JPH0376307A - Comb-line filter - Google Patents

Abstract

PURPOSE:To always extract an excellent separating output while the discrimination is not affected by a change in the absolute level of an input signal by discriminating relative relation of quantity between input values at an arithmetic section so as to apply noncorrelation operation. CONSTITUTION:The input and output of delay lines 2, 3 is fed to an arithmetic section 33 through absolute value circuits 13, 16, and LPFs 31, 32 respectively and a signal from BPFs 6, 8, 9 is fed respectively to the arithmetic section 33 through absolute value circuits 34-36 respectively, and the operation as shown in Table is executed in the arithmetic section 33, where x, y are LPF outputs respectively, and ¦a¦-¦ c ¦ are outputs of the absolute value circuits, and a switch 23 is controlled according to the arithmetic output. Thus, in the case of y>2x, much noncorrelation exists in the output (y) and a signal X is selected. Moreover, in the case of y<1/2x, the signal Y is selected similarly, and then excellent separation output is respectively extracted. In the case of 1/2y<=x<=2y, it is the case that a prescribed level or over of correlation exists or noncorrelation is found out, then a signal Z or W is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a comb filter used for separating luminance signals and chroma signals in color TVs and VTRs.

[Summary of the invention]

The present invention relates to a comb filter, and when switching a plurality of filter outputs by determining non-correlation, by determining the relative magnitude relationship between data, it is possible to always use a comb filter, even when the input signal level is low. This makes it possible to obtain good separation output.

[Conventional technology]

For example, when separating a luminance signal and a chroma signal in an NTSC color video signal, a method of separating the luminance signal and chroma signal using a bandpass filter has conventionally been widely used. However, in the case of this method, for example, 3.58M■2
Since all luminance signals included within the ±500kHz band are considered to be chroma signals, high-frequency components of the luminance signal are mixed into the chroma signal in areas where the luminance signal changes sharply, resulting in image deterioration called cross color. Occur.

In response, a so-called comb filter has been proposed that utilizes the vertical correlation of the screen and the fact that the phase of the subcarrier of the chroma signal is inverted every horizontal period. FIG. 3 shows the circuit, in which a signal from an input terminal (101) is supplied to a delay line (IHDL) (102) for one horizontal period, and a signal at the input/output terminal of this delay line (102) is sent to a subtraction circuit. (103)
supplied to As a result, a signal in which the luminance signal has been canceled is extracted from the subtraction circuit (103), this signal is supplied to a band pass filter (B P F) (104), and the separated chroma signal is sent to the output terminal (105). It is taken out. In addition, the signal from the input terminal (101) is transmitted through a delay line (D
L) (106) to a subtraction circuit (107), the subtraction circuit (107) is supplied with the chroma signal from the bandpass filter (104), and the luminance signal from which the chroma signal has been removed is sent to the output terminal (108). ) is taken out.

[Problem to be solved by the invention]

However, in this case, for example, if a signal is supplied to the above-mentioned comb filter in which the luminance signal level is constant and the phase of the chroma signal is inverted (changed to complementary color) from an intermediate scanning line, then in this changed scanning line, Signal deterioration occurs due to the lack of vertical correlation of chroma signals. That is, the chroma signal remains in the changed scanning line in the luminance signal taken out to the output terminal (108), causing so-called dot interference. Further, in the chroma signal taken out to the output terminal (105), the level of the chroma signal of the changed scanning line decreases, and the vertical resolution of the chroma signal deteriorates.

Alternatively, in scanning lines where the luminance signals have no vertical correlation, residual luminance signals may occur, and if this luminance signal includes band components near the chroma signal, cross color similar to the conventional technique may occur.

In response to this, the applicant of the present application previously proposed a comb filter that can perform separation without signal deterioration as described above by detecting vertical correlation (Japanese Patent Application No. 63-3017).
(see No. 62).

That is, in FIG. 4, a composite signal of the luminance signal "Y" and the chroma signal "Cn" from the input terminal (1) is transmitted to the first and second delay lines (IHDL) each having a delay time of l horizontal period. The signals at the input and output terminals of these delay lines (2) and (3) are supplied to the series circuits (2) and (3), respectively.
is supplied to

The signals at the input and output terminals of these subtraction circuits (4) and (5) are bandpass filters (B P F ) (6) (7) (8H9) (10
).

Output signals of filters (6), (8), and (10) among these are supplied to first and second adder circuits (11) and (12). The addition outputs of these adder circuits (11) and (12) and the output signals of filters (7) and (9) are absolute value circuits (ABS) (13), (14), (15), and (1), respectively.
6) and the coring circuit (17) (1B) (19) (20) which compares this absolute value with a predetermined potential and binarizes it, and is supplied to the logic operation unit (21).

On the other hand, signals ■ and ■ corresponding to the output chroma signals of the above-mentioned comb filter are extracted from the band pass filters (7) and (9), respectively, and the signal from the band pass filter (8) is further extracted from the conventional separation filter. A signal (2) corresponding to a conventional output chroma signal is extracted by being supplied to a bandpass filter (22) that forms a characteristic. These signals are supplied to the first, second and third fixed contacts of the switch (23).

Then, in the above-mentioned calculation unit (21), the coring circuit (1
Using the outputs of 7) to (20) as ■, ■, ■, and ■, respectively, logical operations are performed using the following truth table.

This calculation output is supplied to the switch (23), and the switch (23) is controlled according to the calculation output.

The signal from the switch (23) controlled by this is taken out to the chroma signal output terminal (24).

In addition, the signal from the output end of the delay line (2) is transferred to a delay line (
DL) (25) to the subtraction circuit (26);
The chroma signal from the switch (23) is supplied to this subtraction circuit (26), and a luminance signal from which the chroma signal has been removed is taken out to an output terminal (27).

Therefore, in this circuit, if a signal is supplied to the input terminal (1) in which the level of the luminance signal is constant and the phase of the chroma signal is reversed (changed to a complementary color) from an intermediate scanning line, the signals of each part will be The result will be as shown in Figure 5. Here, the waveform in the figure shows the phase of the chroma signal. In the outputs a - c of the bandpass filters (6), (8), and (10), for example, when the phase is inverted at the position indicated by the broken line, the phases that should originally be inverted every horizontal period are continued in the same phase. become.

Note that c is each delayed by l horizontal periods.

Furthermore, these signals a-c are sent to the adder circuit (11), (
12), a signal appears at the summation output with a scanning line with an inverted phase, and the coring circuit (17) (20)
The outputs ■ and ■ become "1".

On the other hand, signals from bandpass filters (7) and (9)■
.

(2) is a scanning line with an inverted phase, and the subtraction output is missing 7; conventionally, these signals were taken out, causing dot interference and the like. On the other hand, in the above-mentioned embodiment, the operation of the logic operation section (21) causes (■).

Since the signal (2) is taken out only when (2) = (0, 1), the ROMA signal ° "C" is taken out at the output terminal (24) as shown.

In other words, this extracted chroma signal "°C" is exactly equal to the chroma signal component included in the output of the delay line (2),
By supplying these signals to the subtraction circuit (26), a luminance signal 1jY11 from which dot interference has been removed is taken out at the output terminal (27).

In addition, in a signal where the luminance signal level is constant and a chroma signal is added from an intermediate scanning line, the signals of each part are
As shown in the figure, when the signals ① and ② were conventionally extracted, the vertical resolution deteriorated. On the other hand, by making a selection using the signals ■ and ■, the ROMA signal "e" is extracted as shown in the figure.

On the other hand, if there is a luminance signal (the waveform is a luminance signal component near the chroma signal, and the phase of each scanning line is the same) only in two scanning lines in the middle, as shown in Fig. 7, for example, In this case, the signals ■ and ■ become (1, 1). Here, the signals ■ and ■ are determined, and the signal ■ is taken out only when (■, ■) = (0, 1), so that the output terminal (24)
As shown in the figure, a chroma signal "C11" from which the luminance signal component has been removed is extracted.

Furthermore, in this circuit, if a signal is supplied to the input terminal (1) in which the level of the luminance signal is constant and the chroma signal is present in only one scanning line in the middle, the signals of each part are The result will be as shown in the figure. Therefore, in this case, signal deterioration will occur no matter which of the signals (2) and (2) is selected.

On the other hand, in the circuit described above, the chroma signal ■ separated by the usual method from the bandpass filter (8) is supplied to the third fixed contact of the switch (23), while the signals ■, ■ , ■, ■ all become "°l"'', it is determined that there is no vertical correlation in both the luminance signal and the chroma signal, and during this period, by selecting the signal ■ with the switch (23>), the output As shown in the figure, the chroma signal "C'" without signal deterioration can be taken out from the terminal (24).

Therefore, according to this circuit, signals corresponding to the vertical correlation of the luminance signal and chroma signal are respectively taken out from the addition circuit and the subtraction circuit, and the comb filter output with the stronger correlation is selected, and both of the signals corresponding to the vertical correlation are selected. When the separation is poor, a good separated output can be obtained by selecting the output of the normal filter circuit.

Furthermore, in the circuit described above, the bandpass filter (7)
The signals from (9) and (9) are sent to the adder circuit (
This addition circuit (28) is supplied to the adder circuit (28).
), for example, a signal (ba-a) + (b-c) is taken out, and a signal corresponding to the output of a so-called 2H comb filter based on the correlation of three scanning lines is taken out. This signal ■ is then supplied to the fourth fixed contact of the switch (23).

On the other hand, the logic operation section (21) receives the same signal ■ as described above.

(2), (2), and (2) are supplied, and the logic operation section (21) performs a logical operation based on the following truth table, and the switch (23) is controlled according to the output of this operation.

The rest is the same as the circuit described above.

Therefore, in this circuit, the operations under each of the above conditions are performed in the same way, and, for example, when the level of the luminance signal is constant,
Among them, when a signal is supplied to the input terminal (1) in which the phase of the chroma signal is inverted (changed to a complementary color) in an oblique direction with an inclination of approximately half the wavelength of the color subcarrier for each scanning line. The signals of each part are as shown in FIG. 10, and the signals are as shown. Then, by discriminating signals ■, ■, ■, and ■, this signal [stock] is selected in a part where there is not much difference in correlation, so that the output terminal (24) receives a chroma signal "C" without any signal loss. This signal is extracted and supplied to a subtraction circuit (26) to reduce dot interference in the luminance signal.

Although the level of the chroma signal replaced by signal (2) is attenuated to approximately 1/2, the effect of improving dot interference is 6 dB, and the effect of improving image quality is extremely large.

Therefore, according to this circuit, a signal corresponding to the output of a so-called 2H comb filter, which is based on the correlation of the three scanning lines, is extracted from the adder circuit (28), and when there is no difference in correlation, the output of this 2H comb filter is taken out. By selecting , even better separation output can be obtained.

However, in the above circuit, the logic operation section (21)
The data supplied to the coring circuits (17) to (20
) is compared with a predetermined potential and binarized.

In this case, if the level of the input signal changes, there is a possibility that the effect of the above-mentioned comb filter cannot be obtained sufficiently.

That is, when the level of the input signal becomes small due to a weak electric field of the received signal, etc., the coring circuit no longer reaches the predetermined potential. In order to improve this problem, lowering the predetermined potential has resulted in problems such as increased sensitivity to noise.

In consideration of these points, this application provides a comb filter that can always obtain good effects even when the level of the input signal changes.

[Means to solve the problem]

The present invention comprises delay lines (2), (3), subtraction circuits (4), (5) connected to the input and output of the delay line, and addition circuit (11) connected to the input and output of the delay line. ), (1
2) and the output of the above subtraction circuit and filter circuit (22)
It has a switching means (switch (23)) for switching the output of the switching means, and an arithmetic section (33) for controlling this switching means, and this arithmetic section is supplied with the input/output of the delay line and the output of the adding circuit. This is a comb filter that performs decorrelation calculations by determining the relative magnitude relationship between these values.

[Effect]

According to this, since the arithmetic unit determines the relative magnitude relationship between input values and performs non-correlation calculations, the determination is not affected by changes in the absolute level of the input signal. , it is possible to always obtain good separation output.

〔Example〕

FIG. 1 shows the configuration of an embodiment. In this figure, parts corresponding to the circuits shown in the above-mentioned prior art are given the same reference numerals and detailed explanations will be omitted.

In this figure, the signals from the absolute value circuits (13) and (16) are, for example, (1+22-'10Z-''), where Z is a low-pass filter (L P F) with a sampling period (31), (32)
are supplied to an arithmetic unit (33) that determines the relative magnitude relationship of signal levels and performs arithmetic operations. In addition, signals from the filters (6), (8), and (9) are sent to the calculation unit (33) through absolute value circuits (34), (35), and (36), respectively.
supplied to Then, in this arithmetic unit (33), the outputs of the low-pass filters (31) and (32) are
y, and the outputs of the absolute value circuits (34) to (36) are respectively f.
The calculations shown in the following table are performed as at, lbl, and lcl, and the switch (23) is controlled according to the calculation output.

,table.

Therefore, in this device, when y>2x, there is a lot of non-correlation on the y side, and the signal ■ is selected. Alternatively, when y<+x, there is a lot of non-correlation on the y side, and the signal ■ is selected, whereby good separated outputs are extracted. In contrast to this +
y≦X≦2y holds when the correlation is at a predetermined level or higher, or when non-correlation is observed in both cases. Therefore, the conventional signal is selected when there is no color in the upper and lower scanning lines and there is a chroma signal in only one scanning line, that is, when there is non-correlation in both, and when there is no absolute color. For value signals lal lbl lcl, usually la
Since l + IcI≧lbl, the signal ■ is selected when lal + lcl > + lbl in consideration of noise and the like.

Furthermore, in cases other than the above, the correlation of the signals is at a predetermined level or higher, and the signal [stock] is selected.

In addition, in the above calculation formula, when the relative ratio of x, y or X, Y exceeds 2, the smaller value corresponds to the conventional "0" and the larger value corresponds to "1". .

In this way, according to the above-mentioned device, since the arithmetic unit determines the relative magnitude relationship between input values and performs a non-correlation operation, the determination is not affected by changes in the absolute level of the input signal. This allows good separation output to be obtained at all times.

Furthermore, in the above-mentioned device, the absolute value signal 1al lbl l
By providing a coefficient of 10 in the calculation of cl, it is possible to eliminate the possibility of malfunction due to noise or the like. Therefore, it is no longer necessary to provide a noise removal means such as a low-pass filter at the subsequent stage of the absolute value circuits (34> to (36), and the circuit configuration can thereby be greatly simplified.

Furthermore, FIG. 2 shows the configuration of another example. In this example, the number of bandpass filters (6) to (10) is also reduced. In other words, in the figure, a bandpass filter (6) is connected between the input terminal (1) and the delay line (2).
) ~ Bandpass filter (37) with the same characteristics as (10)
is provided. This allows the bandpass filter (6)
~(10) can be deleted. In this case, since it is necessary to obtain a luminance signal system signal from the stage before the bandpass filter (37), it is necessary to newly provide a delay line for one horizontal period (3 days).

Note that in the above-mentioned apparatus, the actual signal waveform etc. are exactly the same as in the case of the apparatus described in the above-mentioned [Problem to be Solved by the Invention] section.

[Effects of the Invention] According to the present invention, since the arithmetic unit determines the relative magnitude relationship between input values and performs a non-correlation operation, the determination does not depend on changes in the absolute level of the input signal. It is now possible to always obtain good separation output without being affected.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an example of a comb filter according to the present invention, FIG. 2 is a configuration diagram of another example of a comb filter, FIG. 3 is a configuration diagram of a conventional comb filter, and FIG. 4 is a configuration diagram of an example of a comb filter according to the present invention. A configuration diagram of an example of the proposed comb filter. Figure 5 is a waveform diagram when the luminance signal level is constant and a signal in which the phase of the chroma signal is inverted is supplied from an intermediate scanning line. Figure 6 is a diagram of the luminance signal. Figure 7 is a waveform diagram when a signal with a constant signal level and a chroma signal added from an intermediate scanning line is supplied, and a signal with a luminance signal added only to two intermediate scanning lines is supplied. Figure 8 is a waveform diagram when a signal is supplied in which the luminance signal level is constant and a chroma signal exists only in one scanning line in the middle, and Figure 9 is a waveform diagram created by the applicant. A configuration diagram of another example of the comb filter proposed earlier by
Figure 10 shows a signal in which the phase of the luminance signal is constant, and the phase of the chroma signal is inverted diagonally at an angle of approximately half the wavelength of the carrier wave for each color for each scanning line. (1) is the input terminal, (2), (3), and (25) are the delay lines.
4) (5) (26) is a subtraction circuit, (6) to (10)
(22) is a band pass filter, (11) (12) is an adder circuit, (13) (16) (34) to (36) are absolute value circuits, (23) is a switch, (24) (27)
is the output terminal, (31) and (32) are the low-pass filters,
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Claims (1)

[Claims] A delay line, a subtraction circuit connected to the input and output of the delay line, an addition circuit connected to the input and output of the delay line, and switching between the output of the subtraction circuit and the output of the filter circuit. It has a switching means and an arithmetic unit that controls the switching means, and the arithmetic unit is supplied with the input/output of the delay line and the output of the adder circuit, and determines the relative magnitude relationship between these values. A comb filter that performs non-correlation calculations.