JPS63209289A - Luminance signal/chrominance signal separating filter corresponding to picture correlation - Google Patents

Abstract

PURPOSE:To reduce the influence of a leakage to the mutual channels of a luminance signal and a chrominance signal in an area intense in the change of a picture and to reduce a dot interference by separately using a luminance signal/chrominance signal separating filter according to the correlation of the vertical and horizontal picture of a composite video signal. CONSTITUTION:On a noticed sampling point, the correlation of the vertical and horizontal picture is detected, when the correlation is especially strong in a vertical direction, the output 105 of a vertical chrominance signal extracting filter 6a is selected, and when the correlation is strong in a horizontal direction, the output of a horizontal chrominance signal extracting filter is selected and in other cases, the output of a horizontal and vertical chrominance signal extracting filter is selected by switching a switch circuit 8. The detection of the correlation of the picture and the control of the switch circuit 8 are executed by a picture correlation decision circuit 7. Thereby, the influence of the leakage to the mutual channels of the luminance signal and the chrominance signal can be reduced and the dot interference can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a luminance signal and chrominance signal separation filter compatible with image correlation, and particularly to a luminance signal and chrominance signal separating filter for separating a luminance signal and a chrominance signal from a composite television signal of the NTSC system, for example. This invention relates to color signal separation filters.

[Prior Art] FIG. 5 is a block diagram showing an example of the configuration of a conventional luminance signal chrominance signal separation filter. In the figure, an NTSC composite color television signal is input to an input terminal 1. The composite color television signal is applied to a vertical filter 6j via an A/D converter 4, and
The signal is applied to the line delay circuit 51. 1 line delay circuit 5
The output of 1 is applied to the vertical filter 6j as is, and after being further delayed by one line in the 1-line delay circuit 5j, it is applied to the vertical filter 6j. The vertical filter 6j is a filter usually called a two-line comb filter, and its output is sent to the bandpass filter 6.
given to k. The output to the bandpass filter 6 is the color signal 20
5 from the output terminal 2 and applied to the first input of the subtraction circuit 9d. Further, the output of the one-line delay circuit 51 is applied to the second input of the subtraction circuit 9d via the compensation delay circuit 5k. The compensation delay circuit 5 is a circuit for compensating for the delay in the bandpass filter 6k. A luminance signal 207 is output from the subtraction circuit 9d and applied to the output terminal 3.

Next, the operation of the filter for an NTSC composite color television signal will be explained.

The composite color television signal 201 sampled in synchronization with the color subcarrier at the sampling frequency fs = 4·fsc (fsc is the color subcarrier frequency) is displayed on the screen as a two-dimensional grid-like array as shown in FIG. Become. That is, fsc-(455/
2) Since it is fl-1, the phase shift 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, C,...
Cλ indicates a color signal.

Now, it is assumed that Z-transform is used to use Z and Z-' as symbols representing a delay of one sample and a delay of one line, respectively. Here, Z-'=exp(j2πf/4fsc). Also,
fsc - (455/2) fl, so #=9
It becomes 10. At this time, the 1-line delayed signal 202 and the 2-line delayed signal 2 delayed using the delay circuits 5i and 5j
03 and the current input signal 201 to the vertical filter 6.
At j, a line support signal 204 is extracted for each line including the color signal. The transmission circuit Hv (Z) of the vertical filter 6j is Hv (Z)= (-1/4) ・(1-Z-')''
becomes. That is, on the screen in Figure 6, line support signal at coordinates (m, n)) (c (m, n),
=(1/4) (S(m,nn-1)-23(,n
)+S(m, n+1) ). Since the line support signal also includes the luminance signal Y, the color signal C(m, n), which is a high frequency component, is filtered by the bandpass filter 6k.
Hc(m.

n). And the color signal 2 obtained by this
05 is sent to the subtraction circuit 9d. The subtraction circuit 9d generates a signal S (m, n) 206 which is obtained by further delaying the one line delayed signal 202 by the compensation delay circuit 5 according to the bandpass filter 6k.
The color signal C'(m, n) 205 is subtracted from the luminance signal Y (m.

n) Separate 207.

Y (m, n) = S (m, n) -〇 (m, n) The transfer function Hh (Z) to the bandpass filter 6 is, for example, Hh (Z) = (-1/32) (1'Z-')2 (
1+Z-")"(1+Z-').

[Problem that the invention seeks to solve]

The conventional luminance signal/chrominance signal separation filter is configured by fixing the characteristics of the vertical filter and the horizontal 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 and horizontal directions. Therefore, in the conventional method, in areas where the brightness and color of the image change rapidly, the brightness signal and the color signal leak into each other's channels, which causes problems such as deterioration of the quality of the reproduced image, especially due to dot interference. Ta.

This invention was made to solve the above-mentioned problems, and provides a luminance signal and chrominance signal separation filter that 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

[Means for solving problems]

The image correlation compatible luminance signal/chrominance signal separation filter according to the present invention includes a delay means for delaying an input sampling signal to simultaneously obtain a sample point of interest and a sample point close to the sample point from which a luminance signal 1 sudden signal is to be separated; Image correlation determination means is provided for detecting vertical image correlation and horizontal image correlation from the values of the sample point of interest and neighboring sample points, respectively, and determining the image correlation. filter,
Either the output of the vertical direction filter or the horizontal/vertical direction filter is used as the color signal output of the luminance signal color signal separation filter.

[Effect]

In this 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 influence of leakage of the luminance signal and chrominance signal to each channel in areas where the image changes rapidly can be reduced, and dot interference can be reduced.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic block diagram showing one embodiment of the present invention. In the figure, reference numeral 1 denotes an input terminal to which an NTSC composite color television signal is applied, and this composite color television 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=4fsc. The composite color television signal sampled by the A/D converter 4 is given to a 1-line delay circuit 5a, and then further passed through a 1-line delay circuit 5b.
The one-line delay circuits 5a and 5 are used to simultaneously extract a sample value at a certain sample point of interest and sample values at sample points one line above and one line below the sample point of interest on the screen.
The sample values extracted by b are given to the vertical color signal extraction filter 5a, the horizontal color signal extraction filter 6b, the horizontal/vertical color signal extraction filter 6C2, and the image correlation determination circuit 7 as follows.

That is, the inputs of the vertical color signal extraction filter 5a, the horizontal/vertical color signal extraction filter 6c, and the image correlation determination circuit 7 include the output 101.1 of the A/D converter 4 and the output 102.1 of the line delay circuit 5a. and the output 103 of the one-line delay circuit 5b. Further, the output 102 of the one-line delay circuit 5a is applied to the horizontal color signal extraction filter 6b.

At this time, for example, the vertical color signal extraction filter 6a is expressed as Cv(Z)=(-1/4) (14')'' using a transfer function, and the horizontal color signal extraction filter 6b is expressed as follows. , ch(Z)=(-1/4) (1-z-')2, and the horizontal/vertical color signal extraction filter 6C is expressed as Chv(Z)=(-1/4)(1- Z')" ・(
-1/4) (1-Z-')2.

The output 104 of the vertical color signal extraction filter 6a is passed through the compensation delay circuit 5C to the horizontal color signal extraction filter 6b.
The output 106 of the horizontal/vertical color signal extraction filter 6C is provided to the switch circuit 8 via the compensation delay circuit 5d, and the output 108 of the horizontal/vertical color signal extraction filter 6C is provided to the switch circuit 8 via the compensation delay circuit 5e. Further, the output 1)0 of the image correlation determination circuit 7 is the switch 8.
is given as a control signal. Output 1 of switch circuit 8
)1 is output as a color signal from the output terminal 2 and is also applied to one input of the subtraction circuit 9a.

The other input of this subtraction circuit 9a is connected to a one-line delay circuit 5.
The output 102 of a is given via the compensation delay circuit 5f. The output 1) 3 of the subtraction circuit 9a is outputted from the output terminal 3 as a luminance signal. Note that the compensation delay circuits 5c, 5d, 5
e and 5f are circuits for compensating for delays in each circuit.

FIG. 2 shows an embodiment of the image correlation determination circuit 7.

The output 101 of the A/D converter 4, the output 102 of the line delay circuit 5a, and the output 103 of the line delay circuit 5b are applied to a vertical low-pass filter 6d and vertical bandpass filters 6f and 6g. Further, the output 102 of the line delay circuit 5a is given to the horizontal band pass filter 61.

The output 1) 4 of the vertical low-pass filter 6d is applied to one input of the subtraction circuit 9b via the horizontal band-pass filter 6e and the absolute value circuit 10a. On the other hand, the output 120 of the vertical band-pass filter 6f is the compensation delay circuit 5g.
is applied to the absolute value circuit 10b via. The compensation delay circuit 5g is a circuit for compensating for the delay in the horizontal band-pass filter 6e.

The output of the absolute value circuit 10b is applied to the other input of the subtraction circuit 9b and one input of the comparison circuit 1)b.

The output 1)7 of the subtraction circuit 9b is applied to one input of the comparison circuit 1)a, and the output 1)8 (Kdy+ to be described later) of the constant generation circuit 12a is applied to the other input of the comparison circuit 1)a. The other input of comparison circuit 1)b is connected to constant generation circuit 1.
An output 123 (Kd+, which will be described later) of 2b is given.

The output 125 of the vertical band-pass filter 6g is applied to one input of the subtraction circuit 9C via the horizontal low-pass filter 6h and the absolute value circuit 10C. On the other hand, the output 131 of the horizontal band-pass filter 61 is the compensation delay circuit 5h.
The signal is applied to the absolute value circuit 10d via. The compensation delay circuit 5h is a circuit for compensating for the delay in the horizontal low-pass filter 6h. The output of the absolute value circuit 10d is applied to the other input of the subtraction circuit 9C and one input of the comparison circuit lid. Output 1) of subtraction circuit 9C is comparison circuit 1)
The output 129 of the constant generating circuit 12C (Fd
v) is given. The other input of the comparator circuit lid is
An output 134 (Kdλ, which will be described later) of the constant generation circuit 12d is provided.

At this time, for example, the vertical low-pass filter 6d has Fv 7! It is expressed as (Z)=(1/4)(1+Z), and the horizontal band-pass filter 6e is Fhh (
Z) -1-Z', that is, it is expressed as extracting a frequency component corresponding to 2 of the color subcarrier frequency in the horizontal direction, and the horizontal band-pass filter 61 is Fdh CZ) -1- Z
', and the vertical bandpass filter 6g is Fvh
(Z) −1−Z−”, that is, it is expressed as extracting a frequency component corresponding to 2 of the color subcarrier frequency in the vertical direction, and the horizontal low pass filter 6h is Fh p ( Z) −(1
/4)(1+z), and the vertical band-pass filter 6f is a digital filter expressed as Fdv (Z) = 1-Z-''.

Comparison circuit 1) The outputs of a and llb are vertical correlation detection circuit 1
3a, and the outputs of comparison circuits 1)c and 1)d are provided to a horizontal correlation detection circuit 13b. An output 136 of the vertical correlation detection circuit 13a and an output 137 of the horizontal correlation detection circuit 13b are provided to the determination circuit 14. The output 1)0 of the determination circuit 14 is sent as the output of the image correlation determination circuit 7.

FIG. 3 shows an example of the configuration of the determination circuit 14 shown in FIG.

The output 136 of the vertical correlation detection circuit 13a is connected to the NOR circuit 15.
is given to one input. In addition, the horizontal correlation detection circuit 13
The output 137 of b is given to the other input of the NOR circuit 15, and is also supplied to the NOT circuit 16a. The output of the NOR circuit 15 and the output of the NOT circuit 16a become the output 1)0 of the image correlation determination circuit 7.

Further, FIG. 4 shows another example of the configuration of the determination circuit 14. The output 136 of the vertical correlation detection circuit 13a is an exclusive NOR
It is applied to one input of the circuit 17 and one input of the AND circuit 18. The output 137 of the horizontal correlation detection circuit 13b is given to the other input of the exclusive NOR circuit 17, and
It is applied to the other input of the AND circuit 18 via the OT circuit 16b. Output of exclusive NOR circuit 17 and AND circuit 1
The output of 8 becomes the output 1)0 of the image correlation determination circuit 7.

Next, the operation will be explained.

The sampling series 101 of the NTSC composite color television signal sampled by the A/D converter 4 at the sampling frequency fs=4fsc is transmitted through delay circuits 5a and 5b, so that Sample values at three sample points are obtained simultaneously. That is, the coordinates (m,
Composite color television signal (sample value) S at position n)
When (m, n) appears on the signal line 102, the signal S (m, n-1) appears on the signal line 103, and the signal S (m, n+1) appears on the signal line 101 (see Figure 6). ). A luminance signal and chrominance signal filter is constructed based on the sample values of sample points over three lines on the screen.

In this method, the vertical color signal extraction filter 6a.

The horizontal color signal extraction filter 6b and the horizontal/vertical color signal extraction filter 6C extract color signals through filter processing having the following transfer function.

Vertical color signal extraction filter Cv (Z) = (-1/4) (1-Z-')'L Horizontal color signal extraction filter Ch (Z) = (-1/4) (1-Z-2) "Horizontal/vertical color signal extraction filter Chv (Z) = <-1/4) (1-Z-')"
, (-1/4) (1-Z-')"Vertical filter output 104 and horizontal filter output 106 thus obtained.Horizontal and vertical color signal extraction filter output 1
08 are respectively sent to the switch circuit 8 via the compensation delay circuit.

Here, the vertical color signal extraction filter 5a.

The operation of the circuit that determines which color output signal to select from the horizontal color signal extraction filter 6b and the horizontal/vertical color signal extraction filter 6C will be described.

Regarding the sample point of interest, the correlation between images in the vertical and horizontal directions is detected, and when the correlation is particularly strong in the vertical direction, the output 105 of the vertical color signal extraction filter 6a is selected, and when the correlation is particularly strong in the horizontal direction, The switch circuit 8 is switched so that the output of the horizontal color signal extraction filter 6b is selected, and in other cases, the output of the horizontal and vertical color signal extraction filters is selected.

Detection of image correlation and control of the switch circuit 8 are performed by the image correlation determination circuit 7. The image correlation determination circuit 7 controls the switch circuit 8 through the following operations.

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

DV(Z)-1)Z I Dh (Z)=ll-Z l The above two equations have filter characteristics that block DC components and color subcarrier frequency components in the vertical and horizontal directions. In addition, the horizontal high-frequency luminance signal energy is DYh
(Z), the vertical high-frequency luminance signal energy is DYv (Z
), we will introduce absolute value approximation and express it using a transfer function as follows.

DYh(Z)=l(1/4)(1+Z-Z)"-(
1-Z-”) 1DYv(Z)=l(1/4)(
1+Z')2.(1-Z-equal 1) At this time, the vertical correlation detection circuit 13a satisfies Dv (Z)≦Kd+ (Kd+: correlation threshold constant) and DYh (Z)-Dv (Z)≧Kdy.

When (Kdy+: high-frequency signal energy threshold constant), it is determined that there is a correlation in the vertical direction, and a signal "1" is sent to the determination circuit 14. Also, Dv (Z) > Kd+ or D Y h (Z) D v (Z) < Kdy+
When , it is determined that there is no correlation in the vertical direction, and the determination circuit 14
Sends a signal “0” to

On the other hand, the horizontal correlation detection circuit 13b satisfies the following conditions: Dh (Z)≦Kd2 (Kd2: correlation threshold constant) and DYv (Z) - Dh (Z)≧Kdy2 (Kdy2:
(high-frequency signal energy threshold constant), it is determined that there is a correlation in the horizontal direction, and a signal "1" is sent to the determination circuit 14, and Dh (Z) > Kd2 or DYv (Z) - Dh (Z) < Kdy2 When , it is determined that there is no correlation in the horizontal direction, and the signal “0” is sent to the determination circuit 14.
send.

The determination circuit 14 controls the switch circuit 8 as follows according to the above correlation detection result.

That is, the relationship between the input and output of the determination circuit 14 shown in FIG. 3 is as shown in FIG. 7. At this time, the switch circuit 8 is N
When the output of the OR circuit 5 is “1”, the switch is connected to the signal line 10.
9 to allow the output of the horizontal/vertical color signal extraction filter 6C to flow. When the output of the NOR circuit 5 is "0", the switch is switched by the output of the NOT circuit 16a, and when it is "0", the output of the horizontal color signal extraction filter b is "1", and the output of the vertical color signal is "1". The output of the signal extraction filter 6a is made to flow.

Therefore, in the embodiment of FIG. 3, the output C(Z) of the switch circuit 8 is switched as follows.

When there is horizontal correlation, C(Z) = Ch (Z) When there is no horizontal correlation, if there is vertical correlation, C(Z) -Cv (Z) If there is no vertical correlation, C(Z) = Chv (Z) Also, the fourth In the determination circuit 14 shown in the figure, the input/output relationship is as shown in FIG. Exclusive N.

The output of the R circuit 17, like the output of the NOR circuit 15, is used in the switch circuit 8 to turn on/off the output of the horizontal/vertical color signal extraction filter 6c, and is used as an AND circuit.
Similarly to the output of the NOT circuit 16a, the output of 8 is used to select the horizontal filter 6b and the vertical filter 6a. Therefore, in the circuit shown in FIG. 4, the output of the switch circuit 8 is: C(Z) - Ch when there is horizontal correlation and no vertical correlation (C(Z) = Cv when there is vertical correlation and no horizontal correlation) (Z) When horizontal and vertical correlations are both present or absent, C(Z)-Chv (Z) is obtained.The color signal output of the switch circuit 8 is the composite video signal of outputs 1 and 2 of the compensation delay circuit 5f. The luminance signal 1)3 is obtained.

In the above embodiment, the composite color television signal is sampled at a frequency four times as high as the color subcarrier synchronized with the horizontal scanning frequency. For example, sampling is not limited to four times the color subcarrier, but may be performed at other frequencies.

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

〔Effect of the invention〕

As described above, according to the present invention, luminance signal and chrominance signal separation filters are used depending on the correlation between vertical and horizontal images of a composite color television signal, so that mutual channels of luminance signals and chrominance signals can be separated. This has the effect of reducing the influence of leakage on the dots and dot interference.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing an NTSC system image correlation compatible luminance signal/chrominance signal separation filter according to an embodiment of the present invention, FIG. 2 is a block diagram showing an embodiment of the image correlation determination circuit, and FIGS. FIG. 4 shows the first part of the judgment part of the above-mentioned image correlation judgment circuit. Figure 5 showing the second embodiment
The figure is a schematic block diagram showing an example of a conventional luminance signal/chrominance signal separation filter, and Figure 6 is an on-screen arrangement of a signal sequence obtained by synchronously sampling an NTSC system composite color television signal at four times the color subcarrier. FIG. 7 is a diagram showing the input/output relationship of the determination section shown in FIG. 3, and FIG. 8 is a diagram showing the input/output relationship of the determination section shown in FIG. 4. ■...Input terminal, 2, 3...Output terminal, 4...A
/D converter, 5a~5k...delay circuit, 62~6k・
...Digital filter, 7...Image correlation determination circuit,
8...Switch circuit, 9a-9d...Subtraction circuit, 1
0a-10d...Absolute value circuit, l1a-1id...
Comparison circuit, 12a to 12d...constant generation circuit, 13a
... Vertical correlation detection circuit, 13b... Horizontal correlation detection circuit, 14... Judgment circuit, 15-NOR circuit, 16a,
16b=-NOT circuit, 17...exclusive NOR circuit,
18...AND circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (3)

[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 calculate the luminance signal component and color from the composite video signal. An image correlation compatible luminance signal/chrominance signal separation filter for separating signal components, the composite video signal being delayed, and a sample point of interest at which the luminance signal and the color signal should be separated, and a sample point perpendicular to the sample point of interest on the screen. 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 a horizontal color subcarrier component; a horizontal color signal extraction filter; and a horizontal/vertical color signal extraction filter that receives sample values of the sample point of interest and a predetermined reference sample point as input, extracts and outputs frequency components corresponding to color subcarrier components in both the vertical and horizontal directions. a directional color signal extraction filter, which inputs sample values of the sample point of interest and a predetermined reference sample point, and extracts frequency components corresponding to a vertical direct current component and a color subcarrier component from frequency components at the sample point of interest; and a vertical direction uncorrelated energy detection means for detecting vertical direction uncorrelated energy by excluding the absolute value of the vertical direction uncorrelated energy; extracting a frequency component that is a low frequency component in the vertical direction and corresponds to one half of the color subcarrier frequency in the horizontal direction;
horizontal high-frequency luminance signal energy detecting means for detecting the horizontal high-frequency luminance signal energy by determining its absolute value;
is compared in magnitude with a set value of If the value obtained by subtracting the vertical uncorrelated energy from the horizontal high-frequency luminance signal energy is larger than the second setting value, there is a correlation in the vertical direction. vertical correlation detection means for determining that the sample values of the sample point of interest and a predetermined reference sample point are input, and the sample values of the sample point of interest and a predetermined reference sample point are input, and a component corresponding to a horizontal direct current component and a color subcarrier component is selected from frequency components at the sample point of interest; horizontal direction uncorrelated energy detection means for detecting horizontal direction uncorrelated energy by excluding the frequency component and determining its absolute value; extracting a frequency component at a point that is a low frequency component in the horizontal direction and corresponds to one half of the color subcarrier frequency in the vertical direction;
vertical high frequency luminance signal energy detection means for detecting the vertical high frequency luminance signal energy by determining its absolute value;
is compared in magnitude with a set value of If the value obtained by subtracting the horizontal non-correlation energy from the vertical high-frequency luminance signal energy is larger than the fourth setting value, there is a correlation in the horizontal direction. horizontal correlation detection detection means for determining the horizontal correlation detection means; and the determination result of the vertical correlation detection means and the determination result of the horizontal correlation detection means are input, and the horizontal color is determined according to the determination result of the presence or absence of correlation in the horizontal and vertical directions. determining means for transmitting a control signal for selecting the output of the signal extraction filter, the vertical color signal extraction filter, or the horizontal/vertical color signal extraction filter; An image correlation compatible luminance signal/color signal separation filter comprising: a switch circuit that outputs a component; and a subtraction circuit that subtracts the output of the switch circuit from the composite video signal to output a luminance signal component. (2) If there is a correlation in the horizontal direction, the determining means sends out a control signal for selecting the horizontal color signal extraction filter output, and if there is no correlation in the horizontal direction and there is a correlation in the vertical direction, the determining means transmits a control signal for selecting the output of the horizontal color signal extraction filter; It shall send a control signal to select the color signal extraction filter output, and if there is no correlation in both the horizontal and vertical directions, it shall send a control signal to select the horizontal and vertical color signal extraction filter outputs. An image correlation compatible luminance signal chrominance signal separation filter according to claim 1. (3) If there is a correlation in the vertical direction and no correlation in the horizontal direction, the determining means sends out a control signal for selecting a vertical color signal extraction filter output, and if there is a correlation in the horizontal direction, and If there is a correlation in the vertical direction, a control signal is sent to select the horizontal color signal extraction filter output, and if there is a correlation in both the horizontal and vertical directions, or there is no correlation, the horizontal and vertical color signal extraction filters are selected. 2. The image correlation-compatible luminance signal/chrominance signal separation filter according to claim 1, wherein the filter sends out a control signal for selecting an output.