JPS6382087A - Adaptive separation filter for luminance signal and chrominance signal - Google Patents

Abstract

PURPOSE:To improve resolution and to prevent a cross color from being generated by applying a time-directional filter in addition to the horizontal and vertical filters of an adaptive YC separation filter, and switching the horizontal, vertical, and time-direction filters adaptively according to local variation of an image. CONSTITUTION:A digital signal sequence S(i, j, k) 102 digitized by an A/D converter 1 is filtered by a horizontal, vertical, and timedirectional selective filter 42. The absolute values of the horizontal difference, vertical difference, and time-directional difference of a video signal are found by using a sampled value at the phase inversion index position of a C signal which is close to the S(i, j, k) horizontally and vertically and in the time direction. Two sampled values in the direction where those values are smallest are used to perform filter arithmetic and remove the low frequency component of the signal, thereby extracting a color signal. Further, a luminance signal may be extracted by removing the high frequency component. Therefore, response to local variation of a television signal is improved, the resolution is high, and picture quality deterioration can be reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides an NTSC system color television.
Luminance signal 2 for extracting a luminance signal (hereinafter referred to as Y signal) or a color signal (hereinafter referred to as C signal) from the TSC signal
This relates to a color signal separation filter (hereinafter referred to as YC 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,
The signal sequence S(i, j) with the screen as a two-dimensional plane
(i=1.2.3-, mS j=1.2
゜3. ..., N) are shown in FIG. However, 11
J indicates the horizontal and vertical array numbers of the sample points, respectively. The sampling frequency fs at this time is usually selected to be four times the color subcarrier frequency rsc. In FIG. 12, the Y signal and C signal of the sample point signal S (L, j) have the following relationship.

S (t, j) = Y (t, j) + C (i, j) Also,
In a normal television signal, the horizontal within one field,
It has the property that the correlation between vertically adjacent sample points is strong. Furthermore, since the NTSC system uses interlaced scanning, the phase of the C signal is inverted line by line and every two sample points, as shown in FIG. YC separation can be performed digitally by utilizing these characteristics.

In addition, as shown by the corresponding symbols in Figures 12 and 13, for the sample point of interest within one field, the color subcarrier phase power is Since they differ by 180 degrees, 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 Unexamined Patent Publication No. 58-242367. In FIG. vessel, 2 is this A/
3 is a horizontal/vertical selection filter that removes the Y signal component from the output 102 of the D converter 1; 3 is a delay element for compensating for the delay in the horizontal/vertical selection filter 2; 4;
is a subtracter that calculates the difference between the output 104 of the horizontal/vertical direction selective filter 2 and the output 105 of the delay element 3.

The structure of the horizontal/vertical direction selective filter 2 is shown in FIG. In the figure, 5 is an IH delay device that delays the input signal 102 by one line, 6 is a 2D delay device that delays the input signal 102 by 2 sample points, and 7 is the output 10 of the IH delay device 5.
8 is an IH delay device that delays the output 111 of 2D delay device 7 by one line; 9 is an IH delay device that delays output 111 of 2D delay device 7 by one line;
2 delays the output 111 of the 2D delay device 7 by two sample points.
D delay device; 10 is an adder that adds the output 110 of the 2D delay device 6 and the output 112 of the IH delay device 8; 11 is a subtracter that subtracts the output 112 of the IH delay device 8 from the output 110 of the 2D delay device 6; , 12 is the IH from the output 113 of the 2D delay device 9
A subtracter that subtracts the output 103 of the delay device 5, 13 is a 2D
An adder that adds the output 113 of the delay device 9 and the output 103 of the IH delay device 5, 14 a multiplier that multiplies the output 115 of the adder IO by 4, and 15 an absolute value that takes the absolute value of the output 121 of the subtracter 11. 16 is a multiplier that multiplies the output 111 of the 2D delay device 7 by 2; 17 is an absolute value circuit that takes the absolute value of the output 122 of the subtracter 12; 18 is the output 116 of the adder 13;
19 is a subtracter that subtracts the output 117 of the multiplier 14 from the output 114 of the multiplier 16; 20 is a subtracter that subtracts the output 118 of the multiplier 1 day from the output 114 of the multiplier 16; 21 is the output 12 of the absolute value circuit 15.17
A comparator that compares 3 and 124, 22 is the output 119 of the subtracter 19 or the output 12 of the subtracter 20 depending on the output of the comparator 21.
This is a switch that changes between 0 and 0.

Next, the operation will be explained. In Figure 14, A/Di
Digital signal sequence S digitized by converter 1
(i,j) 102 is first filtered by horizontal/vertical direction selective filter 2 .

The operation of this horizontal/vertical direction selective filter 2 will be explained with reference to FIG. Digital signal sequence S(i,j)1
The C signal C(i, j) 104 at 11 is indicated by the [stock] mark in FIG. This C(i.

j), the sample value S (i
, j+1), S (i, j-1), and the sample value S (i
+2. j) Calculate the difference numerators v and TH of the video signals in the vertical and horizontal directions using the four sample values of S (i-2, j).

Tv= S(i, j+1) S(i, j-1
)TH= S(i+2.j) -5(i-2,j)
And these signals Tv(121), TH(1
22) are converted into absolute values 1Tvl (123) and ITHI (124) by absolute value circuits 15 and 17, respectively.

Then these ITvl (123), ITHI (
124) is input to the comparator 21, and the comparator 21 selects the output signal 119.120 of the subtractor 19.20 by switching the switch 22 according to the following conditions.
Take out the signal 104.

When 1Tvl<1TH1, ■ side terminal l of switch 22
When THl≦l Tv l, the sample value S (t, j) at the phase-inverted sample position of the C signal adjacent to the vertically and horizontally with respect to S (i, j) at the ■ side terminal of the switch 22
+1), S (i, j-1), S (i
+2, J), S (i-2, 3) to find the vertical difference and horizontal difference of the video signal, and use the two sample values in the direction where these values are smaller to perform the next filter operation. and is adaptively controlled to remove low frequency components of the video signal.

vc(t,j) −−45(i−2+j)+1S(i,
j) -4S (1+2.j) Therefore, in this horizontal/vertical direction selection type filter, when the switch 22 is connected to the ■ side terminal, calculation is performed using the sample value in the vertical direction, and when the switch 22 is connected to the ■ side terminal, At this time, calculations are performed using horizontal sample values.

As a result, the vertical or horizontal video signal component at the sample position S (t, j) is removed, and the above HcC signal 119 or VcC signal 120 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 3 in FIG. 14 and the C signal 104.

Y(i,j) = S(i,j)−C(i,
j) FIG. 16 shows the passbands of the Y signal and C signal when the conventional adaptive separation filter shown above is used.

In FIG. 16, μ and ν are frequency axes in the horizontal and vertical directions, respectively, ft is 525 lines/screen height, and the horizontally lined area 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, the horizontal and vertical frequencies are f sc/2, f, z/4 (fz
Y signals with diagonal components of 525 lines/screen height) or more are blocked. Further, the horizontal component Y signal having 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 near ft/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 it is an adaptive type that can improve the horizontal and vertical resolution of still images, and can also appropriately prevent image quality deterioration and cross color generation in videos. The purpose is to obtain a YC separation filter.

[Means for solving problems]

The adaptive YC separation filter according to the present invention includes a temporal filter in addition to the horizontal and vertical filters in the conventional adaptive YC separation filter, and also provides the horizontal and vertical filters in the conventional adaptive YC separation filter. In addition to the absolute difference value, a three-way comparison is made with the absolute difference value in the time direction, and depending on the magnitude relationship, one of the three filters mentioned above is selected and switched adaptively. .

[Effect]

The adaptive YC separation filter of this invention can separate YC bones with higher resolution and without cross color by adaptively switching filters in the horizontal and vertical 1-time directions according to local changes in the image. shall be.

〔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 an analog NTSC signal 101 into a digital signal, and 42 is this A/D converter.
Horizontal, vertical, and
A time direction selective filter 43 is a delay element for compensating the delay in the horizontal/vertical/time direction selective filter 42; 4 is a horizontal/vertical/time direction selective filter 4;
This subtracter calculates the difference between the output 104 of the delay element 43 and the output 105 of the delay element 43.

The configuration of the horizontal/vertical/time direction selective filter 42 is shown in FIG.
An IF delay device 31 delays the input signal 10 by one frame.
32 is a 2D delay device that delays the output 134 of the IH delay device 31 by two sample points; 5 is an IH delay device that delays the output 130 of the IF delay device 30 by one line; 6 is IFi! ! Extension tool 30 extension 3030
7 is an IH delay device 5 which delays the by two sample points.
This is a 2D delay device that delays the output 103 of 2 by two sample points. 8 is an IH delay device that delays the output 131 of the 2D delay device 7 by one line, 33 is an IF delay device that delays the output 131 of the 2D delay device 7 by one frame, and 9 is an IH delay device that delays the output 131 of the 2D delay device 7 by 2 sample points. This is a 2D delay device that delays the signal by a minute. Further, 10 is an adder that obtains the sum of the output 135 of the 2D delay device 6 and the output 132 of the IH delay S8, 11 is a subtractor that obtains the difference between the output 135 of the 2D delay device 6 and the output 132 of the IH delay a8, and 12 13 is a subtracter that obtains the difference between the output 136 of the 2D delay device 9 and the output 103 of the IH delay device 5; 13 is an adder that obtains the sum of the output 136 of the 2D delay device 9 and the output 103 of the IH delay device 5; 34; is the output 137 of the 2D delay device 32 and the IF delay device 3
3 is an adder that obtains the sum with the output 133 of 3, and 35 is a subtracter that obtains the difference between the output 137 of the 2D delay device 32 and the output 133 of the IF delay 533. 14 is a multiplier that multiplies the output 138 of the adder 10 by k, 15 is an absolute value circuit that takes the absolute value of the output 148 of the subtracter 11, and 16 is the output 13 of the 2D delay device 7.
Multiplier that multiplies 1 by A, 17 is the output 149 of subtracter 12
An absolute value circuit that takes the absolute value of , 18 is the output 1 of the adder 13
39 is a multiplier that multiplies the genus, 36 is the output 14 of the adder 34
A multiplier that multiplies 0 by 0, 37 is the output 150 of the subtracter 35
This is an absolute value circuit that takes the absolute value of . 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 subtracter for obtaining the difference between the output 144 of the multiplier 16 and the output 142 of the multiplier 18; 38 is a multiplier 16 output 1
44 and the output 143 of the multiplier 36, a subtractor, 2
1 is a comparator that compares the outputs 151, 152, and 153 of the three absolute value circuits 15, 17, and 37, and 22 is the output 1 of the subtracters 19, 20, and 38 based on the output of the comparator 21.
This is a switch that changes between 45°, 146.147.

Next, the operation will be explained. In this example, since filter calculation is performed in three-dimensional space and time, analog NTS
The signal sequence when the C signal is digitized is S (i, j
, k) (i-1, 2, 3,...

171% J ”” 1 r 2+ 3 ””*
Assume that the sample point signal s (i, j, k), the Y signal, and the C signal have the following relationship. However, i.

j is the same as above, and k indicates the array number of the sample point in the time direction.

s (LJ, k) m'/ (i, j, k) +c (
il, k) The digital signal sequence S (i, j, k) 102 digitized by the A/D converter 1 is a horizontal
It is filtered by a vertical/time direction selective filter 42. The operation of this horizontal/vertical/time direction selective filter will be explained with reference to FIG. Digital signal sequence S (i,
C signal C(t, j, k) 104 at j, k) 131
is indicated by ◎ in FIGS. 3 and 4. This C(t, j,
In order to find the value of k), the sample value S(
t+2. j, k), S (i-2, j,
k), sample values S (t, J+1.k), S (i
, j-1°k) and the sample point S (t, j
, k+2).

horizontally using six sample values of S (i, j, −2),
Difference numerator H, TV of the video signal in the vertical 2-time direction.

Calculate T7.

Tv=S(i,j+1.k)-S(i,j-1,k
)TH=S(i+2.j,k)-5(i-2,
j, k) TT2S (i, j, +2) -5 (i,
j, k −2) and these signals Tv (148)
, TH (149), and TT (150) are each given an absolute value of 1 Tvl by the absolute value circuit 15.17.37.
(151).

It is converted to IT+l (152) and IT-1 (153).

Next, these absolute values ITV+ (151), 1TH1
(152), ITTl (153) are input to the comparator 21, and the comparator 21 inputs the switch 22 according to the following conditions.
The output signals 145, 146, 147 of the subtracters 19, 20.38 are selected by switching the C signal 10.
Take out 4.

When lTv l<ITHl and ITVI≦ITTI, the ■ side terminal of the switch 22 ITHI<ITTI and IT) When 41≦ITvl, the ■ side terminal of the switch 22 IT7-1; , S (i, j, k), the sample value S (i+2. j, k) , , S (i
−2,3°k), S (i, j+1.k), S (i
, j-1゜k), S (i, j, +2>, S (1,
J*k-2) to find the horizontal difference, vertical difference, and 1 time difference of the video signal, and use the two sample values in the direction where these values are the smallest to perform the following filter operation to calculate the video signal. It is adaptively controlled to remove low frequency components of the signal.

Vc(i,j,k)=-! S(i, j-1, k
) + soil S (t, j, k) - 1FS (i, j + L k)
)1c (i, j, k) ---Is (t-2, j
, k)+fS (i, j, k)-4-3(i+2.
j, k) rc<i, j, k) - 1 to S (i, J, ni - 2) child ± S (i, j, riichiko 5 (LLk 1,000 2) Therefore, this horizontal/vertical/time direction The selective filter performs calculations using sample values in the vertical direction when the switch 22 is connected to the ■ side terminal, and performs calculations using the horizontal sample values when connected to the ■ side terminal. When connected to a terminal, calculations are performed using sampled values in the time direction.

As a result, the video signal components in the horizontal direction, vertical direction, or time direction at the sample point position of S (t, j, k) are removed, and the above VcC signal 145HcC signal 146
Tc signal 147 is immediately obtained as 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 3 and the C signal 104 in FIG.

Y (i j k) S (i j k
) -C(ij k) FIG. 5 shows the passband of the Y signal when using the adaptive YC separation filter according to this embodiment shown above. This passband is as shown in FIG. The passband when the switch 22 is connected to the ■ side terminal,
The passband when the switch 22 as shown in FIG. 8 is connected to the ■ side terminal and the switch 22 as shown in FIG.
This is a composite of the passband when connected to the side terminal.

Furthermore, Figure 7 is a diagram of Figure 6 viewed from the negative direction of the f axis, Figure 9 is a diagram of Figure 8 viewed from the negative direction of the f axis, and Figure 11 is a diagram of Figure 10 viewed from the negative direction of the f axis. It is a figure seen from the positive direction.

In the above embodiment, the simplest configuration of the horizontal/vertical/time direction selective filter 42 was shown, but a circuit for calculating the absolute difference value of sample values for calculating the correlation between images in the horizontal and vertical two time directions and The characteristics of the adaptive YC separation filter are further improved by increasing the orders of the horizontal and vertical two-time direction filters.

In addition, in the above embodiment, the horizontal, vertical, and temporal direction selection filters remove the low frequency components of the video signal and extract 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. In this case, subtractor 19.20.38 in FIG.
Each of them can be used as an adder.

〔Effect of the invention〕

As described above, according to the present invention, by utilizing the three-dimensional characteristics of a television signal, horizontal, vertical, and
Since the time-selective filter operates and YC separation is performed, the response to local changes in the television signal is improved compared to conventional adaptive YC separation, resulting in higher resolution and less deterioration in image quality. A YC separation filter can be configured.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an adaptive YC separation filter in an embodiment of the present invention, FIG. 2 is a specific configuration diagram of a horizontal/vertical/time direction selective filter in an embodiment of the invention, and FIG. 3 and FIG. 4 is an explanatory diagram showing the phase and spatiotemporal arrangement of the color signal phase and sample position regarding the operating principle of the horizontal/vertical/time direction selective filter, and FIGS. 5 to 11 are the Y of the filter in this invention FIG. 6 is a diagram showing a passband of a signal, and FIG. 5 is a diagram showing a passband of a Y signal when an adaptive YC separation filter according to the present invention is used. FIG. 8 and FIG. 10 respectively show the adaptive type Y in this invention.
Figures 7 and 9 show the passbands of the Y signal when the C separation filter is a vertical filter, horizontal filter, or time filter. FIG. 11 is a diagram of FIG. 10 viewed from the positive direction of the μ axis, FIG. 12 is an explanatory diagram showing the arrangement of sample positions of NTSC signals on a single field screen, Fig. 13 is an explanatory diagram showing the arrangement of color signal phases and sample positions on a single field screen regarding the operating principle of the horizontal/vertical direction selective filter, and Fig. 14 is the configuration of a conventional adaptive YC separation filter. 15 is a specific configuration diagram of a horizontal/vertical direction selective filter in a conventional adaptive separation filter, and FIG.
It is a figure which shows the passband of a signal and a C signal. 1... A/D converter, 2... Horizontal/vertical direction selective filter, 3, 43... Delay element, 4, 11.12° 19.20.35.38... Subtractor, 5. 8. 3
1...-IH delay device, 6.7.9.32... 2D delay device, 10.13.34... Adder, 14. 16.
18゜36... Multiplier, 15.17.37... Absolute value circuit, 21... Comparator, 22... Switch, 30
．． 33...IF delay device, 42...Horizontal/vertical/time direction selective filter. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A/D conversion means for sampling and digitizing a composite color television signal at a sampling frequency four times the color subcarrier frequency, and each comprising a delay means, an addition means, a subtraction means, and a multiplication means, A horizontal filter, a vertical filter, and a temporal filter that perform calculations using neighboring sample values in the horizontal, vertical, and temporal directions and remove either the low frequency component or the high frequency component of the video signal. , using the sample value of a sample point vertically or horizontally adjacent to the sample point of interest and whose color subcarrier phase is reversed, or a sample point adjacent to the sample point in the time direction whose color subcarrier phase is reversed from the sample point of interest. , a difference absolute value calculation means for calculating respective absolute difference values in the horizontal direction, vertical direction, and time direction from the sample points in the vicinity of the input image, and comparing the magnitude relationship of each of the above-mentioned absolute difference values, If the absolute difference value in the horizontal direction is the minimum, use the horizontal filter, if the absolute difference in the vertical direction is the minimum, use the vertical filter, and if the absolute difference value in the time direction is the minimum, use the above time filter. 1. An adaptive luminance signal and chrominance signal separation filter comprising filter switching means comprising a comparison switching circuit that adaptively switches directional filters.