JPH0136171B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing device, in which a signal obtained by frequency modulating a pilot signal with a control signal is recorded on a control track, and the pilot signal and control signal are separated from the reproduced modulated wave. By using this fluctuation in the pilot signal frequency to remove the wow and flutter components of the audio signal, the control signal and pilot signal can be recorded and reproduced using a single control track, and the influence of level fluctuations of the reproduced modulated wave is eliminated. It is an object of the present invention to provide a magnetic recording and reproducing device that can eliminate wow and flutter components from a reproduced audio signal.

In conventional video tape recorders, a frequency of approximately 30Hz is recorded on a track different from the audio signal during recording.
The control signal of the capstan flywheel is recorded, and during playback, the phase error is detected by comparing the phase of the reproduced control signal and a reference signal from the oscillator with a frequency of approximately 30Hz.
The rotational speed error was detected from the frequency fluctuations generated by the FG and the rotation of the capstan motor was controlled to prevent wow and flutter components from being included in the reproduced audio signal. However, this rotational control of the capstan motor alone does not sufficiently remove wow and flutter components, and the sound quality deteriorates due to the wow and flutter components 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 separation circuit 3, where the vertical synchronization signal with a frequency of approximately 60Hz shown in FIG. 2A is separated and frequency-divided. It is supplied to the container 4. The frequency divider 4 divides this vertical synchronization signal by 1/2 and converts it into a pulse with a frequency of approximately 30 Hz as shown in FIG. 2B.
6, 7 and a phase comparator 8. The phase comparator 8 is a voltage controlled oscillator (hereinafter referred to as "VCO") 9,
Together with the frequency divider 10, it constitutes a phase locked loop (hereinafter referred to as "PLL"), and the oscillation frequency is divided by 1/16384 by the frequency divider 10.
By comparing the phase of the output signal of VCO9 with the pulse with a frequency of approximately 30Hz, the frequency
30Hz pulse and synchronized frequency approximately 491.0KHz
The pulses are taken out and supplied to the counting input terminals of counters 11 and 12, respectively. Furthermore, the monomulti 5 is triggered by the rising edge of the pulse shown in FIG. 2B and generates the pulse shown in FIG. 2C, which is supplied to the reset terminal of the counter 11. Triggered by the rising edge of the pulse, the pulse shown in FIG. 2D is generated and supplied to the reset terminals of the counters 12 and 13, respectively. A pulse-like control signal shown at E is generated and supplied to the modulator 14.

The counter 11 starts counting the pulses supplied from the VCO 9 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 (first pilot signal) having a frequency of approximately 480 Hz as shown in FIG. In this way, 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. 2F can be advanced or delayed. The high frequency components of the pulse shown in FIG. In addition, the counter 12 is a monomulti 6
From the time the pulse shown in Figure 2 D falls
Start counting the pulses supplied from VCO9,
This pulse is frequency-divided by 1/3 to produce a pulse with a frequency of approximately 163.8 KHz, which is supplied to the counting input terminal of the counter 13. The counter 13 starts counting pulses with a frequency of approximately 163.8 KHz from the time when the pulse shown in FIG.
A pulse (second pilot signal) with a frequency of approximately 160 Hz as shown in Figure H is generated and passed through the low-pass filter 16.
supply to. In this way, by adjusting the time constant of the monomulti 6 and changing the pulse width of FIG. 2D, the phase of the pulse shown in FIG. 2H can be advanced or delayed. The pulse shown in FIG. 2H has its harmonic components removed by the low-pass filter 16, and is converted into a sine wave with a frequency of about 160 Hz shown in FIG. 2I, and is supplied to the modulator 14.

The modulator 14 receives the second
Control is performed to output a sine wave with a frequency of approximately 480 Hz from the low-pass filter 15 during the period when the pulse shown in Figure E is at a low level, and to output a sine wave with a frequency of approximately 160 Hz from the low-pass filter 16 during the period when the pulse is at a high level. Frequency modulation (frequency shift keying method) is performed using the signal as a modulation signal to obtain a modulated wave as shown in Fig. 2 J, which is sent to the amplifier 1.
Supply to 7. The modulated wave shown in FIG. 2 J is
Point a where the frequency changes from approximately 480Hz to approximately 160Hz by adjusting the time constants of monomultis 5 and 6
By changing the time constant of the monomulti 7, it is possible to change the phase at point b where the frequency changes from approximately 160 Hz to approximately 480 Hz. This modulated wave is amplified in an amplifier 17 and then mixed in a mixer 18.
The signal is superimposed on the bias signal from the bias oscillator 19 and supplied to the magnetic head 20, where it is sent to the magnetic tape 21.
recorded on the longitudinal control track. At the same time, the audio signals of the first channel and the second channel coming in from the input terminals 22a and 22b are amplified by amplifiers 23a and 23b, respectively, and then sent to mixers 24a and 24b, respectively, to the bias oscillator 1.
The bias signal from 9 is superimposed on the magnetic head 2.
5a and 25b, and are respectively recorded on two audio tracks different from the control track in the longitudinal direction of the magnetic tape 21.

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 28 denotes an input terminal into which a modulated wave as shown in FIG. Here, the waveform is shaped into the pulse shown in FIG. 4B, and then supplied to the monomulti 31 and the band filter 32. The Mono Multi 31 is a retrigger type, and the metastable period (period in which the output pulse is at a high level) when triggered once is 1.04 ms (half cycle of approximately 480 Hz frequency) or more, and 3.17 ms (half cycle of approximately 160 Hz frequency). Since the pulse frequency shown in FIG. 4B is at a low level only at the approximately 160 Hz portion of the pulse, a signal with the waveform shown in FIG. Supplied to the input terminal of Mono multi 33 is 6.25ms (frequency approximately 160Hz
Monomulti31 has a metastable period of more than one period)
is triggered by the output signal of , generates a pulse shown in FIG. The AND circuit 34 inverts the signal from the monomulti 31 and performs a logical sum with the pulse from the monomulti 33 to generate a pulse-like control signal shown in FIG.
Output from Here, if the pulse shown in FIG. 4B drops out, the monomulti 31 becomes low level and even if the monomulti 33 outputs a pulse, dropout will hardly occur following the period when this pulse is high level. No false control signals are generated.

Also, the pulse shown in Figure 4B has a pass band of 480
Hz, and here the fundamental wave of the pulse with a frequency of approximately 480 Hz and the frequency of approximately 160 Hz are supplied to the band filter 32.
The third harmonic of the Hz pulse is extracted and becomes a signal with the waveform shown in Figure 4F, which is supplied to the zero cross detector 36, where the waveform is shaped into a pulse with a frequency of approximately 480Hz as shown in Figure 4G. It is used as a pilot signal for switch SW terminal SW _a and PLL3.
7. The PLL 37 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 dropped-out pulses.
Output to terminal SW _b of switch SW. switch
SW is a switch that connects terminals SW _a and SW _c when there is little dropout of the pilot signal, and connects terminals SW _b and SW _c when there is a lot of dropout. The pulsed 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 obtain the frequency
Supplied to PLL40 as an 80Hz 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. A frequency fluctuation of approximately 1 Hz or more (wow/flutter) is detected in PLL 40 from a pulse with a frequency of approximately 80 Hz, and PLL 40
It is taken out as a voltage change from a built-in loop filter and supplied to the VCO 41, and the VCO 41 changes its oscillation frequency according to the wow and flutter. The signal generated by this 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 42 and 43 have the same characteristics and only two BBDs can be driven by one clock drive circuit, two clock drive circuits are used. If one clock drive circuit can drive three BBDs, one clock drive circuit is sufficient. The clock pulse obtained by the clock drive circuit 42 is
The signal is supplied to the BBD 39, and the BBD 39 removes the wow and flutter of approximately 1 Hz or more from the pilot signal containing the wow and flutter with a frequency of approximately 480 Hz by varying its delay time, and then is supplied to the zero cross detector 44, where First, a clock component is removed by a low-pass filter (not shown), a zero cross is detected, the pulse is shaped into a pulse, and the pulse 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 remove wow and flutter components of approximately 1 Hz or more, it is necessary to widen the variable range of the delay time of BBD39, 52, and 53.
The delay times 39, 52, and 53 are set long. For this reason, for high frequency wow and flutter components (for example, 10Hz or higher), the phase lag due to the delay becomes large and cannot be removed, and the BBD
The pilot signal which is the output of 39, 52, 53,
The audio signals of the first and second channels similarly contain this high frequency wow and flutter component.

The pilot signal with a frequency of approximately 480 Hz, which has low frequency wow and flutter components removed by the BBD 39 and whose waveform is shaped by the zero cross detector 44, is sent to the PLL.
45. This pulse with a frequency of approximately 480 Hz is detected by the PLL 45 as a frequency fluctuation (wow/flutter) of approximately 10 Hz or more, is extracted as a voltage change by a loop filter built in the PLL 45, and is supplied to the VCO 58. The VCO 58 changes its oscillation frequency according to the flutter and supplies it to the clock drive circuit 60, where the waveform is shaped and the resulting clock pulse is output to the BBD 56, 5.
7. 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, remove the wow and flutter components of 10 to 50 Hz from the audio signals of the first and second channels, and supply the signals to the low-pass filters 61 and 62. do. First,
The audio signals of the second channel are each passed through a low-pass filter 6.
1 and 62, the mixed clock components are removed by BBDs 56 and 57, and then amplified by amplifiers 63 and 64, the output level is adjusted by variable resistors 65 and 66, and output from output terminals 67 and 68.

Since the pilot signal is frequency-modulated by the control signal during recording, the pressure at which the magnetic tape 21 contacts the magnetic head changes due to fluctuations in the tape tension during playback, resulting in a change in the reproduced modulated wave. Even if the level fluctuates, it does not affect the control signal and pilot signal that are extracted.

As described above, the magnetic recording/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 at an integer multiple of the control signal frequency. a modulating means for obtaining a modulated wave by frequency-modulating a pilot signal, which is a frequency, by a control signal; a recording means for recording the modulated wave on a longitudinal control track of a magnetic recording medium different from an audio track; A reproducing means for reproducing a modulated wave, a demodulating means for demodulating a control signal from the regenerated modulated wave, and a pilot that performs band control and zero cross detection of the regenerated modulated wave and synchronizes with the demodulated control signal. A band limit and zero cross detection means for extracting a signal, and a wow and flutter removal means for detecting frequency fluctuations of a pilot signal extracted from a reproduced modulated wave and removing wow and flutter components contained in an audio signal reproduced from an audio track. Therefore, it is possible to record and reproduce control signals and pilot signals using a control track on which conventionally only control signals were recorded and reproduced, and it is not affected by level fluctuations of the reproduced modulated wave due to fluctuations in tape tension. It has the advantage of being able to obtain a distortion-free audio signal by removing the wow and flutter components of the reproduced audio signal from the frequency fluctuations of the reproduced pilot signal.

[Brief explanation of drawings]

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 J 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. FIGS. 4A to 4G are time charts showing signal waveforms at various parts of the circuit shown in FIG. 3. 1, 22a, 22b, 28, 46, 47... Input terminal, 2... Synchronizing signal separation circuit, 3... Vertical synchronizing signal separation circuit, 4, 10, 38... Frequency divider,
5, 6, 7, 31, 33...mono multi, 8...
Phase comparator, 9, 41, 58...VCO, 11,
12, 13...Counter, 14...Modulator, 1
5, 16, 50, 51, 54, 55, 61, 62
...Low pass filter, 17, 23a, 23b, 2
9, 63, 64...Amplifier, 18, 24a, 24
b...Mixer, 19...Bias oscillator, 20,
25a, 25b...magnetic head, 21...magnetic tape, 30, 36, 44...zero cross detector,
34...AND circuit, 35,67,68...Output terminal, 37,40,45...PLL, 42,43,
60...Clock drive circuit, 39, 52, 5
3, 56, 57...BBD.

Claims (1)

[Claims] 1. An audio signal is recorded on an audio track in the longitudinal direction of a magnetic recording medium, and a pilot signal, which is generated from a control signal obtained from a vertical synchronization signal of a video signal and has a frequency that is an integral multiple of the control signal frequency, is changed in frequency by the control signal. a modulating means for modulating to obtain a modulated wave; a recording means for recording the modulated wave on a control track in the longitudinal direction of the magnetic recording medium different from the audio track; and a recording means for reproducing the modulated wave from the control track. a reproducing means, a demodulating means for demodulating a control signal from a reproduced modulated wave, and a band limiter for band-limiting and zero-crossing the reproduced modulated wave and extracting a pilot signal synchronized with the demodulated control signal. and a zero-cross detection means, and a wow and flutter removal means for detecting frequency fluctuations in a pilot signal extracted from the reproduced modulated wave and removing wow and flutter components contained in the audio signal reproduced from the audio track. A magnetic recording/reproducing device characterized by: