JPS63206091A - Y/c separating device - Google Patents

Abstract

PURPOSE:To realize an optimum Y/C separation by selecting respectively a comb-lime filter circuit when a vertical correlation exists, a slanting correlation using Y/C separating circuit when a vertical correlation does not exist and a slanting correlation exists and a frequency separating circuit when the slanting correlation does not exist. CONSTITUTION:A complex video signal sampled by the 4 times as much as the frequency of a color sub-carrier frequency is given to a vertical correlation detecting type Y/C separating circuit 1 and a slanting correlation detecting type Y/C separating circuit 2. The vertical correlation detecting type Y/C separating circuit 1 executes the Y/C separation in accordance with the comb-lime filter separating system at the time of the vertical correlation and executes the Y/C separation in accordance with the frequency separating system when the vertical correlation does not exist. On the other hand, a slanting correlation detecting type Y/C separating circuit 2 executes the Y/C separation with the data of the slanting direction having the correlation to pass an objective point and sends the separating signal to a switching circuit 3. Either of these separating signals is selected and outputted by a control signal from a decoder 4 specified based on respective correlation detecting signals.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a Y/C separation device, and is suitable for application to a two-dimensional adaptive type device that detects vertical and diagonal correlations and switches separated signals. It is something.

[Prior Art] Conventionally, Y/C separation methods include a frequency separation method that uses the frequency spectrum of a composite video signal to separate a luminance signal and a chrominance signal on the frequency axis using, for example, a bandpass filter and a lowpass filter; There is a comb filter separation method that uses correlation between lines of a video signal to separate a luminance signal and a color signal.

Each of these re-separation methods is different from the frequency separation method.In screen conditions where the luminance signal contains high-frequency components near the color subcarrier frequency, leakage occurs between the color signal and the luminance signal, resulting in so-called cross-color deterioration in image quality. The comb filter separation method has the disadvantage that the separation is insufficient due to the collapse of the correlation that is the premise of this method, resulting in deterioration of image quality called dot crawl, where dots flow at the edges of the image. have

Therefore, in the past, Y/C separation circuits of both types were provided in parallel, and the separation methods were switched depending on the image content. Conventionally, such switching between separation methods has been performed based on the correlation detection output of a horizontal correlation detection circuit or a vertical correlation detection circuit.

[Problems to be Solved by the Invention] However, according to the conventional apparatus, the output signal is switched depending on the horizontal correlation or the vertical correlation. It was inevitable that cross colors and dot crawls would occur.

Furthermore, even if a diagonal correlation could be detected, Y/
Since the C separation follows a comb filter separation method that uses vertical correlation and a frequency separation method that uses the frequency axis, separation is not performed using a video signal in the diagonal direction, but is performed using a video signal that is uncorrelated in the diagonal direction. Therefore, even if switching was performed according to the diagonal correlation, the separation would be insufficient and it was inevitable that cross collars and dot crawls would occur in the diagonal direction.

The present invention has been made in consideration of the above points, and is capable of reducing dot crawl and cross color in the diagonal direction without increasing dot crawl and cross color in the horizontal and vertical directions. The present invention aims to provide a C separation device.

[Means for Solving the Problem] In order to solve the problem, the present invention provides a frequency separation circuit that separates a luminance signal and a chroma signal from a composite video signal according to a frequency separation method, and a frequency separation circuit that separates a luminance signal and a chroma signal from a composite video signal. and a comb filter separation circuit that separates the chroma signal according to a comb filter separation method;
Input composite video signal data whose phase is aligned with one color difference signal component axis and sampled at a frequency four times the color subcarrier frequency, and focus on the data in the diagonal direction passing through the point of interest from the data in the diagonal direction. A plurality of diagonal correlation detection type Ys each having a different tilt angle in the diagonal direction obtain a luminance signal of a point and subtract the unobtained luminance signal from the composite video signal to obtain a chroma signal.
/C separation circuit; a vertical correlation detection circuit that inputs data and detects correlation in the vertical direction passing through the point of interest; and a vertical correlation detection circuit that inputs data and detects correlation in the diagonal direction passing through the point of interest from data on the diagonal direction. Based on a plurality of diagonal correlation detection circuits each having a different tilt angle in the diagonal direction, a vertical correlation detection circuit, and the detection output of each diagonal correlation detection circuit, a comb filter separation circuit is installed when there is a vertical correlation. If there is no vertical correlation, the presence or absence of diagonal correlation is determined. If there is no diagonal correlation, the frequency separation circuit is selected. If there is diagonal correlation, the diagonal direction in which the correlation exists is determined and one of the diagonal correlations is selected. Y to select detection type Y/C separation circuit
/C separation circuit selection means.

[Operation] The frequency separation circuit and the comb filter separation circuit perform Y/C according to the frequency separation method and the comb filter separation method, respectively.
To separate. Each diagonal correlation detection type Y/C separation circuit performs Y/C separation in a diagonal direction having a predetermined inclination angle using data in that direction. Each diagonal correlation detection circuit detects a diagonal correlation from data in a diagonal direction having a predetermined inclination angle, and provides the detected diagonal correlation to the Y/C separation circuit selection means.

Further, the vertical correlation detection circuit detects correlation in the vertical direction and provides a detection output to the Y/C separation circuit selection means.

The Y/C separation circuit selection means selects a comb filter separation circuit regardless of the diagonal correlation if there is vertical correlation, and selects one of the comb filter separation circuits based on the diagonal correlation if there is no vertical correlation. A correlation detection type Y/C separation circuit is selected, and if there is no diagonal correlation, a frequency separation circuit is selected.

As a result, since the separation circuit is selected based on the vertical correlation and the diagonal correlation, image quality deterioration in the vertical and diagonal directions can be reduced. Moreover, since the frequency separation circuit is selected when neither the vertical correlation nor the diagonal correlation exists, deterioration of image quality in the horizontal direction can also be reduced. Furthermore, since humans prioritize changes in the vertical direction, which is easier to identify than the diagonal direction,
An image that is easy for the user to view can be obtained.

[Example 1] Hereinafter, an example of the Y/C separation apparatus according to the present invention will be described in detail with reference to the drawings.

(Overall configuration of the embodiment) FIG. 1 shows the overall configuration of the embodiment. In FIG. 1, a composite video signal COMP sampled at a frequency four times the color subcarrier frequency fSC and phase-aligned with one color difference signal component axis is applied to the Y/C separation device. This video signal COMP is applied to a vertical correlation detection type Y/C separation circuit 1 whose detailed configuration is shown in FIG. 2 and a diagonal correlation detection type Y/C separation circuit 2 whose detailed configuration is shown in FIG.

The vertical correlation detection type Y/C separation circuit 1 has a vertical correlation detection circuit whose detailed configuration is shown in FIG. , On the other hand, when there is no vertical correlation, Y/C separation is performed according to the frequency separation method, and the Y/C separated signals YV and Cv are each multiplied by 1/4 via a 1/4 multiplier circuit 7.8 and the switch circuit Give to 3. In addition, 1/4 multiplier circuits 7 and 8
is the output signal C from the diagonal correlation detection type Y/C separation circuit 2.
This is provided to match the levels of 8 and YS.

The diagonal correlation detection type Y/C separation circuit 2 has an internal diagonal correlation detection circuit whose detailed configuration is shown in FIG. The separated signals YS and C8 are applied to the switch circuit 3.

The switch circuit 3 performs a switching operation according to the output signal of the decoder 4. The decoder 4 receives first and second vertical correlation flags VF1, which will be described later, output from the vertical correlation detection circuit.
A vertical correlation signal VF indicating the presence or absence of vertical correlation is provided from an OR circuit 5 which receives the signals VF2 and VF2 and obtains an OR output thereof. Further, second and third vertical correlation flags SF2 and SF3, which will be described later, output from the diagonal correlation detection circuit are inputted to the decoder 4, and a diagonal correlation indicating the presence or absence of diagonal correlation is sent from the NAND circuit 6 which obtains the NAND output. A signal SF is provided.

Based on these correlation signals VF and SF, the decoder 4 obtains an output signal CON according to the table TABI shown in FIG. 6, and supplies it to the switch circuit 3, thereby causing the switch circuit 3 to switch.

If there is no vertical correlation or diagonal correlation, the decoder 4
gives the output signal CON of logic “0” to the switch circuit 3 to separate the separated signal Y from the vertical correlation detection type Y/C separation circuit 1.
The switch circuit 3 is operated to select V and CV. At this time, the vertical correlation detection type Y/C separation circuit 1
Since there is no vertical correlation, a separated signal according to the frequency separation method is sent out, and therefore, in this case, a separated signal according to the frequency separation method is sent out as an output signal.

In this case, since there is no vertical correlation or diagonal correlation, the optimal frequency separation method should be adopted when there is horizontal correlation. Note that if there is no horizontal correlation, image quality deterioration cannot be avoided no matter which separation method is used, and there is almost no difference in image quality deterioration even if a frequency separation method is used than when other methods are used. do not have.

If there is a correlation in either the diagonal correlation or the vertical correlation,
An output signal CON is sent that selects the output signal of the diagonal correlation detection type Y/C separation circuit 2 or the vertical correlation detection type Y/C separation circuit 1 corresponding to the direction in which the correlation exists. Therefore, since a separated signal obtained from data in a correlated direction is selected, deterioration in image quality can be prevented.

If there is both diagonal correlation and vertical correlation, an output signal CON is sent that selects output signals YV and CV of vertical correlation detection type Y/C separation circuit 1. In this case, image quality deterioration can be reduced no matter which direction is adopted, but an image that is easier for the user to see can be obtained by giving priority to the vertical direction, in which changes are more easily noticed by human vision than in the diagonal direction.

Note that when there is a vertical correlation, the vertical correlation detection type Y/C separation circuit 1 sends out a separation signal according to the comb filter separation method.

(Vertical correlation detection type Y/C separation circuit 1) FIG. 2 shows a specific configuration of the vertical correlation detection type Y/C separation circuit 1. The composite video signal COMP1 sampled as described above is applied to a delay stage 12 formed by cascading IH delay circuits 10 and 11.
As shown in FIG.
Data D23, D14, and D5 are extracted.

In FIG. 7, the difference between a circle and a triangle means a difference in color difference signal components, and the difference between black and white shows an inversion of the phase of the color difference signal component.

Data D14 is given to the subtraction circuit 13 as an input to be subtracted, and data D23 is given to the subtraction circuit 13 as a subtraction input, and after being subtracted in the subtraction circuit 13,
If there is a correlation, the luminance signal is canceled out and only the chroma signal C2 is taken out and given to the switch circuit 15 as a first selection input. Further, the data D14 is given to the subtraction circuit 16 as an input to be subtracted,
Data D5 is given to the subtraction circuit 16 as a subtraction input,
After being subtracted in the subtracting circuit 16, it is doubled via the doubling circuit 17, and if there is a correlation, the luminance signal is canceled and only the chroma signal C3 is taken out, and the switch circuit 15
is given as the second selection input. Further, the subtracted outputs of the subtracting circuits 13 and 16 are added in an adding circuit 18, and if there is a correlation from the data D5, D14, D23, the luminance signal is canceled and only the chroma signal C1 is extracted.
It is applied to the switch circuit 15 as a third selection input.

The switch circuit 15 further includes a point of interest P1 so as to supply a composite video signal to a subsequent frequency separation section.
The data D14 of 4 is multiplied by 4 through a 4-multiplying circuit 19 and provided as a fourth selection input. The switch circuit 15 selects an input based on first and second correlation flags VF1 and VF2 provided from the vertical correlation detection circuit 20.

In other words, if there is a vertical correlation around the line LN that includes the point of interest P14, then the line LN
Select the chroma signal C1 obtained from the three lines LN-1 to LN+1 centered on the line LN including the point of interest P14.
If there is a vertical correlation only below the point of interest, select the chroma signal C3 obtained from two lines, the line LN including the point of interest P14 and the line LN+1 below it, and If there is a correlation, the line LN including the point of interest P14 and the line LN- above it
The chroma signal C2 obtained from the two lines with 1 is selected, and if there is no vertical correlation, the data of the point of interest P14 multiplied by 4 is selected.

In this way, the selection signal selected by the switch circuit 15 is given as a first selection input to the switch circuit 22 via the bandpass filter 21 whose passing center frequency is the color subcarrier frequency fsc.
The signal is directly applied to the switch circuit 22 as a second selection input without passing through the bandpass filter 21.

The switch circuit 22 performs a switching operation based on the third correlation flag VF3 given from the vertical correlation detection circuit 20.

The switch circuit 22 selects an input signal that does not go through the band-pass filter 21 when there is a strong vertical correlation, and selects an input signal that goes through the band-pass filter 21 when there is no vertical correlation or when there is some vertical correlation. select. The bandpass filter 21 functions to separate a chroma signal when the incoming signal is data of a composite video signal, and functions to reduce dot crawl when the incoming signal is a chroma signal.

The output signal from this switch circuit 22 is sent out as an output chroma signal CV via a bandpass filter 23. The bandpass filter 23 functions to remove unnecessary components other than chroma signal components when there is a large vertical correlation.

Further, the output signal of the switch circuit 22 is given to a subtraction circuit 24 as a subtraction input. The subtraction circuit 24 also receives a composite video signal whose phase is synchronized with the chroma signal CV, that is, data D14 at the point of interest P14, through a quadrupling circuit 25 so as to match the level of this chroma signal. , are completely synchronized via the delay compensation circuit 26 and are provided as inputs to be subtracted. In this manner, a luminance signal YV is obtained in the subtraction circuit 24, and this luminance signal YV is synchronized with the output chroma signal Cv via the delay compensation circuit 27 and output to the above-mentioned switch circuit 3.

(Vertical Correlation Detection Circuit 20) FIG. 4 shows a detailed configuration of the vertical correlation detection circuit 20. This vertical correlation detection circuit 20 detects not only the presence or absence of vertical correlation but also the In order to detect a certain position, vertical correlation is also detected using data from two points before and after the point of interest P14.

In FIG. 4, the sampled composite video signal COMP2 is applied to a delay stage 35 formed by cascade-connecting delay circuits 31 to 34 for delaying the signal by one horizontal scanning period, and the sampled composite video signal COMP2 is applied to a delay stage 35 formed by cascadingly connected delay circuits 31 to 34, which delay the sampled composite video signal COMP2 by one horizontal scanning period. Two pieces of data D28, C23, and C14 in the vertical direction centering on
, D5, and C29.

The data D28 is given to the subtraction circuit 36 as an input to be subtracted, and the data D14 is given to the subtraction circuit 36 as a subtraction input, and after being subtracted, it is given to the absolute value circuit 37.
The signal is converted into an absolute value and converted into a difference signal 1ΔYll, which is applied to comparison circuits 38 and 39.

Comparison circuit #r38 is also given a reference signal REFI, and takes a logic "0" indicating no correlation when the difference signal 1ΔYll is larger than the reference signal REF1, and on the other hand, when the difference signal 1ΔYll is smaller than the reference signal REF1. A first correlation signal VCOI that takes logic “1” indicating that there is a correlation is output to the decoder 40. On the other hand, the comparison circuit 39 is supplied with a reference signal REF2 smaller than the reference signal REF1, and takes a logic "0" representing no correlation when the difference signal (ΔYll) is greater than the reference signal REF2;
When ΔYll is smaller than the reference signal REF2, a second correlation signal VCO2 is output to the decoder 40, which takes logic "1" indicating that there is a correlation.

Here, the difference signal 1ΔYll is obtained from data above the point of interest P14 and represents the difference in data above the point of interest PC, so the correlation signals VCOI and VCO2 indicate the correlation above the point of interest P14. Become. Also,
Since the second reference signal REF2 is selected to be smaller than the first reference signal REFI, the first correlation signal VCOI indicates whether or not there is a correlation above the point of interest P14. The second correlation signal VCO2 indicates whether or not there is a correlation.

Further, the data D23 and D5 are given to the subtraction circuit 41, and after being subtracted in the subtraction circuit 41, the data D23 and D5 are sent to the absolute value circuit 42.
The signal is converted into an absolute value via the differential signal 1ΔY21, and is applied to comparison circuits 43 and 44. The comparison circuits 43 and 44 operate in the same manner as the comparison circuits 38 and 39 described above, and provide a third correlation signal VCO3 indicating whether or not there is a correlation near the point of interest P14, and a third correlation signal VCO3 indicating whether or not there is a correlation near the point of interest P14. A fourth correlation signal VCO4 indicating whether or not
is output to the decoder 40.

Further, the data D14 and D29 are given to a subtraction circuit 45, and after being subtracted in the subtraction circuit 45, the absolute value circuit 4
6, the signal is converted into an absolute value and converted into a difference signal 1ΔY31, which is applied to comparison circuits 47 and 48. The comparison circuits 47 and 48 operate in the same manner as the comparison circuits 38 and 39 described above, and provide a fifth correlation signal VCO5 indicating whether or not there is a correlation below the point of interest P14 and a fifth correlation signal VCO5 indicating whether or not there is a correlation below the point of interest P14. A sixth correlation signal V indicating whether there is a significant
CO6 is output to the decoder 40.

The decoder 40 is composed of, for example, a ROM, and converts the incoming correlation signals VCOI to VCO6 according to the tables TAB2 and TAB3 shown in FIGS. 8 and 9 to convert the first to third correlation flags VFI to VF3 described above.
is sent to the switch circuit 15.22 and the OR circuit 5.

The decoder 40 performs a conversion operation based on the following design concept. The correlations indicated by the correlation signals VC01 to VCO6 are the correlation COU above the point of interest P14, the correlation COCl near the point of interest P14 (hereinafter referred to as the center), the point of interest P
14 from the point of view of the downward correlation COL, the results are as shown in column CLI of table TAB2. here,
“×” indicates no correlation, “0” indicates correlation, and “
・” indicates a strong correlation.

Based on the information in this column CLI, Y/C as follows
Decide on the separation method.

(1) If there is no correlation in the center, the Y/C separated signal (the chroma signal extracted by the bandpass filter 21 and the corresponding luminance signal) by the frequency separation method regardless of the upper and lower correlation states Select. In addition,
r) (J in column CL2 represents this case.

(2) If there is a correlation only in the center, focus point P14
A 2H-type comb filter separation method (chroma signal C1 and corresponding luminance signal) using three lines before and after including the line LN containing the chroma signal C1 is adopted. Furthermore, in column CL2, “
"v" represents a 2H type comb filter separation method.

(3) If there is a correlation in the center and one above or below, the line L that includes the point of interest P14
Line LN-1 or L adjacent in the direction correlated with N
IH type comb filter separation method using N+1 (chroma signal C2 or C3 and its corresponding luminance signal)
Adopt. Note that rVUJ and rVLJ in column CL2 are the line LN including the point of interest P14, the line LN-1 above it, or the line LN below it, respectively.
This represents an IH type comb filter separation method using +1.

In this case, if both the correlation in the center and the correlation in either the upper or lower part are very large, the bandpass filter 22 is used to remove the dot crawl in the vertical direction.
In other cases, a method is selected in which the signal is output without passing through the band pass filter 21. In addition,
In column CL2, the method in which rvu, .

(4) If there is a correlation in all of the central, upper, and lower parts, select the 2H-type comb filter separation method. In this case, if the central, upper, and lower correlations are all highly correlated, a 2H comb filter separation method that does not involve the bandpass filter 21 is selected to remove dot crawl in the vertical direction; In other cases, a 2H comb filter method is selected in which the signal is output via the bandpass filter 21. In column CL2, the method in which "V" is surrounded by a circle represents the 2) (type comb filter method) in which the output is output without going through a band-pass filter.

In order to be able to select such a separation method, the decoder 40 obtains correlation flags VFI to VF3 according to tables TAB2 and TAB3 and outputs them to the switch circuits 15 and 22 and the OR circuit 5 described above to select various separation methods. Switch.

(Diagonal correlation detection type Y/C separation circuit 2) FIG. 3 shows the detailed configuration of the diagonal correlation detection type Y/C separation circuit 2. This diagonal correlation detection type Y/C separation circuit 2 is a point of interest P.
14 in the diagonal direction to obtain a Y/C separated signal.

In the diagonal correlation detection type Y/C separation circuit 2, the composite video signal COMP3 is delayed by one sampling period as shown in FIG.
8, two delay circuits 59 and 60 that delay by 906 sampling periods, and eight delay circuits 61 to 68 that delay by one sampling period are connected in series. Note that the 910 sampling period is 1
Corresponds to the horizontal scanning period.

Thus, as shown in FIG. 7, data D14 of the point of interest P14, data D5 of the point P5 below it, data D1-D4 of the four points P1-P4, P6-P9 before and after the point P5,
D6 to D9, data D23 of point P23 above the point of interest P14, and four points before and after point P23, P19 to P22, P24
Data D19 to D22 and D24 to D27 of NP27 are obtained by this delay stage 69.

Here, the color difference signal components of each data will be considered in the diagonal directions A to ■ passing through the point of interest P14.

Regarding each data D1, D14, and D27 in the diagonal direction A, in-phase and anti-phase of the same color difference component appear alternately. Therefore, these data D1, D14, D2
By appropriately adding or subtracting 7, only the luminance signal or only the chroma signal can be extracted.

For each data D2, D14, and D26 in the diagonal direction B, a color difference component different from the color difference component of the data D14 is used as the data D.
2 and 26, and the color difference components of data D2 and D26 are in opposite phases. Therefore, in this case, data D2
By adding or subtracting D26 and D26, only the chroma signal or only the luminance signal can be extracted. However, in this direction B, the color difference signal component of the extracted chroma signal does not correspond to the color difference signal component of the point of interest P14, so it is not preferable as a separated signal.

Regarding each data D3, D14, and D25 in the diagonal direction C, all the color difference signal components are in phase, and when added or subtracted, both the color difference signal component and the luminance signal component cancel each other out, so in this case, the luminance signal Neither the chroma signal nor the chroma signal can be extracted.

If we consider and organize in the same way, diagonal directions A, B, D,
F, H, and I can use that data to separate the luminance signal,
In the diagonal directions A and (2), the chroma signals can be separated using the data. Therefore, since there are more diagonal directions in which luminance signals can be separated, in order to increase the types of transitions depending on the correlation in diagonal directions, in this embodiment, first, the luminance signals are separated, and then The system is configured to obtain a chroma signal by subtracting it from a composite video signal.

The data D1 and D27 in the diagonal direction A are given to the adder circuit 70 and added, and then multiplied by 1/2 via the 1/2 multiplier circuit 71.
14, and if there is a correlation, the color difference signal components are canceled to obtain a luminance signal YA in this direction, which is supplied to the data selector 73.

Data D2 and D26 in the diagonal direction B are applied to an adder circuit 74, and added, and if there is a correlation, the color difference signal components are canceled to obtain a luminance signal YB in this direction, which is applied to the data selector 73.

Data D4 and D24 in the diagonal direction are applied to an adder circuit 75, and added, and if there is a correlation, the color difference signal components are canceled to obtain a luminance signal YD in this direction, which is applied to the data selector 73.

A diagonal direction I that is symmetrical to these diagonal directions A, B, and D.
, H, F, adder circuit 76.1/
A doubling circuit 77 and an adder circuit 78 are used to obtain a brightness signal YI, an adder circuit 79 is used to obtain a brightness signal YH, and an adder circuit 80 is used to obtain a brightness signal YF, which is applied to the data selector 73. It will be done.

The data selector 73 receives correlation flags SF1 to S, which are given from a diagonal correlation detection circuit 81 whose detailed a+i configuration is shown in FIG.
Based on F3, a luminance signal obtained from data in a diagonal direction that has a correlation is selected, and the luminance signal is converted to 1/2 through a 1/2 multiplier circuit 84.
The signal is doubled and sent to the switch circuit 3 as an output luminance signal YS. This luminance signal YS is also provided to the subtraction circuit 82 as a subtraction input. The subtraction circuit 82 receives a composite video signal whose phase matches that of the luminance signal YS, that is, data D14 at the point of interest P14, as an input to be subtracted, and subtracts the luminance signal YS from the data D14 to obtain a chroma signal C8. After removing unnecessary components through a bandpass filter 83, the signal is sent to the switch circuit 3.

(Diagonal Correlation Detection Circuit 81) In this embodiment, the diagonal correlation detection circuit 81 is configured to be able to detect a correlation from data in a diagonal direction, as shown in FIG.

This diagonal correlation detection circuit 81 also uses the above-mentioned delay stage 69, and the composite video signal COMP3 is sent to the delay stage 69.
As shown in FIG.
D6 to D9, data D23 of point P23 above the point of interest P14, and four points before and after point P23, P19 to P22, P24
-P27 data D19-D22 and D24-D27 are obtained.

Here, if you try to detect correlation by detecting the level difference between data without obtaining the luminance signal component or color difference signal component, it is difficult to detect data that leaves color difference component and luminance signal component when added or subtracted. No correlation can be detected between the two. Therefore, in order to directly detect the correlation in the diagonal direction from the data in the diagonal direction, it is necessary to have two or more pieces of data in which the color difference signal components are in phase in the diagonal direction.

When considering each of the diagonal directions A to ■ from this point of view, it is clear from Fig. 7 that the diagonal directions A, C, E, G,
It can be seen that a correlation can be detected for I. Therefore, in this embodiment, these diagonal directions A, C, E, G,
Correlation is detected for (2) to obtain correlation flags SF1 to SF3.

In FIG. 5, data D1 and D27 whose color difference signal components in the diagonal direction A are in phase are subtracted through a subtraction circuit 90 and converted into absolute values through an absolute value circuit 91. It is converted into a difference signal SA having an approximately 0 level and is applied to the minimum value circuit 92 and the comparison circuit 93. Data D9 and D19 in the diagonal direction I, which has a symmetrical relationship with the diagonal direction A, are subtracted through a subtraction circuit 94 and then converted into absolute values through an absolute value circuit 95, and when there is a correlation, the data D9 and D19 are at approximately 0 level. The minimum value circuit 92 converts it into a difference signal SI that takes
and is applied to the comparison circuit 93.

Comparison circuit 93 compares the incoming difference signals SA and SI,
When the difference signal SA is small, it takes logic "0" indicating that the correlation in the diagonal direction A is stronger than in the diagonal direction I, and conversely, when the difference signal SI is small, the correlation in the diagonal direction I is stronger than in the diagonal direction A. A diagonal tendency instructing signal AI having a logic "1" indicating that this is the case is output to the decoder 96.

The minimum value circuit 92 selects the smaller of the arriving difference signals SA and SI, that is, selects the difference signal in the direction of the stronger correlation and supplies it to the comparison circuit 97. Further, the comparison circuit 97 is supplied with a reference signal REF7, and the comparison circuit 97 takes a logic "1" indicating that there is a correlation when the difference signal is smaller than the reference signal REF7, and when the difference signal is larger than the reference signal REF7. The first takes logic “0” indicating no correlation in the case
A correlation signal 5COI of is given to the decoder 96.

Data D3 in which the color difference signal components are in phase in the diagonal direction C
, D14, and D25, the difference between them is calculated in the subtraction circuits 98, 99, and 100, and then the differences are converted into absolute values through the respective absolute value circuits 101, 102, and 103, and when there is a correlation, the difference becomes approximately 0. Difference signal SC1 to take the level
, SC2, and SC3 and provided to the average value circuit 104.

The average value circuit 104 receives these difference signals SCI, SC2, SC.
3 is obtained to obtain a difference signal SC indicating the level difference of data in the diagonal direction C, which is outputted from the minimum value circuit 105 and the comparison circuit 106.

Data D7, D14, and D21 having the same color difference signal components in the diagonal direction G that is symmetrical to the diagonal direction C are subtracted by subtraction circuits 107 to 1.
09, the conversion processing performed by the absolute value circuits 110 to 112 and the average value circuit 113 in the same manner as in the diagonal direction C is performed to obtain a difference signal SG in the diagonal direction G, which is provided to the minimum value circuit 105 and the comparison circuit 106. It will be done.

The comparison circuit 106 compares the incoming difference signals SC and SG, and if the difference signal SC is small, the difference signal SC is smaller than the diagonal direction G.
Take the logic "0" indicating that the correlation is strong, and conversely,
When the difference signal SG is small, a diagonal tendency instruction signal CG is output to the decoder 96, which takes logic "1" indicating that the correlation in the diagonal direction G is stronger than in the diagonal direction C.

The minimum value circuit 105 selects the smaller of the arriving difference signals SC and SG, that is, selects the difference signal in the direction of the stronger correlation, and supplies it to the comparison circuit 114.

Further, the comparison circuit 114 is supplied with a reference signal REF8, and when the difference signal is smaller than the reference signal REF8, the comparison circuit 114 takes a logic "1" indicating that there is a correlation.
A second correlation signal 5CO2 is provided to the decoder 96, which takes logic "0" indicating no correlation when the difference signal is larger than the reference signal REF8.

Further, data D5 and D23 in which the color difference signal components in the diagonal direction E (strictly speaking, in the vertical direction) are in phase are given to a subtraction circuit 115, and are subtracted and converted into a difference signal SE that takes approximately 0 level when there is a correlation. and is applied to the comparison circuit 117 via the absolute value circuit 116. The comparison circuit 117 also has
A reference signal REF9 is given, and the comparator circuit 117 takes a logic "1" indicating that there is a correlation when the difference signal SE is smaller than the reference signal REF9, and indicates that there is no correlation when the difference signal SE is larger than the reference signal REF9. Instructing logic “0”
A third correlation signal 5CO3 that takes `` is provided to the decoder 96.

The decoder 96 performs a conversion operation according to the conversion table TAB4 shown in FIG. 10, obtains correlation flags SFI to SF3, and supplies them to the data selector 73 of the diagonal correlation detection type Y/C separation circuit 2 and the NAND circuit 6. Here, the conversion by the decoder 96 is performed based on the following conversion idea.

(1) If there is no correlation between diagonal directions A and I, which have gentle slopes, and diagonal directions C and G, which have steep slopes (both SCOI and 5CO2 are "0"), there is no correlation in diagonal directions. As vertical correlation detection type Y/C separation circuit 1
The luminance signal YV and chroma signal C■ are selected.

Therefore, in this case, the data selector 73 is not allowed to perform the data selection operation, and the switch circuit 3 is caused to select the separation signal of the vertical correlation detection type Y/C separation circuit 1 via the NAND circuit 6. Correlation flag SF
Outputs 1 to SF3. In addition, the horizontal direction of table TAB4! L4 and L5 correspond to this case. Therefore, in this case, the switch circuit 3 gives priority to the vertical correlation as described above.

(2) If there is a correlation in at least one of the diagonal directions A and I with a gentle slope or the diagonal directions C and F with a steep slope (at least one of SCOI or 5CO2 is "1")
, the separation signals YS and C8 of the diagonal correlation detection type Y/C separation circuit 2 are selected. Horizontal column L1 of table TAB4
~L3 and L6~L8 correspond to this case. In this case as well, if there is a vertical correlation, the switch circuit 3 selects the output signal of the vertical correlation detection type Y/C separation circuit 1, so that the vertical correlation is given priority.

(21) In this case, when there is a correlation in the diagonal directions A and I, in which the diagonal direction used for luminance signal separation and the diagonal direction used for correlation detection match, (SCOI is "1") ''), the contents of the correlation flags SF1 to SF3 are determined so as to select the luminance signal YA or YI obtained from the data in the diagonal direction, regardless of the presence or absence of correlation in other diagonal directions. This case corresponds to ILL and L8 in the horizontal direction of table TAB4.

(22) When there is a correlation in the diagonal direction, if there is a correlation only in the diagonal direction C or G where the luminance signal cannot be separated (SCO2 is "1"), the luminance signal cannot be separated in this direction, so the diagonal direction The contents of the correlation flags SFI to SF3 are determined so that the separated luminance signal YB or YH is selected using the data in the adjacent diagonal direction B or H, which has a gentler slope than C or G.

Horizontal columns L2 and L7 of table TAB4 correspond to this case.

(23) When there is a diagonal correlation, there is a correlation in the diagonal direction C or G where the luminance signal cannot be separated (SCO2 is "1"), and there is a correlation in the vertical direction E (SCO3 is "
1), the diagonal direction C and the vertical direction E
The contents of the correlation flags SF1 to SF3 are determined so that the luminance signal YD or YF obtained from the data on F is selected in the diagonal direction intermediate between F and F. Horizontal columns L3 and L6 of table TAB4 correspond to this case.

Therefore, based on the correlation flags SF1 to SF3 from the decoder 96 that performs the conversion operation as described above, the data selector 7
3 and the switch circuit 3 selectively operate, in the case where there is no vertical correlation, if there is a diagonal correlation, the luminance signal YS obtained from data in the diagonal direction with the correlation, and the chroma signal C8 obtained based on the luminance signal YS. can be selected.

(Effects of the Embodiment) Therefore, according to the above-described embodiment, when there is a correlation in the vertical direction, the separation signal based on the comb filter separation method that is most suitable for that case is selected, which improves the image quality in the vertical direction. Deterioration can be prevented.

In addition, if there is no vertical correlation, based on the diagonal correlation obtained using multiple data in the diagonal direction, if there is a diagonal correlation, it is separated from the data in the diagonal direction that has the same or approximate tilt angle as that direction. Since the Y/C separation signal that is not detected is selected, it is possible to further reduce diagonal dot crawl and cross color. Furthermore, when there is no vertical correlation and no diagonal correlation, a separated signal separated by a frequency separation method suitable for horizontal correlation is selected, so dot crawls flowing in the horizontal direction and cross colors are detected. etc. can be reduced.

Incidentally, in the above embodiment, horizontal correlation is not detected, but if there is no horizontal correlation in the case where there is no diagonal correlation or vertical correlation, there is no correlation at all. This is sufficient, and image quality deterioration cannot be avoided. Rather, by adopting the frequency separation method when there is no vertical correlation or diagonal correlation, image quality deterioration in the horizontal direction can also be reduced, and image quality deterioration in all directions can be prevented even without detecting horizontal correlation. Becomes good. .

In this way, since priority is given to the vertical correlation, image quality deterioration in the vertical direction, to which human vision is more sensitive than in the diagonal direction, is particularly prevented, and an easily viewable image can be obtained.

(Other Examples) In addition, in the above-mentioned example, three
Although data from a total of 27 points (x9) are used to perform correlation detection in the diagonal direction and extraction of luminance signals, the present invention is not limited to this. The luminance signal may be separated.

Furthermore, in the above-described embodiment, a direction with a strong correlation is selected before being input to the decoder 96 for symmetrical diagonal directions, and then the correlated direction is input to the decoder 96. may be input directly to the decoder 96.

Furthermore, in the above-mentioned embodiment, the correlation in each diagonal direction is detected based on the level difference of the data.
Although the number of diagonal directions that can be detected is reduced, it is also possible to extract the luminance signal component from the data and detect the correlation in the diagonal direction.

Furthermore, in the above-mentioned embodiments, a so-called 2H type and an IH type are used together as the comb filter separation system, but it is also possible to use only one of them.

Further, in the above-described embodiment, vertical correlation was detected from data at five points, but it may be detected using more or less data.

[Effects of the Invention] As described above, according to the present invention, vertical correlation and diagonal correlation are detected, and when there is vertical correlation, the comb filter separation method is selected, and when there is no vertical correlation, the diagonal correlation is selected. Based on the presence or absence of correlation, if there is diagonal correlation, select a separation method that separates the luminance signal and chroma signal from data in the diagonal direction, and if there is no correlation in the diagonal direction, it is suitable when there is correlation in the horizontal direction. Since a suitable frequency separation method is selected, it is possible to obtain a Y/C separation device that can further reduce image quality deterioration such as horizontal, vertical, and diagonal dot crawl and cross color compared to conventional devices.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a Y/C separation device according to the present invention, and FIG. 2 is a vertical correlation detection type Y/C separation circuit 1.
3 is a block diagram showing the detailed configuration of the diagonal correlation detection type Y/C separation circuit 2, and FIG. 4 is a block diagram showing the detailed configuration of the vertical correlation detection circuit 20. FIG. 5 is a block diagram showing the detailed configuration of the diagonal correlation detection circuit 81, FIG. 6 is a diagram showing the input/output of the decoder 4, and FIG. 7 is a two-dimensional data array of sampling data. The route map, FIGS. 8 and 9 are charts showing the input and output of the decoder 40, and FIG. 10 is a chart showing the input and output of the decoder 96. DESCRIPTION OF SYMBOLS 1... Vertical correlation detection type Y/C separation circuit, 2... Diagonal correlation detection type Y/C separation circuit, 3... Switch circuit, 4
... decoder, 20 ... vertical correlation detection circuit, 81.
...Diagonal correlation detection circuit.

Claims (1)

[Scope of Claims] A frequency separation circuit that separates a luminance signal and a chroma signal from a composite video signal according to a frequency separation method; and a comb filter separation circuit that separates a luminance signal and a chroma signal from the composite video signal according to a comb filter separation method. , Input the data of the composite video signal whose phase is aligned with one color difference signal component axis and sampled at a frequency four times the color subcarrier frequency, and with respect to the diagonal direction passing through the point of interest, A plurality of diagonal correlation detection type Y/C separation circuits each having a different tilt angle in the diagonal direction, which obtains a luminance signal at the point of interest from the data and subtracts the obtained luminance signal from the composite video signal to obtain a chroma signal. and a vertical correlation detection circuit that inputs the above data and detects the correlation in the vertical direction passing through the point of interest, and a vertical correlation detection circuit that inputs the above data and detects the correlation in the diagonal direction passing through the point of interest from the data on the diagonal direction. Based on the detection outputs of a plurality of diagonal correlation detection circuits each having a different tilt angle in the diagonal direction, and the vertical correlation detection circuit and each of the diagonal correlation detection circuits, if there is a vertical correlation, the comb shape is detected. A filter separation circuit is selected, and if there is no vertical correlation, it is determined whether there is a diagonal correlation, and if there is no diagonal correlation, the frequency separation circuit is selected, and if there is a diagonal correlation, the diagonal direction in which the correlation exists is determined. A Y/C separation device comprising: Y/C separation circuit selection means for selecting the above-mentioned diagonal correlation detection type Y/C separation circuit.