JPS63299482A - Luminance signal/chrominance signal separation filter with correlative correspondence of image - Google Patents

Abstract

PURPOSE:To reduce the influence of the leakage of a luminance signal and a chrominance signal to mutual channel at an area where an image changes remarkably and to reduce dot disturbance, by using a luminance signal/chrominance signal separation filter appropriately based on the correlation of a composite video signal in a vertical and a horizontal directions. CONSTITUTION:A composite color TV signal supplied to an input terminal 1 is sampled at an A/D converter 4. And in the sampled signal, a sample value at a remarked sampling point and the sample values at the sampling points at a picture one line above and one line under are extracted simultaneously by passing through delay circuits 5a and 5b. And extracted sample values are supplied to a vertical direction chrominance signal extraction filter 6a, a horizontal direction chrominance signal extraction filter 6b, a horizontal and vertical direction chrominance signal extraction filter 6c, and an image correlation decision circuit 7. The decision circuit 7 detects the correlation of the image with respect to the remarked sample point in the vertical and horizontal directions, and a switch circuit 8 is switched so that the output of the filter 6a can be selected when the correlation in the vertical direction is large especially, and the output of the filter 6b can be selected when correlation in the horizontal direction is large, and the output of the filter 6c can be selected in other cases.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image correlation compatible luminance signal and chrominance signal separation filter that separates luminance signals and chrominance signals from, for example, an NTSC system composite television signal.

[Prior Art] FIG. 3 is a block diagram showing an example of the configuration of a conventional luminance signal/chrominance signal separation filter.
1), an NTSC composite television signal is input. This composite television signal is sent to the A/D converter (4)
The signal is applied to the vertical filter (6j) and also to the l-line delay circuit (5g). The output of the l-line delay circuit (5g) is given as is to the vertical filter (6j), and the l-line delay circuit (5g) is fed as it is to the vertical filter (6j).
sh) and is further delayed by l lines, and then applied to a vertical filter (6j). Vertical filter (6j
) is a filter usually called a two-line comb filter, and its output is given to a bandpass filter (6k). The output of the bandpass filter (6k) is derived from the output terminal (2) as a color signal (205) and is applied to the first input of the subtraction circuit (9b). Also, the subtraction circuit (9
The second input of b) is connected to the above l line delay circuit (5g).
The output of is given via the compensation delay circuit (51). This compensation delay circuit (51) is a circuit for compensating for the delay in the bandpass filter (6k). and the subtraction circuit (
9b) outputs a luminance signal (207), which is applied to the output terminal (3).

Next, the operation of the luminance signal/chrominance signal separation filter for an NTSC composite television signal will be explained.

The composite television signal (February) sampled in synchronization with the color subcarrier at the sampling frequency fs = 4・fsc (fsc is the color subcarrier frequency) is displayed on the screen in a two-dimensional lattice pattern as shown in Figure 4. It becomes an array. That is, fsc = (4
55/2) full, the phase of the color signal C is inverted by 180 degrees for each line, and four samples are extracted in one cycle. Here, in the figure, Y is a luminance signal, C1,
C2 indicates a color signal.

Now, as symbols representing the delay of l samples and the delay of l lines, using Z transformation, z-l and Z-
Use ノ. Here, Z-' = exp(-J2πf
/4fsc). Also, fsc = (455/2
)fH, so the sentence=910. At this time, a vertical direction filter (6
In step j), a line support signal (204) is extracted for each line including the color signal. Vertical filter (6j
) transfer function Hv(Z) is 11v(Z)=(-1/4)·(]-Z). That is, the line support signal 11c(II, n) at the coordinates (m, n) on the screen in FIG.
)-2S(,n)+S(m,n+1)). Since the line support signal also includes the brightness signal Y,
The color signal C, which is a high frequency component, is filtered by a bandpass filter (6k).
Separate (m,n) from Hc(m,n). The color signal (205) thus obtained is then processed by the subtraction circuit (9).
b) sent to The subtraction circuit (9b) generates a signal S (m , n) obtained by further delaying the one-line delayed signal (202) by the compensation delay circuit (51) according to the bandpass filter ([ik).
By subtracting the color signal C(1,n) (2os) from (206), we get the luminance signal Y(m,n)(207) as shown in the following formula.
Separate.

Y= (II, n) =S (m, n) −C(m
, n) Transfer function 11h (
For example, Rh(Z)=(-1/32)(]-Z-'')2 (1÷
It can be configured as "Z-" (t+z-8).

[Problems to be Solved by the Invention] The conventional luminance signal/chrominance signal separation filter is configured by fixing the characteristics of the vertical direction filter and the horizontal direction filter and combining them as described above. That is, the luminance signal and the color signal are separated by bandpass filters in both the vertical direction and the water direction. Therefore, with conventional filters, in areas where the brightness and color of the image change drastically, the brightness signal and 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 has been made to solve the above-mentioned problems, and provides a method for separating luminance signals and chrominance signals corresponding to image correlation, which 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 provide filters.

[Means for Solving the Problems] The image correlation compatible luminance signal and chrominance signal separation filter according to the present invention is capable of separating a luminance signal and a chrominance signal by delaying an input sampling signal at a sample point of interest and its vicinity. a delay means for simultaneously obtaining the sample points of interest, and an image correlation determination means for determining the image correlation by detecting vertical image correlation and horizontal image correlation from the values of the sample point of interest and the neighboring sample points, respectively. The invention is characterized in that, depending on the determination result, the intelligence of the horizontal filter or the vertical filter is used as the output of the luminance signal/chrominance signal separation filter for images that are particularly resistant to correlation.

[Function] According to the present invention, since the luminance signal and chrominance signal separation filters are used depending on the correlation between the vertical and horizontal images of the composite video signal, the luminance signal and chrominance signal are separated into mutual channels in areas where the image changes rapidly. This can reduce the effect of leakage and reduce dot interference.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a schematic block diagram showing the configuration of a luminance signal/chrominance signal separation filter compatible with image correlation according to an embodiment of the present invention. At the input terminal, the composite color television signal applied to this input terminal (+) is
The signal is applied to an A/D converter (4). This A/D converter (
4) is configured to sample the composite color television signal at a sampling frequency fs=4 fsc.

The composite color television signal sampled by the A/D converter (4) is sent to a 1-line delay circuit (5a), and further passes through an 1-line delay circuit (5b) to determine the signal at a certain sampling point. Line on the screen showing the sample value and its sample point of interest - 11. Sample values at sample points one line below are extracted simultaneously. The sample values extracted by the l-line delay circuits (5a) and (5b) are
The following information is applied to the vertical color signal extraction filter (6a), the horizontal color signal extraction filter (6b), the horizontal/vertical color signal extraction filter (6c), and the image correlation determination circuit (7).

That is, the output (3) of the A/D converter (4) is input to the vertical color signal extraction filter (6a), the horizontal/vertical color signal extraction filter (6c), and the image correlation determination circuit (7).
03), the output (10) of the l line delay circuit (5a)
2) and the output (103) of the one-line delay circuit (5b) are respectively given. In addition, the output (10
2) or given. At this time, for example, the vertical color signal extraction filter (6a) uses a transfer function to
v(Z) = (-1/4) (1-Z-i)2t, and the horizontal color signal extraction filter (6b) is
Cv(Z) = (-1/4) (]-Z)
The horizontal/vertical color signal extraction filter (6c) is expressed as (:l-1v(Z)=(-1/4)(1-Z
-2)2 (-1/4) (+ -Z-')'.

Output (104) of vertical color signal extraction filter (6a)
is given to the switch circuit (8) via the compensation delay circuit (5c), and the output (106) of the horizontal color signal extraction filter (6b) is given to the switch circuit (8) via the compensation delay circuit (5d). The output (108) of the horizontal/vertical color signal extraction filter (6c) is given to the switch circuit (8) via the compensation delay circuit (5e). In addition, the output (month 0) of the image correlation determination circuit (7) is output from the switch circuit (8).
is given as a control signal. The output (III) of the switch circuit (8) is output as a color signal from the output terminal (2). Further, this output is given to one input of the subtraction circuit (9a). The other input of this subtraction circuit (9a) is supplied via the output (102) of the l-line delay circuit (5a) or the compensation delay circuit (5r). The output (113) of the subtraction circuit (9a) is output as a luminance signal from the output terminal (3). In addition, a compensation delay circuit (5c).

(5d), (5e), and (5f) are circuits for compensating for delays in each circuit.

FIG. 2 is a block diagram showing an embodiment of the image correlation determination circuit (7), and shows the output (101) of the A/D converter (4).
), output (102) of the 1-line delay circuit (5a)
, the output (1[13) of the l-line delay circuit (5b) is given to a vertical low-pass filter (6d), a vertical band-pass filter (6f), and a vertical high-pass filter (6j). Also, the output (10
2) is applied to the horizontal bandpass filter (61).

The output (114) of the vertical low-pass filter (6d) is connected to the horizontal high-pass filter (6e) and the absolute value circuit (10).
a) to one input of a comparison circuit (lla), and the output (117) of the constant generation circuit (12a) is applied to the other input of this comparison circuit (lla).

The output (119) of the vertical band-pass filter (6f) is given to one input of a comparator circuit (llb) via an absolute value circuit (10b), and the other input of this comparator circuit (llb) has a constant value. Output (121) of generation circuit (12b)
is given.

The output (123) of the vertical high-pass filter (6g) is connected to the horizontal low-pass filter (6h) and the absolute value circuit (10
c) to one input of a comparison circuit (1, Ic), and the output (126) of the constant generation circuit (12c) is applied to the other input of this comparison circuit (llc).

The output (+28) of the horizontal band-pass filter (61) is given to one input of a comparison circuit (lld) via an absolute value circuit (1 (ld), and the other input of this comparison circuit (lld) is , the output (130) of the constant generator circuit (12d)
is given.

At this time, for example, the vertical low-pass filter (6d) is F VL (Z)
=(1/4)(]+Z-')2, and the horizontal high-pass filter (6c) is F+-u-+ (z)
=(-1/4)(]-Z--'ri2, and the horizontal band-pass filter (6f) is FDH(Z)=1-
The vertical high-pass filter (6g) is denoted by Z, and the vertical high-pass filter (6g) is Fvs+ (z
)=(-1/4)(]-Z-')2, and the horizontal low-pass filter (6h) is expressed as F+-+1-(z)=
(1/4)(1+Z-), and the vertical band-pass filter (61) is Fov(z)=1-Z-
It is a digital filter as shown in “&”.

The outputs of the comparator circuits (Ila) and (nb) are learned by the vertical correlation detection circuit (13a), and the outputs of the comparator circuits (Ila) and (nb)
The output (160) of ld) is the horizontal correlation detection circuit (13b)
given to. The output (1) of the vertical correlation detection circuit (13a)
32), output (+33) of the horizontal correlation detection circuit (13b)
) is given to the judgment circuit (14), and this judgment circuit (14
)'s output (110) (is sent out as the output of the image correlation determination circuit.

Next, the operation of the second configuration will be explained.

Sampling frequency fs=4 by A/D converter (4)
The sampling sequence (101) of the NTSC composite color television signal sampled by the fsc is connected to the delay circuit (5a).
), (5b) to display 3 on the vertical-straight line on the screen.
Sample values at two sample points can be obtained simultaneously. That is, when the coordinates (m, n) appear on the signal line (102), as shown in FIG.
A signal S (m, n-1) appears on the signal line (101
) a signal S (m , n+1 ) appears. A luminance signal/chrominance signal separation filter is constructed based on sample values of sample points across three lines on the screen.

This luminance signal color signal separation filter includes a vertical color signal extraction filter (6a), a horizontal color signal extraction filter (6b), and a horizontal/vertical color signal extraction filter (6c).
) extracts the color signal through filter processing with the following transfer function.

Vertical direction color signal extraction filter: Cv (z) = (-1/4) (1-Z-j ri 2 horizontal direction color signal extraction filter: Cn (z) = (-1/4) (1-Z- 2) i horizontal/vertical color signal extraction filter: CI-IV(Z)=(-1/4)(1-Z-2)2(-
1/4) (1-Z-')'The output (104) of the vertical color signal extraction filter (6a) obtained in this way,
Output (106) of horizontal color signal extraction filter (6b)
, the output (+08) of the horizontal/vertical color signal extraction filter (6c) is connected to the compensation delay circuit (5c), (5
d) is sent to the switch circuit (8) via (5e).

Here, a circuit for determining which of the color output signals of the vertical color signal extraction filter (6a), the horizontal color signal extraction filter (6b), and the horizontal/vertical color signal extraction filter (6c) is selected is selected. The operation will be explained.

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 (104) of the vertical color signal extraction filter (6a) is selected, and the correlation is particularly strong in the horizontal direction. When the intensity is strong, select the output (1116) of the horizontal color signal extraction filter (6b); otherwise, select the output (1116) of the horizontal color signal extraction filter (6C).
switch circuit (8) to select the output (108) of
Switch.

Detection of image correlation and control of the switch circuit (8) are performed by:
This is performed by the image correlation determination circuit (7). The image correlation determination circuit (7) controls the switch circuit (8) by the following operations.

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

Dv(z) = l ]-Z-'1 DH(Z) = l 1-Z-'l The above two equations represent filter characteristics that block DC components and color subcarrier frequency components in the vertical and horizontal directions. It becomes.

Furthermore, the horizontal high-frequency luminance signal energy DYh (z) and the vertical high-frequency luminance signal energy DYV (Z) are expressed as follows by introducing absolute value approximation and using a transfer function.

DY)((Z)=I(-1/4)(1-Z-2)'(
-1/4) (1+Z-') LIDYv(z) = I
(]/4) (1+Z-2)' (-1/4) (1-
Z−勺2I At this time, Dv(z)≦MDI (Kpl
: correlation threshold constant), and DYH(Z)≧Kcl
”l (KOYI: High frequency signal engineering energy threshold constant)
If so, it is determined that there is a correlation in the assembly direction, and DH(z)≧
If KD2 and DYv(z)≧KOY2, it is determined that there is a correlation in the horizontal direction.

That is, the image correlation determination circuit (7) is connected to the A/D converter (4).
) output (101), 1-line delay circuit (5a)
The output (102) of , the output (103) of the 1-line delay circuit (5b) is input, and the control signal (110) is output so that it becomes the output of the switch circuit (8) or the filter output as shown below. Control.

Dv(Z)≦Kol and D'Y+<(z)≧KDY
If I, KV= 1 If not, KV=O Dh(Z)≦KD2 and DYv(z)≧Kl)Y2
If K11=1, otherwise old 1=0, then KV=1 or KII=1, then C(Z)=CHv
(Z)KV= 1KH=O then C(Z)=C
If v(Z)KV= 0 or Ktl=I then C(Z)=
CI-1(Z) If KV=0 or -JKH=0 then CC
Z)-CI(V (Z) Also, this switch circuit (8)
The color signal output of the compensation delay circuit (5f) (+12
), the luminance signal (113) is obtained by performing a subtraction operation from the composite video signal of (113).

In this way, the image correlation compatible luminance signal chrominance signal separation filter according to the above embodiment uses the luminance signal chrominance signal separation filter depending on the image correlation in the vertical direction and the horizontal direction.
It can reduce the influence of luminance signal and chrominance signal leakage to each other channel in areas where image changes are intense,
It is possible to reduce dot interference.

In the above embodiment, the composite color television signal was sampled at a frequency four times as high as the color subcarrier synchronized with the horizontal scanning frequency. Sampling may also be performed at other frequencies, such as four times the color subcarrier.

Further, the digital filter used in the above embodiment is merely an example, and the filter may have a higher order, for example.

[Effects of the Invention] As described above, according to the present invention, the luminance signal and chrominance signal separation filters are used depending on the correlation between the vertical and horizontal images of a composite color television signal. It is possible to reduce the influence of leakage of luminance signals and chrominance signals into each other's channels in the area, and has the effect of reducing dot interference.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing a luminance signal/chrominance signal separation filter compatible with NTSC image correlation according to an embodiment of the present invention, FIG. 2 is a block diagram showing an embodiment of the image correlation determination circuit, and FIG. A schematic block diagram showing an example of a conventional luminance signal/chrominance signal separation filter. Fig. 4 shows the arrangement of a screen image of a signal sequence obtained by synchronously sampling an NTSC system composite color television signal at four times the color subcarrier. It is a diagram. (1)...Input terminal, (2), (3)...Output terminal, (4) ・A/D converter, (5a) to (5i)-
Delay circuit, (6a) to (6k)...Digital filter, (7)...Image correlation detection circuit, (8)...Switch circuit, (9a) to (9d)-Subtraction circuit, (10
a) ~ (10d) ... Absolute value circuit, (11a) ~ (
11d)... Comparison circuit (]2a) to (12d)...
Constant generation circuit, (+3a)...Vertical correlation detection circuit, (
13b)--Horizontal correlation detection circuit, (14)--Judgment circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) Input a composite video signal sampled at a predetermined frequency synchronized with the horizontal scanning frequency so that each sampling point is arranged in a grid on the screen, and digitally convert the luminance signal and color signal from this composite video signal. An image correlation compatible luminance signal and chrominance signal separation filter that delays the composite video signal to separate the luminance signal and the chrominance signal at a sample point of interest and a sample point perpendicular to the sample point of interest on the screen. a delay means for simultaneously obtaining sample values of a plurality of reference sample points arranged in a straight line in the direction; a vertical color signal extraction filter that extracts and outputs a frequency component corresponding to the horizontal color subcarrier component; A horizontal color signal extraction filter, and a horizontal/vertical filter that receives the sample values of the sample point of interest and a predetermined reference sample point as input, and extracts and outputs frequency components corresponding to color subcarrier components in both the vertical and horizontal directions. A directional color signal extraction filter, inputting the sample values of the sample point of interest and a predetermined reference sample point, extracts frequency components corresponding to the DC component in the vertical direction and the color subcarrier component from among the frequency components at the sample point of interest. a vertically uncorrelated energy detecting means for detecting the vertically uncorrelated energy by excluding the absolute value of the vertically uncorrelated energy; In the horizontal direction, in the frequency component, the frequency component that is the low frequency component in the vertical direction and the high frequency component in the horizontal direction is extracted, and its absolute value is determined to detect the horizontal high frequency luminance signal energy. a high-frequency luminance signal energy detection means; and a first
The vertical non-correlation energy is smaller than the first setting value, and the horizontal high-frequency luminance signal energy is larger than the second setting value given from the outside. a vertical correlation detection means that compares the horizontal direction high-frequency luminance signal energy and determines that there is a correlation in the vertical direction when the energy is larger than the second set value; and the sample point of interest and the predetermined reference sample point. input the sample value, exclude the horizontal direct current component and the frequency component corresponding to the color subcarrier component from the frequency components at the sample point of interest, calculate their absolute value, and calculate the horizontal uncorrelated energy. A horizontal direction uncorrelated energy detection means to detect, inputs the sample values of the sample point of interest and a predetermined reference sample point, and detects that the frequency component at the sample point of interest is a low frequency component in the horizontal direction, and is a low frequency component in the vertical direction. In the direction, a vertical high frequency luminance signal energy detecting means extracts a frequency component which is a high frequency component and detects vertical high frequency luminance signal energy by determining its absolute value, and a vertical direction high frequency luminance signal energy detection means for detecting vertical high frequency luminance signal energy by extracting a frequency component which is a high frequency component, The third given by
The horizontal non-correlation energy is smaller than the third set value by comparing the magnitude with the set value of horizontal correlation detection means that determines that there is a correlation in the horizontal direction when the vertical high-frequency luminance signal energy is greater than the fourth set value; and a determination result of the vertical correlation detection means and the horizontal correlation. The determination result of the detection means is input, and if there is a correlation in the vertical direction and no correlation in the horizontal direction, a control signal is sent out to select the output of the vertical color signal extraction filter, and in the opposite case, Sends a control signal to select the horizontal color signal extraction filter output, and if there is a correlation in both the vertical and horizontal directions or no correlation, sends a control signal to select the horizontal and vertical color signal extraction filter output. A switching circuit outputting a color signal component according to a signal transmitted from the determining means; and a subtraction circuit subtracting the output of the switching circuit from the composite video signal to output a luminance signal. An image correlation compatible luminance signal chrominance signal separation filter.