JP3011816B2 - Color video signal recording and playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color video signal recording / reproducing apparatus applied to a video tape recorder and the like.
In particular, color video signal recording / reproduction that converts the carrier chrominance signal separated from the color video signal to a frequency lower than the recording band of the luminance signal, records it on a recording medium, and reproduces the original carrier chrominance signal It concerns the device.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a reproducing system based on a conventional color video signal recording / reproducing apparatus disclosed in Japanese Patent Publication No. 56-9073. Note that a recording system that converts the carrier color signal separated from the color video signal to a frequency lower than the recording band of the luminance signal and records it on a recording medium is also disclosed in the above publication and is well known. Description is omitted.

In FIG. 6, video heads 11a, 11
b, the mixed signal reproduced alternately for each track of the magnetic tape 12 is supplied to the high-pass filter 15 via the reproduction preamplifiers 14a and 14b to separate the frequency-modulated luminance signal, while being supplied to the low-pass filter 19. Then, the low-frequency-converted carrier chrominance signal whose phase has been shifted (hereinafter, also referred to as rotation) as described above is separated.

The reproduced frequency modulated luminance signal extracted from the high-pass filter 15 is supplied to an FM demodulator 17 after the AM component is removed by a limiter 16, where it is demodulated to become a reproduced luminance signal.

On the other hand, the phase-rotated reproduced low-frequency converted carrier color signal extracted from the low-frequency filter 19 is supplied to a frequency converter 20, where a predetermined center signal from an APC (automatic phase compensator) circuit 21 is supplied. The color subcarrier frequency fc (3.5 in the case of NTSC color video signals) from which the frequency is converted by the frequency signal and the time axis fluctuation component due to the tape speed deviation or the like is removed.
79545 MHz).

The APC circuit 21 receives the reproduced carrier chrominance signal from a mixer (not shown) as an input signal and outputs a continuous wave synchronized with the phase of the color burst signal extracted therefrom. I have.

When the reproduced carrier chrominance signal passes through the frequency converter 20, the frequency f output from the APC circuit 21
The phase of the reproduced carrier chrominance signal is inverted to produce the original chrominance subcarrier frequency fc as a frequency obtained by subtracting the low-frequency conversion chrominance subcarrier frequency fs from APC. Therefore, the direction of the phase rotation by 90 ° is reversed.

[0008] 1 extracted from the frequency converter 20
The phase rotation reproduction carrier color signal having a different phase by 90 ° for each H is supplied to a phase shifter 22, where four types of waveforms having a different phase by 90 ° are generated. The four signals whose phases have been shifted by 0 °, 90 °, 180 ° and 270 ° from the phase shifter 22 are simultaneously applied to the fixed contacts b1, b2, b3 and b4 of the changeover switch SW2, respectively.

The switch SW2 has a movable contact of 1H in response to a horizontal synchronizing signal separated from the reproduced luminance signal.
Each time, the fixed contacts b1 to b4 are sequentially switched and connected one step at a time. The changeover switch SW2 is configured to alternately switch its switching direction from the X direction to the Y direction or from the Y direction to the X direction for each track scan by a signal synchronized with the rotation of the head. .

The switching direction is set to the same direction as that of the recorded signal at the time of recording, so that the phase is changed back by 90 ° in combination with the phase reversal effect by the frequency converter 20.

Therefore, when the video head 11a is scanning the track A, the changeover switch SW2 is switched in the X direction and the reproduced carrier color signal obtained from the movable piece of the changeover switch SW2 is 90 ° every 1H. When the video head 11b is scanning the track B, the changeover switch SW2 is switched in the Y direction and the phase is substantially shifted by 90 ° every 1H. Then, the signals are input to the one horizontal period delay devices 31 and 32 and delayed, so that three line outputs C2 and C1 are output.
C0 is obtained. That is, the output of the switch SW2 is set to C
Assuming that the output of one horizontal period delay device 31 is −C2,
The output of the one horizontal period delay device 32 is C0, and the output of the inverter 33 as phase inversion means is C1, and three line outputs C2, C1, C0 of these are input to the non-linear synthesizing means 27.

The non-linear synthesizing means 27 has two maximum value selectors (hereinafter referred to as MAX) for selecting the maximum amplitude value and the minimum amplitude value for the three line outputs C2, C1 and C0, respectively.
27a, 27b), two minimum value selectors (hereinafter, referred to as MIN) 27c, 27d, and the two MAs.
MIN27 for selecting the minimum value of the outputs of X27a and 27b
e, a MAX 27f for selecting the maximum value of the outputs of the two MINs 27c and 27d, and an adder 27g for combining the output from the MIN 27e and the output from the MAX 27f.
It is composed of

Therefore, the input three line outputs C
2, C1 and CO are two MAXs 27a and 27b and two MINs 27c and 27d, each of which selects the maximum value and the minimum value of the amplitude, and selects the minimum value (MIN) of the selected maximum value of the amplitude. The obtained maximum value (MAX) of the minimum amplitude value is input to the adder 27g and synthesized.
The composite value is MIN {MAX (C0, C1), MAX (C1, C2)} + MAX {MIN (C0, C1), MIN (C1, C2)}, which is the output reproduction luminance signal of the FM demodulator 17 After being subjected to band sharing multiplexing with the signal delayed by one horizontal period, the signal is output from the output terminal 25 as a reproduced color video signal.

In the above synthetic formula, MAX
(P, Q) means that the two signals P and Q are compared to output the larger one, and MIN (P, Q) means that the two signals P and Q are compared and the smaller one is output. ing.

FIG. 7 is a waveform diagram showing the operation when the signal has a line correlation. In this case, the changeover switch SW2
Are two signal outputs C0 and C2 separated by two horizontal periods.
It is an explanation of

First, the signal components of the track A are restored by the phase shifter 22 and are equal. The signal after two horizontal periods by the recording-side phase shifter is delayed by 180 ° for the crosstalk of the track B, and further delayed by 180 ° by the reproduction-side face shifter 22 to be equal. That is,
The two signal outputs C0 and C2 are equal.

When the signal under the above conditions is input to the non-linear synthesizing means 27, MA signals are output in sections T1 and T2 in FIG.
A signal output is selected by X27a, 27b and MINs 27c, 27d.

Since C0 = C2, where it is not clear which one is to be selected, C2 will be added with C0 as a representative. In this way, the output of the non-linear synthesizing means 27 becomes C0 + C1, which is the output sum before and after the delay of one horizontal period, so that crosstalk and noise for each horizontal period can be removed.

[0019]

Since the conventional color video signal recording / reproducing apparatus is configured as described above, it is possible to remove the crosstalk and the noise every one horizontal period, but it is possible to remove the two horizontal periods. There has been a problem that noise in each cycle cannot be removed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a function of removing noise every two horizontal periods in addition to a function of removing crosstalk and noise every one horizontal period. It is an object of the present invention to obtain a color video signal recording / reproducing apparatus which can be removed.

[0021]

According to a first aspect of the present invention, there is provided a color video signal recording / reproducing apparatus which shifts the phase of a carrier color signal, which has been frequency-converted to a low frequency, in a predetermined direction by approximately 90 ° every one horizontal period. The recording is performed on the recording medium with the phase transition direction being different between the adjacent recording tracks. In the opposite direction and 1
A first cascade-connected first horizontal period delay device and a second chronologically connected first and second horizontal period delay device for obtaining a carrier chrominance signal having an original color sub-carrier frequency shifted in phase by approximately 90 ° every horizontal period, and inputting and delaying the carrier chrominance signal; The horizontal period delay device and the output of the second one horizontal period delay device are fed back to the input side of the first one horizontal period delay device to extract noise every two horizontal period periods, and to transfer the noise component to the carrier First synthesizing means for subtracting and removing from the color signal, an input of the first one horizontal period delay device, an output of the first one horizontal period delay device, and an output of the second one horizontal period delay device And a second synthesizing means for synthesizing and reproducing.

According to a second aspect of the present invention, there is provided a color video signal recording / reproducing apparatus which shifts the phase of a carrier chrominance signal frequency-converted to a low frequency in a predetermined direction by about 90 ° every one horizontal period, and The transition direction is made different between adjacent recording tracks and recorded on the recording medium, and at the time of reproduction, the phase transition direction at the time of recording is substantially opposite to the phase transition direction at the time of recording and reproduction from the low-frequency converted carrier color signal. Approximately 90 per horizontal period
A first one horizontal period delay device and a second one horizontal period delay device connected in cascade to obtain a carrier chrominance signal having the original color subcarrier frequency shifted in phase by °, and to input and delay the carrier chrominance signal; The output of the second one-horizontal-period delay device is fed back to the input side of the first one-horizontal-period delay device to extract noise every two horizontal-period periods in opposite phases, and to convert this noise component into the carrier chrominance signal. First combining means for adding and removing, combining the input of the first one horizontal period delay device, the output of the first one horizontal period delay device, and the output of the second one horizontal period delay device. And a second synthesizing means for reproducing.

According to a third aspect of the present invention, there is provided a color video signal recording / reproducing apparatus which shifts the phase of a carrier chrominance signal, which has been frequency-converted to a low frequency, in a predetermined direction by approximately 90 ° every one horizontal period, and The transition direction is made different between adjacent recording tracks and recorded on the recording medium, and at the time of reproduction, the phase transition direction at the time of recording is substantially opposite to the phase transition direction at the time of recording and reproduction from the low-frequency converted carrier color signal. Approximately 90 per horizontal period
An input of a first cascade-connected first horizontal period delay device and a second one-horizontal period delay device, which cascade-connect and obtain a carrier chrominance signal having an original color subcarrier frequency shifted in phase by degrees and inputting and delaying the carrier chrominance signal Side, and extracts the noise every two horizontal feedback periods in opposite phases, and subtracts the subtracted value of the outputs of the first and second amplitude limiters having different gains into which the noise component has been input by using the carrier color signal. A first synthesizing means for removing the noise component from the carrier chrominance signal by adding the input to the first one horizontal period delay device, the output of the first one horizontal period delay device, and the second A second synthesizing means for synthesizing and reproducing the output of the horizontal period delay device is provided.

[0024]

According to the first aspect of the present invention, in the color video signal recording / reproducing apparatus, the first synthesizing means subtracts the input of the first one horizontal period delay device from the output of the second one horizontal period delay device to obtain two. After extracting a noise component for each horizontal period, subtracting the noise component from the input carrier color signal and removing the noise component, the carrier color signal is input to the second synthesizing means, whereby crosstalk and one horizontal Removes noise for each period cycle.

According to a second aspect of the present invention, in the color video signal recording and reproducing apparatus, the first synthesizing means subtracts the input carrier color signal from the output of the second one-horizontal-period delay device, and subtracts every two horizontal-period periods. After extracting the noise component in the opposite phase, adding the noise component to the carrier chrominance signal and removing the noise component, the carrier chrominance signal is input to the second combining means,
The same effect as that of the first aspect can be obtained.

According to a third aspect of the present invention, in the color video signal recording / reproducing apparatus, the first synthesizing means subtracts the input carrier chrominance signal from the output of the second one-horizontal-period delay device to reduce the noise every two horizontal-period periods. The components are extracted in opposite phases, the outputs of the first and second amplitude limiters having different gains are subtracted, and the subtraction result is added to the carrier chrominance signal to remove the noise component. Thereafter, by inputting the carrier chrominance signal to the second synthesizing means, crosstalk and noise for each horizontal period period are removed, and feedback in a burst portion or a decorrelation portion having a high amplitude level is eliminated. Patrol of these parts can be prevented.

[0027]

Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment according to the first aspect of the present invention. The same parts as those of the conventional apparatus shown in FIG. In FIG. 1, 35
Is a first combining means. As shown in FIG. 2, the first combining means 35 includes a first subtractor 35a for subtracting the input of the first one horizontal period delay device 31 from the output of the second one horizontal period delay device 32, An amplitude limiter 35b for limiting the signal amplitude of the output, and a second subtractor 35c for subtracting the output of the amplitude limiter 35b from the output of the switch SW2 to obtain the input of the first one horizontal period delay device 31. It is configured.

Next, the operation will be described. The operation until the transfer color signal is output from the changeover switch SW2 is exactly the same as that of the conventional apparatus shown in FIG.
The operation of the first combining means to which the carrier color signal is input will be described.

First, by subtracting the input of the first one horizontal period delay device 31 from the output of the second one horizontal period delay device 32, a noise component for every two horizontal period periods is extracted. On the other hand, the amplitude limiter 35b subtracts the extracted noise component for each two horizontal period cycles from the carrier color signal having the original color sub-carrier frequency, which is the output of the changeover switch SW2, by limiting the amount of circulation. The noise component is removed every two horizontal period periods.

The carrier chrominance signal from which the noise component has been removed every two horizontal period periods is converted into a non-linear second synthesizing means 2.
7, the noise component in each horizontal period is also removed.

Embodiment 2 FIG. 3 shows an embodiment of the first synthesizing means 35 according to the second aspect of the present invention, in which the output of the changeover switch SW2 is subtracted from the output of the second one horizontal period delay device 32. 3, a subtractor 35d, an amplitude limiter 35b for limiting the signal amplitude of this output, and a first adder 35e for adding the output of the changeover switch SW2 and the output of the amplitude limiter 35b. .

With this configuration, by subtracting the output of the changeover switch SW2 from the output of the second one-horizontal-period delay device 32, noise components for every two horizontal-period periods are extracted in opposite phases. On the other hand, by adding the noise component for each of the two opposite horizontal period periods, which is the output of the changeover switch SW2, to the carrier color signal having the original color subcarrier frequency while limiting the amount of circulation by the amplitude limiter 35b, it is added. The noise component is removed every two horizontal period periods. Then, the carrier chrominance signal from which the noise component has been removed every two horizontal period periods is converted into a non-linear second synthesizing means 27.
, Also removes crosstalk and noise components for each horizontal period cycle.

Embodiment 3 FIG. 4 shows an embodiment of the first synthesizing means according to the third aspect of the present invention, in which the output of the changeover switch SW2 is subtracted from the output of the second one horizontal period delay device 32. Subtractor 3
5d, a first amplitude limiter 35g for limiting the signal amplitude of the output, and a second amplitude limiter 35h having a smaller gain than the first amplitude limiter 35g but having the same amplitude limit level.
And a fourth subtractor 35f for subtracting the output of the second amplitude limiter 35h from the output of the first amplitude limiter 35g, and adding the output of the changeover switch SW2 and the output of the fourth subtractor 35f. And a first adder 35e.

With this configuration, by subtracting the output of the changeover switch SW2 from the output of the second one-horizontal-period delay device 32, noise components for every two horizontal-period periods are extracted in opposite phases. The noise component of each of the two opposite horizontal period periods is represented by the first,
The signals are input to the second amplitude limiters 35g and 35h, and the outputs of the two amplitude limiters are subtracted by a subtractor 35f. Then, the output of the subtractor 35f and the original color sub-transport, which is the output of the switch SW2, By adding the carrier chrominance signal having the frequency, a noise component for every two horizontal period periods is removed. The carrier chrominance signal from which the noise component has been removed every two horizontal periods is input to the non-linear synthesizing means 27, so that the crosstalk and the noise component every one horizontal period are also removed.

The first amplitude limiter 35g, the second amplitude limiter 35h, and the fourth subtractor 35f have a characteristic that they do not output when the input level exceeds a certain level, as shown in FIG. For example, if the amplitude limit level is set to a level lower than the burst level, feedback in a burst portion or a non-correlated portion having a high amplitude level is eliminated, so that it is possible to prevent these portions from circulating.

In the above embodiment, the second synthesizing means 2
Reference numeral 7 denotes a non-linear type, but the present invention is not limited to this as long as the synthesizing means has a comb-shaped frequency characteristic. For example, C0
It may be a linear type such as + 2C1 + C2, or another non-linear combining means.

[0038]

As described above, claim 1 or claim 2 is provided.
According to the invention, the carrier chrominance signal is input to the first synthesizing means, and noise is extracted every two horizontal periods in the normal or reverse phase, and this noise component is subtracted from the input carrier chrominance signal or The carrier color signal is added to remove the noise component every two horizontal period periods, and then the carrier color signal is input to the second synthesizing means. The noise can be removed and the noise every two horizontal periods can be removed, and the noise removing effect is improved.

According to the third aspect of the present invention, the carrier chrominance signal is input to the first synthesizing means, and the noise obtained by extracting the noise every two horizontal periods in the opposite phase in the same manner as in the second aspect of the present invention. The components are input to first and second amplitude limiters having different gains, and the subtraction value between the outputs of the two amplitude limiters is added to the input carrier color signal, and then to the second synthesis means. Since it is configured to input the signal, it has the same noise removing effect as in the first and second aspects. For example, if the amplitude limit level is set to a level lower than the burst level, it can be used in a burst portion or a non-correlated portion having a high amplitude level. There is such an effect that the feedback is eliminated and the patrol of these portions can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a color video signal recording / reproducing apparatus according to the present invention.

FIG. 2 is a block diagram showing an embodiment of a first synthesizing means according to the invention of claim 1;

FIG. 3 is a block diagram showing an embodiment of a first synthesizing means according to the invention of claim 2;

FIG. 4 is a block diagram showing an embodiment of a first synthesizing means in the invention of claim 3;

FIG. 5 is a diagram illustrating the operation of each unit of the first combining unit shown in FIG.

FIG. 6 is a block diagram showing a conventional color video signal recording / reproducing apparatus.

FIG. 7 is a waveform response diagram of each part for explaining the operation of the conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Magnetic tape (recording medium) 27 2nd synthesizing means 31 1st 1 horizontal period delay device 32 2nd 1 horizontal period delay device 35 1st synthesizing means 35g 1st amplitude limiter 35h 2nd amplitude limitation vessel

Claims (3)

(57) [Claims] 1. A color video signal recording / reproducing apparatus for converting a carrier chrominance signal separated from a color video signal to a low frequency band, recording the converted color signal on a recording medium, and reproducing the original carrier chrominance signal. The phase of the carrier color signal frequency-converted to
The phase is shifted in a predetermined direction by about 90 ° every horizontal period,
And the phase transition direction is made different from each other between adjacent recording tracks and recorded on the recording medium, and at the time of reproduction, the phase transition direction at the time of recording is substantially equal to the phase transition direction at the time of recording / reproduced low-frequency conversion carrier color signal. Approximately 90 in the opposite direction and every horizontal period
A first one horizontal period delay device and a second one horizontal period delay device connected in cascade to obtain a carrier chrominance signal having the original color subcarrier frequency shifted in phase by °, and to input and delay the carrier chrominance signal; The output of the second one horizontal period delay device is fed back to the input side of the first one horizontal period delay device to extract noise every two horizontal period periods, and this noise component is subtracted from the carrier color signal. First synthesizing means for removing, synthesizing and reproducing an input of the first one horizontal period delay device, an output of the first one horizontal period delay device, and an output of the second one horizontal period delay device; And a color video signal recording / reproducing apparatus including a second synthesizing means. 2. A color video signal recording / reproducing apparatus which converts a carrier color signal separated from a color video signal into a low frequency band, records the converted color signal on a recording medium, and reproduces the original carrier color signal. The phase of the carrier color signal frequency-converted to
The phase is shifted in a predetermined direction by about 90 ° every horizontal period,
And the phase transition direction is made different from each other between adjacent recording tracks and recorded on the recording medium, and at the time of reproduction, the phase transition direction at the time of recording is substantially equal to the phase transition direction at the time of recording / reproduced low-frequency conversion carrier color signal. Approximately 90 in the opposite direction and every horizontal period
A first horizontal period delay device and a second horizontal period delay device connected in cascade to obtain a carrier chrominance signal having the original color subcarrier frequency shifted in phase by °, to input and delay the carrier chrominance signal; The output of the second one-horizontal-period delay device is fed back to the input side of the first one-horizontal-period delay device to extract noise every two horizontal period periods in opposite phases, and add this noise component to the carrier color signal. First synthesizing means for eliminating the input of the first one horizontal period delay device, the output of the first one horizontal period delay device, and the output of the second one horizontal period delay device. A color video signal recording / reproducing apparatus provided with a second synthesizing means for reproducing. 3. A color video signal recording / reproducing apparatus which frequency-converts a carrier color signal separated from a color video signal to a low frequency band, records it on a recording medium, and reproduces the original carrier color signal. The phase of the carrier color signal frequency-converted to
The phase is shifted in a predetermined direction by about 90 ° every horizontal period,
And the phase transition direction is made different from each other between the adjacent recording tracks and recorded on the recording medium. Approximately 90 in the opposite direction and every horizontal period
A first horizontal period delay device and a second horizontal period delay device connected in cascade to obtain a carrier chrominance signal having the original color subcarrier frequency shifted in phase by °, to input and delay the carrier chrominance signal; The output of the second one-horizontal-period delay device is fed back to the input side of the first one-horizontal-period delay device to extract noise in opposite phases every two horizontal period periods. First synthesizing means for adding the subtracted value of the outputs of the first and second amplitude limiters to the carrier color signal to remove the noise component from the carrier color signal;
A color video signal comprising second synthesizing means for synthesizing and reproducing the input of the one horizontal period delay device, the output of the first one horizontal period delay device, and the output of the second one horizontal period delay device. Recording and playback device.