JPH0595565A - Automatic mode discriminating and switching device - Google Patents

Abstract

PURPOSE:To automatically discriminate which signal is reproduced, and to automatically set a VTR to a discriminated mode. CONSTITUTION:At the VTR in a system to execute time base correction by executing frequency modulation after adding the pilot signals of continuous waves out of the band of a MUSE signal in the case of recording the MUSE signal, afterwards, adding a prescribed synchronizing signal to a band lower than that of an FM signal, magnetically recording the added signal, separating these synchronizing signal and pilot signal in the case of reproduction, preparing a clock signal for write based on both signals and writing the demodulated MUSE signal in a buffer memory (86) used as a TBC, means (100, 102, 104, 106, 108 and 110) are provided to discriminate whether the synchronizing signal of a prescribed frequency is existent in a regenerative signal or not, a control signal is prepared by this means, a rotary head is rotated at 1800rpm in the case of MUSE and rotated at 2700rpm in the case of NTSC (VHS), and the mode of a reproducing system is automatically switched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing method and a magnetic recording / reproducing apparatus, and more particularly to a MUSE signal and NTSC.
The present invention relates to a magnetic recording / reproducing device capable of recording / reproducing by switching signals such as.

[0002]

2. Description of the Related Art Various HDTV VTRs for recording and reproducing MUSE signals used for HDTV developed by NHK or MTR VTRs have been proposed.

FIG. 11 (a) is a waveform diagram of a band-compressed high-definition signal (hereinafter referred to as MUSE signal), and a positive polarity signal is used as a synchronizing signal. If the MUSE signal including the positive polarity sync signal is recorded on the VTR as it is, the sync signal cannot be separated during reproduction, and thus the sync signal cannot be used for jitter correction. Therefore, FIG.
As shown in (b), the MUSE signal is time-axis-compressed in units of 1H to provide a blanking period, in which a negative sync signal and a burst signal for jitter detection are inserted and added. That is, the VTR is used for recording in the same manner as the sync signal and burst signal in the NTSC signal. This method is based on Mitsubishi Electric Technical Report Vol. 60.N
o. 11 (published in 1986), "High-definition VTR broadband recording technology".

As another recording / reproducing system using the VTR of the MUSE signal, the latter half of the signal is delayed by a predetermined period so as to provide a blanking period at the signal position for rotary head switching at the time of recording, and then at the position for rotary head switching at the time of reproduction. There is one that corrects the skew. This method is shown in "Prototype of home-use high-definition VTR" in the 1987 National Conference of Television Society, and is as follows.

By delaying the latter half of the video signal of each field by 16H and providing a blanking period of 16H at the center of each field, the vertical blanking period is shortened by 16H, but a blanking period of about 20H still remains. In the two blanking periods provided in each field, a positive horizontal sync signal (referred to as pseudo H) that is phase-synchronized with the horizontal sync signal of the video is inserted to maintain continuity of synchronization. The rotation of the heads is controlled so that the switching between the two rotary heads is performed during this blanking period, and recording / reproduction is performed. During reproduction, the pseudo H period is deleted and the continuity of horizontal synchronization is maintained to remove rotary head switching noise and skew.
The horizontal sync signal recorded in the VTR is only the positive sync signal. In the pseudo H period, the horizontal sync signal is reliably detected,
In the video signal period following the pseudo H period, horizontal sync is detected by utilizing the shape and periodicity of the positive horizontal sync signal.

[0006]

Among the above two prior arts, the method of adding a negative sync signal similar to NTSC is
Assuming that the system and the system in which the blanking period is provided at the switching position of the rotary head is the B system, each of the A and B systems has the following problems. That is, it is difficult to correct the jitter (velocity error) within one horizontal period in both A and B systems. Further, in the A system, since the MUSE signal is compressed on the time axis, the band of the recorded video signal is widened to the higher side. Furthermore, in the A method, S / N due to FM deviation
Will deteriorate. Next, in the method B, since the skew correction is the main purpose, if there is a lot of jitter at a position other than the rotary head switching position, it may be difficult to detect the synchronization signal, and therefore it may be difficult to correct the jitter. is there. or,
It is not possible to directly record a signal such as a voice that has entered the vertical blanking period. Therefore, a separate voice head is required. Therefore, the present applicant overcomes the drawbacks of both the conventional A and B types prior to the present invention, and is capable of correcting the time axis even within 1H in recording / reproducing MUSE signals, and also NTSC, PAL, SECAM, etc. Has developed a magnetic recording / reproducing method which can be shared with the standard television signal of the above, a magnetic recording device and a magnetic reproducing method used for the same, and Japanese Patent Application No. 3-12.
We have applied for a patent as No. 2571.

In the invention of the above-mentioned prior application, when the MUSE signal is recorded, a pilot signal of a predetermined frequency is superimposed outside the video signal band of the input MUSE signal, and the resulting multiplexed signal is lower than the frequency-modulated signal. A sync signal of a predetermined frequency is superimposed on the frequency band, and the resulting frequency-multiplexed signal is applied to the magnetic head to separate the sync signal from the signal reproduced from the magnetic recording medium to obtain a reproduction sync signal. The reproduced signal is demodulated to obtain a reproduced multiplexed signal,
The pilot signal is separated from the playback synchronization signal to obtain a playback pilot signal, the playback multiplex signal and the pilot signal are written to a buffer memory in synchronization with a clock signal of a predetermined frequency, and the stable other clock signal is used. The demodulated video signal is read from the buffer memory to correct the time axis.

By the way, in the reproducing system used in the method of the invention of the above-mentioned prior application, whether the reproducing mode is MUSE or NTSC.
It has not been particularly performed to discriminate whether the signal is a standard signal from the related art. Therefore, either one of them has been selected by the manual changeover switch. However, if the mode is changed when the storage medium, that is, the magnetic tape is replaced with another one, the manual switching must be performed one by one in order to switch the rotational speed of the rotary head and the processing circuit of the reproducing system. It is therefore an object of the present invention to automatically determine which mode the reproduction signal belongs to and to generate a control signal for executing the above-mentioned switching so as to match the mode.

To achieve the above object, the present invention responds to at least one of a plurality of channel signals reproduced from a magnetic recording medium by a plurality of magnetic heads rotating at a predetermined rotation speed, Means for detecting whether or not a signal having a predetermined frequency and a predetermined cycle is present, and maintaining a predetermined rotation speed of the plurality of magnetic heads according to the output signals of the detection means, or another predetermined rotation speed. And a control signal generation means for generating a control signal for switching and using at least two signal reproduction systems for processing the reproduced plural channel signals according to the output signal of the detecting means. An automatic mode discrimination switching device is provided.

[0010]

In the automatic mode discrimination switching device of the present invention, means for detecting whether or not a signal having a predetermined frequency and a predetermined cycle is present in the reproduced signal is provided as described above, and therefore, it is superimposed at the time of recording. By determining the presence / absence of a low-frequency synchronization signal, it is possible to determine whether the MUSE signal is another conventional standard signal such as NTSC, and thus the rotation speed of the rotary head and the processing circuit of the reproduction system are switched. You can make control signals for. Therefore, it is not necessary to manually attempt switching.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Before describing the embodiments of the present invention, the contents of the prior application (Japanese Patent Application No. 3-122571) will be described. 4 and 5 are block diagrams of a magnetic recording device and a magnetic reproducing device for implementing the magnetic recording / reproducing method of the above-mentioned prior invention. Needless to say, the magnetic recording device and the magnetic reproducing device shown in FIGS. 4 and 5 can be integrated to form a magnetic recording / reproducing device, but here, the recording system and the reproducing system will be described separately.
Hereinafter, the recording system and the reproducing system will be simply referred to.

The input terminal NTSC IN has NTSC, P
It is assumed that one of standard signals such as AL and SECAM is input, and the MUSE signal used for high-definition is input to the other input terminal MUSE IN. Here, it is assumed that the NTSC signal is input as the standard signal. Two switches SW1, SW2 connected to these input terminals
And the other two switches SW3 and SW4 set the recording system to NT.
It is for switching between the SC mode and the MUSE mode, and it is preferable to use the interlocking one. These switches SW1, SW2, SW3, SW4 are NTSC
On the side, the NTSC signal is given to the VHS / MUSE recording processing circuit 24 and the COLOR / SYNC circuit 42. The VHS / MUSE recording processing circuit 24 frequency-modulates the Y (luminance) signal in the NTSC signal to obtain an FM signal, while the COLOR / SYNC circuit 42 has the switch SW3 of N.
On the TSC side, the C (color) signal in the NTSC signal is VHS
It is converted to the low frequency band according to a predetermined color under system such as (registered trademark). These signals are frequency-multiplexed with each other by an adder 34 to be signals of a predetermined color under system, and are passed through a recording amplifier 46 and a head switching circuit 48, as shown in FIG.
The four magnetic heads 56, 58, 60, 62 mounted on the rotating drum shown in FIG. 50 is a drum servo circuit, input NTSC
A drum motor (not shown) that drives the rotary drum is controlled in response to the signal synchronization signal. This drum servo circuit 5
The head switching pulse is generated by the head switching pulse generation circuit 52 using the signal of 0 and is given to the head switching circuit 48. The circuit components described above are basically the same as the recording system of a conventional VTR of the VHS system, for example.

On the other hand, the MUSE signal supplied to the input terminal MUSE IN is divided into signals of 2 channels for each field, that is, 4 channels in total through the A / D converter 10, the MUSE signal processing circuit 12, and the D / A converter 14 group. To be done. The MUSE signal processing circuit 12 performs predetermined digital signal processing. Pilot signal generation circuit 32
Is a circuit for generating a continuous signal of a predetermined frequency in synchronization with the synchronizing signal of the input MUSE signal. This pilot signal is used for jitter correction in the reproduction system described later with reference to FIG. Assuming that the frequency band of the input MUSE signal is 8.1 MHz, the band of the recording signal per channel is the channel division number 2 and the drum rotation speed ratio of 2: 3 to 8.1 MHz × 1/2 × 2 / 3 = 2.7
It becomes MHz. Horizontal sync frequency of MUSE signal fH = 3
480 fH x 1/3 x 3/5 = based on 480 fH which is 480 times 3.75 kHz (the number of MUSE signal samples)
If it is 96 fH, the pilot signal will be 3.24 MHz.

As shown in FIG. 6, the diameter of the rotary drum is 41 mm, and the magnetic tape is wound around 270 °. The rotation speed of the rotating drum is set to 1800 rpm in the MUSE mode and 2,700 rpm in the NTSC mode by switching the switch SW4.

FIG. 7 is a spectrum diagram showing the frequency relationship between the channel-divided MUSE signal and the pilot signal having a frequency of 96 fH. The pilot signal is adder 1
MUSE recording processing circuits 24, 26, which are respectively superposed on the MUSE signals divided by 6, 18, 20, and 22,
Given to 28 and 30. Of these, circuit 24 is NTS
It is also used as a C-based VHS. The MUSE recording processing circuits 24, 26, 28, 30 have an emphasis circuit, a frequency modulation circuit, etc., and have basically the same configuration as that for VHS. In this example, the same pilot signal is added and superposed on each channel, but it is more preferable to perform four different pilot signals by performing fine phase control in consideration of the H arrangement and the magnetic tape speed. is there.

MUSE recording processing circuits 24, 26, 28,
The output FM signal of 30 has adders 34, 36, 38, 40
At, the synchronization signal output from the COLOR / SYNC circuit 42 is superimposed. That is, switch SW3 is MUSE
When set to the side, the COLOR / SYNC circuit 42 receives the input MU.
For example, a ternary synchronizing signal as shown in FIG. 9 synchronized with the horizontal synchronizing signal of the SE signal is generated. The frequency of this synchronizing signal is 40 fH × 1/4 = 10 fH = 337.5 kHz, which is lower than the frequency-modulated MUSE signal band as shown in FIG. The synchronization signal is superimposed on this band because the MUSE signal is the TCI signal and the VH
Since it is not necessary to add the low-frequency converted C signal to the frequency-modulated Y signal like the S signal, the additional band of the C signal in VHS can be used as the additional band of the synchronization signal.

4-channel FM with sync signal added
The signals are sequentially applied to the four magnetic heads 56, 58, 60 and 62 via the recording amplifier group 46 and the head switching circuit 48.

Next, the reproducing system shown in FIG. 5 will be described.
The magnetic heads 56, 58, 60 and 62 are shown as the same heads by using the same numbers as those of the recording system, but it goes without saying that they can be read-only machines. Switch SW5,
SW6, SW7, and SW8 are for switching between the MUSE mode and the NTSC mode as in the recording system. Drum servo circuit 50
A, switch SW5, head switching pulse generation circuit 52
A, head switching circuit 48A is for sequentially selecting one of the heads as in the recording system, and is also for NTSC and MUS.
With E, the speed of the rotary drum is switched as in the recording system. The clock signal generation circuit 64 is the drum servo circuit 50.
The reference clock is sent to A. The preamplifier group 66 amplifies the reproduction signal from the selected head and has four preamplifiers. Preamplifier group 6
The output signal of 6 is given to the P / S (parallel-serial) conversion circuit 68, and in the case of reproduction of an NTSC signal, a parallel sequential signal of 4 channels is converted into a serial signal. A clock signal for P / S conversion is sent from the drum servo circuit 50A. The serial signal is applied to the VHS / MUSE reproduction processing circuit 72, FM demodulated therein, and then applied to the NTSC processing circuit 80 via the switch SW8. The COLOR / SYNC circuit 70 converts the C signal of the VHS signal into a high frequency band in the NTSC mode, and separates the sync signal superimposed during recording in the MUSE mode. This mode switching is performed by the switch SW6. Therefore, in the NTSC mode, the high frequency converted C signal is applied to the NTSC processing circuit 80 via the switch SW7 and is superimposed on the FM demodulated Y signal to generate a composite video signal at the NTSC signal output terminal NTSC.
It is output from OUT. It should be noted that the Y / C separated state can be output as necessary.

The MUSE reproduction processing circuits 74, 76 and 78 are the same as those other than the VHS system portion of the VHS / MUSE reproduction processing circuit 72, and are for FM demodulating the MUSE signal. Each of these reproduction processing circuits 72, 74, 7
The output signals of 6 and 78 are supplied to the A / D converter group 84 and also to the clock signal generation circuit 82. The clock signal generation circuit 82 has a BPF for separating the pilot signal superimposed at the time of recording, and creates a write clock signal using the synchronization signal separated by the COLOR / SYNC circuit 70 described above as a reference signal. Is. As shown in FIG. 10, this write clock signal is 5/3 times as large as the pilot signal of 3.96 MHz (96 fH), that is, 5.4 MHz (160 fH). This write clock signal is used as a sampling clock for the A / D converter group 84 and for writing the A / D converted signal to the buffer memory 86 used as a TBC (time base collector) for time axis correction. COLOR /
The 1H cycle write reference pulse obtained by the SYNC circuit 70 is used.

In the TBC 86, digital signals sequentially written in 4 channels (2 fields × 2 channels) are read using a stable 480 fH clock for reading generated by the clock signal generation circuit 88, thereby converting serial data. Conversion and time axis correction, that is, jitter removal is performed. The output signal of TBC86 is MUSE
After a predetermined digital signal processing is performed by the signal processing circuit 90, it is converted into an analog MUSE signal by the D / A converter 92, and is output from the output terminal MUSE OUT as a MUSE output signal via an LPF (not shown).

In the above example, the pilot signal is 96 fH.
However, even if the frequency is other than this frequency, T
160 f as a write clock signal to be given to BC86
Any frequency that can generate the H frequency and can be frequency-modulated within the VHS signal band may be used.

The present invention is used with the reproduction system of the above-mentioned prior invention. FIG. 1 is a block diagram showing an embodiment of an automatic mode discriminating apparatus of the present invention. Since this automatic mode discriminating apparatus operates integrally with the reproducing system shown in FIG. 5, it will be described in connection with FIG. Now, it is assumed that the switches SW5 to SW8 in FIG. 5 are on the MUSE side. The BPF 100 is a bandpass filter having a center frequency of 168.75 KHz and responds to the output of any one preamplifier in the preamplifier group in FIG. This frequency is 1 of 10fH = 337.5KHz mentioned above.
This corresponds to / 2, which corresponds to the fact that the reproduction frequency becomes 1/2 of 10 fH when the MUSE signal is divided into two channels and recorded on the magnetic tape.

The output of the BPF 100 is the waveform shaping circuit 102.
Is shaped into a positive pulse signal by the first monomulti 1
04 and the gate circuit 108. The output signal of the first mono-multi 104 is given to the second mono-multi 106,
The output signal is given to the gate circuit 108. The output signal of the gate circuit 108 is a retriggerable monomulti 110.
Given to. The output signal of the retriggerable mono-multi 110 is used as a control signal for each switch SW5, SW in FIG.
6, SW7 and SW8, respectively, to control these. The time constant of the first mono-multi 104 is set to 80 μS, for example. That is, as shown in FIG. 2, one horizontal period (1H) of the MUSE signal is about 88.5.
Since it is μS, the time is set to be slightly shorter than this. The time constant (pulse width) of the second mono-multi 106 is set to, for example, 10 μS, and is supposed to cover the beginning of the next horizontal cycle of the MUSE signal from the fall of the output signal of the first mono-multi 104. ing. The time constant of the retriggerable monomulti 110 is set to be slightly longer than 88.5 μS.

The operation of the automatic mode discriminating apparatus of FIG. 1 will be described with reference to FIGS. In FIG. 2, the MUSE signal is reproduced from the magnetic tape and the output of the preamplifier group 16 is 1
It is given as one. Moreover, FIG. 3 shows M
The case where an NTSC signal is similarly reproduced as a standard television signal other than USE is shown. When the MUSE signal is being reproduced, a positive pulse every 1H whose waveform is shaped by the output signal of the second monomulti 106, that is, the gate signal, passes through the gate circuit 108 and is given to the retriggerable monomulti 110. Therefore, once triggered, the output signal of the retriggerable mono-multi 110 is fixed to the H level while the MUSE signal is being reproduced.

On the other hand, when the NTSC signal is reproduced as shown in FIG. 3, the output signal of the BPF 100 becomes an irregular signal because the color signal does not have the periodicity unlike the signal of 10 fH described above, and therefore the second mono signal is generated. When the output signal (gate signal) of the multi 106 is at the H level, there is no waveform-shaped positive pulse. As a result, the retriggerable mono-multi 110 is not triggered and its output signal remains at the L level.

As described above, the automatic mode discrimination switching device of the present invention can discriminate which one of the MUSE signal and the standard television signal other than that is being reproduced and generate the control signal. That is, when it is determined that the MUSE signal is being reproduced, the switches SW5 to SW8 are kept in the same state, while when it is determined that signals other than the MUSE signal are being reproduced, the switches SW5 to SW8 are kept.
SW8 is switched to the other contact. In order to improve the stability of the determination, M is output only when the output pulse of the gate circuit 108 continues for a certain period or a certain number or more.
The USE side may be selected.

In the above description, the switches SW5 to SW5 in FIG.
There was a premise that SW8 was on the MUSE side in advance, but this setting may be done manually, or it may be automatically set on the MUSE side when the power switch of the VTR is turned on. May be. Although it is far from the present invention, if a circuit for detecting a VHS or S-VHS color signal is provided, the VHS or S-VHS signal is reproduced when the switches SW5 to SW8 are initially on the NTSC side. Therefore, it is not necessary to set it on the MUSE side.

VH in the reproduction mode of the NTSC signal
The S system and the S-VHS (registered trademark) system can be discriminated by using the FM frequency difference between them. Since such a technique has already been adopted in the conventional VTR, the description of the determination and the means for automatically switching between VHS and S-VHS will be omitted.

In the above embodiment, 10 fH was used as the horizontal sync detection reference pulse of the MUSE signal, but another frequency is selected if it is a frequency different from the low frequency conversion color subcarrier of the VHS signal in the VHS color signal band. You may.

[0030]

As is clear from the above description, according to the automatic mode discrimination switching device of the present invention,
Since the sync signal of a predetermined frequency that is superimposed at the time of recording the USE signal is detected, the MUSE signal and the other signals are automatically discriminated, and the discriminating mode of the entire reproducing apparatus can be automatically set. Therefore, it is no longer necessary to manually operate the changeover switch to check whether the data can be reproduced. Further, in the present invention, since the signal after FM demodulation is not used for discrimination of the MUSE signal, stable operation can be performed without being affected by the demodulation system. Further MU
Since a signal in a low frequency range is used to determine the SE signal, it is also resistant to dropout due to scratches on the magnetic tape.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an automatic mode discrimination switching device of the present invention.

FIG. 2 shows the operation of the automatic mode discrimination switching device of the present invention as a MU.
It is a wave form diagram shown about SE signal re-correction.

FIG. 3 shows the operation of the automatic mode discrimination switching device of the present invention.
FIG. 7 is a waveform diagram showing the time of reproducing an SC signal.

FIG. 4 is a block diagram showing an example of a recording system showing a recording system of a MUSE signal which is a premise of the automatic mode discrimination switching device of the present invention.

FIG. 5 is a block diagram showing an example of a reproduction system to which the automatic mode discrimination switching device of the present invention is applied.

FIG. 6 is a plan view showing a relationship between a rotary drum, a magnetic head and a magnetic tape used in a VTR to which the present invention is applied.

FIG. 7 is a spectrum diagram showing a frequency relationship between a pilot signal and a MUSE signal in a VTR to which the present invention is applied.

FIG. 8 is a spectrum diagram showing a frequency relationship between a synchronization signal and a frequency modulation MUSE signal in a VTR to which the present invention is applied.

FIG. 9 is a timing chart of a recording system in a VTR to which the present invention is applied.

FIG. 10 is a timing chart of a reproduction system in a VTR to which the present invention is applied.

[Explanation of symbols]

10 AD Converter 12 MUSE Signal Processing Circuit 13 Switch Circuit 14 D / A Converter Group 16, 18, 20, 22, 34, 36, 38, 40 Adder 24 VHS / MUSE Recording Processing Circuit 26, 28, 30 MUSE Recording Processing Circuit 32 pilot signal generation circuit 42,70 COLOR / SYNC circuit 46 recording amplifier group 48,48A head switching circuit 52,52A head switching pulse generation circuit 100 BPF 102 waveform shaping circuit 104 first mono-multi 106 second mono-multi 108 gate circuit 110 Retriggerable mono multi

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[Procedure amendment]

[Submission date] September 17, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 11

[Correction method] Added

[Correction content]

FIG. 11 is a waveform diagram showing time axis compression of a MUSE signal.

Claims (1)

[Claims] 1. A signal having a predetermined frequency and a predetermined cycle in the reproduced signal in response to at least one of a plurality of channel signals reproduced from a magnetic recording medium by a plurality of magnetic heads rotating at a predetermined rotation speed. Means for detecting the presence or absence of, and for maintaining a predetermined rotation speed of the plurality of magnetic heads or changing to another predetermined rotation speed according to the output signal of the detecting means, and An automatic mode discriminating and switching device having control signal generating means for generating a control signal for switching and using at least two signal reproducing systems for processing the reproduced plural channel signals according to an output signal of the detecting means.