JP2560932B2 - Adaptive Y / C separation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a television receiver or the like, and is an adaptive Y / C separation for separating a luminance signal (Y signal) and a carrier color signal (C signal) from a composite color television signal. Regarding the device. Further, according to the present invention, even when the oblique direction change of the luminance signal is erroneously detected as the change of the color signal, the generation of the cross color can be minimized, and at the same time, the dot interference can be suppressed. The purpose is to provide a device.

[0002]

2. Description of the Related Art In a composite color television signal such as the NTSC system currently used in television broadcasting, a luminance signal component and a color signal component are frequency-multiplexed. Therefore, unless the luminance signal and the chrominance signal are correctly separated on the receiving side, crosstalk between the luminance signal and the chrominance signal and a decrease in resolution occur.

As a Y / C separation circuit which has been widely used from the past, there is a fixed two-dimensional filter using a comb filter. On the other hand, in the applicant company, adaptive Y /
Developed a C separation device and applied for a patent (Japanese Patent Application No. 62-320965)
And published at the Institute of Electronics, Information and Communication Engineers and the Television Society of Japan. ). In the adaptive Y / C separation device, the band of the vertical direction variable band pass filter (vertical direction variable BPF) and the horizontal direction variable band pass filter according to the output signals from the vertical direction change detecting unit and the horizontal direction change detecting unit. The color signal output is obtained from the horizontal variable band pass filter by controlling the band of the filter (horizontal variable BPF). Further, a luminance signal is obtained by subtracting the color signal output from the composite color television signal. In this case, the high-frequency component remains in the direction in which the change is drastic, that is, the direction in which the high-frequency component is large in the two-dimensional spatial frequency range, while the crosstalk component is removed. As a result, dot interference and cross color can be reduced without significantly reducing the resolution. The adaptive Y / C separation device converts the difference between sample points in the vertical direction of the image into absolute values and performs non-linear conversion, and the vertical direction change detecting means and the difference between sample points in the horizontal direction of the image into absolute values, and performs non-linear conversion. It has a horizontal change detecting means. The separating device controls the bands of the vertical direction variable bandpass filter and the horizontal direction variable bandpass filter according to the output signals of the vertical direction change detecting means and the horizontal direction change detecting means ( For details, see Japanese Patent Application No. 62-320965). In this case, the spectral distribution of the signal makes it possible to set a suitable filter characteristic, and it is possible to reduce dot interference without reducing the S / N and resolution. Further, when there are a large number of change components in both the vertical and horizontal directions, it is possible to suppress the occurrence of cross color by narrowing the pass band of the variable band pass filter in both the vertical and horizontal directions.

However, in the vertical and horizontal direction change detecting means, the difference between two sample points is converted into an absolute value,
Since non-linear conversion is performed into vertical and horizontal direction change detection signals, only a simple one-dimensional or two-dimensional band can be detected. Therefore, for a more accurate Y / C separation, the number of taps increases when trying to configure a filter having a complicated detection band, and particularly in the vertical band detection filter, the number of line memories increases. As described above, in the adaptive Y / C separation device, the structure of the filter becomes complicated and large, which is not practical.

Further, in the vertical and horizontal direction change detecting means, the same change detection signal is output regardless of the frequency of the signal in the pass band, and the vertical change is made after grasping the two-dimensional spectrum distribution. And, it cannot be said that the horizontal change detection signal is generated. That is, the change in the vertical direction and the change in the horizontal direction of the image is merely detected, and it is not judged whether the change component is the change of the color signal or the change of the luminance signal. In the adaptive Y / C separation device, what is necessary for accurate Y / C separation is detection of vertical and horizontal color signal changes independent of changes in the luminance signal. If it cannot be discriminated from, it is impossible to control the variable bandpass filter accurately.

Therefore, in order to solve the above problems, the present applicant company developed a vertical and horizontal direction change detection circuit prior to the present invention and applied for a patent (Japanese Patent Application No. 1-99359).
did. In this vertical and horizontal direction change detection circuit, a plurality of two-dimensional filters having different pass bands are provided, and the output of each filter is converted into an absolute value and subjected to nonlinear conversion,
Vertical and horizontal direction change detection signals are obtained by comparing and synthesizing. The vertical direction and horizontal direction change detection circuit uses a plurality of two-dimensional filters having a simple structure, realizes a complicated detection band without complicating the internal structure of each filter, and achieves the vertical direction and horizontal direction of the color signal. The change in direction and the change in the vertical and horizontal directions of the luminance signal can be detected independently. In the above-mentioned non-linear conversion, the dead zone, slope and saturation zone can be set separately for each two-dimensional filter.

In recent years, an adaptive Y / C separation device has been developed which uses this vertical direction and horizontal direction change detection circuit as a control circuit for the vertical direction variable BPF and the horizontal direction variable BPF. The control method of the vertical direction variable BPF in this device is such that when the color signal is changing in the vertical direction (when the color signal includes a lot of vertical high frequency components), the vertical direction is adjusted to reduce dot interference. In this method, the band of the variable BPF is expanded, and when the color signal does not change in the vertical direction, the band of the variable BPF in the vertical direction is narrowed in order to reduce cross color. Similarly, the control method of the horizontal variable BPF is such that when the color signal changes in the horizontal direction (when the color signal includes many horizontal high frequency components), the horizontal variable BPF can be changed.
In this method, the band of the PF is widened, and when the color signal does not change in the horizontal direction, the band of the horizontally variable BPF is narrowed. Therefore, when the color signals are changing in both the vertical direction and the horizontal direction, the pass bands of both the vertical variable BPF and the horizontal variable BPF are widened.

If the change detection of the color signal is perfect, the above control has no problem. However, in reality, since the change in the color signal is detected from the composite color television signal in which the color signal and the luminance signal are superposed, the change component in the diagonal direction of the luminance signal (the diagonal direction of the luminance signal is inevitable). The high frequency component) is erroneously detected as a color signal change component. Therefore,
Despite the oblique change in the luminance signal, this device may widen the pass band of both the vertical and horizontal variable BPFs, which results in increased cross color. That is, it is dangerous to unnecessarily widen the pass band of the variable BPF as long as inaccurate points remain in the detection.

Here, both vertical and horizontal variable B
The relationship between the pass band of the PF, cross color, and dot interference will be described. Since this relationship is the same in the vertical direction and the horizontal direction, only the horizontal direction will be described here. In the composite color television signal, the color signal is superimposed on the outside of the highest frequency component of the luminance signal. The function of both the vertical and horizontal variable BPFs is to pass only the color signal and extract the color signal from the composite color television signal. Cross color is caused by a luminance signal component mixed in a color signal. When the oblique high frequency component (diagonal change component) of the luminance signal is erroneously detected as the horizontal high frequency component (horizontal change component) of the color signal and the pass band of the horizontal variable BPF is widened, Simultaneously with the color signal, the diagonal high frequency component of the luminance signal passes through the horizontal variable BPF. Therefore, the luminance signal component is mixed in the color signal, and cross color is generated.

On the other hand, the dot interference is caused by the color signal component remaining in the luminance signal. When there are many horizontal high frequency components of the color signal, the frequency of the color signal extends in the horizontal direction. Therefore, the horizontal direction variable BP
When the pass band of F (of course, the pass band in the horizontal direction) is narrow, only a part of the color signal component can pass through the horizontal variable BPF, and the color signal cannot be sufficiently extracted from the composite color television signal. Therefore, even if the color signal separated by the horizontal variable BPF is subtracted from the composite color television signal, the color signal component that cannot pass due to the narrow pass band of the horizontal variable BPF remains in the luminance signal, resulting in dot interference. Occurs. Therefore, in order to reduce dot interference, it is necessary to widen the pass band of the horizontal variable BPF.

As described above, in order to reduce the dot interference and the cross color, the control method for the variable BPF is completely opposite depending on the change component of the color signal or the change component of the luminance signal in the oblique direction. Therefore, if it is detected that the color signal is changing in both the vertical and horizontal directions,
Widening the pass bands of both the vertical direction variable BPF and the horizontal direction variable BPF allows the high frequency components of the color signal to pass sufficiently, and is effective in reducing dot interference. However, if the detection of the change in the color signal is an erroneous detection of the change in the diagonal direction of the luminance signal, the high frequency component of the luminance signal passes through both BPFs and is mixed in the color signal.
This results in increased cross color.

[0012]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to minimize the occurrence of cross color even when the oblique direction change of the luminance signal is erroneously detected as the change of the color signal. , Y / C with reduced dot interference
What means should be taken to obtain an adaptive Y / C separation device that can be separated.

[0013]

In order to solve the above problems, the present invention provides a vertical variable band pass filter to which a composite color television signal in which a carrier color signal is superimposed on a luminance signal is supplied, A horizontal variable bandpass filter that is supplied with the output of the vertical variable bandpass filter to obtain a carrier color signal output; and a subtractor that subtracts the carrier color signal output from the composite color television signal to obtain a luminance signal output, The vertical color variable band pass filter and the horizontal direction variable are synthesized by combining the outputs of the plurality of two-dimensional filters to which the composite color television signals are respectively supplied and have different pass bands. An adaptive Y / C separation device provided with a bandpass filter and a control signal generation circuit for generating a control signal for controlling a passband. The control signal generation circuit is supplied with the outputs of the plurality of two-dimensional filters, and outputs a color signal horizontal direction change detection signal and a color signal vertical direction change detection signal. Depending on the judgment circuit for judging the magnitude relationship between the change detection signal and the color signal vertical direction change detection signal and the judgment signal supplied from the judgment circuit, (a) the color signal horizontal direction change detection signal is If it is larger than the color signal vertical direction change detection signal, the pass band of the vertical direction variable band pass filter is made narrowest, and the pass band of the horizontal direction variable band pass filter is set to the magnitude of the color signal horizontal direction change detection signal. (B) When the color signal vertical direction change detection signal is larger than the color signal horizontal direction change detection signal, the horizontal variable band pass flag is generated. The passband of the filter, and a signal generator for generating a control signal for controlling the passband of the vertical direction variable bandpass filter according to the magnitude of the color signal vertical direction change detection signal. A characteristic adaptive Y / C separation device is provided.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention compares a color signal horizontal direction change detection signal with a color signal vertical direction change detection signal, widens the pass band of the variable BPF in the direction in which the value is larger, and changes the variable BPF in the other direction. Of the passband of both the variable B
Do not expand the pass band of the PF at the same time.
As a result, it is possible to effectively reduce dot interference and minimize the occurrence of cross color even when a diagonal change in the luminance signal is erroneously detected as a change in the color signal.

First, the operating points of the present invention will be described. FIG. 1 is a block diagram of an embodiment, FIG. 2 is a diagram showing a pass frequency band of a two-dimensional filter, and FIG. 3 is a block diagram of the control signal generating circuit shown in FIG. A synthesizing circuit 9a (see FIG. 3) for generating the color signal horizontal direction change detection signal FH and the color signal vertical direction change detection signal FV, the color signal horizontal change detection signal FH, and the color signal vertical direction change detection signal FV. The control signal generating circuit 9 is provided with a subtractor 9f for comparing When the color signal horizontal direction change detection signal FH is larger, the frequency band of the color signal extends in the horizontal direction (the color signal includes many horizontal high frequency components), and the dots are arranged in vertical lines. The control signal generation circuit 9 determines that the interference has occurred. Then, the control signal generation circuit 9 generates a control signal SH that widens the pass band of the horizontal variable BPF 4 according to the magnitude of the color signal horizontal direction change detection signal FH. At the same time, the control signal generation circuit 9 generates the control signal SV that narrows the pass band of the vertically variable BPF 3 to the minimum. Therefore, this adaptive Y / C separation device can effectively reduce the occurrence of vertical line-shaped dot interference by widening the pass band of the horizontal variable BPF 4.
Further, by narrowing the pass band of the vertically variable BPF 3 to the minimum, the change in the luminance signal in the oblique direction is erroneously changed to
Even when it is detected that the color signal changes in the vertical direction, it is possible to minimize the occurrence of cross color.

It is to be noted that, when the detection signal FH> the detection signal FV, the probability of erroneously detecting the change in the diagonal direction of the luminance signal as the change in the horizontal direction of the color signal, that is, the horizontal direction variable BPF4.
By widening the pass band of, the probability that cross color will occur is very low.

On the other hand, the color signal horizontal direction change detection signal FH is compared with the color signal vertical direction change detection signal FV. If the color signal vertical direction change detection signal FV is larger, the frequency band of the color signal is The control signal generation circuit 9 determines that the dot disturbances that extend in the vertical direction (the color signal includes a large amount of vertical high-frequency components) and the dots arranged in a horizontal line form have occurred. Then, the control signal generation circuit 9 generates the control signal SV that widens the pass band of the vertical variable BPF 3 according to the magnitude of the color signal vertical direction change detection signal FV. At the same time, the control signal generation circuit 9 generates the control signal SH that narrows the pass band of the horizontal variable BPF 4 to the minimum. Therefore, this adaptive Y / C separation device is used in the vertical variable BPF.
By widening the pass band of No. 3, it is possible to effectively reduce the occurrence of horizontal line dot interference. Further, by making the pass band of the horizontal variable BPF 4 narrowest, even if the diagonal change of the luminance signal is erroneously detected as the horizontal change of the color signal, the occurrence of cross color is minimized. You can

It should be noted that when the detection signal FV> the detection signal FH, the probability of erroneously detecting a change in the luminance signal in the diagonal direction as a change in the color signal in the vertical direction, that is, the vertical variable BPF 3
By widening the pass band of, the probability that cross color will occur is very low.

An embodiment of the present invention will be described below with reference to FIGS. First, the basic Y / C separation operation of this embodiment will be described. Basic Y / C separation operation is based on previous application
(Japanese Patent Application No. 62-320965), it will be briefly described here. As shown in FIG. 1, a luminance signal (Y signal)
The video signal on which the carrier color signal (C signal) is superimposed, that is, the composite color television signal is supplied to the 1H delay circuits 1 and 2 connected in series. The composite color television signal is assumed to be a digital signal by an A / D conversion circuit (not shown). The output of the 1H delay circuit 1 is supplied to the vertical direction variable BPF 3, and the vertical direction variable BPF 3 is further supplied.
The output of PF3 is supplied to the horizontal variable BPF4.
The separated C signal is output from the horizontally variable BPF 4. Vertical variable BPF3, horizontal variable BPF4
For the construction of the above, the same structure as in Japanese Patent Application No. 62-320965 may be used.

On the other hand, the output of the 1H delay circuit 1 is the subtractor 1
It is also supplied to 0, where the C signal which is the output of the horizontal variable BPF 4 is subtracted from the output of the 1H delay circuit 1 (composite color television signal). And the subtractor 10
Outputs a Y signal. Thus, basically,
Y / C separation is performed.

Next, the control operation of the vertical variable BPF 3 and the horizontal variable BPF 4 will be described in detail. The vertical band pass filter (vertical BPF) 5 is supplied with the composite color television signal, the output of the 1H delay circuit 1 and the output of the 1H delay circuit 2. The composite color television signal is divided by the vertical BPF 5 into a vertical low frequency component (VL), a vertical mid frequency component (VM), and a vertical high frequency component (VH), each of which is a two-dimensional horizontal band pass. The filters (horizontal BPF) 6 to 8 are supplied. The horizontal direction BPF 6 has a two-dimensional A to C filter, and the A to C filter outputs the band components A, B, and C shown in FIG. 2, respectively. The horizontal direction BPF 7 has two-dimensional D and F filters, and the D and F filters are respectively shown in FIG.
The band components D and F shown in are output. Horizontal direction BPF8
Has a two-dimensional G, H filter, and the G, H filter outputs the band components G, H shown in FIG. 2, respectively. Here, seven two-dimensional filters are used, but the number of two-dimensional filters and the pass band may be changed depending on the usage conditions. The component A of this embodiment is the vertical and horizontal change detection circuit (Japanese Patent Application No. 1-99359) of the previous patent application.
Signal B in this embodiment, the B component in this embodiment is the signal G, the C component is the signals C and F, and the D component is the signal B.
, The F component and the H component become the signal D, the G component becomes the signal E,
Equivalent to each.

Here, fh is a horizontal frequency (unit is MHz)
), Fv is the vertical frequency (unit is Cycle / Height), fsc
Is the color subcarrier frequency, the two-dimensional center frequencies (fh, fv) of the A to H filters are: (fh, fv) = (0, 525/4) for the A filter and (fh, fv) = for the B filter. (fsc / 2, 525/4) C filter is (fh, fv) = (fsc, 525/4) D filter is (fh, fv) = (0, 525/8) F filter is (fh, fv) = The (fsc, 525/8) G filter has (fh, fv) = (fsc / 2, 0) and the H filter has (fh, fv) = (fsc, 0).

The A to H components which are the outputs of the horizontal BPFs 6 to 8 are supplied to the control signal generating circuit 9. The A to H components are converted into absolute values by the absolute value circuit, if necessary, and then non-linearly converted by the non-linear circuit and supplied to the control signal generation circuit 9. The control signal generation circuit 9
Control signal S for controlling the pass band of the vertically variable BPF 3
V is generated and supplied to the vertically variable BPF 3. Also,
The control signal generation circuit 9 generates a control signal SH for controlling the pass band of the horizontal variable BPF 4 and outputs the horizontal variable BP.
Output to F4. The horizontal variable BPF 4 outputs the color signal separated from the composite color television signal as described above. The subtractor 10 outputs a luminance signal by subtracting the color signal from the composite color television signal.

FIG. 3 shows a concrete block diagram of the control signal generating circuit 9. The synthesizing circuit 9a shown in FIG. 3 synthesizes the supplied A, B, C, D, F, G, and H components to generate a color signal vertical direction change detection signal FV and a color signal horizontal direction change detection signal FH. To do. There are various methods of synthesizing each component. For example, FV = (A + D + F + H) / 4, FH = (B + G) / 2 However, if F> C, then FV = 0, B> C FH = 0 FV = MAX (A, D, F, H), FH = MAX (B, G) FV = (MAX (A, D) + MAX (F, H)) / 2, FH = (B + G) / 2 In addition, MAX (B, G) means selecting the larger one of B and G. Etc. are possible.

The subtractor 9f calculates the signal FH-the signal FV and supplies the calculation result of the magnitude relation between the signals FH and FV to the selectors 9d and 9e. If the calculation result is FH ≧ FV (that is, when the change in the horizontal direction of the color signal is greater than or equal to the change in the vertical direction), the selector 9e causes the control signal SH = F.
It is output as H, and the selector 9d outputs the control signal SV = 0.
(Here, it is set to 0, but it may be any fixed value). The control signal SV is a control signal that makes the pass band of the vertical variable BPF 3 the narrowest when 0 and widens the pass band of the vertical variable BPF 3 as the value increases. Similarly, the control signal SH is a control signal that makes the pass band of the horizontal variable BPF 4 the narrowest when 0, and widens the pass band of the horizontal variable BPF 4 as the value increases.

Since FH> 0, the control signal SH = FH
That is, when the color signal includes many horizontal high frequency components, the pass band of the horizontal variable BPF 4 is widened, and the high frequency components of the color signal sufficiently pass through the BPF 4. Therefore, the horizontal variable BPF 4 can accurately separate the color signal component from the composite color television signal, and the color signal does not remain in the luminance signal. Therefore, this device can suppress the occurrence of dot interference arranged in vertical lines. Further, since the control signal SV = 0, the vertical variable BPF
The pass band of 3 is the narrowest, and the luminance signal is not mixed with the color signal. Therefore, this apparatus can minimize the occurrence of cross color even when the diagonal change of the luminance signal is erroneously detected as the vertical change of the color signal. In addition, when erroneous detection is not performed, the dot interference arranged in a horizontal line cannot be reduced by making the pass band of the vertical direction variable BPF 3 narrowest. But,
The dot interference (dot interference arranged in a vertical line) due to the horizontal change component of the color signal, which is a direction in which the change is large and conspicuous, can be reduced as described above. Therefore, when considered as a whole, it can be said that this device has a sufficient dot interference reduction effect.

Next, the calculation result by the subtractor 9f is FH <
When it is FV (that is, when the change in the vertical direction of the color signal is larger than the change in the horizontal direction), the selector 9e controls the control signal S.
Output as H = 0, and the selector 9d outputs the control signal SV =
Output as FV. Since FV> 0, the control signal S
When V = FV and the color signal includes many vertical high frequency components, the pass band of the vertical variable BPF 3 is widened. Therefore, for the same reason as described above, this device can suppress the occurrence of dot interference arranged in a horizontal line. Further, since the control signal SF = 0, the pass band of the horizontal variable BPF 4 is the narrowest, and even if the diagonal change of the luminance signal is erroneously detected as the horizontal change of the color signal, the cross color Occurrence can be minimized. In addition, when the erroneous detection is not performed, the horizontal variable BPF 4
By making the pass band of the narrowest, it is not possible to reduce the interference of dots arranged in a vertical line. However, the dot interference (dot interference arranged in a horizontal line) due to the vertical change component of the color signal, which is a direction in which the change is large and conspicuous, can be reduced as described above. Therefore, when considered as a whole, it can be said that this device has a sufficient dot interference reduction effect.

[0028]

As described above, the adaptive Y / C separation apparatus of the present invention minimizes the occurrence of cross color even when the oblique direction change of the luminance signal is erroneously detected as the change of the color signal. It is possible to perform Y / C separation that suppresses the dot interference and further reduces dot interference.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment.

FIG. 2 is a diagram showing a pass frequency band of a two-dimensional filter.

FIG. 3 is a block configuration diagram of a control signal generation circuit shown in FIG.

[Explanation of symbols]

 1, 2 1H delay circuit 3 vertical direction variable BPF 4 horizontal direction variable BPF 5 vertical direction BPF 6 to 8 horizontal direction BPF 9 control signal generation circuit 10 subtractor

Claims (1)

(57) [Claims] 1. A vertical direction variable band pass filter to which a composite color television signal in which a carrier color signal is superimposed on a luminance signal is supplied, and an output of the vertical direction variable band pass filter to supply a carrier color signal output. Obtaining a horizontal variable band pass filter, a subtractor for subtracting the carrier color signal output from the composite color television signal to obtain a luminance signal output, the composite color television signal is respectively supplied,
Control for controlling pass bands of the vertical direction variable band pass filter and the horizontal direction variable band pass filter by synthesizing outputs of the plurality of two-dimensional filters having different pass bands, respectively. An adaptive Y / C separation device comprising a control signal generation circuit for generating a signal, wherein the control signal generation circuit is supplied with the outputs of the plurality of two-dimensional filters, and outputs a color signal horizontal direction change detection signal. A combination circuit that outputs a color signal vertical direction change detection signal, a determination circuit that determines a magnitude relationship between the color signal horizontal direction change detection signal and the color signal vertical direction change detection signal, and a determination circuit According to the determination signal, (a) if the color signal horizontal direction change detection signal is larger than the color signal vertical direction change detection signal, the vertical direction variable band pass filter A control signal for controlling the pass band of the horizontal variable band pass filter in accordance with the magnitude of the color signal horizontal direction change detection signal, and (b) the color signal vertical direction. When the change detection signal is larger than the color signal horizontal direction change detection signal, the pass band of the horizontal variable band pass filter is narrowed to the narrowest, and the pass band of the vertical variable band pass filter is set to the color signal vertical. An adaptive Y / C separation device comprising: a signal generator that generates a control signal that is controlled according to the magnitude of a direction change detection signal.