JP3360457B2 - Magnetic recording / reproducing device - Google Patents

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 apparatus for digital image signals, and more particularly to a magnetic recording / reproducing apparatus compatible with existing analog VTRs.

[0002]

2. Description of the Related Art At present, as a home magnetic recording / reproducing apparatus, an analog VTR using an 1/2 inch wide oxide tape has been put to practical use.

On the other hand, practical use of digital broadcasting has been promoted as next-generation TV broadcasting. For example, in the United States,
Compared with the current image signal of the NTSC system or the PAL system (hereinafter, referred to as Standard Definition; SD image signal), a broadband image signal having a higher resolution (hereinafter, High Definit
An ATV (Advanced Television) that encodes high-efficiency digital compression coding of an ion (HD: image signal) and broadcasts it with the same 6 MHz bandwidth as the current TV broadcast is known. Also,
Regarding SD image signals, MPEG (Moving PictureExp
erts Group) method is known.

[0004] These digital broadcasting systems are described in the Journal of the Institute of Television Engineers of Japan, Vol. 47, No. 4 (199).
3rd year), pp. 486-503.

[0005]

It is considered that these digital TV broadcasts will be put to practical use in the near future, and will be implemented in a form mixed with analog TV broadcasts. Could not be recorded and reproduced as a digital signal.

When a magnetic recording / reproducing apparatus which is compatible with a current analog VTR and is capable of recording and reproducing digitally-compressed image and audio signals of digital TV broadcasts and the like as digital signals is assumed. Discrimination of the mode (analog VTR / digital VTR) at the time of reproduction becomes a problem. In the current analog VTR, a VTR in which an audio-only head is provided independently of a video head on a rotating drum and an FM modulation signal is recorded in a deep portion of a magnetic tape is mainly used. Therefore, the digital VT on the rotating drum
Mounting a dedicated magnetic head for R is a major problem in terms of cost and productivity, and there is a proposal to use the dedicated head for audio as a digital VTR. in this way,
When the audio head and the digital head are used together, the audio signal processing circuit operates when the part where the digital signal is recorded is reproduced, the digital signal is processed as audio, and abnormal sound is generated when transmitted to the speaker side, In some cases, the speakers may be destroyed. In a conventional VTR, automatic tracking control has been developed so as to maximize the reproduction output level. However, in a digital VTR mode, new automatic tracking control means is required. In order to further improve the usability, when a VTR is equipped with a decoder circuit or the like that converts a digitally compressed and encoded image signal into a composite video signal, it is necessary to switch each unit based on the information of the mode determination. .

An object of the present invention is to provide a VT capable of recording and reproducing a digital signal while maintaining compatibility with a current analog VTR.
It is an object of the present invention to provide an easy-to-use magnetic recording / reproducing apparatus having an automatic discrimination function of an analog / digital mode and an automatic tracking control function.

[0008]

In order to achieve the above object, a magnetic recording / reproducing apparatus according to the present invention is provided on a rotating drum.
Helical recording / reproducing with a pair of magnetic heads facing 180 degrees
Scan-type magnetic recording / reproducing device,
Video signal into FM luminance signal and low-frequency conversion color signal
Recording and reproducing on a magnetic tape with the first pair of magnetic heads,
The audio signal is FM-modulated, and the magnetic tape is
The first mode of recording and playback in the deep part of the
Signal to a band higher than the FM signal voice signal band.
Digitally modulated and recorded on magnetic tape with a second pair of magnetic heads
And a second mode for reproducing, and the first and second modes for reproducing.
And / or based on information from the second pair of magnetic heads.
A configuration having mode determination means for determining two modes;
I do.

[0009]

[0010]

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a recording system block configuration of a magnetic recording / reproducing apparatus according to the present invention, wherein 1 is a rotary drum, 2 and 3 are guide posts, 4 is a magnetic tape, 5 and 6 are magnetic heads, and 7 is a DPG (Drum). 8 is a pinch roller, 9 is a CTL head, 10 is a capstan shaft, 11 is a capstan motor, 97 is a linear audio head, 55 is a cassette tape, 50, 5
6, 95 is a recording amplifier, 96 is a linear audio processing circuit, 51 and 60 are switch circuits, 52 is an LPF (low-pass filter), 53 is an FM audio processing circuit, 54 is a digital signal processing circuit, and 25 is a servo system. A controller (hereinafter referred to as a servo system controller) block; 24, a motor driver; 57, an analog video signal processing circuit;
Is a tuner block, 58 is a cassette hole detection circuit, 2
2, 61, 62 are input terminals, 21, 17, 31 are output terminals, 12 is a VTR, 34 is a tuner and an MPEG decoder, 40 is a monitor television, 33 is a bit compression digital signal input terminal, 35 to 39, 41 to 44. Are input / output terminals. This system is an example of a VTR capable of recording digital signals based on a VHS standard VTR, and its operation will be briefly described. The bit-compressed and modulated digital signal input to the terminal 33 is demodulated by the tuner and the MPEG decoder, and is then input from the terminal 36 to the input terminal 2 of the VTR 12 as a bit-compressed digital signal.
2 is transmitted. The digital signal reproduced by the VTR 12 is output from the terminal 21 and input to the input terminal 37 of the decoder 34.
Are decoded into a composite video signal, a video signal is output from a terminal 38, and an audio signal is output from a terminal 39, and is sent to a monitor television. The signal from the VTR 12 is also output from the terminals 17 and 31 and sent to the monitor television. The operation of the VTR 12 will be briefly described. Analog V
In the TR mode, an audio signal from the tuner 59 is transmitted to an audio head 97 via a linear audio processing circuit 96 and a recording amplifier 95, and is written on a linear track on a magnetic tape. Further, the FM audio processing circuit 53, the LPF 52,
The data is sent to the pair of magnetic heads 5a and 5b via the switch circuit 51 and the recording amplifier 50, and is recorded in the deep portion of the magnetic tape. Here, a pair of magnetic heads 5a and 5b for FM audio signals
Have a azimuth angle of ± 30 degrees so that the pair of video signal magnetic heads 6a and 6b (azimuth angles ± 6 degrees) have a sufficient azimuth angle and can suppress interference between them. The video signal is frequency-multiplexed with a luminance signal FM-modulated and a color signal subjected to low-frequency conversion by a video signal processing circuit 57, and then sent to the magnetic heads 6a and 6b via the recording amplifier 56 to be transmitted to the surface layer of the FM audio signal. Will be recorded. In the digital mode, the digital signal input from the terminal 22 is sent to the magnetic heads 5a and 5b via the digital signal processing circuit 54, the switch circuit 51, and the recording amplifier 50, and is recorded on the magnetic tape. If the FM audio head has an azimuth angle of ± 30 degrees, sufficient performance can be ensured even for digital signal recording. Here, the signal input to the terminal 22 is a bit-compressed digital signal, but the processing as a VTR does not change even for a digital signal that is not bit-compressed.

Next, a brief description will be given of analog / digital mode discrimination during recording. FIG. 9 shows a flowchart of the mode determination. In this embodiment, it is assumed that a high-performance magnetic tape capable of recording digital signals is used as a cassette tape. In the VHS standard VTR, there is a standard called S-VHS aiming at high image quality, but a magnetic tape having a high holding force Hc is also used as a magnetic tape. This S-VHS tape will be described as an example. First, in S-VHS tape, VHS / S
There is a detection hole for determining −VHS, and the cassette hole detection circuit 58 mechanically makes a determination. The result of the determination is a signal (D4)
Is sent to the servo system controller 25, and in the case of the VHS cassette, the analog recording mode is determined. In the case of an S-VHS cassette, the user determines analog recording / digital recording by a button set on the set body. That is, the switch circuit 60 is controlled by the setting signal from the user input from the input terminal 61, and the H / L signal (D5)
Is sent to the servo system controller 25. As a result of the above determination, a control signal (D2) is sent from the servo system controller 25 to the switch circuit 51 to switch between analog recording and digital recording. The tape speed setting depending on the mode is (CC
NT), the motor driver 24 is controlled to control the speed and phase of the capstan motor 11.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 shows a block diagram of a reproducing system of the magnetic recording / reproducing apparatus according to the present invention. Reference numerals 98, 13, 26 denote reproducing head amplifiers, 99 denotes a linear audio signal processing circuit,
0 is a switch circuit, 14 is an LPF, 15 is an FM audio signal processing circuit, 16 and 20 are mute circuits, 18 is a PLL circuit, 19 is a digital signal processing circuit, 32 is a frequency detection and envelope detection circuit, 32 is an envelope detection circuit , 28 is a reproduction analog video signal processing circuit, 29 is a synchronization signal detection circuit, 30 is an OSD (abbreviation of On Screen Display) circuit for inserting a character and replacing a blue screen, and the others are the same as in the embodiment of FIG. The same number is written in.

The configuration of a reproducing head preamplifier which is one of the features of this embodiment will be described. The present invention is based on the current VHS
In this system, a Hi-Fi audio head of a standard VTR is used for digital recording. As shown in FIG. 7, the FM audio signal has a bandwidth of 1 to 2 MHz. Is 18.6 bps (b
The maximum frequency of the carrier signal of the digital signal of “it per sec” is 9.3 MHz. Conventionally, a reproducing head amplifier for FM audio signal processing is dedicated to audio, and a narrow band is used as a pass band for reproducing with good S / N. In the present invention, in order to use both the FM audio head and the digital head, the present inventor devises a dual use as a preamplifier. In order to reproduce a digital signal, the pass band of the reproduction head preamplifier 13 is set to a wide band as shown by a curve 102 in FIG.
Curve 10 for the audio signal using LPF 14 at the input stage
Bandwidth is limited as in 1. The above point is the sound head /
This is the point of a system that combines digital heads.

Next, the mode determining means will be described.
After sufficiently amplifying the outputs of the audio head / digital heads 5a and 5b by the reproducing head amplifier 13, the frequency detection and envelope detection circuit 32 outputs the digital signal detection signal (D1).
And the detection output of the audio signal band (ENV1) and the detection output of the digital carrier signal (ENV2)
Send to Details of the frequency detection and envelope detection circuit 32 will be described with reference to FIG. The reproduction signal input from the terminal 80 is adjusted by the amplifiers 81 and 84 so that the FM audio signal and the digital signal level become almost the same. After the audio signal is extracted by the BPF 82, the audio signal is envelope-detected by a detection circuit 83 and output to a terminal 89. The digital signal is extracted by a BPF 86 and then subjected to envelope detection by a detection circuit 86 and output to a terminal 90. Each band characteristic is a characteristic shown by curves 97 and 98 in FIG. Also,
Regarding digital signal detection, the envelope detection circuit 8
The result of detection by the comparator 88 of the presence or absence of the output of No. 6 is output to the terminal 91. The DC voltage source 87 is connected to the comparator 8
8 is given. FIG. 10 shows a flowchart of the mode determination procedure at the time of reproduction. First, before detecting the frequency, the recording tape is reproduced with the same azimuth head, and the envelope detection is performed based on one of the envelope detection outputs (ENV1) and (ENV2) so that a sufficient detection output can be obtained. It is necessary to run auto-tracking control by the servo system controller 25 so that the output becomes maximum. As an example of the auto tracking control, there is hill climbing control as shown in FIG. That is, the maximum amplitude is obtained as indicated by 3, 5, 7 while shifting the tracking by the step width ΔX of the tracking and comparing the reproduction output with 0 → 1 → 2 → 3 → 4 → 5 → 6 → 7. Control. After tracking is performed in this manner, the frequency of the output signal of the reproducing head preamplifier 13 is detected. That is, if a digital signal is present, it may be determined that the digital mode is substantially set, but the PLL circuit 18 for further adjusting the phase of the reproduced digital signal.
If the phase is locked, the digital mode is determined. If the phases are not locked, the state returns to the state where the frequency detection result is reviewed again. If there is no digital signal, the presence / absence of a horizontal synchronization signal is detected by the synchronization signal detection circuit 29 from the demodulated signal of the video signal processing circuit 28 (the detection signal is D3). If not, it is determined that there is no recording, and at the same time, the OSD circuit
At 0, for example, it is common to set the television screen to a blue-blue state.

Next, switching of each unit according to the result of the determination will be described.
First, the audio signal is switched between the linear audio signal and the FM audio signal by the switch circuit 100, and then the mute circuit 1
In the analog mode at 6, 20, for example, (D2) is L
The low level and (D2 ') become the high level, the mute of 16 is released, and the mute of 20 is operated. Conversely, in the digital mode, (D2) is at the high level,
(D2 ') becomes Low level, 16 is set to mute operation, and 20 is unmuted. In particular, until the determination is completely completed, both (D2) and (D2 ') remain at the High level, and the mute circuits 16 and 20 are muted by the servo system controller 25 so that the audio signal and the digital signal are muted. To prevent occurrence of abnormal sound and disturbance of an image at the time of determination transition. The waveforms of the respective parts at the time of the above determination transition will be described with reference to FIG. After the reproduction is started and the loading of the mechanism is completed, the tracking operation is started by observing the signal level on the audio head side. At this time, an adjacent crosstalk component is generated as shown in the figure, but until the tracking is turned on, the mute signals (D2) and (D2 ') are Hi.
After the gh level is maintained and tracking is turned on,
(D2) and (D2 ') show how the levels change to High and Low levels, respectively.

Here, the automatic tracking control means mentioned above will be described. For example, a conventional analog VHS
In the standard VTR, in the standard recording mode (SP mode) without adjacent crosstalk interference, the output is maximized by the servo system circuit 25 based on the envelope detection output (27 outputs) (ENV3) of the video signal. The control signal (CCNT) is sent to the motor driver circuit 24 to control the capstan motor 11. In the case of a long-time recording mode (eg, EP mode) with adjacent crosstalk interference, auto-tracking control is performed using information on the FM audio head side having an azimuth of 30 degrees and being less susceptible to adjacent crosstalk interference. . In the analog / digital VTR of the present invention, in the case of the analog mode, the envelope detection signals (ENV1) and (ENV1) are used.
3), and in the digital mode, (ENV1) (ENV3) / (ENV2) based on the mode discrimination signal (D2) so that the automatic tracking control can be run using (ENV2). Is switched by the servo system controller 25.

From another point of view, as shown in Table 1, the reproduction mode determination method is divided into two types depending on the difference in the tape speed.

[0018]

[Table 1]

In the VHS standard VTR, the tape speed L is 1/2 that of the standard recording mode (SP mode).
There are a P mode and an EP mode with a tape speed of 1/3 times.
In contrast, the digital VTR (digital VTR) of this system
Regarding HS), when a digitally recorded tape is played back in the analog mode, the audio signal processing circuit operates to process the digital signal when the part where the digital signal is recorded is played back. When a signal is transmitted to the speaker side, an abnormal sound is generated, and in some cases, the speaker may be destroyed. In order to cancel this, for example, the SD mode and LD (hereinafter, Low Defin
The tape speed is set to 1/4, 1/12 (SP mode ratio) different from the analog VHS like in the mode, and the servo is not locked in the analog mode for the digital recording tape. It is conceivable to prevent the above-mentioned voice abnormalities. Thus, if the tape speed is different, the CTL signal recorded at the lower end of the tape reproduced by the CTL head 9 and the capstan motor 1
The determination can be made based on a frequency ratio or a period ratio with one FG signal (CFG). On the other hand, there is a possibility that a higher image quality mode may be set for a digital VTR.
For example, HD mode or ED (hereinafter Extended Definition:
In the high image quality mode, which is called the ED image signal) mode, the amount of information increases, so that it is necessary to increase the tape speed. H
When D and ED are set to the same tape speed as those in the SP and LP modes, the frequency detection and the phase lock state detection of the PLL circuit described above with reference to FIG. 10 are required. As described above, when the tape speed differs between the analog mode and the digital mode, the discrimination is performed by the CTL / CFG ratio, and when the tape speed is the same, the mode discrimination is performed by the frequency detection and the PLL discrimination. This is one point.

Next, another embodiment of the present invention will be described with reference to FIG. The present invention is the same as the embodiment of FIG. 2 except that the opening of the audio signal is taken after the LPF 14 in the frequency detection and envelope detection circuit 45. The frequency detection and envelope detection circuit 45 is shown in FIG.
Shown in At the same time that the terminal 92 is newly set as an input for the audio signal, the BPF for band limitation shown in FIG.
82 has been deleted. The above band limitation can be substituted by using the output of the LPF 14 located after the reproducing head amplifier 13.

Next, another embodiment of the present invention will be described with reference to FIGS. This embodiment is an MPEG which receives a bit-compressed digital signal and converts it into a composite video signal.
Analog and digital recording V with built-in decoder
It is related to TR. FIG. 4 is a block diagram of a recording system, and FIG. 5 is a block diagram of a reproducing system.

First, the recording system will be described with reference to FIG. A digital signal transmitted from a satellite broadcast, an optical cable, or the like is input from an input terminal 65, converted into a bit-compressed digital signal based on the MPEG specification by a tuner 66, and passed through a switch circuit 67 for switching between recording and reproduction. It is input to the processing circuit 54 and the MPEG decoder 68. Recording processing after the digital signal processing circuit 54 is the same as in the embodiment of FIG. MPEG decoder 68
Output (Video2) and analog video signal processing circuit 5
7 (Video1: general monitor output with AGC) is switched by the switch circuit 70 and then input to the OSD circuit 30, and the output is input to the monitor television 40 via the output terminal 71. Also, the MPEG decoder 68
After switching between the audio output (Audio2) from and the audio signal (Audio1) output from the tuner 59 by the switch circuit 69, the audio signal is input to the monitor television 40 via the output terminal 72.

Next, the operation of the reproducing system will be described with reference to FIG. The digital signal reproduced from the VTR is input to the MPEG decoder 68 via the switch circuit 67. MP
Video output (Video2) and audio output (Audio
Switching between 2) and the analog reproduction signals (Video1) and (Audio1) is performed by the switch circuits 70 and 69 in the same manner as in the recording system. The feature of this embodiment is that, first, after switching between the linear audio and the FM audio signal by the switch circuit 100 for the audio signal,
The switch circuit 69 switches between analog and digital modes and outputs the result to the terminal 72. The second is that the video signal is switched to analog and digital modes by the switch circuit 70 and then output to the terminal 71 via the OSD circuit. In this way, the OSD circuit can be united and both the analog and digital modes can be used. Can supply a stable signal to the monitor television. Third, switching of recording / reproduction for digital signals is performed by using a switch circuit 67 at a stage preceding the MPEG decoder.

[0024]

As described above, according to the present invention,
In an analog / digital mixed VTR that records and reproduces digital signals with an FM audio head while maintaining compatibility with the VHS standard VTR, frequency detection and phase lock state detection of the PLL circuit are performed using information on the output of the FM audio head. By doing so, high-performance analog / digital discrimination becomes possible. Further, the reproduced audio signal and the digital signal are muted until the discrimination is sufficiently completed, whereby the occurrence of abnormal sound and the disturbance of the image which occur at the time of the discrimination malfunction can be prevented. When the tape speeds of the analog mode and the digital mode match, the mode is determined by the ratio between the CTL signal and the CFG signal. When the speeds do not match, the mode is determined by frequency detection and PLL phase lock detection. Stable discrimination performance can be obtained even for various mode settings.

In the analog mode, the auto-tracking control by detecting the output envelope of the video head and the audio head is performed. In the digital mode, the auto-tracking control means by detecting the output envelope of the audio head (digital head) is switched by the mode discriminating output. An auto-tracking function can be realized in a digitally mixed VTR, and there is also an effect that a stable reproduced image can be obtained.

The reproduction head preamplifier has a band characteristic wide enough to reproduce a digital signal, and a low-pass filter capable of passing an FM audio signal again at the input stage of audio signal processing is provided. The reproduction head preamplifier on the side of the ()) can be made into one system, and rationalization can be achieved.

In addition, an analog / audio signal with a built-in MPEG decoder
For digital mixed VTRs, linear audio output and F
By switching the audio output of the MPEG decoder after switching the M audio output, streamlining can be achieved, and the circuit can be simplified by providing the OSD circuit after switching between the analog video output and the MPEG decoder video output (digital video output). And a stable signal can be output to the monitor television to improve image distortion.

[Brief description of the drawings]

FIG. 1 is a block diagram of a recording system of a VTR according to an embodiment of the present invention.

FIG. 2 is a block diagram of a reproduction system of a VTR according to an embodiment of the present invention.

FIG. 3 is a block diagram of a reproduction system of a VTR showing an embodiment of the present invention.

FIG. 4 is a block diagram showing a recording system of a VTR according to an embodiment of the present invention.

FIG. 5 is a block diagram of a reproduction system of a VTR according to an embodiment of the present invention.

FIG. 6 is a block diagram showing a frequency detection and envelope detection circuit.

FIG. 7 is a diagram showing an output spectrum of an audio head.

FIG. 8 is a block diagram showing a frequency detection and envelope detection circuit.

FIG. 9 is a flowchart of analog / digital discrimination during recording.

FIG. 10 is a flowchart of analog / digital discrimination during reproduction.

FIG. 11 is a diagram showing an operation of auto tracking of a VTR.

FIG. 12 is a diagram showing frequency characteristics of a reproduction head preamplifier on the FM audio head side.

FIG. 13 is a diagram showing operation waveforms of each part during reproduction.

[Explanation of symbols]

 19, 54 ... digital signal processing circuit, 15, 53 ... FM audio signal processing circuit, 28, 58 ... analog video signal processing circuit, 32, 45 ... frequency detection and envelope detection circuit, 25 ... servo system control circuit, 34 ... Tuner and MPEG decoder circuit 18 PLL circuit 16, 20 Mute circuit 68 MPEG decoder circuit 5a, 5b FM audio head.

Continuation of the front page (56) References JP-A-8-180501 (JP, A) JP-A-5-207507 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 15 / 087 G11B 5/588 G11B 15/02 G11B 15/467

Claims (13)

(57) [Claims] 1. A helical scan type magnetic recording / reproducing apparatus for recording / reproducing with a pair of magnetic heads 180 ° facing each other on a rotating drum, wherein the composite video signal is converted into an FM luminance signal and a low-frequency conversion color signal, and Recording / reproducing on a magnetic tape with a magnetic head pair having an azimuth angle, and FM-modulating an audio signal, and recording / reproducing on a deep portion of the magnetic tape with a magnetic head pair having a second azimuth angle different from the first azimuth angle. And a second mode in which a digital signal is digitally modulated to a band higher than the FM-modulated audio signal band, and the magnetic head pair having the second azimuth angle records and reproduces data on a magnetic tape. And a mode discriminating means for discriminating the two modes based on information from the magnetic head pair having the second azimuth angle at the time of reproduction. First tracking control means for performing automatic tracking control based on reproduction signals of the magnetic head pair having the first azimuth angle and / or the magnetic head pair having the second azimuth angle in the first mode at birth And in the second mode, a second tracking control means for performing automatic tracking control based on a reproduction signal of the magnetic head pair having the second azimuth angle, and a discrimination signal from the mode discrimination means. A magnetic recording / reproducing apparatus, wherein the first or second tracking control means is switched. 2. A helical scan type magnetic recording / reproducing apparatus for recording / reproducing with a pair of magnetic heads 180 ° opposite to each other on a rotating drum, wherein the composite video signal is converted into an FM luminance signal and a low-frequency conversion color signal, and Recording / reproducing on a magnetic tape with a magnetic head pair having an azimuth angle, and FM-modulating an audio signal, and recording / reproducing on a deep portion of the magnetic tape with a magnetic head pair having a second azimuth angle different from the first azimuth angle. And a second mode in which a digital signal is digitally modulated to a band higher than the FM-modulated audio signal band, and the magnetic head pair having the second azimuth angle records and reproduces data on a magnetic tape. A first recording amplifier and a first reproducing head preamplifier for the magnetic head pair having the first azimuth angle, and the second azimuth angle A second recording amplifier and a second reproducing head preamplifier for the pair of magnetic heads, wherein the second recording amplifier and the second reproducing head preamplifier are a wideband amplifier capable of recording and reproducing a digital modulation signal; A first low-pass filter for band-limiting the recording output of the audio signal processing circuit that processes the audio signal in the first mode, and a second low-pass filter for band-limiting the reproduction input; and A magnetic head having mode discriminating means for discriminating the two modes based on information from a magnetic head pair having a second azimuth angle, and having the first azimuth angle in the first mode during reproduction A first tracking control means for performing automatic tracking control based on a reproduction signal of a pair and / or a magnetic head pair having the second azimuth angle; Has a second tracking control means for performing automatic tracking control based on a reproduction signal of the magnetic head pair having the second azimuth angle, and the first or the second in the discrimination signal from the mode discrimination means Switching means for switching the tracking control means, wherein the mode determination means starts after automatic tracking control is executed based on an output signal of the magnetic head pair having the second azimuth angle in its initial state. Magnetic recording and reproducing apparatus. 3. A helical scan type magnetic recording / reproducing apparatus for recording / reproducing with a pair of magnetic heads 180 ° facing each other on a rotating drum, wherein the composite video signal is converted into an FM luminance signal and a low-frequency conversion color signal, and Recording / reproducing on a magnetic tape with a magnetic head pair having an azimuth angle, and FM-modulating an audio signal, and recording / reproducing on a deep portion of the magnetic tape with a magnetic head pair having a second azimuth angle different from the first azimuth angle. And a second mode in which a digital signal is digitally modulated to a band higher than the FM-modulated audio signal band, and the magnetic head pair having the second azimuth angle records and reproduces data on a magnetic tape. And a mode discriminating means for discriminating between the two modes based on information from the magnetic head pair having the second azimuth angle during reproduction. A first mute circuit is provided at an output stage of the voice signal processing circuit, a second mute circuit is provided at an output stage of the reproduced digital signal processing circuit, and when the second mode is determined, the first mute circuit is provided. , And the second mute circuit is set to a non-operation state, and both the first and second mute circuits are set to an operation state until a mode is determined. 4. A helical scan type magnetic recording / reproducing apparatus for recording / reproducing with a pair of magnetic heads 180 ° facing each other on a rotating drum, wherein the composite video signal is converted into an FM luminance signal and a low-frequency conversion color signal, and Recording / reproducing on a magnetic tape with a magnetic head pair having an azimuth angle, and FM-modulating an audio signal, and recording / reproducing on a deep portion of the magnetic tape with a magnetic head pair having a second azimuth angle different from the first azimuth angle. And a second mode in which a digital signal is digitally modulated to a band higher than the FM-modulated audio signal band, and the magnetic head pair having the second azimuth angle records and reproduces data on a magnetic tape. And a mode discriminating means for discriminating between the two modes based on information from a magnetic head pair having the second azimuth angle during reproduction. A receiving device for receiving the bit-compressed digital information and converting the bit information into a desired bit-compressed signal, and a decoder circuit for bit-expanding and converting it to a composite video signal (video signal) and an audio signal; A first switch circuit for switching a reproduced digital signal in the second mode and an output signal of the receiving device in a previous stage; and a video signal output from the decoder circuit and an output from the video signal processing circuit in the first mode. A second switch circuit for switching between the reproduced video signal and a first audio signal reproduced from the head pair having the second azimuth angle in the first mode and a second audio reproduced from a linear track. A third switch circuit for switching between a signal and an output of the third switch circuit and a third audio signal output from the decoder circuit. And a fourth switch circuit for switching between the first and second switch circuits, wherein the second and fourth switch circuits are controlled by an output signal of the mode determining means. 5. A synchronization detecting circuit for detecting a synchronizing signal from a video signal obtained as an output of the second switch circuit, wherein when the synchronizing signal is lost, another output signal of the second switch circuit is output. 5. The magnetic recording / reproducing apparatus according to claim 4, further comprising a replacement circuit for replacing the information with image information. 6. A helical scan type magnetic recording / reproducing apparatus for recording / reproducing with a pair of magnetic heads 180 ° opposed to each other on a rotating drum, wherein the composite video signal is converted into an FM luminance signal and a low-frequency conversion chrominance signal. Recording / reproducing on a magnetic tape with a magnetic head pair having an azimuth angle, and FM-modulating an audio signal, and recording / reproducing on a deep portion of the magnetic tape with a magnetic head pair having a second azimuth angle different from the first azimuth angle. And a second mode in which a digital signal is digitally modulated to a band higher than the FM-modulated audio signal band, and the magnetic head pair having the second azimuth angle records and reproduces data on a magnetic tape. When the first mode and the second mode run at the same tape speed, a pair of magnetic heads having the first azimuth angle during reproduction Has first mode discriminating means for discriminating between the two modes based on information from a magnetic head pair having the second azimuth angle, and a tape in which the first mode and the second mode are different. When traveling at a speed, there is provided a second mode discriminating means for discriminating by a frequency or a period ratio of a signal on a control track and a signal proportional to a rotation frequency of a capstan motor. Playback device. 7. A mode discriminating means for discriminating presence / absence of a digitally modulated carrier signal reproduced from a magnetic head having the second azimuth angle, and a mode discriminating circuit based on phase synchronization information of the reproduced digital signal. 2. A circuit according to claim 1, comprising: a second discriminating circuit; and a third discriminating circuit for discriminating presence / absence of a horizontal synchronization signal of a signal reproduced from the magnetic head having the first azimuth angle. 7. The magnetic recording / reproducing apparatus according to claim 2, wherein the magnetic recording / reproducing apparatus is a magnetic recording / reproducing apparatus. 8. The apparatus according to claim 1, wherein said first discriminating circuit comprises a band-pass filter, an amplitude detecting circuit, and a comparator, and said second discriminating circuit comprises a synchronization determining circuit of a PLL circuit. 8. The magnetic recording and reproducing apparatus according to 7. 9. The first tracking control means includes: a first envelope detection circuit for detecting a video signal from a pair of magnetic heads having the first azimuth angle; and a magnetic head having the second azimuth angle. It has a first band-pass filter that extracts the audio signal from the pair, and a second envelope detection circuit that detects the output, and captures the output of each detection circuit into a microcomputer so that the capstan motor maximizes the output. A second band-pass filter for extracting a digital modulation signal from the magnetic head pair having the second azimuth angle, and detecting an output of the second tracking control unit. A third envelope detection circuit that controls the speed of the capstan motor so that its output is maximized 3. The magnetic recording / reproducing apparatus according to claim 1, wherein the magnetic recording / reproducing apparatus is constituted by control means for performing the operation. 10. A helical scan type magnetic recording / reproducing apparatus for recording / reproducing with a pair of magnetic heads 180 ° opposed to each other on a rotating drum, wherein the composite video signal is converted into an FM luminance signal and a low-frequency conversion chrominance signal. A first mode in which a magnetic head pair records and reproduces data on a magnetic tape, and an audio signal is FM-modulated, and a second magnetic head pair records and reproduces data in a deep portion of the magnetic tape; A second mode of digitally modulating the band higher than the band and recording / reproducing on a magnetic tape with a second pair of magnetic heads, and information from the first and / or second pair of magnetic heads during reproduction. And a mode discriminating means for discriminating between the two modes based on the information. 11. A helical scan type magnetic recording / reproducing apparatus for recording / reproducing with a pair of magnetic heads 180 ° facing each other on a rotating drum, wherein a composite video signal is converted into an FM luminance signal and a low-frequency conversion color signal, and an audio signal is outputted. A first mode in which the FM signal is FM-modulated and recorded / reproduced on a magnetic tape with a pair of magnetic heads, and a digital signal is digitally modulated into a band higher than the FM-modulated audio signal band and recorded / reproduced on a magnetic tape with a pair of magnetic heads And a mode discriminating means for discriminating between the two modes based on information from the magnetic head pair during reproduction. 12. A helical scan type magnetic recording / reproducing apparatus for recording / reproducing with a pair of magnetic heads 180 ° opposed to each other on a rotating drum, wherein the audio signal is FM-modulated and the magnetic head pair records / reproduces a deep portion of a magnetic tape. And a second mode in which a digital signal is digitally modulated to a band higher than the FM-modulated audio signal band and recorded and reproduced on a magnetic tape by a pair of magnetic heads. And a mode discriminating means for discriminating between the two modes based on the information of (1). 13. A helical scan type magnetic recording / reproducing apparatus for recording / reproducing with a pair of magnetic heads 180 ° opposed to each other on a rotating drum, wherein the composite video signal is converted into an FM luminance signal and a low-frequency conversion color signal, and And a second mode in which digital signals are digitally modulated and recorded and reproduced on a magnetic tape by a pair of magnetic heads, and information from the pair of magnetic heads is reproduced during reproduction. A magnetic recording / reproducing apparatus having a mode discriminating means for discriminating between the two modes.