JPH01170191A - Vtr - Google Patents

Abstract

PURPOSE:To execute a proper correlation detection by switching plural methods for the correlation detection according to a crosstalk quantity at the time of switching the characteristics of a tandem-compound filter for removing the crosstalk of a chroma signal according to a signal correlation. CONSTITUTION:To a deciding circuit 8, a signal Sc based on the line correlation of the chroma signal and a signal Sr based on the line correlation of a luminance signal are supplied, and simultaneously, a signal Dc corresponding to the crosstalk quantity of the chroma signal is supplied. The deciding circuit 8 switches a switching circuit 6 corresponding to a line correlation detecting signal detected by the most proper detection method according to the intensity of the crosstalk quantity detecting signal Dc, and thereby, the characteristics of the tandem-compound filter are switched. Namely, when the crosstalk quantity detecting signal Dc is large, a line correlation signal Sv by the luminance signal is used, and when the signal is small, the detecting signal Sc of the line correlation signal by the chroma signal is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a VTR, and more particularly to a comb filter for removing crosstalk from adjacent tracks.

[Summary of the invention]

According to the present invention, in a VTR, when switching the characteristics of a comb filter for removing crosstalk from adjacent tracks according to signal correlation, a plurality of correlation detection methods are switched according to the amount of crosstalk, This is to perform appropriate correlation detection.

[Conventional technology]

In order to eliminate chroma signal crosstalk, recording is performed by inverting the phase of the chroma signal of one of the adjacent tracks by 180 degrees every IH (horizontal period). Such a recording method is called P 1 (Phase I
nvert) method.

If the chroma signal has a line correlation, if the phase of the chroma signal on one track is inverted by 180° for each IH and recorded, crosstalk components can be canceled by a comb filter during reproduction. However, when the chroma signal has almost no line correlation, passing through this crosstalk removal comb filter causes color distortion and degrades the chroma vertical resolution.

Therefore, in conventional VTRs, line correlation is detected during reproduction, and the characteristics of a comb filter for crosstalk removal are controlled in accordance with this line correlation.

FIG. 4 shows an example of the configuration of a conventional rectangular filter used to cancel crosstalk of reproduced chroma signals. In FIG. 4, the IH delay circuit 1
03, the subtraction circuit 102, and the addition circuits 104 and 105 constitute a comb filter for canceling crosstalk of the reproduced chroma signal. The characteristics of this comb filter are switched by a switch circuit 106. The switch circuit 106 is controlled by line correlation of the luminance signal.

IH delay circuit 113, subtraction circuit 112 and addition circuit 11
The comb filter consisting of
provided to improve the ratio. Correlation between luminance signals of adjacent lines is detected from this comb filter.

In FIG. 4, 101 is an input terminal for a reproduced chroma signal. The reproduced chroma signal from the input terminal 101 is supplied to the subtraction circuit 102 and the addition circuit 104, and the IH
The signal is supplied to the delay circuit 103. The reproduced chroma signal from the input terminal 101 is delayed by IH by the IH delay circuit 103.

The output of the IH delay circuit 103 is supplied to the subtraction circuit 102 and also to the addition circuit 104. Subtraction circuit 1
At step 02, the pre-IH chroma signal CD from the IH delay circuit 103 is subtracted from the chroma signal C from the input terminal 101. A chroma signal (C-C
D) is supplied to the adder circuit 105.

Further, the adder circuit 104 adds the chroma signal C from the input terminal 101 and the pre-IH chroma signal CD from the IH delay circuit 103. A chroma signal (C+CD) obtained by adding this input chroma signal and the chroma signal before l)I is sent from the adder circuit 104 to the adder circuit 106 via the switch circuit 106.
05. The output of adder circuit 105 is output terminal 1
It is taken out from 07.

If the switch circuit 106 is off, the chroma signal () obtained by subtracting the chroma signal CD before IH from the input chroma signal C
C-CD) is taken out from the subtraction circuit 102 via the addition circuit 105 and from the output terminal 107. In the PI method, by subtracting the input chroma signal and the chroma signal before IH, when there is a line correlation,
The main chroma signal is doubled and crosstalk components are canceled.

When the switch circuit 106 is on, a chroma signal (C+CD) obtained by adding the input chroma signal output from the adder circuit 104 and the chroma signal before IH, and a chroma signal (C+CD) obtained by adding the input chroma signal output from the adder circuit 104 and the chroma signal before IH from the input chroma signal output from the subtraction circuit 102 are added. A chroma signal (C-CD) obtained by subtracting the chroma signal of is supplied to the adder circuit 105. Therefore, the adder circuit 105 outputs a chroma signal 2C that is twice the input chroma signal.

At this time, the crosstalk component is not canceled. However, when there is no line correlation, it is possible to prevent the vertical resolution of the chroma signal from deteriorating.

The comparator 119 outputs a signal based on the line correlation of the luminance signal. The output of this comparator 119 is supplied to the switch circuit 106 as a switch control signal.

That is, the reproduced luminance signal is supplied to the input terminal 111. The reproduced luminance signal from the input terminal 111 is sent to the subtraction circuit 112.
and the subtraction circuit 114 as well as the IH delay circuit 113. The reproduced luminance signal from the input terminal 111 is delayed by IH by the IH delay circuit 113, and when the luminance signal Y is supplied to the input terminal 111, the IH delay circuit 113 outputs the luminance signal YD before IH. The output of this IH delay circuit 113Φ is supplied to the subtraction circuit 112. The subtraction circuit 112 extracts the pre-IH luminance signal V from the IH delay circuit 113 from the chroma signal Y from the input terminal 111.
D is subtracted, and the subtraction circuit 112 outputs a luminance signal (Y-YD) obtained by subtracting the luminance signal before IH from the input luminance signal.

The output of the subtraction circuit 112 is supplied to the subtraction circuit 114 via a limiter 115 and an attenuator 116, and
The signal is supplied to the detection circuit 117.

If there is a correlation between the input luminance signal and the pre-IH luminance signal, the subtraction circuit 112 mainly outputs noise components. The output of this subtraction circuit 112 is supplied to a subtraction circuit 114 via a limiter 115 and an attenuator 116, and input terminal 1
Noise components in the luminance signal from 11 are canceled. The output of subtraction circuit 114 is taken out from output terminal 118.

If the correlation between the input luminance signal and the pre-IH luminance signal is strong, the output of the subtraction circuit 112 will be small, and if the correlation between the input luminance signal and the pre-IH luminance signal is weak, the output of the subtraction circuit 112 will be large.

The output of the subtraction circuit 112 is supplied to the detection circuit 117.

The output of the detection circuit 117 is supplied to a comparator 119. The comparator 119 sets the output of the detection circuit 119 to a predetermined threshold voltage Vrl. .

compared to The output of comparator 119 is supplied to switch circuit 106 as a switch control signal. If the output of the subtraction circuit 112 is below the threshold level Vrllll, the line correlation of the luminance signal is strong, so the switch circuit 106 is turned off. If the output of the subtraction circuit 112 is above the predetermined threshold level ■1..., the line correlation of the luminance signal is weak, so the switch circuit 106 is turned on.

[Problem that the invention seeks to solve]

As described above, when there is almost no correlation between chroma signals of adjacent lines, the chroma vertical resolution is degraded by passing through a comb filter for crosstalk removal. Therefore, it is desirable to detect the line correlation of the chroma signal and control the characteristics of the comb filter for crosstalk removal in accordance with the line correlation of the chroma signal.

However, the above-mentioned conventional comb filter for canceling the crosstalk of the reproduced chroma signal detects the line correlation of the luminance signal, not the line correlation of the chroma signal.
The switch circuit 106 is controlled to turn on/off the operation of the comb filter in accordance with the line correlation of the luminance signals of the lines of the luminance signals.

This is because the reproduced chroma signal contains not only a signal indicating the correlation of the chroma signals but also a crosstalk component, and if this crosstalk component is large, the line correlation of the chroma signal cannot be detected. be.

That is, as shown in FIG. 5, the output of the adder circuit 104 is detected by the detection circuit 121, and the comparator 122 detects whether the output of the detection circuit 121 is equal to or higher than a predetermined threshold level Vr. It is conceivable to control the switch circuit 106 using the output of the comparator 122 to switch the characteristics of the comb filter. The adder circuit 104 outputs a chroma signal (C+CD) obtained by adding the input chroma signal and the chroma signal before IH. In the NTSC system, the phase of the chroma signal is inverted for each LH, so if there is no crosstalk in the reproduced chroma signal, the correlation component in the output of the adder circuit 104 is canceled by the adder circuit 104. Therefore, it indicates the magnitude of the line correlation of the chroma signal.

However, the reproduced chroma signal contains crosstalk components. If this crosstalk component is large,
Due to the output of the adder circuit 104, line correlation of the chroma signal cannot be detected.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a VTR that can perform optimal line correlation detection according to crosstalk components and optimally control the characteristics of a comb filter for removing crosstalk.

[Means for solving problems]

The present invention is characterized in that when switching the characteristics of a comb filter for removing crosstalk from adjacent tracks according to signal correlation, a plurality of correlation detection methods are switched according to the amount of crosstalk. This is a VTR.

[Effect]

The characteristics of the comb filter for crosstalk removal of the chroma signal are switched depending on the line correlation detected by the most appropriate detection method. That is, when the amount of crosstalk is large and the line correlation of the chroma signal cannot be detected, the line correlation of the luminance signal is detected and the characteristics of the comb filter for removing the crosstalk of the chroma signal are switched.

Further, when the amount of crosstalk is small and the line correlation of the chroma signal can be detected, the line correlation of the chroma signal is detected and the characteristics of the comb filter for removing the crosstalk of the chroma signal are switched. When the amount of crosstalk is at an intermediate level, both the line correlation of the luminance signal and the line correlation of the chroma signal are detected, and the characteristics of the comb filter for removing crosstalk of the chroma signal are switched.

〔Example〕

An embodiment of the present invention will be described in the following order.

a. One embodiment Other examples C1 modification example a.-Example FIG. 1 shows an embodiment of the present invention.

In FIG. 1, 1 is an input terminal for a reproduced chroma signal. A reproduced chroma signal from an input terminal 1 is supplied to a subtraction circuit 2 and an addition circuit 4. At the same time, the reproduced chroma signal from the input terminal 1 is supplied to the IH delay circuit 3. IH
The delay circuit 3 delays the reproduced chroma signal from the input terminal 1 by 1) one.

In the NTSC system, the phase of the chroma signal is inverted for each IH. When chroma signal C is supplied to input terminal 1,
The IH delay circuit 103 outputs the chroma signal CD before LH.

The output of the IH delay circuit 3 is supplied to the subtraction circuit 2 and also to the addition circuit 4. Input terminal 1 with subtraction circuit 2
The pre-IH chroma signal CD from the IH delay circuit 3 is subtracted from the chroma signal C from the IH delay circuit 3. A chroma signal (C-CD) obtained by subtracting the chroma signal before IH from the input chroma signal output from the subtraction circuit 2 is supplied to the addition circuit 5.

In addition, the adder circuit 4 receives the chroma signal C from the input terminal 1,
The pre-IH chroma signal CD from the IH delay circuit 3 is added. A chroma signal (C+CD) obtained by adding this human-powered chroma signal and the pre-IH chroma signal is supplied from the adder circuit 4 to the adder circuit 5 via the switch circuit 6. The output of the adder circuit 5 is taken out from the output terminal 7.

The switch circuit 6 is controlled by the switch control signal output from the judgment circuit 8.The 0 judgment circuit 8 is controlled by the switch control signal outputted from the judgment circuit 8.
A signal S-1 based on the line correlation of the luminance signal is supplied, and a signal S-1 corresponding to the amount of crosstalk of the chroma signal is supplied. Then, the line correlation detection method is appropriately switched depending on the amount of crosstalk of this chroma signal. Line correlation is detected using the optimum detection method, and a switch control signal is generated from judgment circuit 7 in accordance with the magnitude of this line correlation. The switch circuit 6 is turned on/off by this switch control signal.

If the switch circuit 6 is off, the chroma signal (C-CD) obtained by subtracting the chroma signal before IH from the input chroma signal
is taken out from the subtraction circuit 2 via the addition circuit 5 and from the output terminal 7. In the PI method, by adding the input chroma signal and the chroma signal before IH in this way, when there is a line correlation, the main chroma signal is doubled and the crosstalk component is canceled.

When the switch circuit 6 is on, the chroma signal (C+CD) is the sum of the input chroma signal output from the adder circuit 4 and the chroma signal before IH, and the chroma signal (C+CD) obtained by adding the input chroma signal output from the subtraction circuit 2 to the chroma signal before IH. A chroma signal (C-CD) obtained by subtracting the chroma signal of is supplied to the adder circuit 5. Therefore, from the adder circuit 5, two of the input chroma signals are
A double chroma signal 2C is output. At this time, the crosstalk component is not canceled. however,
When there is no line correlation, it is possible to prevent the vertical resolution of the chroma signal from deteriorating.

As described above, the switch circuit 6 is controlled by the switch control signal output from the judgment circuit 8.
is supplied with a signal Sc based on the line correlation of the chroma signal and a signal Sv based on the line correlation of the luminance signal, and a signal corresponding to the amount of crosstalk of the chroma signal.
is supplied.

Then, the line correlation detection method can be switched as appropriate depending on the amount of crosstalk of this chroma signal.

Based on the line correlation of the luminance signal (signal Sv is detected from the output obtained by subtracting the input luminance signal and the luminance signal before IH).

That is, the reproduced luminance signal is supplied to the input terminal 11.

A reproduced luminance signal from an input terminal 11 is supplied to a subtraction circuit 12 and a subtraction circuit 14. Along with this, the input terminal 11
A reproduced luminance signal from the IH delay circuit 13 is supplied to the IH delay circuit 13.

The reproduced luminance signal from the input terminal 11 is delayed by IH by the IH delay circuit 13, and when the luminance signal Y is supplied to the input terminal 11, the luminance signal Y before IH is output from the IH delay circuit 13.
D is output. The output of this IH delay circuit 13 is supplied to a subtraction circuit 12. The subtraction circuit I2 subtracts the pre-IH luminance signal YD from the IH delay circuit 13 from the chroma signal Y from the input terminal 11, and the subtraction circuit 12 outputs a luminance signal obtained by subtracting the pre-IH luminance signal from the input luminance signal. (Y-
YD) is output.

The output of the subtraction circuit 12 is the limiter 15 and the attenuator 16.
The signal is supplied to the subtraction circuit 14 via the subtraction circuit 14 and also to the detection circuit 17 .

If there is a correlation between the input luminance signal and the pre-IH luminance signal, the subtraction circuit 12 mainly outputs noise components. The output of the subtraction circuit 12 is supplied to the subtraction circuit 14 via a limiter 15 and an attenuator 16, and noise components in the luminance signal from the input terminal 11 are canceled. Subtraction circuit 1
The output of 4 is taken out from the output terminal 18.

Furthermore, if the correlation between the input luminance signal and the luminance signal before IH is strong, the output of the subtraction circuit 12 will be small, and the input luminance signal will be 1
) If the correlation of the previous luminance signal is weak, the output of the subtraction circuit 12 will be large. The output of the subtraction circuit 12 is supplied to the detection circuit 17. The output of the detection circuit 17° is supplied to the comparator 19. A comparator 19 compares the output of the detection circuit 17 with a predetermined threshold voltage v,,1. From the output of the comparator 19, a detection signal S of the line correlation of the luminance signal is obtained. This line correlation detection signal Sv of the luminance signal is supplied to the judgment circuit 8.

A signal based on the line correlation of the chroma signal is detected from the output of the adder circuit 4.

That is, the adder circuit 4 outputs a chroma signal (C+CD) obtained by adding the input chroma signal and the chroma signal before IH. The output of the adder circuit 4 includes a signal indicating the magnitude of line correlation of the chroma signal and a crosstalk component in the reproduced chroma signal. The output of this adder circuit 4 is supplied to a detection circuit 20. The output of the detection circuit 20 is supplied to a comparator 21 . A comparator 21 compares the output of the detection circuit 20 with a predetermined threshold voltage v1. From the output of the comparator 21, a detection signal Sc of line correlation of the chroma signal is obtained. The line correlation detection signal Sc of this chroma signal is supplied to the judgment circuit 8.

A signal corresponding to the amount of crosstalk of the chroma signal is obtained from the output of the adder circuit 4 during the burst period. That is, the output of the adder circuit 4 is supplied to the switch circuit 22. A burst flag is supplied to the switch circuit 22 from a terminal 23 . During the period when the burst flag is applied, the switch circuit 22 is turned on, and the output of the adder circuit 4 during the burst period is extracted. Since the burst signals are the same for each line, the adder circuit 4
What is output from is mainly the crosstalk component.

The output of the adder circuit 4 during this burst period is transmitted to the detection circuit 24.
is supplied to The output of the detection circuit 24 is supplied to a sample hold circuit 25. A burst flag is supplied to the sample hold circuit 25 from the terminal 23 .

The output of the sample hold circuit 25 is sent to the level detection circuit 26.
is supplied to The level detection circuit 26 has mutually different threshold voltages (1), 11. It is composed of a plurality of comparators 27A, 27B1, . . . to which vr12, . . . are given.

The level detection circuit 26 allows the sample hold circuit 25
The range of the output level is detected. This detection output is used as the crosstalk amount detection signal DC by the judgment circuit 8.
is supplied to

The judgment circuit 8 selects the line correlation detection signal detected by the most appropriate detection method according to the magnitude of the crosstalk amount detection signal RI output from the level detection circuit 26, and detects it by the appropriate detection method. The switch circuit 6 is switched in accordance with the detected line correlation detection signal. In other words, if the crosstalk amount detection signal Dc output from the level detection circuit 26 is large, it is the line correlation detection signal S based on the chroma signal.

Therefore, it is difficult to obtain a correct line correlation signal.

Therefore, in this case, the line correlation signal Sv based on the luminance signal is used. If the crosstalk amount detection signal DC output from the level detection circuit 26 is small, a correct line correlation signal can be obtained using the line correlation detection signal Sc based on the chroma signal. Therefore, in this case, a line correlation signal S based on a chroma signal is used.

If the crosstalk amount detection signal DC output from the level detection circuit 26 is approximately at the center value, the line correlation signal Sv due to the luminance signal and the line correlation signal S due to the chroma signal,
Both are used.

b. Other Embodiments In the embodiment described above, the amount of crosstalk is detected by detecting the output of the adder circuit 4 during the burst period, but since the amount of crosstalk corresponds to the tape speed, , the line correlation detection signal may be selected depending on the tape speed.

In other words, if the head width is wider than the track width,
The amount of crosstalk increases. In a mode where the tape speed is slow, the track width is narrower, so the amount of crosstalk is correspondingly large. is used. In a mode with a high tape speed, such as the β mode of the β method, a line correlation signal S, which is a chroma signal, is used. In a mode with an intermediate tape speed, such as the β mode of the β method, Here, the line correlation signal Sv is a luminance signal and the line correlation signal S is a chroma signal.

Both are used.

That is, when selecting a line correlation detection signal according to the tape speed, the configuration shown in FIG. 2 is used as the determination circuit 8. In FIG. 2, the input terminal 31
is supplied with a line correlation signal S based on a chroma signal output from the comparator 21 in FIG. The input terminal 32 is supplied with a line correlation signal Sy based on a luminance signal output from the comparator 19 in FIG. Input terminals 33 to 35 have, depending on the setting mode,
Setting signal A determined as shown in FIG. ~At is supplied. The output from the output terminal 36 is supplied to the switch circuit 6 as a switch control signal.

In the β■ mode, the setting signal A0 is at high level and the setting signals AI and A2 are at low level. Therefore, the line correlation signal Sc due to the chroma signal from the input terminal 31 is AN
It is output from the output terminal 36 via the D gate 37 and the OR gate 38.

In the β■ mode, the setting signal A1 is at high level and the setting signals Ao and A2 are at low level. Therefore, the logical sum output of the line correlation signal S based on the chroma signal from the input terminal 31 and the line correlation signal Sv based on the luminance signal from the input terminal 32 is outputted via the OR gate 39, the AND gate 40, and the OR gate 38. It is output from 36.

In β■ mode, setting signal A! is at high level and setting signals A0 and A are at low level. Therefore, the line correlation signal SV based on the luminance signal from the input terminal 32 is AND
It is output from the output terminal 36 via the gate 41 and the OR gate 38.

Note that during variable speed reproduction, the setting signals A0 to A2 are set to low level. Therefore, line correlation detection is not detected.

C1 Modification In the above-described embodiment, a comb filter without feedback is used, but a comb filter with a feedback configuration may be used.

Further, the present invention can be similarly applied to a PAL video signal.

〔Effect of the invention〕

According to this invention, the characteristics of the comb filter for removing crosstalk from chroma signals are switched in accordance with the line correlation detected by the most appropriate detection method. In other words, when the amount of crosstalk is large and the line correlation of the chroma signal cannot be detected, the line correlation of the luminance signal is detected and the characteristics of the rectangular filter for removing the crosstalk of the chroma signal are switched. When the amount of crosstalk is small and the line correlation of the chroma signal can be detected, the line correlation of the chroma signal is detected and the characteristics of the comb filter for removing crosstalk of the chroma signal are switched. Sometimes, both the line correlation of the luminance signal and the line correlation of the chroma signal are detected, and the characteristics of the comb filter for removing crosstalk of the chroma signal are switched.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of this invention, FIG. 2 is a block diagram of an example of a judgment circuit in another embodiment of this invention, and FIG. 3 is a route used to explain another embodiment of this invention. 4 is a block diagram of an example of a conventional comb-shaped filter for removing crosstalk, and FIG. 5 is a block diagram of another example of a conventional comb-shaped filter for removing crosstalk. Explanation of symbols l: chroma signal input terminal, 2, 12, 14: subtraction circuit, 3.13: IH delay circuit, 4.5: addition circuit, 6: switch circuit, 8: judgment circuit. Agent: Patent attorney Tadashi Sugiura Tomoteri 1st year 1st course Figure 2 Flood fJ award example 1 Crossing Figure 3 Figure 5

Claims (1)

[Claims] When switching the characteristics of a comb filter to remove crosstalk from adjacent tracks according to signal correlation,
A VTR characterized in that a plurality of correlation detection methods are switched according to the amount of crosstalk.