JPS63124696A - Adaptive type luminance signal/chrominance signal separation filter - Google Patents

Abstract

PURPOSE:To improve the resolution by utilizing the 3-dimensional characteristic of a signal and selecting adaptively three kinds of 2dimension filters applying filtering in two directions having no maximum change among three directions (horizontal, vertical or timewise direction) so as to execute the YC separation thereby improving the response to a change in a local TV signal. CONSTITUTION:A vertical/horizontal/timewise direction selection filter 2 provided with a timewise direction filter in addition to the horizontal/ vertical filter in a conventional filter is connected to an output of an A/B converter 1, and the three values, the difference absolute value in the timewise direction in addition to the horizontal and vertical difference absolute values in a conventional filter are compared, and three kinds of 2-dimension filters applying filtering in two directions whose differential absolute value is not maximum, that is, three kinds of filters in the vertical and timewise direction, horizontal and timewise direction or horizontal and vertical direction are switched adaptively. In this way, the three kinds of the 2-dimension filters comprising filters in two directions among the horizontal/vertical/timewise directions in response to the local change in the picture are switched adaptively, the YC separation with high resolution without production of cross color is attained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a method for extracting a luminance signal (hereinafter referred to as Y signal) or a color signal (hereinafter referred to as C signal) from an NTSC signal in an NTSC color television. VC for
This relates to a separation filter, which digitally performs YC separation after A/D conversion of an analog NTSC signal.

[Conventional technology]

First, when you digitize an analog NTSC signal,
Assuming the screen as a two-dimensional plane, its signal sequence S(t,j)(i
=1.2.3. -mSj=1.2°3,...n) is shown in FIG. However, i and j indicate the horizontal and vertical array numbers of the sample points, respectively. Sampling frequency f at this time
s is typically chosen to be four times the color subcarrier frequency fsc. In FIG. 2, the Y signal and C signal of the sample point signal S(i,j) have the following relationship.

S (i, j) = Y (i, j) -I-C (i, j)
Further, a normal television signal has a property that there is a strong correlation between adjacent sample points in the horizontal and vertical directions within one field. Furthermore, since the NTSC system uses increment scanning, the phase of the C signal is inverted line by line and every two sample points as shown in FIG. Utilizing this characteristic, YC separation can be performed digitally.

Also, as shown by the corresponding symbols in Figures 2 and 3, for the sample point of interest within one field,
Since the color subcarrier phases differ by 180 degrees between the four points before and after the sampling point and at the top and bottom of one line, YC separation can also be performed by adaptively switching the digital filter within one field.

FIG. 4 is a block diagram showing the configuration of a conventional adaptive YC separation filter disclosed in, for example, Japanese Patent Laid-Open No. 58-242367. In the figure, 1 is analog NTSC signal 1
01 is an A/D converter that digitizes, 5 is this A/D
A horizontal signal that removes the Y signal component from the output 102 of converter 1.
a vertical selection filter; 6 is a delay element for compensating the delay in the horizontal/vertical selection filter 5;
4 is a subtracter for calculating the difference between the output 104 of the horizontal/vertical direction selective filter 5 and the output 105 of the delay element 6.

The configuration of the horizontal/vertical direction selective filter 5 is shown in FIG. In the figure, 7 is an IHH delayer that delays the input signal 102 by one line, 8 is a 2D delayer that delays the input signal 102 by 2 sample points, and 9 is the IH delay element 7 output 103
10 is an IHH delayer that delays the output 111 of the 2D delay device 9 by one line; 11 is a 2D delay device that delays the output 111 of the 2D delay device 9 by two sample points;
It is a delay device. In addition, 12 is the output 110 of the 2D delay device 8.
and the output 112 of the IH delay device 10, an adder 1
3 is a subtracter that subtracts the output 112 of the IH delay device 10 from the output 110 of the 2D delay device 8, 14 is a subtracter that subtracts the output 103 of the IH delay device 7 from the output 113 of the 2D delay device 11, and 15 is a 2D delay This is an adder that adds the output 113 of the device 11 and the output 103 of the IH delay element 7. 16 is a multiplier that multiplies the output 115 of the adder 12 by 1/4, 17 is an absolute value circuit that takes the absolute value of the output 121 of the subtracter 13, and 18 is a multiplier that multiplies the output 111 of the 2D delay device 9 by 1/2. vessel, 1
9 is an absolute value circuit that takes the absolute value of the output 122 of the subtracter 14, and 20 is a multiplier that multiplies the output 116 of the adder 15 by 1/4. 21 is from the output 114 of the multiplier 18 to the multiplier 1
22 is a subtracter that subtracts the output 118 of multiplier 20 from the output 114 of multiplier 18, 23 is the output 123 and 124 of absolute value circuit 17.19.
A comparator 24 is a switch that switches between the output 119 of the subtracter 21 and the output 120 of the subtracter 22 according to the output of the comparator 23.

Next, the operation will be explained.

In FIG. 4, a digital signal sequence S (i, j) 102 digitized by the A/D converter 1
is first filtered by the horizontal/vertical direction selective filter 5. The operation of this horizontal/vertical direction selective filter 5 is as follows.

That is, the digital signal sequence S(i,
The C signal C(i,j) 104 at j>1i1 is indicated by a ■ mark in FIG. In order to find the value of C(i, j), sample values S (i, j+
1), S (i, j-1) and the sample value S (i + 2. 3
), S (i-2, 3), the difference numerator of the video signal in the vertical and horizontal directions v (121), TH
(122) is calculated.

Tv=S (i, j+1)-3(i, j
1) T? l=S (i+2.3) S
(i 2. j) and these signals Tv
(121) and T+ (122) are respectively converted to the absolute value ITV+ (123) by the absolute value circuit 17.19.
, I'r+ 1 (124).

Next, these absolute values 1Tvl, lT+l are calculated by comparator 2.
3 and the comparator 23 outputs the output signal 119 (Hc (i, j)) of the subtractor 21.22 by switching the switch 24 according to the following conditions:

120 (Vc (i, j)) and C signal 1
Take out 04.

When ITVI<IT) 41, the ■ side terminal of the switch 24 When 1Tsl≦ITV+, the ■ side terminal of the switch 24, that is, the phase inversion sample position of the C signal adjacent to S (i, j) in the vertical and horizontal directions. Sample value S (i
, j+1), S (t, j-1), S (i+2, j)
, S (i-2, 3) to find the absolute difference value in the vertical direction and the absolute value in the horizontal direction of the video signal, and use the two sample values in the direction in which these values are smaller to apply the following filter. It is adaptively controlled to perform calculations and remove low frequency components of the video signal.

Hc (i, j = 4S (i, j-1) + 45 (1,
j')-;S(i, J+1)vc<i mountain =4S<i-
2,j)+4S(i,j)4S(i+2.j) Therefore,
This horizontal/vertical direction selection type filter performs calculations using vertical sample values when the switch 24 is connected to the ■ side terminal, and performs calculations using horizontal sample values when connected to the ■ side terminal. I do.

As a result, the low frequency components of the vertical or horizontal video signal at the sampling position S(i, J) are removed, and the He signal 119 or VcC signal 120 described above is immediately obtained as the C signal 104.

Further, the Y signal 106 at this time is determined by the following calculation as the difference between the output signal 105 of the delay element 6 and the C signal 104 in FIG.

Y (i, j) -3 (i, j) - C (t, j) Figure 6 shows the passbands of the Y signal and C signal when using the conventional adaptive YC separation filter shown above. . In Figure 6,
μ and ν are the frequency axes in the horizontal and vertical directions, respectively, fL is the horizontal scanning frequency, the area marked with a horizontal line is the passband for the Y signal, and the rest is the passband for the C signal.

[Problem that the invention seeks to solve]

Since the conventional adaptive YC separation filter is configured as described above, as shown in FIG. The Y signal having a horizontal component with a horizontal frequency near fsc is blocked if there is even a slight vertical component.

On the other hand, the vertical component Y signal with a vertical frequency around f t /2 is also blocked if there is even a slight horizontal component. In this way, regardless of whether it is a still image or a moving image, the band of the Y signal is limited, so there is a problem that the resolution is low.

This invention was made to solve the above-mentioned problems, and is an adaptation that can improve the horizontal and vertical resolution of still images, and can also appropriately prevent image quality deterioration and cross color generation in moving images. The purpose is to obtain a type YC separation filter.

[Means for solving problems]

The adaptive YC separation filter according to the present invention includes a time direction filter in addition to the horizontal and vertical filters in the conventional adaptive YC separation filter, and also provides a filter for the horizontal and vertical directions in the conventional adaptive YC separation filter. In addition to the absolute value, a three-way comparison is made with the absolute difference value in the time direction, and three types of two-dimensional filters are used: vertical and temporal, horizontal and temporal. The filters of 3fjH1 in the horizontal and vertical directions are adaptively switched.

[Effect]

The adaptive YC separation filter according to the present invention can improve the image quality by adaptively switching between three types of two-dimensional filters, which are composed of filters in two of the horizontal and vertical two-time directions, according to local changes in the image. High resolution;
Furthermore, it is possible to perform YC separation without generating cross colors.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, ■ is an A/D converter that converts an analog NTSC signal 101 into a digital signal 102, and 2 is this A/D converter.
A horizontal/vertical/time direction selective filter removes the Y signal component from the output of the D converter 1; 3 is a delay element for compensating for the delay in the horizontal/vertical/time direction selective filter 2; 4 is a horizontal/vertical filter - A subtracter that calculates the difference between the output 104 of the time direction selective filter 2 and the output 105 of the delay element 3.

The configuration of the horizontal/vertical/time direction selective filter 2 is shown in FIG. In the figure, 30 is an IF delay device that delays the input signal 102 by one frame, and 31 is an IF delay device 30.
an IF delay device for delaying the output signal 131 by one frame;
32 is an IHH delayer that delays the output 147 of the IF delayer 31 by one line, 33 is a 2D delayer that delays the output 148 of the IH delayer 32 by two sample points, and 34 is the IF delayer 3.
This is a 2D delay device that delays the output 147 of 1 by 2 sample points. 35 is an IH that delays the input signal 102 by one line.
The H delay device 36 is a 2D delay device that delays the output 146 of the IH delay device 35 by two sample points, and the reference numeral 37 is a 2D delay device that delays the input signal 102 by two sample points.

7 is an IHH delay device that delays the output 131 of the IF delay device 30 by one line; 8 is a 2D delay device that delays the output 131 of the IF delay device 30 by two sample points; 9 is an IH delay device 7 output 1
10 is an IHH delayer that delays the output 133 of the 2D delay device 9 by one line; 11 is a 2D delay device that delays the output 133 of the 2D delay device 9 by two sample points. , 38 sets the IH delay element 7 output 132 to 1
It is an IHH extender that delays by a line. 39 is a subtracter that takes the difference between the IH delay element 7 output 132 and the 2D delay device 110 output 137, 19 is an absolute value circuit that takes the absolute value of the output 138 of the subtraction 539, and 40 is the output 136 of the IH delay device 10
and the output 135 of the 2D delay device 8, a subtractor 17
is an absolute value circuit that takes the absolute value of the output 139 of the subtracter 40,
41 is a subtracter that takes the difference between the output 149 of the 2D delay device 33 and the output 151 of the 2D delay device 36, and 42 is an absolute value circuit that takes the absolute value of the output 140 of the subtracter 41.

43 is a vertical filter which receives three outputs: the output 131 of the IF delay device 30, the output 132 of the IH delay element 7, and the output 134 of the IH delay device 38. 44 is a 2D delay device that delays the output 141 of the vertical filter 43 by two sample points, 45 is a 2D delay device that delays the output 142 of the 2D delay device 44 by two sample points, and 46 is the output 141 of the vertical filter 43. Output 142 of 2D delay device 44 and 2D delay device 45
This is a horizontal direction filter that receives three outputs 143 as inputs. 47 is IH delay element 7 output 132 and IH delay element 3
5 and the output 148 of the IH delay device 32 as inputs.

48 is a 2D delay device that delays the output 156 of the time direction filter 47 by two sample points; 49 is the output 1 of the 2D delay device 48;
50 is the output 156 of the time direction filter 47 and the output 1 of the 2D delay device 48.
57 and the output 158 of the 2D delay device 49 as inputs. 51 is the output 135 of the 2D delay device 8
This is a time-direction filter that receives as inputs the output 150 of the 2D delay device 34 and the output 152 of the 2D delay device 37. 52 is an IHH delayer that delays the output 160 of the time direction filter 51 by one line, 53 is an IHH delayer that delays the output 161 of the IH delay device 52 by one line, and 54 is the output 160 of the time direction filter 51 and the IH delay. This is a vertical filter that receives the output 161 of the IHH extension 52 and the output 162 of the IHH extension 553 as inputs. Here, each of the above filters 43, 46.4
7.50.51.54 are adders 56, 60, 64, 68, 72.76, respectively, as shown in FIGS. 8 to 13.
and multipliers 57, 59, 61, 63.65.67.69
．． 71, 73, 75, 77, 79 and subtractor 5B, 62
, 66.70, and 74.78.

Further, 23 is a comparator that compares the output 144 of the absolute value circuit 19, the output 145 of the absolute value circuit 17, and the output 153 of the absolute value circuit 42, and 55 is the output 155 of the comparator 23.
The output 154 of the horizontal filter 46, the output 159 of the horizontal filter 50, or the output 1 of the vertical filter 54
This is a selection circuit that selects one of 63.

Next, the operation of this YC separation filter will be explained. Here, we will perform filter operations in three-dimensional space, so
The signal sequence when the analog NTSC signal is digitized is S (t, j, k) (i=1.2, 3...t
m-, j-L 2. 3. ..., nl = 1.2,
3. ..., X), and the sample point signal S(i, j,
It is assumed that the following relationship exists between k), the Y signal, and the C signal.

(However, it J is the same as above, and indicates the array number of the sample point in the time direction.) S(iljlk)=Y(ilj
lk) + C(iljlk) In Figure 1, A/D
The digital signal sequence S (i, j, k) 102 digitized by the converter 1 is filtered by the horizontal/vertical/time direction selective filter 2 . The operation of this horizontal/vertical/time open direction selective filter 2 is as follows.

That is, the digital signal sequence S(i, j.

The C signal C(i, j, k) 104 at k) 102 is
It is indicated by the mark ◎ in FIGS. 14 and 15. This C(i,
In order to find the value of j, k), the sample value S (il2.j, k) at a position (marked [stock] on the X axis) that is two sample points away from that position on the left and right.

S (i-2, j, k), sample values S (i.

j+l, k), S (i, j-1, k),
and sample points S (i, j, +2), S (
i.

↓ Six sample values of j, -2) are obtained from each delay device, and using these, the difference numerator of the video signal in the horizontal and vertical two time directions is obtained.
4 (138), Tv (139), TT (140)
Calculate.

Tl4-3(i-2+j+k) S(Tl2.j,k
)Tv-S(i, il1.k)-3(ilj-1+k)
Tv=S(i, j, +2)-3(i, j, -2) and these signals TI-! (138), Tv (1
39) and TT (140) are the absolute value circuits 19, respectively.
．． 17.42, the absolute value lT+1(144), 1
It is converted into Tvl (145) and ITvl (153).

Next, these absolute values lTHl (144), ITV
I (145), lT1-1 (153) are input to the comparator 23, where IT+l, ITvl.

Among ITvl, the one with the maximum absolute value is determined.

The output of this comparator 23 is further input to a selection circuit 55.

On the other hand, S (il2. j 1. k) 131
．． S (Tl2.j,k)132. 'S (il2.
Vertical filter 43 whose input is il1゜k) 134
(See Figure 8) output 141 as s'(Tl2.j
, k), then S'(il2.L k) 11τS(il2.il1.k) JujōS(il21J
+k)-S(il2+j-1, nin).Furthermore,
S'(i, L k) 142, which is S'(il2.j, k) 141 delayed by two sample points, and this S'(i, j, k
)142 further delayed by two sample points S (i-2,j
, k) 143 and the above S'(il2.j, k)
If the output 154 of the horizontal filter 46 (see FIG. 9) which inputs 141 is CVH (il j, k), then CvH (1+J
)+XS (il'+k)-5S'(il2.j+k)
It can be expressed as

Also, S (il2.j, kJ-2)146. S (”
2. J,k)132. S H+2. j, k-2
) 148 as an input time direction filter 47 (10th
S” (1+21 J).

k), then S”(1+21 J l k> 11th S(il2.3. -2)+HS(il2.j,
It can be expressed as kJ-KuS (+2 to il2.3.). This S”
(i + 2.
, j, k) 157 is further delayed by two sample points.
-2,j,k)15B and S”(il2.j,k)15
If the output 159 of the horizontal filter 50 (see Fig. 11) which inputs 6 and 6 is CTI-1 (i, j, k), then ) ten tongue S
It can be expressed as "(i+j+k>-cumS" (il2.3.k).

Next, S (i, j-1, +2) 152.3 (t,
j-1, k) 135.3 (i, j 1. -2) 1
If the output 160 of the temporal filter 51 (see Fig. 12) inputting 50 is S (i, j-1, k), then ``'(il J-1+ k) = -``ηS(-2 for i+rl+) +HS(ilJ-1+
It can be expressed as ni-man S (t + J-1+ k +2). This S"'(i, j-1, k) 160 is delayed by one line, S"'(i, j, k) 16 L
, this S''(i, j, k) 161 is further delayed by one line, S''(i, il1.k) 162, and the above s''
CTv<i,
L k), then C7v(t, J l k)=-rls"Cil J+1
1 k)+XS (11J +, k)-zS (il
J-Lk).

As described above, the output CvH (i, j, k) 154 of the transverse-horizontal two-dimensional filter via the vertical filter 43 and the horizontal filter 46 and the temporal filter 4
7 and the output C7H (i, j, k) 159 of the horizontal direction filter 50, that is, the time-horizontal two-dimensional filter;
The output CTv(i,
j, k) 163 are input to the selection circuit 55.

In the selection circuit 55, the output CvI-
IH, j, k) 154. CTl-1(i,Lk)159
．． (, rvci, j, k) 163 is selected. The two-dimensional filter can be selected in the following seven cases.

1) When max = ITvl, Cv+(i
, j, k) 1542) max = 1Tv
When l, C7H (i, J, kn1593
) When max -1TH1 C-rv(i
, j, k) 1634) tnax = IT
TI = (T? When Ll Cy) 4 (i, j
, k) 1545) max = ITTI = I
At the time of TVI Cv+ (ilj, Nin 1546) ts
When ax −ITHI = ITVI CT)l(i
, j, k) 159 or CT i, j, k)
163 7) max = 1Trl = 1Tvl = 1T
When H7, Cw (i, j, k) 154 As a result, the high frequency component of the video signal extracted by the two-dimensional filter is the C signal (i, j, k) of S (i, j, k).

j, k) 104. Further, the Y signal 106 at this time is the output signal 10 of the delay element 3 in FIG.
The difference between C signal 104 and C signal 104 is determined by the following calculation.

Y (i, j+k) = s (j+J+ni -C
j, k) In the above embodiment, the two-dimensional filter was applied even when there were two maximum absolute values, but the C signal was extracted using the one-dimensional filter in the direction where the absolute value was the minimum. It's okay.

In addition, in the above embodiment, the simplest configuration of the horizontal, vertical, and temporal direction selective filters was shown, but a circuit that calculates the absolute difference value of sample values that calculates the correlation between images in the horizontal, vertical, and temporal directions. The characteristics of the adaptive YC separation filter are further improved by increasing the orders of the horizontal, vertical, and temporal filters.

Furthermore, in the above embodiment, the horizontal/vertical/time direction selective filter removes the low frequency components of the video signal and extracts the color signal, but in this case, the high frequency components are removed and the luminance signal is extracted. Of course, it is also possible to do so.

〔Effect of the invention〕

As described above, according to the present invention, the three-dimensional characteristics of a television signal are utilized to provide a two-dimensional Three types of filters are adaptively switched to perform yc separation, so it is possible to
Compared to separation, it is possible to construct a yc separation filter with improved responsiveness to local changes in television signals, high resolution, and less deterioration in image quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an adaptive YC separation filter according to an embodiment of the present invention, and FIG. 2 is a diagram of one sampling position of an NTSC signal.
FIG. 3 is an explanatory diagram showing the arrangement on a single field screen of the phase of a color signal and sample position regarding the operating principle of a horizontal/vertical direction selective filter; Fig. 4 is a block diagram of a conventional adaptive YC separation filter, Fig. 5 is a specific block diagram of a horizontal/vertical direction selective filter in the conventional adaptive YC separation filter, and Fig. 6 is a block diagram of a conventional adaptive YC separation filter. FIG. 7 is a diagram showing the passbands of the Y signal and C signal when a separation filter is used. FIG. 7 is a specific configuration diagram of the horizontal/vertical/time direction selective filter in an embodiment of the present invention. FIG. FIG. 9 is a block diagram showing an example of the vertical filter 43 in FIG. 7, FIG. 9 is a block diagram showing an example of the horizontal filter 46 in FIG. 7, and FIG. A block diagram showing one embodiment of the directional filter 47, FIG. 11 is the horizontal filter 50 in FIG.
FIG. 12 is a block diagram showing one embodiment of the time direction filter 51 in FIG. 7. A/D converter, 2
・・・Horizontal/vertical/time direction selective filter, 3,6・
...Delay element, 4.13.14°21.22,39,4
0,41.58.62.66゜70.74.78...
Subtractor, 7.10, 32, 35°38.52.53...
・IH delay device, 8.9, 11, 33, 34. 36.
37. 44. 45. 48. 49...2D delay device, 12.15, 56, 60.64, 68°72.7
6... Adder, 16.18.20, 57, 59.61
, 63.65. 67, 69. 71. 73°75
．． 77.79... Multiplier, 17.19.42... Absolute value circuit, 23... Comparator, 30.31... IF delay device, 55... Selection circuit, 5... Horizontal・Vertical selection type filter. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] A/D conversion means for sampling and digitizing a composite color television signal at a sampling frequency four times the color subcarrier frequency, and delay means, addition means, subtraction means, and multiplication means, respectively. a horizontal band-pass filter that performs calculations using neighboring sample values in the horizontal, vertical, and temporal directions and removes either the low-frequency or high-frequency components of the video signal;
A vertical band-pass filter, a temporal band-pass filter, and a neighboring sample point in the vertical or horizontal direction on the screen whose color subcarrier phase is inverted with respect to the sample point of interest, or whose color subcarrier phase is inverted with respect to the sample point of interest. absolute difference calculation means for calculating respective absolute difference values in the horizontal direction, vertical direction, and time direction from the sampling points in the vicinity of the input image using sample values of sampling points adjacent to the temporal direction; , and the magnitude relationship of each of the absolute difference values, and if the absolute difference value in the horizontal direction is the maximum, the two-dimensional filter consisting of the vertical band-pass filter and the temporal band-pass filter is used in the vertical direction. If the absolute value of the difference is maximum, then
If the absolute value of the difference in the time direction is maximum, a two-dimensional filter composed of the horizontal band-pass filter and the temporal band-pass filter is composed of the horizontal band-pass filter and the vertical band-pass filter. 1. An adaptive luminance signal/chrominance signal separation filter comprising filter switching means comprising a comparison switching circuit that adaptively switches a two-dimensional filter.