JPS6256593B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording/reproducing device, in which a signal obtained by modulating a pilot signal with a control signal is recorded on a control track, and the pilot signal is separated from the reproduced modulated wave signal to reproduce the pilot signal. To provide a magnetic recording and reproducing device that can record and reproduce control signals and pilot signals with a single track by removing wow and flutter from an audio signal using frequency fluctuations, and which can eliminate wow and flutter from the reproduced audio signal. The purpose is to provide.

In conventional video tape recorders, a frequency of approximately 30Hz is recorded on a track different from the audio signal during recording.
record the control signal, and compare the phase of the reproduced control signal with the rotating drum pulse or the reference signal of the reference signal generator to control the rotation of the capstan motor, and generate the FG of the capstan flywheel. The rotational speed of the capstan motor was controlled by detecting the rotational speed from the signal from the device to prevent wow and flutter from being included in the reproduced audio signal. However, this rotational control of the capstan motor alone does not sufficiently remove jitter, and has the disadvantage that the sound quality deteriorates due to wow and flutter contained in the reproduced audio signal.

The present invention eliminates the above-mentioned drawbacks, and one embodiment thereof will be described below with reference to the drawings.

FIG. 1 shows a block system diagram of one embodiment of the recording system of the apparatus of the present invention. In the figure, 1 is an input terminal to which a video signal is input, and this video signal is supplied to a synchronization signal separation circuit 2. The horizontal synchronization signal and vertical synchronization signal extracted from the video signal by the synchronization signal separation circuit 2 are supplied to the vertical synchronization signal separation circuit 3, where the vertical synchronization signal with a frequency of approximately 60Hz shown in FIG. 2A is separated and separated. It is supplied to the frequency generator 4. Frequency divider 4 divides this vertical synchronization signal by 1/2 and divides the frequency of this vertical synchronization signal into
This is supplied to monostable multivibrators (hereinafter referred to as "monomulti") 5 and 6 and a phase comparator 7 as pulses having a frequency of approximately 30 Hz as shown in FIG. The phase comparator 7 constitutes a phase locked loop (hereinafter referred to as "PLL") together with a voltage controlled oscillator (hereinafter referred to as "VCO") and a frequency divider 9, and the frequency divider 9 divides the oscillation frequency by 1/1. Divided by 16384
By comparing the phase of the output signal of VCO8 with a pulse with a frequency of approximately 30Hz, the output signal of VCO8 is
A pulse having a frequency of approximately 491.0 kHz that is synchronized with the 30 Hz pulse is extracted and supplied to the counting input terminal of the counter 10. Also, Monomulti 5 is shown in Figure 2 B.
The second pulse is triggered by the rising edge of the pulse shown in
The pulse shown in Figure C is generated and supplied to the reset terminal of the counter 10, and the monomulti 6 is operated as shown in Figure 2B.
Figure 2D is triggered by the rising edge of the pulse.
A pulse-like control signal shown in is generated and supplied to the modulator 11.

The counter 10 starts counting the pulses supplied from the VCO 8 from the time when the pulse shown in FIG. 2C from the monomulti 5 falls, and divides this pulse by 1/
The frequency is divided by 1024 to generate a pulse (pilot signal) having a frequency of approximately 480 Hz as shown in FIG. Here, by adjusting the time constant of the monomulti 5 and changing the pulse width of the pulse shown in FIG. 2C, the phase of the pulse shown in FIG. 2E can be advanced or delayed. Second
The pulse shown in FIG. The modulator 11 modulates the amplitude of this sine wave with a frequency of approximately 480 Hz using the pulse from the monomulti 6, and as shown in FIG. Frequency at which the amplitude is small
A modulated wave of 480 Hz is generated and supplied to the amplifier 13. The phase of the modulated wave shown in FIG. By changing the pulse width in FIG. 2D, the phase at point b, where the amplitude changes from small to large, can be changed, and the amplitude c can be set at an appropriate level in the modulator 11.
This modulated wave is amplified in an amplifier 13, then superimposed on a bias signal from a bias oscillator 15 in a mixer 14, supplied to a magnetic head 16, and recorded on a control track in the longitudinal direction of a magnetic tape 17. Along with this, input terminals 18a and 18b
The incoming audio signals of the first channel and the second channel are amplified by amplifiers 19a and 19b, respectively, and then superimposed on the bias signal from the bias oscillator 15 in mixers 20a and 20b, respectively, and supplied to magnetic heads 21a and 21b. magnetic tape 17
are recorded on two audio tracks different from the control track in the longitudinal direction.

FIG. 3 shows a block system diagram of one embodiment of the reproducing system of the magnetic recording/reproducing apparatus according to the present invention. Reference numeral 30 denotes an input terminal into which a modulated wave as shown in FIG. There, long-cycle level fluctuations are removed, the signal is amplified, and the signal is supplied to a demodulator 32 and a limiter 33. The demodulator 32 performs full-wave rectification on this modulated wave to obtain the waveform shown in FIG. 4A, smoothes it to obtain the waveform shown in FIG. The zero cross detector 34 compares the waveform shown in FIG.
The control signal shown in FIG. C is detected and outputted from the output terminal 35. Here, the detection point e of the control signal is the amplitude change point a in FIG. 4A, which is the point where the control signal was generated during recording.
There is a phase shift f from I can do it.

Further, the modulated wave from the AGC amplifier 31 is kept constant in amplitude by a limiter 33, and then supplied to a zero cross detector 36, where a pulse-shaped control signal is generated which becomes a high level when it is above 0V and a low level when it is below 0V. Terminal SW ₁ of switch SW
and is supplied to the PLL 37. The PLL37 is set to follow the frequency fluctuations of the supplied pulse-like pilot signal, and even if the pilot signal drops out, it continues to oscillate within the variable range of the built-in VCO and generates the dropped-out pulses to control the switch SW. Output to terminal SW ₂ . The switch SW is a switch that connects terminals SW ₁ and SW ₃ when there is no dropout of the pilot signal, and connects terminals SW ₂ and SW ₃ when there is a dropout. The resulting pilot signal is supplied to a frequency divider 38 and a bucket brigade device (hereinafter referred to as "BBD") 39. The frequency divider 38 divides the above pulse by 1/6 to give a frequency of approximately 80Hz.
is supplied to the PLL 40 as a pulse. Since it is difficult to detect low frequency fluctuations with a pilot signal having a frequency of approximately 480 Hz, the frequency is divided to a frequency of approximately 80 Hz. Frequency fluctuations (wow and flutter) of approximately 1 Hz or more are detected by the PLL 40 from pulses with a frequency of approximately 80 Hz, and are extracted as voltage changes by the loop filter built into the PLL 40.
The signal is supplied to the VCO 41, and the VCO 41 changes its oscillation frequency according to the wow and flutter. this
The signal generated by the VCO 41 is supplied to clock drive circuits 42 and 43, where the waveform is shaped into a clock pulse for BBD. Since the clock drive circuits 41 and 43 have the same characteristics and only two BBDs can be driven by one clock drive circuit, two clock drive circuits are used. 1
If you can drive three BBDs with one clock drive circuit, you only need one clock drive circuit. Clock drive circuit 42
The clock pulse obtained in is supplied to the BBD 39, and the BBD 39 adjusts the frequency including the wow and flutter by varying the delay time to about 480.
After removing wow and flutter of about 1 Hz or more from the Hz pilot signal, it is supplied to a zero-cross detector 44, where the clock component is first removed by a low-pass filter (not shown), and then zero-cross is detected and shaped into a pulse. and is supplied to the PLL 45.

In addition, the first
The input sensitivity of the channel and second channel audio signals is adjusted by variable resistors 48 and 49, respectively, and high-frequency components that cannot be transferred by the BBD are removed by low-pass filters 50 and 51, and the signals are supplied to BBDs 52 and 53, respectively. . These BBDs 52 and 53 have the same number of stages as the BBD 39, and the clock drive circuit 43 mentioned above has the same number of stages as the BBD 39.
The delay time is varied by a clock pulse supplied from the audio signals of the first and second channels to remove wow and flutter of approximately 1 Hz or more from the audio signals of the first and second channels, respectively, and the resulting signals are supplied to low-pass filters 54 and 55. 1st, 2nd
The audio signals of the channels are respectively passed through low pass filters 54,
55 removes clock components mixed in BBDs 52 and 53, and supplies the clock components to BBDs 56 and 57.

Here, in order to eliminate wow and flutter of approximately 1 Hz or more, it is necessary to widen the variable range of the delay time of BBD39, 52, and 53, and BBD3
The delay times of 9, 52, and 53 are set long. Therefore, for wow and flutter with high frequency (for example, 10Hz or higher), the phase lag due to the delay becomes large and cannot be removed, and the BBD3
The pilot signals output from the channels 9, 52, and 53 and the audio signals of the first and second channels similarly contain this high-frequency flutter component.

The pilot signal having a frequency of approximately 480 Hz, which has had low frequency wow and flutter removed by the BBD 39 and whose waveform has been shaped by the zero cross detector 44, is supplied to the PLL 45. This pulse with a frequency of approximately 480Hz is the PLL
45, a frequency fluctuation (flutter) of about 10 Hz or more is detected, extracted as a voltage change by a loop filter built in the PLL 45, and supplied to the VCO 58. The VCO 58 changes its oscillation frequency in accordance with the flutter and supplies it to a clock drive circuit 60, where the waveform is shaped and the resulting clock pulse is supplied to the BBDs 56 and 57. The BBDs 56 and 57 have the same number of stages and are considered to have an optimal delay time for removing flutter in the range of 10 to 50 Hz. The BBDs 56 and 57 vary the delay time using the clock pulses from the clock drive circuit 60, respectively, and are connected to the audio signals of the first and second channels.
Low-pass filter 6 removes flutter from 10 to 50Hz
1,62. The audio signals of the first and second channels are passed through low-pass filters 61 and 62, respectively, to BBD5.
After the mixed clock components are removed by the steps 6 and 57, the clock components are amplified by the amplifiers 63 and 64, and the variable resistors 65,
The output level is adjusted at 66 and the output terminals 67, 6
Output from 8.

Here, the phase at point a where the modulated wave changes from large amplitude to small amplitude shown in FIG. 2F during recording,
There is a relationship as shown in FIG. 5 between the wow and flutter contained in the reproduced audio signal. Figure 5 shows the reproduced audio signal by changing this phase by ±π [rad], assuming that the phase is 0 when the point where the large amplitude sine wave shown in Figure 2 F takes its minimum value is the above-mentioned change point a. This is a measurement of the wow and flutter included in the figure. As is clear from FIG. 5, when the phase of change point a is approximately 0, wow and flutter are the least.
The phase of this change point a is shown in Figure 1 by the monomulti 5
It can be made approximately 0 by changing the time constant of .

As described above, the magnetic recording and reproducing apparatus according to the present invention records an audio signal on an audio track in the longitudinal direction of a magnetic recording medium, and generates a control signal obtained from a vertical synchronization signal of a video signal, which is an integral multiple of the control signal frequency. A modulated wave is obtained by modulating a pilot signal with a frequency of The control signal is demodulated and a pilot signal synchronized with the control signal is separated from the modulated wave, and the frequency fluctuation of this pilot signal is detected to eliminate wow and flutter contained in the audio signal reproduced from the audio track. In order to eliminate this, the control signal and pilot signal can be recorded and reproduced using a control track on which conventionally only the control signal was recorded and reproduced, and the wow and flutter, which could not be eliminated in the past, can be removed from the frequency fluctuation of the pilot signal and distorted. It has the advantage that it is possible to obtain an audio signal free of noise, and that wow and flutter can be minimized by adjusting the phase of the pilot signal and control signal.

[Brief explanation of the drawing]

Fig. 1 is a block system diagram of one embodiment of the recording system of the apparatus of the present invention, Fig. 2 A to F are time charts showing signal waveforms of various parts of the circuit shown in Fig. 1, and Fig. 3 is a reproduction system of the apparatus of the present invention. 4A to 4C are time charts showing the signal waveforms of each part of the circuit shown in FIG. 3. FIG. 5 shows the phase and reproduction at the point where the modulation signal changes from large amplitude to small amplitude. FIG. 3 is a diagram showing the relationship between wow and flutter remaining in an audio signal. 1, 18a, 18b, 30, 46, 47... Input terminal, 2... Synchronization signal separation circuit, 3... Vertical synchronization signal separation circuit, 4, 9, 38... Frequency divider, 5,
6...Mono multi, 7...Phase comparator, 8,4
1,58...VCO, 10...Counter, 11...
...Modulator, 12, 50, 51, 54, 55, 6
1, 62...low-pass filter, 13, 19a, 19
b, 63, 64...Amplifier, 14, 20a, 20
b...Mixer, 15...Bias oscillator, 16,
21a, 21b...Magnetic head, 17...Magnetic tape, 31...DGC amplifier, 32...Double modulator,
33... Limiter, 34, 36, 44... Zero cross detector, 37, 40, 45... PLL, 39,
52, 53, 56, 57...BBD, 42, 4
3, 60...Clock drive circuit, 67, 68
...Output terminal.

Claims (1)

[Claims] 1. A pilot signal generated from a control signal obtained from a vertical synchronization signal of a video signal and having a frequency that is an integral multiple of the control signal frequency while recording an audio signal on an audio track in the longitudinal direction of a magnetic recording medium. is modulated by the control signal to obtain a modulated wave, the modulated wave is recorded on a control track in the longitudinal direction of the magnetic recording medium that is different from the audio track, and the modulated wave reproduced from the control track is demodulated. At the same time, a pilot signal synchronized with the control signal is separated from the modulated wave, and frequency fluctuations of the pilot signal are detected to detect wow and flutter contained in the audio signal reproduced from the audio track. A magnetic recording/reproducing device characterized by removing. 2. The magnetic recording and reproducing apparatus according to claim 1, wherein the modulated wave is obtained by amplitude modulating the pilot signal using the control.