JPS608525B2 - Magnetic recording and reproducing method - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rotary head type magnetic green picture reproducing device (hereinafter referred to as a VTR) in which two rotary heads sequentially record one field of video signals as a recording trajectory inclined with respect to the longitudinal direction of a magnetic tape. , it is intended to enable recording and reproduction of audio signals of multiple channels even if the moving speed of the magnetic recording medium becomes sufficiently low. Traditionally, VTRs have a configuration in which video signals are sequentially recorded as a recording trajectory inclined with respect to the longitudinal direction of the magnetic tape by a rotating head, and audio signals are recorded at the ends of the magnetic tape by a fixed head. is taken. In such VTRs, the recording density of video signals has significantly increased due to improvements in magnetic tapes and heads, advances in signal processing technology, improvements in mechanical precision, and advances in control technology. For example, if we take a VHS system (4-hour recording) VTR, it has a recording density that is approximately 92 times that of a broadcast VTR (2-inch tape, 4-head type), and an ElM unified type 1 VTR, which has a recording density that is approximately 11 times that of a broadcast VTR (2-inch tape, 4-head type). has reached. In addition, the above VHS system VT
In R, a medium-sized tape is used, and the tape running speed is 1.65 mm. Even in VTRs capable of high-density recording, the characteristics of tapes and heads are improving, and the trend is for higher-density recording to continue in the future. If we were to be able to double the recording density from now, the tape speed would be as slow as approximately 0.8 s when using Kyo-inch tape. When recording audio signals using the conventional fixed head recording method, it becomes extremely difficult to obtain good sound quality for the following reasons. (a) At lower speeds, the recording wavelength becomes shorter, making it difficult to record and reproduce high frequencies, making it impossible to obtain a sufficient audio band (10 KHz or more) (at a tape speed of 1 S, arc Hz is the limit of current technology) (b) As the speed decreases, the playback head output decreases, the S/N ratio deteriorates, and it becomes more susceptible to hum. tc) As the speed decreases, the dynamic range of the signal recording level narrows and distortion occurs. It becomes easier.

[d
- There is a limit to the mechanical accuracy, and the float and flutter become large. Based on the various conditions mentioned above, while there is plenty of room for higher density for video signals, factors have arisen that are hindering higher density in terms of audio signal recording. Recognize. One way to increase the tape speed even when increasing the recording density of video signals is to make the tape narrower, for example, by inches or inches. Although the length of the tape cassette is twice as long as that of a tape (assuming a constant recording density), and the thickness of the tape cassette is slightly thinner (the thickness of the case, the thickness of the reel hub, the space between the reel and the case, etc. remain the same). As a result, the surface ruts become large (due to the thickness), and for cassettes intended for 2-hour recording, they become very large and unbalanced compared to the cassette shape when using inch tape. The disadvantage is that the cassette shape is extremely unbalanced.If the inside of the tape is made even narrower by an inch, the tape speed can be increased, but the surface area becomes larger and the cassette shape becomes extremely unbalanced.What is the problem with such a shape? Separately, when recording and playing back video signals, narrowing the tape can cause skew distortion (due to tape expansion and contraction).
Temporal discontinuities in signals at head switching positions are more likely to occur, and the tilt angle of the video track (with respect to the tape running direction) becomes smaller, resulting in tapering. It is easily affected by waping while driving, making compatible playback difficult.
Furthermore, there are other problems such as insufficient air film formation between the rotating cylinder and the tape, which worsens the stability of tape running and causes jitter. It is well known that it is advantageous from this point of view. As mentioned above, when trying to further improve the recording density of VTRs and keep the cassette shape in a desirable shape, the bottleneck lies in the recording and playback of audio signals, which cannot be solved with the conventional fixed head recording and playback system. Understood. One way to solve this problem is to record and play back the FM-modulated audio signal by multiplexing it on the low frequency side outside the band of the FM-modulated video signal, for example, as is used in video discs. is possible. If the audio signal is frequency-multiplexed with the video signal and recorded, it becomes impossible to re-record only the audio signal (hereinafter referred to as after-recording). A playback-only device such as a video disc may be fine, but a device capable of recording and playback such as a VTR that cannot perform dubbing is a fatal flaw. In view of the above-mentioned problems, the present invention provides an audio signal recording method that allows for high density recording and allows for post-recording. Let's explain using a specific example below. FIG. 1 is a diagram for explaining the tape recording state of a conventional rotary two-head type helical scan VTR. The magnetic tape 1 is wound approximately 180 degrees (180 degrees 12Q) around a rotating head cylinder 2 in which rotating heads H^ and HB are arranged, and the rotating heads HA and HB sequentially transmit video signals onto the tape in diagonal discontinuities. It is recorded as a recording trajectory 3. An audio signal is recorded on the upper end of the tape by a fixed audio head 4. Further, a control signal as a reference signal during reproduction is recorded by the control head 5 at the lower end of the tape. In contrast to such a follow-up system, the present invention records audio signals using rotating heads H and HB without providing a fixed head for audio signals, as shown in a specific example in FIG. . The magnetic tape has 8 parts on the rotating head cylinder 2 compared to the conventional method.
The audio signal is compressed and recorded on the upper end 6 of the tape corresponding to the section a (180 o x 2 Q + 180 degrees of winding). Next, a specific circuit configuration for realizing the above-mentioned recording method will first be described with reference to FIGS. 3 and 4 for the case of recording a one-channel audio signal. Note that FIG. 5 is a timing diagram to supplement FIGS. 3 and 4. In FIG. 3, a video signal to be recorded is input to a terminal 7, and a frequency modulator (FM modulator) 8 outputs an FM signal.
wave converted. This FM wave is gated by a gate circuit 9 and a pulse from a gate pulse generator 15. This gate pulse generator 15 is configured to generate various timing pulses based on the output signal of the detector PG that detects the rotational phase of the rotary heads H^, HB.
That is, as shown in FIG. 5, with respect to the vertical synchronization signal of the input video signal A, the timing of the PG pulse low is configured to occur at a position that is advanced by, for example, seven horizontal synchronization periods (represented as 7 days) from the vertical synchronization signal. The pulses for gating the gate circuits 9 and 10 are given as shown in C and 2, respectively, such that the gate periods overlap each other by a period of approximately 4 days with the mouth pulse as a reference. That is, gated FM waves as shown in FIGS.
Guided by 12. On the other hand, the audio signal inputted to the terminal 161 becomes a time-compressed signal by the time compression circuit 17, and its output is guided to the FM modulator 19. Note that a synchronization signal separated by a synchronization separation circuit 18 from the input video signal is introduced into the time compressor 17. This time compression circuit will be described in detail later. The audio signal compressed and converted into FM waves in this way is sent to the gate circuit 20.
and 21, and are gated by gate pulses of chi and li, respectively, and are led to adders 1 and 12 as gated FM waves, respectively, as gate pulses of chi and ri, respectively, to the pre-FM video signal. The audio FM signal is added together with the video signal and the audio signal. The pulses 1 and 2 are created, for example, by driving a monostable multi at the falling edge of the pulses 3 and 2. The outputs of the adders 11 and 12 are connected to the recording amplifiers 13 and 14, and the R of the recording/reproducing switch SW, SW2.
The information is recorded on the magnetic medium through the terminals and the rotating magnetic heads HA and HB in the form shown in FIG. 2, respectively. When reproducing the composite signal recorded as described above,
The signals reproduced by the magnetic heads H^, HB pass through the P terminals of the switches SW, , SW2, respectively, and are led to the front layer intensifiers 22, 23, respectively. Front layer intensifier 22, 23
The outputs of gate circuits 24, 25 and 29, 30 respectively
1 will be guided. A pulse E created by driving a flip-flop circuit with a PG pulse L is introduced to the gate circuit 24, and a reproduced FM video signal is taken out during the Hj period of the wooden pulse. Further, a pulse with a polarity opposite to that of the pulse is applied to the gate circuit 25, and the reproduced FM video signal (V) is gated during the Hi period of the pulse with the opposite polarity (E). and gate circuit 24
, 25 are added by an adder 26 to produce continuous reproduction FM.
A video signal is obtained. On the other hand, gate circuits 29, 30
Pulses 1 and 2 are added as gate pulses to the outputs, respectively, and FM audio signals of null and ru are obtained, respectively.
2. The FM video signal that is the output of the adder circuit 26 is guided to the FM demodulator 27 and its output terminal 28.
A playback video signal is obtained. On the other hand, the compressed audio signal demodulated by the FM demodulator 32 is led to a time base expansion circuit 33, where it is time expanded with reference to the output of the synchronization signal separation circuit 34, and a continuous reproduced audio signal is obtained at its output terminal 35. Note that the time expansion circuit 33 will be described later. Next, the audio signal time compression circuit 17 will be explained with reference to FIG. The audio signal input to the terminal 16 is guided to two systems of memory circuits 36 and 37. On the other hand, the output of the sync separation circuit 18 is led to the input terminal 18' in FIG. 4, and is led to a horizontal sync signal separation circuit 38 and a vertical sync signal separation circuit 39, respectively. The output of the horizontal synchronization signal separation circuit 38 is led to a write clock generator 40 and a read clock generator 45. In the write clock generator 40, a clock signal having a frequency of, for example, twice the horizontal synchronizing signal frequency, that is, approximately 3 Hz, is generated.
An audio signal having a frequency component up to approximately half the clock frequency, that is, approximately the frequency of one song, can be written into each memory. On the other hand, based on the output of the vertical synchronization signal separation circuit 39, a gate pulse Q of 30Hz (in the case of NTSC signal, 25Hz in the case of PAL signal) is applied to the flip-flop circuit 41.
Get Q. These gate pulses Q and Q gate the write clock gate circuits 43 and 44, respectively, and apply the write clock to the memory circuits 36 and 361 alternately every one field period, thereby alternately storing the input audio signal. urge In this case, the number of bits stored in the memory is 525 bits (N
TSC). That is, the input audio signal A, , A in Fig. 5
For example, the two parts are stored in the memory 36 as the A, ', N' part of the force, and the B,, B2 part of the input voice is stored in the memory 37 as the B, 'PB2'... part of the force. Make me remember. The signals thus stored in the memory are read out by the clock of the read clock generator 45. If this readout clock pulse is selected, for example, on the 4th pitch NaR = 40th day of the horizontal synchronization signal frequency deadline, NaR/Pw: 40mm no 2NaH = 20
Therefore, the audio signal written in the period ↑v:1 nona v (where v is the vertical scanning frequency) will be read out in the 20 period of ↑v. In other words, the A1 and A2 stored in the memory 36 will be read out in the 20 period ↑v. ---
- The information of... is compressed into the time at home and becomes A, ′, of the fifth diagram.
The information B, B2, etc. read out as A2'... and stored in the memory 37 are B', B5' in FIG.
It is compressed and read out in the period of the house as ``-----...-''. The read compressed audio signal is then obtained at the output of the adder circuit 48 in a similar format. Now, the timing of creating this read clock pulse can be configured as follows, for example. That is, using the leading edge of the vertical synchronizing signal separated by 39 as a reference, a gate pulse generator 42 generates gate pulses equivalent to 525 read clocks, and the gate pulses are read out alternately for each field by the gate circuits 46 and 47. Gate the clock. Also, the timing of gates 46 and 47 is synchronized with the timing of flip-flop 41, so that the output of gate 41 is synchronized with that of flip-flop 41.
The top pulse generator 42 is controlled. In addition, 42
In order to synchronize the pulse generated by 525 clocks with 525 clocks, it is a reliable method to count the clocks, but in the case of recording, it is not always necessary to
It is not necessary to set the pulse to 5, and a pulse slightly wider than that is fine. The thus compressed audio signal y is obtained at the terminal 49, and this signal is turned into an FM wave by the FM modulation circuit ig in FIG. 3 and gated by the gate circuits 20 and 21. In this case, the gate timing is as described above, and the gate timing is wider than the period in which the compressed layer number Y exists. By doing so, it is possible to prevent noise caused by transients occurring when switching the FM carrier during FM demodulation from interfering with the audio signal. Next, the expansion circuit 33 during reproduction will be described. The reproduction side decompression circuit can also have the same configuration as the recording side compression circuit. The only difference is that the write clock generator 40 during recording shown in FIG. 4 is used as a read clock generator during reproduction, and the read clock generator 45 during recording is used as a read clock generator during reproduction.
is used as a write clock generator during playback, and instead of driving the flip-flop 1 with a vertical synchronizing pulse (output of 39), the write pulse generated by the gate pulse generator 42 (during playback) is used as shown by the dotted line. )
What is necessary is to configure it so that it is triggered at the rear of the line. Furthermore, in order to determine the polarity of the flip-flop 41,
It is necessary to reset the four pulse flip-flops that occur. The compressed signals reproduced in this manner are shown in FIG. ',B. ',A2',B
2'...'' is expanded to Mr. ``Ar,B,'',n'',
&''......The output terminal of the decompression circuit receives approximately one field (approximately 16 seconds) of the video signal.
) a continuous audio signal with a delay is obtained. Generally, if the delay time difference between the video signal and the audio signal is less than about 50 msec, it will not be detected.
A deviation of about c is not a problem at all. Now, in the above explanation, the memory element was assumed to be an analog memory element such as BBD, capacitor memory, or CCD, but if an A/D converter is provided in front of the memory element in the above explanation, it can be used as a memory. Obviously, digital memory can be used. In this case, by providing a D/A at the memory output to restore the compressed analog signal, the subsequent processing will be exactly the same. Now, let's consider the frequency band of the audio signal when it is compressed. When an audio signal of approximately 1 part Hz is time-compressed 20 times as described above, its frequency band becomes 300 KHz. The frequency band of 300 KHz is still sufficiently narrow compared to the video signal band of about Hosokawa Z, and as a carrier for FM, it can be arbitrarily set between several hundred KHz and several MHz, and S is sufficient.
/N good recording and playback is possible. This increases the degree of audio compression. approximately low
This shows that it is possible to record data even if it is compressed to the level of sound, and it is also possible to frequency-modulate different carriers with two or more signals.
This shows that frequency division recording is also possible. In addition, in the case of the above-mentioned specific example, the angle 8 for wrapping around the conventional dodge in FIG. 2 is approximately 180o/20≦9
It is sufficient to make it slightly larger than o, and the influence on tape running properties can be ignored. Although the method of recording a compressed audio signal by FM modulation has been described, it is clear that it is possible to use other methods such as phase modulation, amplitude modulation, etc. in place of FM modulation. Now, in the explanation of the specific example above, when a compressed and recorded audio signal is expanded by an expansion circuit during playback, we talked about a method in which the starting point when writing to memory is the leading edge of the playback vertical synchronization signal. Another method for accurately determining the memory write timing during playback without using the playback vertical synchronization signal will be explained with reference to Figure 6. Figure 6A shows the waveform of the video signal near vertical synchronization. V indicates a vertical synchronization signal. Figure 6 (a) and (c) are signals FM modulated by the video signal O in Figure 5, and are approximately 4 days before and after the playback head switching point b. The audio signals are overlapping and recorded by separate rotating heads.On the other hand, the audio signal is compressed as described above and becomes as shown in a in Figure 6, 2. A burst signal P is inserted into the memory so that writing to the memory can be started after a certain period of time (may be 0) from the end point of this burst signal P during playback.Second signal is FM modulated and gated for a wider period before and after the second signal to obtain an FM wave like E.
The M wave is added to the mouth FM wave to form a composite signal such as .A sound FM signal is recorded on the winding angle 8 of the magnetic tape by a rotating magnetic head. Next, a recording pattern of audio signals that is slightly different from that shown in FIG. 2 will be explained. In Fig. 7, the audio signal is compressed and recorded on the end of the tape by the rotating head as in Fig. 2, but unlike the case in Fig. 2, the audio signal is Only the head records, and the other rotating magnetic head does not record. In this case, the audio signal for two fields is time-compressed by following the example.The compressed audio frequency band will be, for example, 600 KHz, but as mentioned above, it cannot be fully accommodated in the recording and reproducing band by the rotating magnetic head. Yes, the third
The circuit configurations shown in FIGS. and 4 can be used almost as they are. The difference is that the memory capacity is doubled, the flip-flop 41 in FIG. 4 is replaced with a two-stage flip-flop, and the signal path passing through the gate circuits 21 and 30 in FIG. 3 is omitted. In the case of FIG. 7, even if the tracking deviates, the adjacent audio signal will not be reproduced, so the risk of crosstalk can be eliminated. Alternatively, as shown in FIG. 8, a method can be considered in which the audio signal is compressed into four field periods and similarly recorded once every four tracks at the end of the tape using a rotating head, but in this case, the memory capacity becomes large.
Another possible method is to compress the audio signal by 3 field periods and record it once in 3 tracks using a rotating magnetic head, but in the case of a 2-head method, the recording heads alternate and the circuit configuration becomes complicated. Become. However, in the case of three rotating heads, recording and reproducing can be performed using the same magnetic head, which simplifies the circuit configuration, which is advantageous. Furthermore, the above-mentioned method of recording once every four tracks can also be said to be advantageous in the case of the rotating four-head method. In addition, as a method to prevent crosstalk interference even when tracking deviation occurs during playback, a method is adopted in which the FM carrier frequency of the audio signal FM circuit is changed for each track, and the bands do not overlap with each other. You can also. For this purpose, for example, the FM carrier shown in FIG.
After that, a bandpass filter corresponding to each FM carrier may be provided. Note that one possible method for eliminating crosstalk interference from adjacent tracks is to record on every other track as shown in Figure 7, but as another method, it is possible to record on every other track as shown in Figure 9. It is also effective to reduce reproduction signals from adjacent tracks by utilizing the azimuth recording employed. That is, by tilting the side angles of the gap between the rotating magnetic heads H^ and HB in opposite directions, crosstalk from adjacent tracks can be reduced by taking advantage of the fact that azimuth loss increases when reproducing adjacent tracks. . Furthermore, in the above explanation, a specific example was described in which the control signal is recorded at the bottom edge of the tape, and the audio signal is compressed and recorded at the top edge of the tape. However, as shown in FIG. It is also possible to compress the audio signal and record it at the bottom end of the tape (depending on the system, a control track may not be necessary). The circuit configuration in this case can be configured using the same idea as in the specific example described above, although the timing relationship will change slightly. It is sufficient to wrap more of the tape around the side where the head enters (the left side of the figure).The above describes the case where the audio signal is compressed and recorded with a rotating head in a two-head helical scan VTR, but regardless of the two-head system,
It can be applied to devices that overlap record continuous signals as discontinuous trajectories using multiple heads. Therefore, the present invention can be used not only in tape-shaped recording media but also in devices that record on card-shaped recording media. In addition, in the above explanation, the case where one field of video signal is recorded on one recording track was explained, but when recording two fields on one track, or when recording only three fields (n is an integer), can also be applied. Now, in the above explanation, a case has been described in which only one channel of audio signals is recorded, but a method for recording two channels of audio signals will now be explained. As a first specific example, we propose the method shown in FIG. 11. In FIG. 11, the audio signal of CH, is compressed and
As in the case shown in the figure, the audio signal is recorded by one rotary magnetic head, for example HA, and the C-ratio audio signal is similarly compressed and recorded on the edge of the tape by the other rotary magnetic head HB. Note that there is a risk of crosstalk occurring if the tracking deviates, but by tilting the gap between the magnetic heads H^ and HB in opposite directions as explained in Fig. 9, the high-frequency signals are compressed and Mutual crosstalk between the modulated audio signals can be suppressed by azimuth loss. Next, a concrete block diagram of the circuit configuration for recording the audio ephemeris as shown in FIG. 11 will be explained with reference to FIG. 12. The explanation will be made with reference to FIG. 13 as a waveform diagram for explaining FIG. 12. In FIG. 12, parts common to those in the circuit block diagram of FIG. 3 are shown with the same numbers, and newly added circuits are shown with numbers 101 to 117. In FIG. 12, 101 is a vertical synchronizing signal separation circuit;
02 is a flip-flop circuit, 103 is a horizontal synchronizing signal separation circuit, and 104 and 105 are CH, ?, respectively. CH2 audio signal input terminal, 106 and 107 are time compression circuits,
108 is an adder circuit, 109, 110' is a gate circuit, 1
117 and 112 are all time expanded video signals, 113,
Balls 14 are playback audio output terminals for CH, CH2, respectively,
1 1 5, the vertical synchronizing signal separation circuit 116 is F IJ, SOP F. 117 is a horizontal synchronizing signal separation circuit. In the above circuit, the characteristics of the flip-flop 102 driven by the vertical synchronization signal (IQI output) are, for example,
The PG pulse, which indicates the rotational phase of the head, is made constant by the input signal in FIG. 13, and, for example, a signal as shown in FIG. 13C is obtained as its output Q signal. Then, at the rising edge of this Q signal, writing of the audio signal of CH input to the terminal 104 into one memory of the time compression circuit 106 is started, and the period corresponding to 2 fields (
≦32 sec) A signal in FIG. 13, 2, is written.
Then, as soon as the writing is completed, the A. ′ is obtained. Furthermore, when the writing in one memory of the compression circuit 106 is completed, the continuation of the audio signal of CH, A2 in FIG. . The above operation is repeated for the audio signal of CH. On the other hand, the audio signal of CH2 is stored as an audio signal B corresponding to two fields in one memory circuit of the time compression circuit 107 with reference to the falling part of the signal in FIG.
13 is stored, and upon completion of storage, it is read out at a speed of two stitches (B'). The B portion of the audio signal having the same C ratio is stored in the other memory of the same compression circuit as shown in FIG. 13, and read out as B2'. This operation is repeated one after another in the time compression circuit 107. Therefore, the output of the adder circuit 108 is as shown in FIG.
CH compressed field by field like......
The audio signal of CH2 will be obtained alternately. This signal passes through the FM circuit 19, gate circuits 20 and 21, and is added to the FM video signal in the calculation circuits 11 and 12.
The HA head will record a signal as shown in Figure 13, and the HB head will record a signal as shown in Figure 13. During playback, the FM demodulated synthesized audio signal passes through gates 109, 110 and is separated into compressed signals of CH, , CH2, which are expanded by time expansion circuits 111 and 112, respectively, to form continuous CH, , C ratios. The reproduced audio signals of are obtained from terminals 13 and 114, respectively. The flip-flop 115 is used to define the timing of writing to each memory, and its suitability is made constant by the PG pulse indicating the rotational phase of the opening in FIG. Further, the horizontal synchronization signal separation circuits 103 and 117 are used as reference signal generators for creating memory write and read clocks.
, 107 and the time expansion circuits 111, 112 can be easily obtained by partially changing the configuration of FIG. 4 and using the same concept. As a second specific example of recording 2-channel audio signals, as shown in Figure 14, CH is recorded at both ends of the tape (inside the control track if there is one).
, and C ratio separately. It is clear that the specific circuit configuration for recording as shown in Figure 14 can be realized by combining the circuit configurations described so far, and the tape running path can be realized by a rotating magnetic head cylinder as shown in Figure 15. On the other hand, it is sufficient to wrap the tape 0 more on both sides than the tape wrapping angle of 1800x2Q for the subordinate. Furthermore, in order to accurately obtain the timing of the compressed audio signal during reproduction, it is effective to record a burst signal as a pilot signal immediately before the compressed audio signal, as shown in FIG. Furthermore, as a modification of the specific example shown in FIG. 14, a configuration as shown in FIG. 16 is proposed. In the system shown in FIG. 16, in the head H^, CH. The head HB records CH2, and the respective recording positions are distributed to both ends of the tape. In this way, crosstalk will not occur even if a track shift occurs, and the control signal can also be recorded in the blank area of CH2, which can also be used in common with the control track. (However, FIG. 16 shows the case where the control track is provided separately.) In this case as well, the above explanation can be put into practice. As a third specific example of recording two-channel audio, we propose a method for recording compressed two-channel audio signals at the end of the tape in a time-division manner as shown in FIG. The circuit configuration in FIG. 17 is also a combination of FIGS. 3 and 12,
Although it can be constructed from the above-mentioned content, the compression timing of CH2 can be based on the timing of the end of compression (during recording) of CH, and the pilot burst shown in Fig. 6 can be set just before the compressed audio signal. An effective method is to record the information in As a modification of FIG. 17, there is a method of recording on one additional track as shown in FIG. There is also a recording pattern configuration as shown in FIG. 18 as a modification of FIGS. 7 and 17. As a fourth specific example of recording two-channel audio, as shown in FIG.
, frequency-divided into the signal of Fig. 2 or Fig. 7 or Fig. 1
We propose a method for recording data in the format shown in Figure 0. Note that the pilot signal shown in FIG. 19 is a pilot signal indicating H recording, and is also used as a demodulation carrier for the C ratio. The frequency multiplexed signal as shown in Fig. i8 is further modulated (FM is preferable) and recorded on the end of the tape by a rotating head. Note that, as shown in FIG. 19, the C side may be given the SSB title, but as another form, it may be taken as a VSB signal or a residual sidewave FM signal, and various modifications are possible. As mentioned above, two-channel audio signals can be compressed and recorded at the end of the tape using various methods. , 14 or 16, it is possible to record after erasing with a fixed erase head;
The case shown in FIG. 17 can be realized by overwriting the previously recorded signal. As mentioned above, "According to the present invention, it is possible to record two-channel audio signals regardless of whether the tape speed becomes slower due to further increase in density in accordance with VT rules, and has the following features. 1. One arc of the audio band can be maintained regardless of the tape speed. 2. It is almost unaffected by wow and flutter. In other words, the uneven rotation of the VTR is extremely small, and the tape running speed is Wow, flutter increases tape speed with magnetic head VT,
If the rotating peripheral speed of the hend is vH, then the wow and flutter components are vt/vH'. And normally Vt/VH cooperates below cloth. Therefore, by recording with a rotating head, the wow and flutter of the audio signal can be reduced to a negligible level. 3. A fixed head for audio recording and playback is no longer required, and the rotating head for video recording can be shared. 4. This is a method in which both video and audio signals are recorded and played back using a rotating magnetic head, but it is not possible to perform after-recording of the audio signal. In other words, it is possible to erase the edge of the tape corresponding to the audio recording portion with a fixed erasing head and re-record it, or
Re-recording on top of a recorded audio signal erases the previously recorded signal and leaves behind a new signal. This is possible because the audio signal is modulated at a high frequency and recorded at a short wavelength.

[Brief explanation of the drawing]

Figure 1A is a side view showing an outline of a conventional video tape recorder, the opening is a plan view of the same, Figure 2A is a side view showing an outline of the video tape recorder of the present invention,
The figure is a block diagram for explaining a concrete example for realizing the present invention, Figure 4 is a block diagram of a concrete example of the time compression (expansion) circuit in Figure 3, and Figure 5 shows the operation of Figure 3. Timing and waveform diagram for explanation, Figure 6 shows memory during playback.
Waveform diagrams for explaining other specific examples of determining the writing timing to the circuit, FIGS. 7 to 10 are diagrams each showing the audio signal recording position on the magnetic tape, and FIG. 11 is a diagram showing the audio signal recording position on the magnetic tape according to the present invention. Figure 1 showing the audio signal recording position of
Fig. 2 is a block diagram showing one embodiment of the present invention, Fig. 13 is an explanatory diagram of the same operation, Fig. 14 is a diagram showing a recording pattern of another embodiment of the invention, and Fig. 15 realizes Fig. 14. 16 to 18 are plan views showing main parts of a tape running system for recording, and FIGS. 16 to 18 are views showing recording patterns of other embodiments of the present invention.
The figure shows the frequency relationship when a two-channel audio signal is frequency-divided and transmitted. 7...Video signal input terminal "8, 19...F
M modulator, 9, 10, 20, 21, 24, 25, 29,
30...River gate circuit, 16,104,105...
Audio signal input terminal, 17, 106, 107... Time compression circuit, 27, 32... FM demodulator, 33, 111 Ch. 112... Time expansion circuit, H^, HB... Rotating head. Figure 1 Figure 2 Number 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 2 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19

Claims (1)

[Claims] 1. In a magnetic recording and reproducing system in which two rotary heads sequentially record and reproduce one field of video signals as one recording locus inclined with respect to the longitudinal direction of a magnetic tape, a rotary head cylinder in which the rotary heads are disposed; A magnetic tape is wound around the magnetic tape by a winding angle (180° + 2α + θ) (however, αθ≠0), and during recording, an image is recorded in one recording trajectory by the rotating head at a portion corresponding to the winding angle θ. Two channels of audio signals corresponding to the time length of the signal are time-compressed and recorded in a time-division state, and during playback, the two-channel reproduced compressed audio signals reproduced by the rotary head are time-expanded to produce two channels of reproduced audio. A magnetic recording and reproducing method characterized by obtaining signals.