JPH07264540A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To highly accurately execute switching for converting a discontinuous reproduced signals read out from plural heads into a continuous signal. CONSTITUTION:A head switching signal synchronized with the phases of a rotary drum frequency detecting signal and a phase detecting signal is generated and a switching circuit 117 converts plural reproduced signals into a continuous reproduced signal based upon the head switching signal. A head switching pulse generating circuit 121 generates a head switching pulse synchronized with the phases of horizontal and vertical synchronizing signals in the continuous reproduced signal. A switching circuit 122 converts plural reproduced outputs outputted from plural heads into a continuous reproduced output and the reproduced output led out from the circuit 122 is used as a reproduced video signal.

Description

Detailed Description of the Invention

[0001]

The present invention relates to MUSE (Multip
le Sub-Nygust Sampling En
The present invention relates to a magnetic recording / reproducing apparatus for recording / reproducing a video signal such as a cording signal, particularly when recording a video signal on a tape by at least two video heads mounted on a rotating drum and reproducing the video signal. The present invention relates to a so-called helical scan type magnetic recording / reproducing apparatus in which at least two discontinuous reproduction signals read from the head are switched with high accuracy so as to be a continuous signal.

[0002]

2. Description of the Related Art In a helical scan type magnetic recording / reproducing apparatus, in order to record a video signal, a track is formed on a video tape by at least two heads mounted on a rotary drum and recorded as a discontinuous signal. It is carried out.

At the time of reproduction, the recorded discontinuous signal is read from the two heads. This reproduced signal is a discontinuous signal, and it is necessary to make it a continuous signal in order to perform signal processing in one system. is there. The signal used for this is the head switching signal.

Generally, this head switching signal is sent from a frequency detector 307 and a phase detector 308 attached to a drum assembly of a rotary drum 306 having two heads A, B, 304 and 305, as shown in FIG. It is often generated from the frequency detection signal (hereinafter referred to as FG signal) and the phase detection signal (hereinafter referred to as PG signal).

FIG. 7 is a block diagram of a conventional head switching signal generating circuit for generating a head switching signal from the FG signal and the PG signal. In FIG. 7, reference numeral 300 is a comparator circuit that converts the FG signal from the frequency detector 307 attached to the drum assembly of the rotary drum 306 into a digital signal, and 301 is also the rotary drum 3
This is a comparator circuit that converts the PG signal from the phase detector 308 attached to the 06 drum assembly into a digital signal.

Reference numeral 302 is a counter circuit that divides the FG signal into a specific frequency by using the output of the comparator circuit 300 as an input clock signal and the output of the comparator circuit 301 as a phase reset signal, and 303 is an output of the counter circuit 302. It is a shift register circuit that receives and adjusts to a specific phase for each frequency of the FG signal. Therefore, from the shift register circuit 303, a head switching signal adjusted to a specific phase by the PG signal is derived for each frequency of the FG signal generated from the drum servo system. Then, by this head switching signal, two discontinuous reproduction signals derived from the head A 304 and the head B 305 are alternately derived to obtain continuous reproduction signals.

[0007] Usually, at the switching point by the above head switching signal, switching noise is generated due to the skew, but at this switching point, the rotational phase of the video head is recorded and reproduced by the control of the servo system within the blanking period. By controlling it, the position is controlled so that it cannot be seen on the screen.

On the other hand, the time axis of the reproduced video signal may fluctuate due to the expansion and contraction of the tape and the fluctuation of the accuracy of the running system. In connection with the time axis fluctuation correction method for correcting the fluctuation of the time axis, FM A method of resetting the phase of the carrier for each horizontal synchronization is disclosed in Japanese Patent Laid-Open No. 63-274290.

This is a video tape recorder for FM-modulating and recording and reproducing a video signal. In order to obtain a jitter detection signal for correcting jitter during reproduction, the horizontal sync signal portion of the FM carrier is recorded at the time of recording the video signal. The phase is reset and recorded for each horizontal synchronization, and the jitter is detected and corrected as a reference burst during reproduction.

When the FM carrier is reset as described above, a discontinuity of the FM carrier occurs before and after the reset point. To improve this, the following technique has been proposed. The following are examples of these. A method of partially adding a DC component to the front porch of the horizontal synchronizing signal of the video signal and controlling the level thereof to control the phase of the FM carrier is disclosed in JP-A-1-264492, and an oscillation stop period is provided to FM. Japanese Unexamined Patent Publication No. 3-262392 discloses a method for improving the accuracy of the FM carrier reset operation by using several carrier reset pulses.

Further, there is a method for improving the accuracy of FM carrier resetting operation by performing FM carrier resetting at a front porch of a horizontal synchronizing signal and at two points of a synchronizing front end, as disclosed in Japanese Patent Laid-Open No. 4-257181 and at the time of FM modulation. An FM modulation system that reduces the generated harmonic components and resets the carrier is disclosed in Japanese Patent Laid-Open No. 4-284796, and also a high pass which is indispensable in a double FM demodulator used in a UNIHI-VTR for business use. An FM modulation system that can omit the filter is disclosed in Japanese Patent Laid-Open No. 04-00089.
No.

[0012]

According to the above-mentioned conventional technique, the head switching signal is a signal generated from the drum servo system, whereas it is derived from the heads 304 and 305 of the rotary drum 306 shown in FIG. Playback video signal is drum,
Since the signal is influenced by the jitter of the capstan servo, the head switching signal and the reproduced video signal are not in phase synchronization.

For example, in the case of recording and reproducing a video signal having a blanking period of about several tens of H such as the NTSC system or the PAL system as a video source, as in the case of VHS video, even if phase synchronization cannot be achieved. Although there is no problem in the phase shift within the blanking period, in the case of the MUSE signal, if the head switching signal and the reproduced video signal are not regulated to a specific phase, this is an extreme example, but in FIG. As shown in a, the head switching point appears on the screen.

In the case of the MUSE signal, the head switching point is defined only on the unused 564 line. Even in this case, however, the transmission control signal is affected when it is shifted in the forward direction due to the jitter. Also, when it is shifted backward, the voice / data signal may be affected.

That is, in the above-mentioned conventional technique, the head switching timing does not always correspond to a specific line of the recording signal or the reproducing signal due to the influence of the time axis fluctuation due to the expansion and contraction of the tape and the variation in the accuracy of the running system. . Also,
During playback, time axis fluctuations occur due to variations in the accuracy of the mechanism of the drum and capstan system and the accuracy of the servo system, but the head switching signal is generated from the frequency detector and phase detector attached to the rotating drum. Therefore, the time-axis fluctuation of the reproduced video signal and the time-axis fluctuation of the head switching signal are not phase-synchronized and are not fixed, which is not appropriate when the switching timing of a specific line is necessary.

For example, even if the unspecified period is only one line like the MUSE signal and the switching point is set at the end of the luminance component and the chroma component, the head switching signal is a voice signal or transmission due to the time axis fluctuation. This may lead to the loss of digital information in the control signal. Further, when noise occurs due to head switching, it is easier to perform subsequent signal processing by interpolating the noise and defining it on a specific line.

It is an object of the present invention to provide a magnetic recording / reproducing apparatus for a magnetic recording / reproducing apparatus for a video signal such as a MUSE signal, in which a head switching signal is accurately applied to the reproduced signal.

[0018]

In order to achieve the above object, the present invention has the following constitution. As described in claim 1, the magnetic recording apparatus of the present invention performs signal processing of a MUSE signal converted into a digital signal, converts the signal into an analog signal again, and then performs FM modulation, and a plurality of heads perform a helical scan method on a magnetic tape. In the magnetic recording apparatus for recording by the above method, horizontal sync replacing means for replacing the positive horizontal sync signal with the negative horizontal sync signal for the MUSE signal converted into the digital signal, and a part of the clamp level with the negative signal. It is characterized in that a vertical synchronization replacing means and a carrier reset FM modulating means for resetting the phase of the FM carrier at every horizontal synchronization during the FM modulation are provided.

According to a second aspect of the magnetic reproducing apparatus of the present invention, a plurality of reproduction outputs are derived from a plurality of heads provided on the rotary drum, and a frequency detection signal (FG signal) and phase of the rotary drum are obtained. Reading means for deriving a detection signal (PG signal); first switching means for switching the plurality of reproduction outputs by a head switching signal phase-synchronized with the FG signal and the PG signal to make continuous reproduction outputs; and the first switching means. First FM demodulation means for demodulating a continuous reproduction output from the switching means, horizontal / vertical synchronization separation means for separating the horizontal and vertical synchronization signals from the reproduction signal demodulated by the first FM demodulation means, Head switching pulse generating means for generating a head switching pulse phase-synchronized with the horizontal / vertical synchronizing signal, and the head switching pulse Ri switching the plurality of reproduced output,
A second switching means for producing a continuous reproduction output and a second FM demodulation means for FM-demodulating the continuous reproduction output derived from the second switching means to derive a reproduction video signal are provided. And

According to a third aspect of the magnetic reproducing apparatus of the present invention, the positive horizontal synchronizing signal of the MUSE signal is replaced with the negative horizontal synchronizing signal, and a part of the clamp level is replaced with the negative polarity. , An FM carrier that is FM-modulated and reset in phase for each horizontal synchronization is read out as a plurality of reproduction outputs by a plurality of reproduction heads from a magnetic tape recorded by a helical scan method, and the plurality of reproduction outputs are converted into continuous reproduction outputs. After that, in a magnetic reproducing apparatus for performing FM demodulation to obtain a reproduced video signal, a plurality of reproduced outputs from the plurality of reproducing heads are used to detect a frequency detection signal (FG signal) and a phase detection signal of a rotary drum provided with the reproducing heads. (PG
Signal), and a first switching means for deriving a continuous FM carrier by switching with a phase-synchronized head switching signal, and a first FM demodulation for FM demodulating the continuous FM carrier derived by the first switching means. Means, a horizontal sync separation means for receiving the output of the first FM demodulation means and separating the negative horizontal sync signal, and a part of the clamp level for receiving the output of the first FM demodulation means. Vertical synchronizing signal separating means for separating the vertical synchronizing signal which has been replaced with a signal, a head switching pulse generating means for deriving a head switching pulse phase-synchronized with the horizontal and vertical synchronizing signals, and a head switching pulse from the plurality of reproducing heads. Second switching means for switching a plurality of read reproduction outputs to make continuous reproduction output, and the second switching means. A second FM demodulating means for FM demodulating the continuous playback output from the quenching means, said 2 FM
For the reproduced video signal demodulated by the demodulation means, a time axis correction means for performing time axis correction using the FM carrier whose phase is reset for each horizontal synchronization as a reference burst signal, a horizontal synchronization signal replaced with a negative polarity, and a clamp level The present invention is characterized in that a vertical sync signal, a part of which is replaced with a negative polarity, is provided with a positive horizontal sync signal and a MUSE positive sync restoring means for returning to a positive clamp level.

According to a fourth aspect of the magnetic reproducing apparatus of the present invention, the head switching pulse generating means in the third aspect is a vertical direction in which a part of the clamp level from the vertical synchronizing separating means is made negative. It is characterized in that the head switching pulse is generated in synchronism with the synchronizing signal and synchronized with a frequency which is an integral multiple of the frequency of the negative polarity horizontal synchronizing signal derived from the horizontal synchronizing separating means.

According to a fifth aspect of the magnetic recording / reproducing apparatus of the present invention, a recording system for recording on a magnetic tape by a helical scan system by a plurality of magnetic heads provided on a rotary drum, and the magnetic drum provided on the rotary drum. And a reproducing system for deriving a plurality of reproduction outputs from a plurality of reproducing heads, converting the reproduced outputs into continuous signals, and then performing FM demodulation to derive reproduced video signals. Signal (FG signal) and phase detection signal (PG signal)
And a first switching means for switching the plurality of reproduction outputs to a continuous reproduction output by a head switching signal phase-synchronized with the FG signal and the PG signal, and the first switching means.
A first FM demodulation means for demodulating a continuous reproduction output from the switching means, and a horizontal / vertical sync signal for separating a horizontal and vertical synchronization signal from the reproduction signal demodulated by the first FM demodulation means.
A vertical sync separation means, a head switching pulse generation means for generating a head switching pulse phase-synchronized with the horizontal / vertical sync signals, and a plurality of reproduction outputs which are switched by the head switching pulse to make a continuous reproduction output. The switching means and the second FM demodulation means for FM-demodulating the continuous reproduction output derived from the second switching means to derive a reproduction video signal are provided.

[0023]

According to the magnetic recording apparatus of the present invention, the MUSE signal converted into the digital signal is replaced by the horizontal synchronizing signal replacing means for the positive horizontal synchronizing signal by the negative horizontal synchronizing signal, and by the vertical synchronizing replacing means. A part of the clamp level is replaced with a negative signal. After that, after being converted into an analog signal, the FM carrier is phase-reset for each horizontal synchronizing signal at the time of FM modulation by the carrier reset FM modulating means and is recorded on a magnetic tape by a helical scan method via a plurality of heads.

According to another aspect of the magnetic reproducing apparatus of the present invention, a plurality of reproducing signals are read from a plurality of heads provided on the rotating drum, and the FG signal and PG of the rotating drum are read.
A signal, and supplies a head switching signal phase-synchronized with the FG signal and the PG signal to the first switching means,
The first switching means switches the plurality of reproduction signals to derive continuous reproduction output. After this continuous reproduction output is demodulated by the first FM demodulation means, the horizontal / vertical synchronization separation means separates the horizontal and vertical synchronization signals, and the head switching pulse generation means performs phase synchronization with the horizontal and vertical synchronization signals. Derive the head switching pulse.

This head switching pulse is guided to the second switching means, where the plurality of reproduction signals are switched to make a continuous reproduction output and the second FM demodulation means F
The reproduced video signal is derived by M demodulation.

According to the magnetic reproducing apparatus of the third aspect, a plurality of reproducing outputs are derived from a plurality of reproducing heads provided on the rotating drum, and the FG signal and P of the rotating drum are outputted.
G is derived to generate a head switching signal that is in phase with the FG signal and the PG signal. Then, the head switching signal controls the first switching means to convert the plurality of reproduction outputs into continuous FM carriers. This continuous FM carrier is FM demodulated by the first FM demodulation means, and then the horizontal and vertical sync separation means clamps the negative horizontal sync signal and the MUSE signal in which the positive horizontal sync signal of the MUSE signal is replaced by the negative polarity. The vertical synchronizing signal in which a part of the level is replaced with the negative polarity is separated.

The horizontal and vertical synchronizing signals separated by the horizontal / vertical synchronizing separating means are supplied to a head switching pulse generating means, where a head switching pulse phase-synchronized with the horizontal and vertical synchronizing signals is derived. The head switching pulse is supplied to the second switching means, and the plurality of reproduction outputs are switched at the timing of the head switching pulse to make a continuous reproduction output.

The continuous reproduced output derived from the second switching means is demodulated into a reproduced video signal by the second FM demodulating means at the next stage, and further, the phase is reset at each horizontal synchronization by the time axis correcting means. Time-axis correction is performed using the carrier as a reference burst signal, and the horizontal sync signal replaced with the negative polarity by the MUSE positive sync recovery means is converted into the positive horizontal sync signal, and a part of the clamp level replaced with the negative polarity is used as a basis. To reproduce the reproduced MUSE signal.

According to the magnetic reproducing apparatus of the fourth aspect, the head switching pulse derived from the head switching pulse generating means is synchronized with the vertical synchronizing signal from the vertical synchronizing separating means and the horizontal synchronizing from the horizontal synchronizing separating means. A head switching pulse synchronized with a frequency that is an integral multiple of the frequency of the signal is generated.

According to the magnetic recording / reproducing apparatus of the fifth aspect, the magnetic recording / reproducing apparatus is provided with a plurality of magnetic heads provided on the rotating drum.
The M-modulated video signal is recorded on the magnetic tape by the helical scan method, and the reproduction of the video signal recorded on the magnetic tape is performed in the same manner as the reproducing operation in the magnetic reproducing apparatus according to the second aspect. The reproduced video signal is derived from the FM demodulation means of.

[0031]

1 is a block diagram of an embodiment of the present invention. In FIG. 1, 101 is a normal MUS for the MUSE input signal supplied from the input terminal 100.
An input signal processing circuit that performs AGC (automatic gain adjustment), clamp processing, and the like similarly to the E decoder, 102 is an A / D converter that receives a signal from the input signal processing circuit 101 and converts an analog signal into a digital signal, 103 is the above A /
A horizontal sync separation circuit 104 that receives the output of the D converter 102, detects the horizontal sync signal of the input MUSE signal, and separates the horizontal sync signal.
Is a frame signal separation circuit for detecting and separating the frame signal of the input MUSE signal, and 105 is the horizontal synchronization separation circuit 1
03 and the output of the frame signal separation circuit 104, and is a clock generator that supplies various timing signals to each unit of the magnetic recording / reproducing apparatus.

Further, 106 is a MUSE de-emphasis circuit which receives the output of the A / D converter 102 and performs transmission de-emphasis processing of the MUSE signal, and 107 is the M
MU receives the output of USE de-emphasis circuit 106
The horizontal and vertical sync replacement circuit replaces the positive horizontal sync signal of the SE signal with the negative horizontal sync signal and replaces a part of the clamp level period with the negative polarity signal.

Reference numeral 108 denotes the horizontal / vertical sync replacement circuit 10 described above.
7. A D / A converter for converting a digital signal of the MUSE signal derived from 7 into an analog signal, 109 receives the output of the D / A converter 108, resets the phase for each horizontal synchronization, and resets the carrier for FM modulation. FM modulator, 110
Is a recording amplifier that adjusts the recording current supplied to the recording head to the optimum value by the carrier reset FM modulator 109, and 111 is the output from the recording amplifier 110, and at least two Is a head-tape system that records a video signal in a helical scan system on a magnetic tape as a discontinuous signal obtained by dividing a video signal by a magnetic head.

In the embodiment shown in FIG. 1, the MUSE signal converted into a digital signal is de-emphasized by the MUSE de-emphasis circuit 106,
Although supplied to the horizontal / vertical sync replacement circuit 107, the order is reversed so that the horizontal / vertical sync replacement circuit 107 first performs signal processing and then leads to the MUSE de-emphasis circuit 106 to perform de-emphasis processing. May be.
Each of the above blocks constitutes the recording system of the magnetic recording / reproducing apparatus of the present invention.

Next, the structure of the reproducing system will be described. 112 and 113 are at least 2 from the head tape system 111.
Discontinuous reproduction F read by one reproduction magnetic head
A reproducing amplifier for amplifying each M carrier, 114,
An equalizer 115 receives the outputs of the reproduction amplifiers 112 and 113 and corrects the imbalance of the upper and lower sidebands of the FM carrier caused by the electromagnetic conversion characteristics reproduced by the tape head system 111.

Reference numeral 116 denotes a drum frequency detector 307 attached to the drum motor assembly of the rotary drum 306 (FIG. 7) in the head tape system 111.
And a reference signal such as a frequency detection signal (FG signal) and a phase detection signal (PG signal) from the drum phase detector 308 (FIG. 7) are input to control the rotary drum 306 to a constant rotation and the FG signal and A drum servo circuit that generates a head switching signal based on a PG signal.

Reference numeral 117 denotes the equalizers 114 and 115.
Output from the drum servo circuit 1
A switching circuit for switching with a head switching signal from 16; 118, a simple FM demodulator for simply FM demodulating a series of reproduced video signals derived from the switching circuit 117; 119, an output of the simple FM demodulator 118;
A horizontal sync separation circuit for separating the horizontal sync signal of the reproduced video signal, a vertical sync for receiving the output of the FM demodulator 118 and separating a part of the clamp level period replaced with a negative polarity signal at the time of recording as a vertical sync signal. It is a separation circuit.

Reference numeral 121 denotes a head switching pulse generation circuit which receives the horizontal and vertical synchronization signals from the horizontal synchronization separation circuit 119 and the vertical synchronization separation circuit 120 and generates a head switching pulse. 122 denotes the equalizer 11.
4 and 115, and a switching circuit for switching both outputs to a series of reproduced video signals by switching the head switching pulse from the head switching pulse generating circuit 121, and 123 is the switching circuit 122.
FM for FM demodulating a series of reproduced video signals supplied from
It is a demodulator.

An A / D 124 receives the output of the FM demodulator 123 and converts an analog signal into a digital signal.
A converter 125 is a time axis fluctuation correction circuit that corrects a time axis fluctuation that occurs in the recording / reproducing system, and a 126 restores the negative polarity horizontal sync signal that was replaced during recording to the original positive polarity horizontal sync signal and MUS that restores part of the clamp level period replaced with the sex signal to the original clamp level
E positive polarity sync recovery circuit 127 is an M
A MUSE emphasis circuit for restoring USE de-emphasis, and 128 is a D / A converter for converting a digital signal into an analog signal. The MUSE positive polarity synchronization restoration circuit 126 and the MUSE emphasis circuit 1
The configuration order of 27 may be reversed. Each of the above blocks constitutes a reproducing system of the magnetic recording / reproducing apparatus of the present invention.

Next, the operation of the magnetic recording / reproducing apparatus of the present invention will be described in detail. MU from MUSE signal input terminal 100
When the SE input signal is input to the input signal processing circuit 101, the input signal processing circuit 101 performs signal processing such as AGC and clamp processing as in a normal MUSE decoder, and then the A / D converter 102. It is A / D converted into a digital signal.

In the horizontal sync separation circuit 103, the A / D
The converter 102 detects and separates the positive horizontal synchronizing signal of the MUSE signal converted into a digital signal, the frame signal separation circuit 104 detects and separates the frame signal, and the clock generator 105 further detects From the outputs of the horizontal sync separation circuit 103 and the frame signal separation circuit 104, various timing signals to be supplied to each part of the magnetic recording / reproducing apparatus are generated.

The MUSE de-emphasis circuit 106 receives the output of the A / D converter 102, restores the transmission emphasis applied to the MUSE signal to the original, and supplies it to the horizontal / vertical sync replacement circuit 107 in the next stage. . In the horizontal / vertical sync replacement circuit 107, the MU as shown in FIG.
A positive horizontal sync signal of the SE signal is replaced with a negative horizontal sync signal as shown in FIG. 3B, and one line is inserted in the final line of one field as shown in FIG. 4A. A part of the level period is replaced with a negative polarity signal as shown in FIG. 4B, and a signal obtained by replacing a part of the clamp level period with a negative polarity signal is used as a vertical synchronizing signal. Then, the MUSE of the digital signal subjected to the signal processing as described above by the horizontal / vertical sync replacement circuit 107.
The signal is converted into an analog signal by the D / A converter 108 at the next stage and supplied to the carrier reset FM modulator 109.

The carrier reset FM modulator 109 resets the phase of the FM carrier of the MUSE signal for each horizontal synchronization and performs FM modulation. And this FM-modulated MU
The SE signal is supplied to the head tape system 111 by adjusting the recording current supplied to the recording head in the recording amplifier 110 to an optimum value, and the head tape system 111 uses the helical scan method to generate at least two magnetic heads. It is recorded on a magnetic tape as a discontinuous video signal.

Next, the operation of the reproducing system will be described. The discontinuous reproducing FM carriers read from at least two reproducing magnetic heads of the head tape system 111 are amplified by reproducing amplifiers 112 and 113, respectively, and then equalized by the equalizer 1.
14 and 115, where the imbalance of the upper and lower sidebands of the FM carrier due to the electromagnetic conversion characteristics during recording and reproduction is corrected. And both equalizers 114 and 11
The outputs of No. 5 are supplied to the switching circuits 117 and 122 at the next stage, respectively.

On the other hand, in the drum servo circuit 116, as shown in FIG. 7, the frequency detector 307 and the phase detector 308 provided in the drum motor assembly of the rotary drum 306 are shown.
The drum FG signal and the drum PG signal are respectively taken out, and the rotation of the rotary drum is controlled by these signals so that the rotation is constant, and a head switching signal is generated from these signals and supplied to the switching circuit 117.

As a result, the switching circuit 117 is
The head switching signal from the drum servo circuit 116 alternately switches both outputs of the equalizers 114 and 115 to derive a series of reproduced video signals. In this case, since the reproduced video signal is influenced by the jitter of the drum capstan servo, it is not phase-synchronized with the head switching signal. This reproduced video signal is guided to the simple FM demodulator 118, and the horizontal / vertical sync separation circuits 119 and 12 in the next stage are provided.
Simple FM that can separate horizontal and vertical sync signals at 0
Demodulation is performed.

The reproduced video signal demodulated by the simple FM demodulator 118 is supplied to the horizontal sync separation circuit 119 and the vertical sync separation circuit 120, and the horizontal sync separation circuit 1 is supplied.
At 19, the negative horizontal sync signal replaced by the recording system is detected and separated from the reproduced video signal, and at the vertical sync separation circuit 120, a part of the clamp level period when the reproduced video signal is replaced by the recording system is detected. Is detected and separated, and this horizontal / vertical synchronization signal is supplied to the head switching pulse generation circuit 121 of the next stage.
Then, the head switching pulse generation circuit 121
As a result, a head switching pulse that is phase-synchronized with both the synchronization signals is generated.

The switching circuit 122 receives the head switching pulse and receives both the equalizers 1
Two intermittent FM reproducing carriers from 14 and 115 are alternately switched to reproduce continuous FM carriers which are phase-synchronized with the horizontal and vertical synchronizing signals. This reproduced continuous F
The M carrier is guided to the FM demodulator 123 at the next stage, where it is FM demodulated and becomes a reproduced video signal.

After the series of video signals demodulated by the FM demodulator 123 are guided to the A / D converter 124 and converted into digital signals, the time axis fluctuation correcting circuit 125 corrects the jitter generated during recording and reproduction. In the MUSE positive polarity sync restoration circuit 126, the negative polarity horizontal sync signal replaced at the time of recording is restored to the positive polarity sync signal and a part of the clamp level period also replaced is restored to the original clamp level, that is, MUSE.
Return to level 128 of the horizontal sync signal in the signal.

The MUSE signal in which the sync signal replaced by the recording system is restored to the original sync signal is subjected to transmission emphasis processing of the MUSE signal returned at the time of recording by the MUSE emphasis circuit 127 in the next stage, and further D / A converted. The converter 128 converts it into an analog signal and derives a reproduced MUSE signal.
Next, the horizontal / vertical sync replacement circuit 10 in the above recording system
The negative polarity sync signal replacement method in 7 will be described with reference to FIGS. 2, 3 and 4. FIG. 2 is a block diagram of the MUSE transmission signal.

Of the MUSE signal, the horizontal synchronizing signal will be described first with reference to FIG. The horizontal sync signal of the MUSE signal is a positive sync signal interpolated in the video signal component as shown in FIG. 3A, and has a sync form in which the polarities of the n line and the n + 1 line change line by line. When recording / reproducing in this state, it is difficult to accurately capture the sync signal portion due to the time axis fluctuation. Therefore, in the present invention, the horizontal / vertical sync replacement circuit 107 causes the positive horizontal sync shown in FIG. The signal processing is performed by replacing the signal with a negative horizontal synchronizing signal as shown in FIG. 3B, and recording is performed on the tape.

Next, the operation of replacing the clamp level signal will be described with reference to FIG. First, as shown in FIG. 2, the MUSE signal is a horizontal synchronization signal on lines 563 and 1125,
The transmission control signal is followed by a clamp level signal, and this signal is inserted into each field at the end of one field. Normally, in the clamp processing of the MUSE signal, the point (level 12) of the sample No. 6 of the horizontal synchronizing signal shown in FIG.
In step 8), it is performed every horizontal synchronization. In the case of the present invention, however, this operation cannot be performed because the horizontal synchronization signal is replaced with the negative polarity synchronization signal as described above.

Therefore, in order to perform the clamping operation in units of fields, as shown in FIG. 4B, signal processing for replacing a part of the clamp level signal with a negative polarity signal is performed, and the replaced negative polarity signal is captured. By doing so, the position of the clamp level is confirmed, and the clamp operation is performed for each field. The negative polarity signal shown in FIG. 4 inserted in the clamp level signals of the 563th line and the 1125th line is called a vertical synchronizing signal in the present invention. This vertical synchronizing signal can also be used as a reference signal in other field units. As described above, the replacement operation of the negative sync signal in the horizontal / vertical sync replacement circuit 107 is performed.

Next, details of the head switching pulse generation circuit 121 in the embodiment of the present invention described with reference to FIG. 1 will be described with reference to FIGS. 5 and 6. During playback, two playback heads A mounted on the rotating drum as shown in FIG.
The output of B becomes a temporally discontinuous signal as shown in the first and second stages of FIG. 5, respectively. These two discontinuous reproduction outputs are alternately switched by a head switching signal as shown in the third stage of FIG. 5 so that the subsequent signal processing can be performed by a simple one-system circuit, and finally, FM demodulation is performed after forming continuous FM carriers as shown in the fourth row of FIG.

In this case, it is assumed that the head switching signal is generated based on the FG signal and the PG signal from the frequency detector and the phase detector attached to the drum assembly of the rotary drum as in the conventional example. Due to the expansion and contraction of the tape and the variation in the accuracy of the running system, there is a problem that the timing shifts and high-precision switching cannot be performed. FIG. 6 is a block diagram of a specific example of a head switching signal generating circuit according to the present invention in which such a problem is eliminated, and the portions corresponding to those in FIG.

In FIG. 6, reference numerals 112 and 113 denote reproduction amplifiers for amplifying reproduction FM carrier signals from the heads A and B. The outputs of the reproduction amplifiers 112 and 113 are guided to the equalizers 114 and 115, respectively, and the heads are output. The imbalance of the upper and lower sidebands caused by the electromagnetic conversion characteristics of the tape system is corrected and supplied to the switching circuit 117.

The switching circuit 117 uses the head switching signal generated based on the FG signal and the PG signal from the drum assembly in the drum servo circuit as described above to continuously reproduce the FM carrier which is discontinuous with respect to time. The carrier is converted into a carrier, and the continuous reproduction FM carrier is guided to the simple FM demodulator 118 in the next stage, where the FM demodulation is performed. The simple FM demodulation circuit 118 may be a circuit for performing simple FM demodulation to the extent that the sync signal can be restored by the horizontal and vertical sync separation circuits in the next stage.

FM demodulated by the simple FM demodulator 118
The demodulated outputs are respectively guided to the horizontal sync separation circuit 119 and the vertical sync separation circuit 120, where the horizontal sync separation circuit 119 separates the negative horizontal sync signal f _H replaced at the time of recording, and the vertical sync separation circuit 120 replaces at the time of recording. The vertical synchronizing signal f _V obtained by replacing a part of the clamp level period with the negative polarity is separated.

The negative horizontal sync signal f _H derived from the horizontal sync separation circuit 119 is supplied to the AFC circuit 208, and in the AFC circuit 208, the horizontal sync signal 2 f _H having a double frequency and the horizontal sync signal having an 8-fold horizontal frequency. The synchronizing signal 8f _H is generated, the horizontal synchronizing signal 2f _H having the double frequency is supplied to the vertical synchronizing separation circuit 120 and the line counter 209, and the horizontal synchronizing signal 8f _H having the double frequency is used in the shift register 211.
Supply to.

The line counter 209 is connected to the AFC.
The horizontal sync signal 2f _H from the circuit 208 and the vertical sync signal f _V from the vertical sync separation circuit 120 are received, and the number of horizontal sync signals is counted. In this case, the frequency of the horizontal synchronizing signal supplied from the AFC circuit 208 is doubled so that the line counting operation can be performed normally even if the synchronizing signal is lost due to dropout or the like.

The count output of the line counter 209 is supplied to the ROM circuit 210 as an address signal, the data of the head switching pulse is output from the ROM circuit 210 to the shift register 211 of the next stage, and the phase reset pulse is output to the line counter 209. To reset the line counter 209.

The shift register 211 is the ROM
The data of the head switching pulse from the circuit 210 and the horizontal synchronizing signal 8f _H of 8 times the frequency from the AFC circuit 208 are received, and the head switching pulse adjusted to a specific phase is output. In this case, the input clock of the shift register 211 is set to the horizontal synchronizing signal 8f _H having a frequency of 8 times in order to finely adjust the phase of the head switching pulse, and depending on the circuit configuration and the required accuracy, A value that is an integral multiple may be selected as appropriate. In this way, since the head switching pulse derived from the shift register 211 is obtained from the reproduced video signal, it is not affected by the expansion and contraction of the tape or the variation in the accuracy of the running system.

Therefore, when this head switching pulse is used as the output of the head switching pulse generating circuit 121 of FIG. 1 to switch the FM carrier, the switching point is defined on a specific line as shown in FIG. 8B. However, it can be fixed at a specific point.

[0064]

As described above, according to the present invention, the sync signal is detected from the reproduced video signal, and the head switching pulse is generated based on this sync signal. Therefore, the switching point is always set at a fixed position with respect to the reproduced signal. It can be set accurately. Therefore, it is particularly effective for recording / reproducing a special signal such as a MUSE signal which is easily affected by the switching point, and the signal processing as a countermeasure against switching noise can be easily performed.

Further, according to the present invention, since the horizontal / vertical sync signals are absolutely replaced with the negative sync signals, it is possible to restore the sync signals without specifying the phases of the video and audio signals during reproduction. , The phase can be accurately restored,
Even in the MUSE decoder, there is no risk of malfunction or failure to obtain a normal baseband signal.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a configuration diagram of a MUSE transmission signal.

FIG. 3 is an explanatory diagram of a horizontal synchronization signal replacement method.

FIG. 4 is an explanatory diagram of a clamp level signal replacement method.

FIG. 5 is an explanatory diagram of a head switching signal.

FIG. 6 is a block diagram of an example of a head switching signal generation circuit used in the present invention.

FIG. 7 is a block diagram of a conventional head switching signal generation circuit.

FIG. 8 is an explanatory diagram of an image display example.

[Explanation of symbols]

 101 Input Signal Processing Circuit 102 A / D Converter 107 Horizontal / Vertical Synchronization Substitution Circuit 108 D / A Converter 109 Carrier Reset FM Modulator 111 Head Tape System 116 Drum Servo Circuit 117, 122 Switching Circuit 118 Simple FM Demodulator 119 Horizontal Sync separation circuit 120 Vertical sync separation circuit 121 Head switching pulse generation circuit 123 FM demodulator 125 Time axis fluctuation correction circuit 126 MUSE Positive sync recovery circuit

Claims (5)

[Claims] 1. A magnetic recording apparatus for performing signal processing of a MUSE signal converted into a digital signal, converting it into an analog signal again, FM modulation, and recording on a magnetic tape by a plurality of heads in a helical scan system. In the FM modulation described above, horizontal sync replacement means for replacing the positive horizontal sync signal with the negative horizontal sync signal for the MUSE signal converted into the negative sync signal, vertical sync replacement means for replacing a part of the clamp level with the negative sync signal. A magnetic recording device comprising a carrier reset FM modulator for resetting the phase of an FM carrier for each horizontal synchronization. 2. A reading means for deriving a plurality of reproduction outputs from a plurality of heads provided on a rotary drum and deriving a frequency detection signal (FG signal) and a phase detection signal (PG signal) of the rotary drum, and the FG signal. And a first switching means for switching the plurality of reproduction outputs by a head switching signal phase-synchronized with the PG signal to make continuous reproduction outputs.
First FM demodulation means for demodulating the continuous reproduction output from the first switching means, and horizontal / vertical synchronization separation means for separating the horizontal and vertical synchronization signals from the reproduction signal demodulated by the first FM demodulation means. A head switching pulse generating means for generating a head switching pulse phase-synchronized with the horizontal / vertical synchronizing signal; and a second switching means for switching the plurality of reproduction outputs by the head switching pulse to make a continuous reproduction output. , The second
The continuous reproduction output derived from the switching means of
A magnetic reproducing apparatus comprising: a second FM demodulating means for performing M demodulation and deriving a reproduced video signal. 3. A positive horizontal synchronizing signal of the MUSE signal is replaced with a negative horizontal synchronizing signal, a part of the clamp level is replaced with negative polarity, and an FM carrier is FM-modulated and the phase is reset for each horizontal synchronization. In a magnetic reproducing apparatus for reading a plurality of reproducing outputs from a magnetic tape recorded by a helical scan method as a plurality of reproducing outputs, converting the plurality of reproducing outputs into continuous reproducing outputs, and performing FM demodulation to obtain a reproduced video signal. , A plurality of reproduction outputs from the plurality of reproduction heads are switched by a head switching signal phase-synchronized with a frequency detection signal (FG signal) and a phase detection signal (PG signal) of a rotary drum provided with the reproduction heads. A first switching means for deriving a continuous FM carrier and a continuous FM carrier for deriving from the first switching means. A first FM demodulating means for M demodulated,
Horizontal sync separation means for receiving the output of the first FM demodulation means and separating the negative polarity horizontal sync signal; and the first FM.
Vertical sync separating means for receiving the output of the demodulating means for separating a vertical sync signal in which a part of the lump level is replaced with a negative polarity, and a head switching pulse for deriving a head switching pulse phase-synchronized with the horizontal and vertical sync signals. Generating means, a second switching means for switching a plurality of reproduction outputs read from the plurality of reproduction heads by the head switching pulse to make a continuous reproduction output, and a continuous reproduction output from the second switching means. Second FM demodulation means for FM demodulation, and time axis correction for performing time axis correction on the reproduced video signal demodulated by the second FM demodulation means using the FM carrier whose phase is reset for each horizontal synchronization as a reference burst signal. Means, a horizontal sync signal with a negative polarity replaced, and a vertical sync signal with a part of the clamp level replaced with a negative polarity. Magnetic reproducing apparatus characterized by comprising a MUSE positive polarity synchronization restoring means for returning the door to a positive polarity horizontal synchronizing signal and the positive polarity clamp level. 4. The head switching pulse generating means synchronizes with a vertical synchronizing signal in which a part of the clamp level from the vertical synchronizing separating means has a negative polarity and derives from the horizontal synchronizing separating means. 4. The magnetic reproducing apparatus according to claim 3, wherein the head switching pulse is generated in synchronization with a frequency that is an integral multiple of the frequency. 5. A recording system for FM-modulating a video signal to record it on a magnetic tape by a helical scan method by a plurality of magnetic heads provided on a rotating drum, and a plurality of reproduction outputs from a plurality of reproducing heads provided on the rotating drum. In a magnetic recording / reproducing apparatus having a reproducing system for deriving a reproduction signal for converting a continuous signal into a continuous signal and performing FM demodulation to derive a reproduction video signal. PG signal), and a first switching means for switching the plurality of reproduction outputs to a continuous reproduction output by a head switching signal that is phase-synchronized with the FG signal and the PG signal, and continuous from the first switching means. A first FM demodulation means for demodulating the reproduced output thus generated, and a horizontal / vertical separation means for separating the horizontal and vertical sync signals from the reproduction signal demodulated by the first FM demodulation means. A second sync switching means, a head switching pulse generating means for generating a head switching pulse that is phase-synchronized with the horizontal / vertical synchronizing signals, and a plurality of reproduction outputs that are switched by the head switching pulse to make a continuous reproduction output. A switching unit and a second F for FM-demodulating a continuous reproduction output derived from the second switching unit to derive a reproduction video signal.
A magnetic recording / reproducing apparatus provided with M demodulating means.