JPS63189094A - Y/c isolation device - Google Patents

Abstract

PURPOSE:To suitably switch a Y/C isolation system by detecting horizontal correlation with data on >=5 points before and behind and including an aimed point in a device which switches the Y/C isolation system based on the output of a horizontal correlation detection circuit. CONSTITUTION:The horizontal correlation detection circuit 23 inputs a composite video signal sampled by fourfold color subcarrier frequency and by fitting a phase to a B-Y axis and detects the horizontal correlation with odd number of data on >=5 points before and behind the aimed point being the center of the correlation detection. A comb line filter isolation part 10 and a frequency isolation part 20 are connected with a switch circuit 18 and the switch circuit 18 is switched based on the said correlation detection signal FLG. Thus as the horizontal correlation can be detected with high accuracy, the Y/C isolation system can be suitably selected and the deterioration frequency of image quality caused by crossed color or dot crawling and so on can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a Y/C separation device, and is particularly suitable for application to an adaptive type device that switches the Y/C separation method as appropriate.

[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 a band-pass filter and a low-pass filter; There is a comb filter separation method that separates a luminance signal and a color signal by using the correlation between lines.

These two separation methods are different from each other.In a screen condition where the luminance signal contains high-frequency components near the color subcarrier, leakage occurs between the color signal and the luminance signal, resulting in so-called cross-color deterioration of image quality. It has the disadvantage of
The comb filter separation method has the disadvantage that the separation becomes insufficient due to the collapse of the correlation that is the premise of the method, resulting in a deterioration in image quality called dot crawl, in which dots flow in the direction of the edges of the image.

Therefore, in the past, Y/C separation circuits of both types were installed in parallel, and the Y/C separation signal using the comb filter separation method, which causes less image quality deterioration than the frequency separation method, was selected. /C separation signal)
In the case of selecting b, for example, when a dot crawl flowing in the horizontal direction occurs, the Y/C separation signal of the frequency separation method is selected. Conventionally, such switching between separation methods has been performed based on the output of a horizontal correlation detection device as shown in FIG.

In FIG. 5, 4 of the color subcarrier frequency fSC is
A composite video signal COMP sampled at a frequency of 4fSC in phase alignment with the BY axis is applied to a delay stage 5 formed by cascadingly connected dot delay circuits 1 to 4 which delay the signal by a sampling period. Here, since the sampling frequency is 4fSC and sampling is performed with the phase aligned with the B-Y axis, the luminance signal component Y and one color difference signal component B-Y, R-Y as shown in FIG. Todenaru Y
-(B-Y), Y+ (R-Y), Y+ (B-Y
), Y-(R-Y) data series are obtained, and the input video signal and the video signal output via the final stage delay circuit 4 are added with the same color difference signal component to the luminance signal or It becomes the same phase after subtraction.

Therefore, the in-phase portion of the video signal is subtracted in a subtracting circuit 6, converted into an absolute value via an absolute value circuit 7 to obtain a difference, and this difference DIF is compared with a reference signal REF in a comparator circuit 8 to obtain a correlation flag FLG. That's what I do. That is, if there is a correlation, the in-phase portions of the video signals have almost the same level, and the comparison circuit 8 outputs the logic r) (correlation flag F of J).
LG is obtained, and on the other hand, if there is no correlation, the levels of the in-phase components are different, and the correlation flag FLG of logic "L" is output from the comparator circuit 8.
is obtained, and based on this correlation flag FLG, when the logic is rH, the Y/C separated signal separated by the frequency separation method is selected.

[Problems to be Solved by the Invention] However, according to the conventional device, since the correlation is detected using the in-phase portions of the video signals, it is difficult to detect the correlation using the video signal information between the video signals of the in-phase portions. Therefore, there was a risk that the correlation detection output would result in misjudgment. That is,
For example, when black and white are inverted at frequency 2fsc, which is twice the color subcarrier frequency fSC, the in-phase video signals both have a black level and a correlated detection output is sent out, but there is a white level in between. Therefore, there is no correlation in nature and an incorrect detection output is sent out. Further, according to the conventional apparatus, a video signal at a position distant from the video signal at the output point is used for correlation detection, and the detection accuracy is also low from this point of view.

Therefore, switching of the separation method was not performed appropriately, and the overall quality of the image was sometimes lower than when simply using the comb filter separation method. In addition, since the accuracy of correlation detection is low, when the S/N ratio is poor or there is a lot of movement, correlation and no correlation are frequently switched.
In some cases, the Y/C separation method was switched frequently, resulting in unstable and unnatural images.

The present invention has been made in consideration of the above points, and aims to provide a Y/C separation device that can accurately detect horizontal correlation and appropriately select a Y/C separation method. It is.

[Means for Solving the Problems] In order to solve the problems, the present invention includes a comb filter separation section that separates luminance signals and chroma signals using a comb filter separation method, and a comb filter separation section that separates luminance signals and chroma signals using a frequency separation method. A frequency separation unit that separates signals, a switch circuit that switches between the luminance signal and chroma signal separated by the comb filter separation unit or frequency separation unit, and horizontal correlation detection that detects the horizontal correlation of the composite video signal and switches the switch circuit. In the Y/C separation device comprising a circuit, the horizontal correlation detection circuit inputs a composite video signal sampled at a frequency four times the color subcarrier frequency and in phase with one color difference signal component axis. Horizontal correlation is detected using all data of a composite video signal between points that are separated by at least two sampling periods before and after in the horizontal direction around a point of interest that is the center of correlation detection.

[Operation] The horizontal correlation detection circuit detects horizontal correlation using all the data of 5 or more odd-numbered points before and after the point of interest, and based on this detection output, switches the switch circuit to detect the luminance signal and chroma signal by the comb filter separation section. signal, and the brightness signal and chroma signal by the frequency separator.

As a result, horizontal correlation can be detected with high precision, so switching can be performed appropriately, and image quality deterioration such as cross color and dot crawl can be reduced.

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

In Figure 1, the color subcarrier frequency is 4f
A composite video signal COMP sampled at SC and in phase with the BY axis is provided to a comb filter separation unit 10.

Here, as shown in FIG. 2, the two-dimensional data series of the composite video signal COMP alternately repeats in-phase and anti-phase of the same color difference components in the vertical direction. Therefore, if the data of the point of interest PH is H1, and the data of points PC and PM vertically adjacent to the point of interest PH are C and M,
When there is a correlation in the vertical direction, the color signal component C1 of the point of interest PH can be separated by executing the calculation shown in the following equation (1).

Therefore, in the comb filter separation unit 10, delay circuits 11 and 12 that delay by one horizontal scanning period are connected in series, and the data of the point of interest PH and the points PC and PM that are vertically adjacent to the point of interest PH is I'm trying to get H, C, and M.

After data C and M are added in the adder circuit 13,
The data H is given as a subtraction input to the subtraction circuit 14, and the data H is doubled via the doubling circuit 15 and sent to the subtraction circuit 1.4.
is given as an input to be subtracted, and after being subtracted, the chroma signal component C1 is obtained by performing calculation according to the above-mentioned equation (1) via the 1/4 multiplier circuit 16. This chroma signal C1 has a color subcarrier frequency fsc
Unnecessary components are removed through a bandpass filter 17 whose passing center frequency is .
The signal is applied to the chroma signal switching section 18C.

Also, the chroma signal C1 via the bandpass filter 17
is given to the subtraction circuit 19 as a subtraction input. One subtraction circuit is given data H at the point of interest PH from the delay circuit 11, and the chroma signal C1 is subtracted from the data H to obtain a luminance signal Y1 at the point of interest PH. The brightness signal is applied to the brightness signal switching section 18Y.

Also, a composite video signal via the delay circuit 10,
That is, data H corresponding to the point of interest PH is provided to the frequency separation section 20. The frequency separation unit 20 uses the color subcarrier frequency fsc as the passing center frequency of the incoming data H, passes it through a bandpass filter 21 that passes the band of the chroma signal component, obtains a chroma signal C2, and switches the chroma signal of the switch circuit 18. Further, the data H is passed through a low-pass filter 22 whose passband is lower than the band of the chroma signal component, and a luminance signal Y2 is obtained and supplied to the luminance signal switching section 18Y of the switch circuit 18.

When the correlation flag FLG given from the horizontal correlation detection circuit 23 indicates that there is a correlation, the switch circuit 18 switches the chroma signal switching section 18C and the luminance signal switching section 18Y to the signal side from the frequency separation section 20, and sets the correlation flag FLG.
indicates no correlation, the chroma signal switching unit 18C
and the luminance signal switching section 18Y are connected to the comb filter separation section 10.
Switch to .

In this embodiment, the horizontal correlation detection circuit 23 uses data F of two points PF, PG, P■, and PJ, including the point of interest PH, in order to appropriately switch the Y/C separation method.
A correlation flag FLG that uses all of ~J and indicates that there is a correlation only when there is a strong correlation in the vicinity of the point of interest PH
It is designed to send out.

7 mouths
23 t 1 FIG. 3 shows a first example of the horizontal correlation circuit 23 using data F to J. In FIG. 3, a composite video signal COMP1 synchronized and applied to a comb filter separator 10 and a frequency separator 20 is applied to two delay stages formed by branch-connecting delay circuits 25 to 28 that delay by a sampling period. Then, data F to J are obtained at two points in front and behind each other in the horizontal direction centering on the point of interest PH as shown in FIG. Data F and H are given to an adder circuit 30, and added in the adder circuit 30. If there is a correlation, the color difference signal component is canceled out, and the two of the luminance signals corresponding to the point PG, which is delayed by one sampling period from the point of interest PH, are added. A signal Y1 having a double value is output. Also,
Data G and I are given to the adder circuit 31, and the adder circuit 3
1, and if there is a correlation, a signal Y2 having a value twice that of the luminance signal corresponding to the point of interest PH is output.

Further, the data H and J are given to an adder circuit 32, and added in the adder circuit 32. If there is a correlation, the color difference signal component is canceled and a luminance signal corresponding to a point PI which is one sampling period ahead of the point of interest PH is generated. A signal Y3 having a value twice that of is output.

A signal Y2 corresponding to the luminance of the point of interest PH and a signal Y1 corresponding to the luminance of a point PG delayed by one sampling period from the point of interest PH are supplied to the subtraction circuit 33 for subtraction, and then supplied to the absolute value circuit 34. The absolute value is taken, and a difference signal IΔYll corresponding to the difference in luminance signal level between the point of interest PH and a point PG delayed by one sampling period is obtained and applied to the comparison circuit 35.

The comparison circuit 35 uses this difference signal 1ΔYll as a reference signal REF.
When the difference signal 1ΔYll is smaller than 1, the logic rH, which means there is a correlation, is taken, and when it is larger, the first correlation signal C01, which means there is no correlation, is taken, and the first correlation signal C01 is output to the AND circuit 37. .

Brightness signal Y2 according to the point of interest PH and 1 from the point of interest PH
Luminance signal Y3 corresponding to point PI with advanced sampling period
is applied to the subtraction circuit 38 for subtraction, and then applied to the absolute value circuit 39 to take the absolute value, thereby producing a difference signal corresponding to the difference in luminance signal level between the point of interest PH and the point PI advanced by one sampling period. 1ΔY2+ is obtained and applied to the comparator circuit 40. The comparison circuit 40 uses this difference signal 1ΔY2+ as a reference signal RE.
When the difference signal 1ΔY2+ is smaller than F2, it takes logic rH, which means there is a correlation, and when it is larger, it takes logic "L", which means there is no correlation, and outputs it to the AND circuit 37. .

Luminance signals Y1 and Y3 corresponding to points PI and PG, which are different by one sampling period before and after the point of interest PH, are supplied to a subtraction circuit 41 for subtraction, and then supplied to an absolute value circuit 42 to obtain the absolute value. Then, a difference signal 1ΔY31 corresponding to the difference in luminance signal levels before and after the point of interest PH is obtained and applied to the comparison circuit 43. The comparison circuit 43 receives this difference signal 1ΔY3
1 is compared with the reference signal REF3, and when the difference signal 1ΔY31 is small, it takes the logic rHJ that means there is a correlation, and when it is large, it takes the logic "L" that means there is no correlation.The AND circuit generates the third correlation signal CO3. Output to 37.

The AND circuit 37 receives the incoming first to third correlation signals CO1.
- Correlation flag F that means correlation exists ('HJ) only when all correlation signals indicate correlation based on CO3
LG is sent to the switch circuit 18.

In the above configuration, when the composite video signal COMP1 in which both the luminance signal and the chrominance signal are correlated is given, the adder circuits 30 to 32 output signals Y1 to Y of approximately the same level.
3 is output, and a difference signal 1ΔY11.1ΔY21.1ΔY31 of almost 0 level is output from each absolute value circuit 34, 39, 42.
is output.

As a result, each comparison circuit 35, 40, 43 sends out correlation signals COI to C○3 of logic r) (J indicating that there is a correlation), and the AND circuit 37 sends out an interphase flag FLG of logic rH, indicating that there is a correlation. do.

On the other hand, if, for example, a composite video signal COMP1 is provided in which the luminance signal component of data H is smaller than the luminance signal components of other data F, G, I, and J,
Signal Y2 is larger than signals Y1 and Y3. Therefore, the absolute value circuits 34 and 39 output difference signals 1ΔYll and 1ΔY21 having large values, while the absolute value circuit 42 outputs a difference signal 1ΔY31 of approximately O level. As a result, the first and second correlation signals CO1 and C
Even if O2 takes a logic "L" level indicating no correlation, and the third correlation signal CO3 takes a logic rH level indicating a correlation, the AND circuit 37 outputs a logic "L" level indicating no correlation.
A level correlation flag FLG is sent.

Furthermore, if a composite video signal COMPI is given in which the luminance signal component is at the same level but the color signal component changes between, for example, a point of interest PH and a point RI that is one sampling cycle ahead of the point of interest PH, this color signal The level difference of the components also affects the luminance signal, and the signal Y1 is different from other signals ¥2
and take a different level from Y3. As a result, comparison circuit 3
From 5.40.43, the logic rl, J, r)(
Correlation signals COI, CO2, and CO3 that take "L" are output, and the AND circuit 37 outputs a correlation flag F indicating no correlation.
Send out LG.

Therefore, according to this horizontal correlation detection circuit 23, the point of interest P
If there is a point near H where the value suddenly changes even in a short period of time, the correlation is denied and the correlation is strictly judged. By switching the switch circuit 18 using the correlation flag FLG from this circuit 23, the separation method can be appropriately selected, and image quality deterioration such as dot crawl and cross color can be reduced.

7-0 23-2 Figure 4 shows data F to J at two points before and after the point of interest PH.
The second horizontal correlation detection circuit 23 uses all of the above for correlation detection.
Give an example. Also in FIG. 4, data FJ at five points centered on data H at the point of interest PH are obtained by two delay stages.

Data G and ■ of the points PG and PI before and after the point of interest PH are given to an adder circuit 45, and the adder circuit 45 adds these, and if there is a correlation, the color difference signal component is canceled and the luminance of the point of interest PH is calculated. A signal Y4 having a value twice that of is obtained and is applied to the subtraction circuit 46 as a subtraction input. Further, data F and J are multiplied by 1/2 through 1/2 multiplier circuits 47 and 48, respectively, and given to an adder circuit 49. After being added in the adder circuit 49, data F and J are further added to data H in an adder circuit 50. If there is a correlation, the color difference signal components are canceled in the adder circuit 50 to obtain a signal Y5 having a value twice the luminance of the point of interest PH, which is supplied to the subtracter circuit 46 as a signal to be subtracted.

The subtraction circuit 46 subtracts the signal Y4 from the incoming signal Y5 and supplies it to the absolute value circuit 51, which converts it into an absolute value and converts it into a difference signal 1ΔY41, which is supplied to the comparison circuit 52. The comparison circuit 52 is also supplied with a reference signal REF4, and takes a logic rl,J indicating no correlation when the difference signal IΔY41 is larger than the reference signal REF4, and on the other hand, a logic rl, J indicating no correlation when the difference signal IΔY4+ is smaller than the reference signal REF4. A correlation signal CO4 that takes logic r) (J) is output to the AND circuit 53. Here, the signals Y4 and Y5
There is a difference between using data G, ■ near the point of interest PH and using data F, J outside of it, so the correlation signal CO4 indicates the correlation between the vicinity of the point of interest and the outside. It can be said that

Further, data F and J are given to a subtracting circuit 54, and after being subtracted in the subtracting circuit 54, they are converted into absolute values via an absolute value circuit 55 to obtain a difference signal 1ΔY51, and a comparison circuit °5
given to 6. The comparison circuit 56 also includes a reference signal RE.
F5 is given, and the difference signal 1ΔY51 is the reference signal R
When the difference signal 1ΔY51 is smaller than the reference signal REF5, the correlation signal C0 takes logic rl, J, which indicates no correlation, and takes the logic rH, which indicates there is a correlation when the difference signal 1ΔY51 is smaller than the reference signal REF5.
5 is output to the AND circuit 53. Here, the difference signal 1Δ
Since Y51 corresponds to the difference between data F and J before and after the point of interest PH, it indicates whether there is a difference in the luminance signal level before and after the point of interest PH, and the correlation signal CO5 is based on such a correlation. This indicates that

When both the correlation signals CO4 and CO5 indicate that there is a correlation, the AND circuit 53 raises a correlation flag FLG at logic r (J) indicating that there is a correlation, and on the other hand, at least one of the correlation signals CO4 and CO5 indicates that there is no correlation. When the correlation flag is indicated, a correlation flag FLG which takes a logic "L" indicating no correlation is sent to the switch circuit 18.

In the above configuration, when the correlated composite video signal COMP1 is given, the adder circuits 45 and 50 output luminance signals Y4 and Y5 of approximately the same level, and the absolute value circuit 51 outputs a difference signal of approximately O level. (ΔY4
1 is output. Furthermore, since the data F and J are almost the same, the absolute value circuit 55 also outputs the difference signal 1 of approximately O level.
ΔY51 is output. As a result, each comparison circuit 52.5
Correlation signal C04, C of logic rH, indicating that correlation exists from 6
O5 is sent out, and the AND circuit 53 sends out a correlation flag FLG of logic rH, indicating that there is a correlation.

On the other hand, if, for example, a composite video signal COMP1 is given in which the luminance signal component of data H is smaller than the luminance signal components of other data F, G, ■, J, the luminance signal ¥4 is smaller than the luminance signal Y5. growing. Therefore, the absolute value circuit 51 outputs a difference signal 1ΔY41 having a large value. On the other hand, data F and J are output from the absolute value circuit 55.
Since they are almost equal, a difference signal 1ΔY51 of approximately 0 level is output. As a result, the correlation signal CO4 takes a logic rl, J level indicating no correlation, the correlation signal CO5 takes a logic rH level, indicating a correlation, and the AND circuit 53 outputs a logic "L" level correlation indicating no correlation. Flag FLG is sent.

Furthermore, if a composite video signal COMP1 is given in which the luminance signal component is at the same level but the color signal component changes between, for example, a point of interest PH and a point PI that is one sampling cycle ahead of the point of interest PH, this color signal The level difference between the components also affects the luminance signal, and data F and J take different values. As a result, the comparison circuit 56 outputs the correlation signal C○5 which takes logic "L", and the AND circuit 53 outputs the correlation flag FLG indicating no correlation, regardless of the correlation signal CO4.
Send out.

Therefore, also by this second horizontal correlation detection circuit 23,
Using data F to J at five points, if there is a sudden change in value near the point of interest PH, even for a short period of time, the correlation is denied and the correlation is strictly judged, and the correlation flag FLG from this circuit 23 is By switching the switch circuit 18, the separation method can be appropriately selected, and image quality deterioration such as dot crawl and cross color can be reduced.

In addition, in the above-mentioned embodiment, the comb filter separation unit 1
Although 0 is shown as a so-called 2H type, the present invention can also be applied to a so-called IH type.

Further, in the above embodiment, the horizontal correlation detection circuit 23
Although 5 points of data are used, the number of data is not limited to this, and correlations may be detected using all data of 5 or more odd points.

[Effects of the Invention] As described above, according to the present invention, five points of interest are achieved.
Since the horizontal correlation is detected using all the data of consecutive points or more and the separation method is switched, the correlation can be accurately detected and the separation method can be switched appropriately to prevent image quality deterioration such as cross color or dot crawl. can be reduced. In addition, if there is a point near the point of interest where the level changes even for a short period of time, the correlation is denied, so the number of switching of the separation method is not increased unnecessarily, and the Natural-looking images can be obtained even when a video signal is applied.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the Y'/C separation device according to the present invention, Fig. 2 is a route map showing the phase relationship of sampled data, and Figs. 3 and 4 are horizontal correlation detection. A block diagram showing a first example and a second example of the circuit,
FIG. 5 is a block diagram showing a horizontal correlation detection circuit used in a conventional device, and FIG. 6 is a route diagram showing a data series in the horizontal direction. DESCRIPTION OF SYMBOLS 10... Comb filter separation part, 18... Switch circuit, 20... Frequency separation part, 23... Horizontal correlation detection circuit.

Claims (1)

[Claims] A comb filter separation section that separates a luminance signal and a chroma signal using a comb filter separation method; a frequency separation section that separates a luminance signal and a chroma signal using a frequency separation method; and a comb filter separation section that separates the luminance signal and chroma signal using a frequency separation method; A Y/C separation device comprising a switch circuit that switches between the luminance signal and the chroma signal separated by a separation section, and a horizontal correlation detection circuit that detects horizontal correlation of a composite video signal and switches the switch circuit, The above-mentioned horizontal correlation detection circuit inputs a composite video signal sampled at a frequency four times the color subcarrier frequency and in phase with one of the color difference signal component axes, and detects the focal point that is the center of correlation detection. A Y/C separation device characterized in that a horizontal correlation is detected using all data of the composite video signal located between points separated by at least two sampling periods before and after the center in the horizontal direction.