JPH05274752A - Tracking control system for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reproduce the tape of a PCM sound signal with high definition by monitoring a HIFI sound head output and track-control so that the error rate of a PCM sound signal becomes minimum when an O-QDPSK signal is detected. CONSTITUTION:Only the O-QDPSK signal is picked up from the signal of a HIFI sound head amplifier circuit 42 by a BPF 101, and a DC voltage detected by an O-QDPSK signal detection circuit 102 is compared with a reference voltage by a comparator 104 and whether a tape is the tape recorded with the PCM sound signal or not is decided. When the tape is recorded with the PCM sound signal, an automatically tracking system 50 tracking-controls so that the number of pulse of an error pulse counter 107 measuring the number of error pulse outputted from a signal processing circuit 106 for converting digital data to a sound signal per unit time becomes minimum. Thus, the tape recorded with the PCM sound signal is reproduced with high definition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control system for a magnetic recording / reproducing apparatus, and more particularly to a magnetic recording / reproducing apparatus for superposing and recording a video signal, a HIFI audio signal and a PCM audio signal on a rotary video head during reproduction. H
The present invention relates to a tracking control system capable of tracking an IFI voice head at an optimum position.

[0002]

2. Description of the Related Art FIG. 2 is a conventional magnetic recording / reproducing apparatus, for example, a type for recording / reproducing a video signal, a HIFI audio signal and a PCM audio signal, which are described in Japanese Patent Laid-Open No. 1-105301. FIG. 3 is a block diagram showing the configuration of the magnetic recording / reproducing apparatus of FIG.

In FIG. 2, the color video signal of the standard color system input to the video signal input terminal 125 is supplied to the recording video signal processing circuit 126, and the recording video signal processing circuit 126 synchronizes the luminance signal component of the video signal. It is FM-modulated so that the front end level is 5.4 MHz and the white peak level is 7.0 MHz, and converted into a Y-FM signal. The color signal component of the video signal has a carrier frequency of about 629K.
The low-frequency conversion is performed so that the frequency becomes Hz, and the signal is converted into a C (L) signal. Thereafter, the Y-FM signal and the C (L) signal are added, and the recording amplifier 127, a rotary transformer (not shown) built in the rotary drum, and a rotary head 128 for video are added.
It is recorded on the magnetic tape 143 via a and 128b.

On the other hand, the recording video signal processing circuit 126 supplies the color video signal as it is to the sync signal separation circuit 129, and the sync signal separation circuit 129 separates the vertical sync signal from the color video signal and supplies it to the servo circuit 130. To do. The servo circuit 130 generates a control pulse signal according to the vertical synchronizing signal and supplies it to the control head 142. The control head 142 forms a control track along the longitudinal direction of the magnetic tape and records the control pulse signal.

In addition, the rotary heads 128a and 128 for video are used.
The FM video signal and the low-frequency conversion color signal reproduced in b are
It is amplified by the switching amplifier 156 and the preamplifier 157, and is converted into a standard color video signal by the reproduction video signal processing circuit 158.

Analog voice signal input terminals 131a, 13
The left-channel analog audio signal and the right-channel analog audio signal input to 1b are input to switches 169a, 16
Ordinary HIFI audio signal recording processing circuit 20 via 9b
By 0, it is modulated into an FM signal having a carrier wave of 1.3 MHz and 1.7 MHz and input to the mixer 175.

On the other hand, the analog audio signal input terminal 131
The analog audio signals input to a and 131b are converted into low-pass filters 132a and 132a by switches 169a and 169b.
After being input to 132b and the unnecessary high frequency components exceeding the audible frequency band are removed, the sampling frequency is, for example, 4
After passing through the 8 KHz sample and hold circuits 133a and 133b, the A / D converters 134a and 134b linearly quantize the quantization bit number to 16 bits and then encode the P bit.
It becomes a CM voice signal.

This PCM audio signal is input to the encoder 135, subjected to time-base compression and interleave processing, and then added with parity for error correction to a bit rate of 2.62 Mb.
Converted to ps serial data. This serial data is converted by an offset type four-phase differential phase modulation modulator 136 into an offset type four-phase differential phase modulation signal (hereinafter, O-QDPSK signal) having a carrier of about 3.0 MHz. This O-QDPSK signal is input to the bandpass filter 137 to remove unnecessary harmonic components, passes through the bandpass filter 137, and then is input to the mixer 175.

In the mixer 175, the FM audio signal from the HIFI audio signal recording processing circuit 200 and the band filter 13 are supplied.
The O-QDPSK signal from No. 7 is frequency division multiplexed and supplied to the bias superposition circuit 139. Bias superposition circuit 13
In No. 9, the output signal of the mixer 175 is amplified to a level required for recording, and then a high frequency bias signal of about 11 MHz is superimposed and supplied to the rotary heads 141a and 141b for voice and recorded on the magnetic tape 143.

The rotary heads 141a and 141 for voices are used.
Reference numeral b denotes a rotary cylinder (not shown) which is mounted 180 ° opposite to the rotary surface of the rotary cylinder and has rotary heads for image 128a, 128a.
It is attached by a certain angle ahead of the attachment position of 8b. In addition, the rotary heads 141a and 141 for voices
One of the azimuth angles of b is + 30 ° and the other is -30 °, and the azimuth angles of the image rotary heads 128a and 128b are set to + 6 ° and -6 °, respectively. Such voice rotary heads 141a, 14
1b, the O-QDPSK-modulated digital audio signal and the HIFI audio signal travel while being wound around the rotary cylinder in an angle range of slightly over 180 °.
High frequency bias recording is performed up to the deep portion of the magnetic layer to form an audio track, and then a video signal for recording is recorded by the video rotary heads 128a and 128b on the surface layer of the magnetic layer on the audio track to form a video track. To do.
The cross stroke between the recording video track and the recording audio track is reduced by setting the azimuth angle provided on each head.

On the other hand, regarding the reproducing system for reproducing the magnetic tape 143 recorded by the recording system of the above-mentioned magnetic recording / reproducing apparatus, audio is recorded from the audio track formed in the deep portion of the magnetic layer of the recorded magnetic tape 143. Rotating head 14
It is reproduced by 1a and 141b. The reproduced audio signal obtained by mixing the O-QDPSK-converted digital audio signal and the HIFI audio signal is amplified by the audio preamplifier 155, and the HIFI audio signal is divided into two left and right channels, and the HIFI audio signal reproduction processing is performed. Circuit 30
It is converted into an analog voice signal by 0.

The O-QDPSK modulated signal is also supplied to the reproduction equalizer 180 to enhance the high frequency component attenuated during recording. The output signal of the reproduction equalizer 180 is the bandpass filter 1
The unnecessary component of the O-QDPSK signal of the 3 MHz carrier is removed by 60, and then the O-QDPSK demodulator 16
It is converted into a digital signal by 1. This digital signal is input to the decoder 162, error correction is performed by the error correction parity added at the time of recording, and then deinterleave and D / A converters 163a and 163 (not shown).
b, the deglitcher circuits 164a and 164b, and the low-pass filters 165a and 165b to be converted into two analog audio signals of the left channel and the right channel and output.

Next, a conventional automatic tracking control system will be described. Among the conventional automatic tracking control systems, for example, those disclosed in Japanese Patent Publication No. 55-51256 or Japanese Patent Publication No. 55-51257 are
This is an automatic tracking control system that uses only FM video signals used in VTRs and the like. In addition, the tracking control system shown in FIG.
FIG. 3 is a block diagram of an automatic tracking control system that applies both HIFI audio signals recorded on an IFI audio signal track.

In the figure, a video signal and a control signal used for automatic tracking adjustment during reproduction are recorded on the magnetic tape 11, and the rotary video head 14 is recorded.
a, 14b, and the fixed control head 15 respectively reproduce. The rotary video heads 14a and 14b for reading the magnetic tape are mounted on a rotary drum 16, and the rotary drum 16 is rotated at a predetermined rotation speed by a drum motor 18 controlled by a drum motor drive circuit 17.

On the other hand, the magnetic tape 11 is driven by a capstan motor 20. That is, the capstan drive control circuit 21 has a frequency generator (FG) that generates a frequency signal proportional to the rotation speed of the capstan motor 20, and outputs the FG signal output from this frequency generator to the capstan motor 20. Apply to. Capstan motor 20
Is controlled by the FG signal applied by the capstan drive control circuit 21, and the magnetic tape 11 is driven in the direction of arrow 23 shown in the figure.

The reference signal generator 30 includes servo control circuits 31 and 3 for both the rotary drum 16 and the capstan 22.
2 provides a reference signal for operating the 2. In the case of the NTSC system, the reference signal generator 30 is composed of a 3.58 MHz oscillation circuit 30a and down counters 30c and 30d for counting down the oscillation signal from the oscillation circuit 30a.

The drum servo control circuit 31 correctly rotates the rotary drum 16 at 1800 rpm, and the rotary drum 1 is rotated.
Rotating video head 14 mounted opposite to 6
The rotation phases of a and 14b are controlled. The drum servo control circuit 31 includes a drum phase comparison circuit 31a, a drum frequency comparison circuit 31b, a drum flip-flop signal creation circuit (D-FF) 31c, and the comparison circuits 31a, 31.
The output signal b is mixed and smoothed by a mixing filter 31d.

Capstan (CP) servo control circuit 32
Correctly rotates the capstan 22 and the magnetic tape 11
Of the CP phase comparison circuit 32a, the CP frequency comparison circuit 32b, and the mixing filter 32c for mixing and smoothing the outputs of the comparison circuits 32a, 32b.

The delay circuit 33 is a drum phase comparison circuit 31.
Delay the reference signal of a. A 1/2 frequency division vertical reference signal generation circuit (1/2 V generation circuit) 34 generates a 1/2 frequency division vertical reference signal based on the delay signal from the delay circuit 33. This ½ divided vertical reference signal is used in the arithmetic unit to generate the tracking control signal in the microcomputer circuit 49.

The delay circuit 35 is a circuit for delaying the drum flip-flop signal from the drum flip-flop signal generating circuit 31c to generate a HIFI head switch signal, and its output signal is sent to the HIFI voice head amplifier circuit 42. It has been applied. The rotary HIFI audio heads 40a and 40b are attached to the rotary drum 16, and as described above, the rotary HIFI voice heads 40a and 40b are attached to be offset from the rotary video heads 14a and 14b by a certain angle. For example, FIG. 4 shows a rotary video head mounted on a rotary cylinder of such a conventional magnetic recording / reproducing apparatus and a HIFI.
It is a figure which shows the example of arrangement | positioning of an audio head.

The video head amplifier circuit 41 amplifies the video signals from the rotary video heads 14a and 14b,
The signalized video signal is output to the video signal envelope detection circuit 43. The video signal envelope detection circuit 43 detects the FM-converted video signal, and its output is applied to the video envelope A / D conversion circuit 45. The video envelope A / D conversion circuit 45 converts the video envelope detection signal, which is an analog signal, into a digital signal. The video signal memory circuit 47 stores the digitized video envelope signal.

Similarly, the HIFI voice head amplifier circuit 4
Reference numeral 2 denotes an HI which is an FM signal, which amplifies a HIFI audio signal output from the rotary HIFI audio heads 40a and 40b.
The FI audio signal is output to the HIFI audio signal envelope detection circuit 44. The HIFI audio signal envelope detection circuit 44 detects the amplitude of the FM signal HIFI audio signal, and the output thereof is applied to the HIFI audio / video envelope detection signal A / D conversion circuit 46. The HIFI audio / video envelope detection signal A / D conversion circuit 46 converts the analog HIFI audio / envelope detection signal into a digital signal. The HIFI signal memory circuit 48 stores the digitized HIFI envelope signal.

Then, the microcomputer 49 adds the digital signals from the memory circuits 47 and 48 by an adder to create a discriminant value, and the discriminant value and the 1
The output signal from the / 2 frequency division vertical reference signal generation circuit 34 is compared by an arithmetic unit, and a tracking control signal is created by the output signal of the arithmetic unit.

The operation of the conventional tracking control system of the magnetic recording / reproducing apparatus configured as described above will be described.

First, a drum frequency generator (referred to as DRUM-FG) attached to the drum motor 18, for example, 7
20 Hz) FG signal and 3.58 MHz oscillator circuit 30
The output signal of the down counter 30c that counts down the reference signal from a is compared with the drum frequency comparison circuit 31b.
Compare with. Further, a DRUM-FG pulse signal (30 Hz) generated by magnetically detecting the rotational phase of the head by the magnet piece 25 attached to the rotary drum 16 and the drum phase detection head 26, 3.58
The drum phase comparison circuit 31a compares the output signal of the down counter 30b that counts down the reference signal from the MHz oscillation circuit 30a. The output signals of the drum frequency comparison circuit 31b and the drum phase comparison circuit 31a are mixed and smoothed by the mixing filter 31d, and applied to the drum motor drive circuit 17 to control the speed and the phase.
Rotate at 00 rpm.

Next, a capstan frequency generator attached to the capstan motor 19 (called CP-FG,
For example, the FG signal of 720 Hz) and the output signal of the down counter 30d that counts down the reference signal from the 3.58 MHz oscillation circuit 30a are compared by the capstan frequency comparison circuit 32b. The control track signal of the magnetic tape 11 is detected by the control head 15, and the control track signal amplified by the control track signal amplifier circuit 24 and the tracking control signal generated by the microcomputer 49 are compared with each other by a capstan phase comparison circuit. 32a for comparison. The capstan frequency comparison circuit 32b and the capstan phase comparison circuit 3
The output signal of 2a is mixed and smoothed by the mixing filter 32c,
It is applied to the capstan drive control circuit 21 to control the speed and phase to maintain a stable tape speed.

On the other hand, the output signal of the drum flip-flop signal generating circuit 31c is applied to the video head amplifier circuit 41 as a head switch signal for the rotary video head, and switches the rotary video heads 14a and 14b. Further, as shown in FIG. 4, the delay circuit 35 delays the flip-flop signal corresponding to the HIFI voice heads 40a and 40b mounted with the mounting angle of 60 °, and outputs the flip-flop signal to the HIFI voice head amplifier. It is applied to the circuit 42. In this way, the video head amplifier circuit 4
1. The video signal and the HIFI audio signal amplified by the HIFI audio head amplifier circuit 42 are switched according to the phase of each head, and a continuous envelope signal is taken out.

The video signal converted into the FM signal and amplified by the video head amplifier circuit 41 is detected by the video signal envelope detection circuit 43, and the detected analog envelope signal is digitalized by the video envelope A / D conversion circuit 45. The converted signal is stored in the memory circuit 47. Similarly, the HIFI audio signal amplified by the HIFI audio head amplifier circuit 42 is detected by the HIFI audio signal envelope detection circuit 44, and the detected analog envelope signal is digitalized by the HIFI audio envelope signal A / D conversion circuit 46. It is converted into a signal and stored in the memory circuit 48.

The two voltage values of the memory circuits 47 and 48 are applied to the microcomputer 49 and added by the adder. In this microcomputer 49, the drum phase comparison circuit 31a passes through the delay circuit 33
1/2 created by the frequency-divided vertical reference signal generation circuit 34, 1 /
A tracking control pulse signal is created with reference to the divided-by-2 vertical reference signal (30 Hz), and this tracking control pulse signal is applied to the capstan phase comparison circuit 32a to perform phase comparison with the control track signal. In the conventional magnetic recording / reproducing apparatus, the image quality is often prioritized over the sound quality with respect to the tracking control signal, and the envelope of the video signal is also prioritized with respect to the calculation of the microcomputer 49.

[0030]

Since the conventional tracking control system of the magnetic recording / reproducing apparatus is constructed as described above, for example, another magnetic recording / reproducing apparatus (hereinafter referred to as V
Even when reproducing a magnetic tape recorded by superimposing the HIFI audio signal and the O-QDPSK signal in (TR), a certain degree of sound quality and image quality can be secured. However, the O-Q recorded by superposition with the HIFI voice signal by frequency multiplexing is recorded.
It cannot be said that the optimal tracking is necessarily realized when the DPSK signal alone is viewed, and therefore the QDPSK signal cannot obtain a sufficient C / N,
There is a problem that the error rate of the M voice signal is also deteriorated.

The present invention has been made in order to solve the above-mentioned problems, and includes a video signal, a HIFI audio signal,
And deep-recording VTR capable of recording PCM audio signals
In, when the magnetic tape on which the PCM audio signal is recorded is reproduced, the tracking can be driven to the optimum position so that the error rate of the PCM audio signal is minimized, and only the conventional HIFI audio signal is recorded. In the case of tape, since the tracking position where the HIFI envelope becomes maximum can be obtained without using an unstable envelope detection circuit, it is possible to automatically track the HIFI audio signal to the optimum tracking position so that the sound quality becomes higher. The purpose is to get a control system.

[0032]

In order to achieve the above object, a tracking control system of a magnetic recording / reproducing apparatus according to a first aspect of the present invention detects an envelope signal of a reproduced signal reproduced by a rotary video head. H for detecting the envelope signal of the reproduction signal reproduced by the video signal envelope detection circuit and the rotary HIFI audio head.
An IFI audio signal envelope detection circuit and a detection circuit for detecting an offset type four-phase differential phase modulation signal recorded by superimposing the HIFI audio signal by frequency multiplexing are provided, and the video head is determined by the envelope amount from each envelope detection circuit. The relative position of the HIFI voice head and the magnetic tape is selectively controlled to perform tracking control during reproduction, and when the offset type four-phase differential phase modulation signal is detected, the relative position of the HIFI voice head and the magnetic tape. Is preferentially controlled.

The tracking control system according to the second aspect of the present invention is an O-reproduced by a HIFI voice head.
Offset type 4-phase differential phase modulation signal demodulation circuit for demodulating a QDPSK signal into a PCM signal, digital signal processing circuit for converting digital data output from the demodulation circuit into a PCM signal, and digital signal processing circuit The error pulse counter for counting the number of error pulses generated in the above, and the D / A converter for converting the output of the error pulse counter into an analog amount are provided, and the error pulse per unit time in the digital signal processing circuit is It is characterized in that the relative position between the HIFI voice head and the magnetic tape is controlled so that the count number is minimized.

[0034]

Therefore, according to the tracking control system of the present invention, only the O-QDPSK signal is extracted from the reproduction signal of the magnetic tape on which the HIFI voice signal and the O-QDPSK signal are superposed and recorded, and detection and sample hold are obtained. Based on the comparison result between the DC voltage and the reference voltage, it is determined whether or not the tape has a PCM audio signal recorded, and when it is determined that the magnetic tape has a PCM audio signal recorded, it is per unit time in the digital signal processing circuit. Optimal tracking is realized by controlling the relative position of the HIFI voice head and the magnetic tape so that the number of error pulse counts of 1 is minimized. Further, when the conventional magnetic tape on which only the HIFI audio signal is recorded is reproduced, the tracking position where the HIFI envelope becomes maximum can be obtained without using the envelope detection circuit, and therefore the same tracking control as the conventional one is used. be able to.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a tracking control system of a magnetic recording / reproducing apparatus according to this embodiment. In addition,
In the figure, the same or corresponding parts as those of the conventional tracking control system are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, the tracking control system of the present embodiment extracts only the O-QDPSK signal from the signal in which the HIFI audio signal amplified by the HIFI audio head amplifier circuit 42 and the O-QDPSK signal are superposed. Bandpass filter 101, O-QDPSK signal detection circuit 102 for detecting the O-QDPSK signal obtained by bandpass filter 101, and sample hold circuit for sampling and holding the detection signal obtained by detection circuit 102 When the magnetic tape on which the PCM audio signal is recorded is reproduced, that is, when the O-QDPSK signal is detected, 103 is compared with the DC voltage obtained by the sample hold circuit 103 and the reference voltage. HI ”, otherwise output“ LO ”signal And a comparator circuit 104.

The tracking control system of the present embodiment also includes a demodulation circuit (hereinafter referred to as a modem circuit) 105 for converting the reproduced O-QDPSK signal output from the HIFI voice head amplifier circuit 42 into digital data,
A signal processing circuit (hereinafter referred to as a DSP) 106 for converting digital data demodulated by the modem circuit 105 into an audio signal, and for measuring the number of error pulses output during signal processing by the DSP 106 per unit time. Error pulse counter 107, a D / A converter 108 for converting the number of pulses obtained by the error pulse counter 107 into an analog quantity that can be used in the automatic tracking control system 50, and a HIFI voice signal envelope detection circuit 44. Output signal and D / A converter 1
08 of the output signals is selected according to the output of the comparator circuit 104, and the automatic tracking control system 5 is selected.
The selector 109 for inputting 0 is provided. And
The selector 109 is composed of switches 111 and 112.

Next, the operation of the tracking control system of the present embodiment constructed as described above will be described. First, when the magnetic tape on which the PCM audio signal is not recorded is reproduced, the output of the comparator circuit 104 becomes "LO" as described above, so the selector 109 selects the output signal of the HIFI audio signal envelope detection circuit 44. hand,
Output to the automatic tracking control system 50. As a result, the automatic tracking control system 50 becomes a conventional VT.
Control similar to that of R, that is, control is performed while constantly monitoring the playback status of both the envelope of the video signal and the envelope of the HIFI audio signal.

On the other hand, when the magnetic tape on which the PCM audio signal is recorded is reproduced, the O-QDPSK signal detection circuit 102 detects the O-QDPSK signal,
Further, the output signal of the D / A converter 108 becomes "HI". Therefore, the output signal of the D / A converter 108 is selected as the output signal of the selector 109. The output signal of the D / A converter 108 changes in the same manner as the output signal of the HIFI audio signal envelope detection circuit 44, that is, the HIFI audio signal has the best HIFI envelope and the best sound quality is obtained.
The analog signal output of the D / A converter 108 is set to be maximum when the error pulse of the PCM audio signal is minimum.

When the magnetic tape on which the PCM audio signal is recorded is reproduced, the output signal of the envelope detection circuit 49 for reprioritizing the sound quality of the PCM audio signal is cut by the switch 111, and the automatic tracking control system is operated. D / A converter 1 for 50 tracking control
08 output signal only. In addition, the size of the HIFI envelope and the 3 MHz of the O-QDPSK signal
Since the C / N has a correlation, the tracking position where the error pulse of the PCM audio signal is the minimum, that is, O-QDP
The HIFI envelope is maximum at the tracking position where the 3 MHz C / N of the SK signal is maximum.

Although a series of operations for counting the error pulses generated by the DSP 106 and converting the count value into an analog value has been described in the above embodiment, the error pulse counter 107 and the D / A converter 108 are used. Alternatively, a microcomputer may be used instead.

[0042]

As described above, according to the tracking control system of the magnetic recording / reproducing apparatus of the present invention, only the O-QDPSK signal is extracted from the reproduction signal of the magnetic tape, and the DC is obtained by detecting and sample-holding. It is determined from the comparison result of the voltage and the reference voltage whether or not the tape has a PCM audio signal recorded, and when it is determined that the PCM audio signal has been recorded, an error pulse per unit time in the digital signal processing circuit. Since the tracking control is performed so that the count number of
There is an effect that high quality sound can be realized when reproducing a tape on which a CM audio signal is recorded.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a tracking control system of a magnetic recording / reproducing apparatus of this embodiment.

FIG. 2 is a block diagram showing a configuration of a conventional magnetic recording / reproducing apparatus for superposing and recording a video signal, a HIFI audio signal, and a PCM audio signal.

FIG. 3 is a block diagram of a conventional automatic tracking control system that applies both an FM video signal and a HIFI audio signal.

FIG. 4 is a diagram showing an arrangement example of a rotary video head and a HIFI audio head attached to a rotary cylinder of a conventional magnetic recording / reproducing apparatus.

[Explanation of symbols]

 101 3 MHz band pass filter 102 O-QDPSK signal detection circuit 103 Sample hold circuit 104 Comparator circuit 105 PCM modem circuit 106 PCMDSP 107 Error pulse counter 108 D / A converter 109 Selector 125 Video signal input terminal 126 Recording video signal processing circuit 127 Recording amplifier 128a, 128b Video rotary head 129 Synchronous signal separation circuit 130 Servo circuit 131a, 131b Analog audio signal input terminals 132a, 132b Low-pass filter 133a, 133b Sample hold circuit 134a, 134b A / D converter 135 Encoder 136 Offset type four-phase difference Dynamic phase modulation modulator 137 3 MHz bandpass filter 139 Bias superposition circuit 141a, 141b Voice rotary head 143 Magnetic tape 155 Audio preamplifier 156 Switching amplifier 157 Video preamplifier 158 Playback video signal processing circuit 160 Band filter 161 O-QDPSK demodulation circuit 162 Decoder 163a, 163b D / A converter 164a, 164b Deglitcher circuit 165a, 165b Low-pass filter 169a , 169b Switch 175 Mixer 180 Reproduction equalizer 200 HIFI audio signal recording processing circuit 300 HIFI audio signal reproduction processing circuit

Claims (2)

[Claims] 1. A video signal envelope detection circuit for detecting an envelope signal of a reproduction signal reproduced by a rotating video head, a HIFI audio signal envelope detection circuit for detecting an envelope signal of a reproduction signal reproduced by a rotating HIFI audio head, and HIFI. A magnetic tape for a video head and a HIFI audio head is provided, which has a detection circuit for detecting an offset type four-phase differential phase modulation signal recorded by superposition with an audio signal by frequency multiplexing. In a tracking control system of a magnetic recording / reproducing apparatus for selectively controlling the relative position with respect to the tracking control during reproduction, when the offset type four-phase differential phase modulation signal is detected, the HIFI voice head and the magnetic tape are separated. The relative position can be controlled with priority. Tracking control system of the magnetic recording and reproducing apparatus according to claim. 2. A video signal envelope detection circuit for detecting an envelope signal of a reproduction signal reproduced by a rotating video head, a HIFI audio signal envelope detection circuit for detecting an envelope signal of a reproduction signal reproduced by a rotating HIFI audio head, and HIFI. A magnetic tape for a video head and a HIFI audio head is provided, which has a detection circuit for detecting an offset type four-phase differential phase modulation signal recorded by superposition with an audio signal by frequency multiplexing. In a tracking control system of a magnetic recording / reproducing apparatus for selectively controlling a relative position with respect to a tracking control during reproduction, an offset type 4 for demodulating an O-QDPSK signal reproduced by a HIFI voice head into a PCM signal. Phase Differential Phase modulation signal recovery A circuit, a digital signal processing circuit for converting digital data output from the demodulation circuit into a PCM signal, an error pulse counter for counting the number of error pulses generated in the digital signal processing circuit, and an error pulse counter It has a D / A converter for converting the output to an analog quantity, and the relative position of the HIFI voice head and the magnetic tape so that the count number of error pulses per unit time in the digital signal processing circuit is minimized. A tracking control system characterized by controlling.