 21 switches the switch 22 in accordance with the following conditions to subtract the subtractors 19 and 2.
The output signals 145, 146, 147 of 0, 38 are selected, and the C signal 104 is taken out.

| Tv | <| T _H | and | Tv | ≦ | T _T | switch 22 side terminal | T _H | <| T _T | and | T _H | ≦ | Tv | switch 22 side terminal | When T _T | <| Tv | and | T _T | ≦ | T _H |, the side terminal of the switch 22, that is, the phase of the neighboring C signal in the horizontal, vertical, and time directions with respect to S (i, j, k) Sample value S (i +
2, j, k), 2 (i-2, j, k), S (i, j + 1, k), S (i, j−1,
k), S (i, j, k + 2), S (i, j, k-2) are used to obtain the horizontal direction absolute difference value, vertical direction difference absolute value, and time direction difference absolute value. The following filter calculation is performed using the two sample values in the direction in which the value is the smallest, and adaptive control is performed so as to remove the low frequency components of the video signal.

Therefore, this horizontal / vertical / time direction selective filter is
When the switch 22 is connected to the side terminal, the vertical sampled value is used for the calculation.When the switch 22 is connected to the side terminal, the horizontal sampled value is used for the calculation, and the side terminal is connected.
Calculation is performed using sampled values in the time direction.

As a result, the low frequency component of the video signal in the horizontal direction, the vertical direction, or the time direction at the sampling point position of S (i, j, k) is removed, and the Vc signal 145, Hc signal 146, and Tc signal 147 are immediately output. It is obtained as a C signal 104. Also, Y at this time
The signal 106 is the output signal 105 and C of the delay element 3 in FIG.
The difference from the signal 104 is obtained by the following calculation.

Y (ijk) = S (ijk) -C (ijk) FIG. 5 shows the pass band of the Y signal when the adaptive YC separation filter according to this embodiment described above is used. This pass band includes a pass band when the switch 22 shown in FIG. 6 is connected to the side terminal, a pass band when the switch 22 shown in FIG. 8 is connected to the side terminal, and FIG. The switch 22 is combined with the pass band when it is connected to the side terminal. 7. FIG. 7 is a view of FIG. 6 viewed from the negative direction of the f-axis, FIG. 9 is a view of FIG. 8 viewed from the negative direction of the f-axis, and FIG. It is the figure seen from the positive direction of.

Although the horizontal / vertical / temporal direction selective filter 42 has the simplest configuration in the above embodiment, a circuit for obtaining the absolute value of the difference between the sample values for obtaining the correlation between the horizontal, vertical, and temporal images, and The characteristics of the adaptive YC separation filter are further improved by increasing the order of the horizontal, vertical and temporal filters.

In the above embodiment, the horizontal / vertical / temporal direction selection filter removes the low frequency component of the video signal and extracts the chrominance signal, but it removes the high frequency component to extract the luminance signal. Of course, it is okay. In this case, each of the subtractors 19, 20, 38 in FIG. 2 may be an adder.

〔The invention's effect〕

As described above, according to the adaptive luminance signal / color signal separation filter of the present invention, the A / D conversion means for digitizing the composite color television signal and the neighboring sample values in the horizontal, vertical, and time directions are used. A horizontal filter, a vertical filter, and a temporal filter that remove the frequency component of either the low band or the high band of the video signal, and the sample point of interest and the color subcarrier phase are inverted. Use the sample values of the neighboring sampling points in the vertical or horizontal direction on the screen, or the neighboring sampling points in the time direction in which the color subcarrier phase inverts the relevant sampling point, and use the sampling values of A difference absolute value calculating means for calculating each difference absolute value in the horizontal direction, the vertical direction, and the time direction from the sample point is compared with the above-mentioned difference absolute value. If so, the horizontal filter is adaptively switched, if the vertical difference absolute value is the minimum, the vertical filter is adaptively switched, and if the temporal difference absolute value is the minimum, the temporal filter is adaptively switched. A filter switching means composed of a circuit is provided, and the three-dimensional characteristic of the television signal is utilized to
The horizontal / vertical / time-selective filter operates according to the direction with the least change in the vertical direction or the time direction, and YC separation is performed, so that the TV is more localized than the conventional adaptive YC separation. It is possible to construct a YC separation filter having improved responsiveness to changes in the John signal, high resolution, and little deterioration in image quality.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an adaptive YC separation filter according to an embodiment of the present invention, and FIG. 2 is a concrete configuration diagram of a horizontal / vertical / time direction selection type filter according to an embodiment of the present invention.
FIGS. 3 and 4 are explanatory diagrams showing the arrangement of the phase of the color signal and the sample position in space-time relating to the operating principle of the horizontal / vertical / temporal direction selective filter, and FIGS. 5 to 11 in this invention. FIG. 5 is a diagram showing a pass band of a Y signal of a filter, FIG. 5 is a diagram showing a pass band of a Y signal when an adaptive YC separation filter according to the present invention is used, FIG. 6, FIG. 8, FIG. Shows the pass band of the Y signal when the adaptive YC separation filter in the present invention selects the vertical filter, horizontal filter, and time filter, respectively, FIG. 7, FIG.
Figures 6 and 8 are views as seen from the negative direction of the f-axis, and Figure 11 is a view of Figure 10 as seen from the positive direction of the μ-axis, and Figure 12
The figure is an explanatory diagram showing the arrangement of the sampling position of the NTSC signal on the 1-field screen, and Fig. 13 is the arrangement of the phase of the color signal and the sampling position on the 1-field screen of the operating principle of the horizontal / vertical direction selective filter. Fig. 14 is a block diagram of a conventional adaptive YC separation filter, Fig. 15 is a concrete block diagram of a horizontal / vertical direction selection filter in the conventional adaptive separation filter, and Fig. 16 is a conventional structure. FIG. 6 is a diagram showing passbands of a Y signal and a C signal when using the adaptive YC separation filter of FIG. 1 ... A / D converter, 2 ... horizontal / vertical selection filter, 3,43 ... delay element, 4,11,12,19,20,35,38 ... subtractor, 5,8, 31 …… 1H delay device, 6,7,9,32 …… 2D delay device, 10,1
3,34 …… Adder, 14,16,18,36 …… Multiplier, 15,17,37…
… Absolute value circuit, 21 …… Comparator, 22 …… Switch, 30,33
…… 1F delay device, 42 …… Horizontal / vertical / time direction selective filter. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An A / D conversion means for digitizing a composite color television signal, and an arithmetic operation using sample values in the horizontal, vertical and temporal directions, to obtain a low or high frequency band of a video signal. A horizontal filter, a vertical filter, or a time filter that removes one of the frequency components, and a neighboring sampling point in the vertical or horizontal direction on the screen where the sample point of interest and the color subcarrier phase are inverted, or the sample of interest. The absolute value of the difference between the sample point of the point and the sample point of the neighboring sample point in the time direction in which the color subcarrier phase is inverted in the horizontal direction, the vertical direction, and the time direction from the sample point of the above neighborhood with respect to the input image is used. Absolute difference value calculation means for calculating the difference absolute value and the absolute value of each difference absolute value are compared, and if the difference absolute value in the horizontal direction is the minimum, the horizontal direction filter is used, and the difference absolute value in the vertical direction is calculated. An adaptive type comprising: a vertical switching filter if it is minimum, and a filter switching means composed of a comparison switching circuit that adaptively switches the temporal filter if the absolute difference in the time direction is minimum. Luminance signal and color signal separation filter.