JPS63114382A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain the recording of a sound signal of multichannels capable of post-recording suitable for densification by recording the sound signal separately on the extension of preceding and succeeding video signal recording track recorded on the center of a tape. CONSTITUTION:A video signal is FM-converted by a FM modulator 8 and gated by using a pulse of a gate pulse generator 15 at gate circuits 9, 10. The sound signal is subjected to time compression by a time compression circuit 17, FM-converted by a FM modulator 19, gated by gate circuits 20, 21 and the video signal and the sound signal are added by adders 11, 12. The output of the adders 11, 12 are recorded on a magnetic tape 1 via recording amplifiers 13, 14, recording/reproducing changeover switches SW1, SW2 and rotary magnetic heads HA, HB respectively. The magnetic tape 1 is wound around the rotary head cylinder more than by an angle theta than a conventional system and the sound signal is recorded on ends 6, 6' of the tape corresponding to the angle theta.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotary head type magnetic recording and reproducing apparatus (hereinafter referred to as a VTR) in which a plurality of rotary heads sequentially record video signals as discontinuous recording trajectories on a magnetic recording medium. This makes it possible to record and reproduce audio signals of multiple channels even if the moving speed of the magnetic recording medium becomes sufficiently low.

Conventionally, VTRs have been configured such that video signals are sequentially recorded by a rotating head as a recording trajectory inclined with respect to the longitudinal direction of the magnetic tape, and audio signals are recorded by a fixed head at the edge of the magnetic tape. There is.

In such VTRs, the recording density of video signals has significantly improved due to improvements in magnetic tapes and heads, advances in signal processing technology, improvements in mechanical capacity, and advances in control technology.

For example, if we take a VH8 format (4-hour recording) VTR, it is approximately 92 times more efficient than a broadcasting TR (2-inch tape, 4-head type), and approximately 1 times more efficient than an E IAT-1 type VTR.
It has reached a recording density of 1x. In the VH5 type VTR described above, a -inch width tape is used, and the tape running speed is 1.65 crJS. Even in VTRs with high-density recording, tape,
The characteristics of heads are improving, and the trend is toward higher density recording in the future.

Even if it were possible to double the recording density, the tape speed would be as low as about 0.8 cnV'S if Finchtag was used. As described above, when the speed becomes extremely low, it becomes extremely difficult to record audio signals using the conventional fixed head recording method to obtain good sound quality for the following reasons. (a) When the speed becomes low, the recording wavelength becomes short, making it difficult to record and reproduce high frequencies, and it becomes impossible to obtain a sufficient audio band (10 KHz or more) (
At a tape speed of 11S, about 5 KHz is the limit of the current technology. ).

(b) As the speed decreases, the playback head output decreases and S/
N deteriorates and becomes more susceptible to hum.

(0) As the speed becomes lower, the dynamic range of the signal recording level becomes narrower and distortion becomes more likely to occur.

(There is a limit to the accuracy of the mountain mechanism, and the 7/7 rattles become larger.

Given 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 for audio signal recording. I understand.

It is possible to reduce the tape speed to 1 inch even if the recording density of the video signal is increased, but it would not be twice as long as the chief inte tape (assuming the recording density is constant), and the shape of the tape cassette Although the thickness is slightly thinner (the case thickness, reel hub thickness, space between the reel and case, etc. remain the same, the thickness will not be halved but will be about ボ), but the surface area will be larger. A cassette designed for time recording has the disadvantage that it has a very large cassette shape compared to when a 1-inch tape is used. If the tape width is further narrowed to 100 inches, the tape speed can be increased, but the cassette shape, which has a larger surface area, results in extremely poor balanne. Apart from these shape problems, there are also problems when recording and reproducing video signals: when the tape width is narrowed, skew distortion (temporal discontinuity of the signal at the head switching position) is more likely to occur due to expansion and contraction of the tape. The tilt angle of the video track (with respect to the tape running direction) becomes smaller, making it susceptible to wave pinking during tape running, making compatible playback difficult, and furthermore, the air film formation between the rotating cylinder and the tape becomes insufficient. However, it is well known that the tape width is advantageous from the viewpoint of recording and reproducing video signals, although it has problems such as poor tape running stability and jitter generation.

As mentioned above, further improving the recording density of VTR,
It has been found that the bottleneck in trying to maintain the desired shape of the cassette is the recording and reproduction of audio signals, which cannot be solved using conventional fixed head recording and reproduction methods.

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. However, 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 used, but V
The inability to perform dubbing with recording and playback equipment like TR is a fatal flaw.

In view of the above-mentioned problems, the present research aims to provide a multi-channel audio signal recording method that is suitable for high density recording and also allows for dubbing. A specific example will be explained below.

Figure 1 shows a conventional two-head rotating helical scan VT.
FIG. 3 is a diagram for explaining the tape recording state of R. The magnetic tape 1 is rotated approximately 180 degrees (180 degrees + 27Z) around a rotating head cylinder 2 in which rotating heads HA and HB are disposed.
), and the video signals are sequentially recorded onto the tape as a diagonal discontinuous recording trajectory 3 by the rotary heads HA and HB.

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 conventional methods, the present invention records at least two channels of audio signals using a rotating head without providing a fixed head for audio signals. First, a method for recording audio signals with a rotary head will be explained using FIGS. 2 to 6.

In Fig. 2, the magnetic tape 1 is wound around the rotary head cylinder 2 more by θ than in the conventional method.
00+2α+θ) The audio signal is compressed and recorded on the upper end 6 of the tape corresponding to this θ portion.

Next, a specific circuit configuration for realizing the above-described recording method will first be described with reference to FIGS. 3 and 4 for the case where one channel of audio signals is recorded. Note that FIG. 6 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 is converted into an FM wave by a frequency modulator (FM modulator) 8. This FM wave is gated in gate circuits 9 and 10 by pulses from a gate pulse generator 15.

This gate pulse generation 1i15 is generated by the rotating heads HA and H.
It is configured to generate various timing pulses based on the output signal of a detector PG that detects the rotational phase of B. That is, as shown in FIG. 6, with respect to the vertical synchronizing signal of the input video signal A, the timing of the PG pulse low is configured to occur at a position advanced by, for example, 7 horizontal opening periods (expressed as 7H) from the vertical synchronizing signal. , pulses for gating gate circuits 9 and 10 are given as pulses such as 8 and 2, respectively, such that the gate periods overlap each other by approximately 4H period with respect to the gate pulse. .

On the other hand, the audio signal input to the terminal 16 is transmitted to the time compression circuit 1.
The time-compressed signal and its output are guided to an FM modulator 19 by 7. Note that a synchronization signal separated by a synchronization separation circuit 18 from the input video signal is introduced into the time pressure m unit 17. This time compression circuit will be described in detail later. The audio signals thus compressed and converted into FM waves are guided to gate circuits 20 and 21, respectively.

The audio FM signals are gated by gate pulses of 1 and 11, respectively, and are guided to adders 11 and 12 as gated FM waves, respectively, to the FM video signal.
The signal N, the video signal G, and the audio signal L are added together.

The pulses H and S are created, for example, by driving a monostable multi at the falling edge of the pulses C and II.

The outputs of the adders 11 and 12 are sent to the recording amplifiers 13 and 14° recording/reproduction changeover switches SW1. The information is recorded on the magnetic medium through the R terminal of SW2 and the rotating magnetic heads HA and HB in the form shown in FIG. 2.

When reproducing the composite signal recorded as described above,
The signals reproduced by the magnetic heads HA and HB are sent to the switches sw1. The signals are passed through the P terminal of sw2 and led to the preamplifiers 22 and 23, respectively.

The outputs of the preamplifiers 22 and 23 are respectively connected to gate circuits 24.
．． 25, 29, and 30. The gate circuit 24 receives a pulse E generated by driving a 7-lip 70-tub circuit with a PG pulse low, and extracts the Hi period of the pulse E into the reproduced FM video signal. Further, a pulse of opposite polarity to E is applied to the gate circuit 25, and the reproduced FM video signal of G is gated during the Hi period of the pulse of opposite polarity E. The outputs of the gate circuits 24 and 25 are then added together by an adder 26 to obtain a continuous reproduced video signal.

On the other hand, gate pulses 29 and 30 are respectively applied as gate pulses, and FM audio signals of nu and ru are obtained as the outputs, respectively. guided by.

The FM video signal output from the adder circuit 26 is led to an FM demodulator 27, and a reproduced video signal is obtained at its output terminal 28.

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 the horizontal sync signal separation circuit 38 and the vertical sync signal separation circuit 39, respectively.

The output of the horizontal synchronization signal separation circuit 38 is guided to a write clock generator 4o and a read clock generator 46. In the write clock generator 4o, for example, a clock of twice the horizontal synchronizing signal frequency fH, that is, approximately fw = 32 KHz, is generated, but this clock signal of 2fM = 32 KHz generates a clock that is approximately half the clock frequency, that is,
Audio signals with frequency components up to approximately KHz can be written into each memory.

On the other hand, the output of the vertical synchronization signal separation circuit 39 is
Based on the tube circuit 41, gate pulses Q and Q141 of 30 Hz (NT, SC: signals, 25 Hz in the case of PAL signals) are used to gate the write clock gate circuits 43 and 44, respectively. Then, a write clock is applied alternately to the memory circuits 3θ, 37 every one field period, so that the input audio signals are alternately stored.

In this case, the number of samples stored in memory is 625 samples (
NTSC). That is, the input audio signal A4.
For example, transfer part A2 to memory 36.

A' is stored as part B1 of the input voice. B2
The parts are stored in the memory 37 as parts B4, 14, . . . of Wa. The signals thus stored in the memory are read out by the tarlock of the read clock generator 46. This read clock pulse is, for example, 40 times fH of the horizontal synchronization signal frequency fR=4
If you choose Of H, fR/fw=4ofH
/2fH=20, and the audio signal written in the period τ7=1/fv (fv is the vertical scanning frequency) is read out in the period τ7/2o. That is, A1 stored in the memory 36
．． The information of A2... is compressed into the time of Hiroshi' and read out as the 6th diagram λtor..., and the information B1, B2... is stored in the memory 37. ... is the fifth
The data is compressed and read between positive igJ as B, , B6, etc. in the figure. Then, the read compressed audio signal is obtained at the output of the adder circuit 48 in the form shown in FIG.

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 625 readout clocks, and the gate pulses are read out alternately for each field by gate circuits 46 and 47. Gate the clock.

Further, a gate pulse generator 42 is controlled by the output of gate 41 so that the timing of gates 46 and 47 is synchronized with the timing of 7-lip/70-tub 41.

Note that the pulse width generated by 42 is read out from the clock 626.
Counting the read clock is a reliable method to match the pulse width to 626, but in the case of recording, the pulse width does not necessarily have to match 626, and a slightly wider pulse may be used. The audio signal compressed in this manner is obtained at the terminal 49, and this signal is converted into an FM wave by the FM modulation circuit 19 in FIG.
gated with. In this case, the gate timing is as described above, and is gated wider than the period in which the compressed signal Y exists. By doing this, F
It is possible to prevent noise caused by transients occurring when switching the FM carrier during M 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 4o during recording in FIG. 4 is used as a read clock generator during playback, and the read clock generator 46 during recording
is used as a write clock generator during reproduction, and instead of driving the flip-flop 41 with the vertical synchronizing pulse (output of 39), the write pulse generated by the gate pulse generator 42 (reproducing of time)
The trigger may be configured to be triggered at the trailing edge of the trigger. Note that in order to determine the polarity of the flip-flop 41, it is necessary to reset the flip-flop 41 with a pulse generated by the PG. Compressed signals reproduced in this manner (Fig. 6: r) O%, AQ, B', , A4.
B et al... are extended and become B B.

M, y, t, p4. Bl! , . . . At the output terminal of the decompression circuit, a continuous audio signal delayed by approximately one field (approximately 1 emsec) with respect to the video signal is obtained.

The delay time difference between video signal and audio signal is generally 50m5e
If it is less than c, it will not be detected, so in this case 18m
A deviation of about 5eC is not a problem at all.

Now, in the above explanation, the memory element is BBD.

Although the explanation has been made assuming an analog memory element such as a capacitor memory or COD, it is clear that a digital memory can be used as the memory by providing an A/D converter in front of the memory element in the above explanation.

In this case, by providing a D/A to 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 about 15 KHz is time-compressed 20 times as described above, its frequency band becomes 300 KHz.

The frequency band of 300KH2 is the video signal band approximately 3M
Hz (for FM, the carrier can be arbitrarily set between several hundred KHz and several MHz, and recording and reproduction with a sufficiently good S/N can be performed.

This means that the degree of audio compression is not just 5, but approximately 100.
This shows that it is possible to record data even if it is compressed to about twice as much, and it also becomes possible to digitally record it as a PCM signal.

Further, in FIG. 2, the winding angle θ, which is more than the conventional one, can be made slightly larger than approximately 18°0/2° (9°), and the effect on the tape runnability can be ignored. Although the method of recording a compressed audio signal by FM modulation has been described, it is clear that it is also possible to use phase modulation, amplitude modulation, pulse code modulation (PCM), etc. instead of FM modulation.

Now, in the above explanation, when decompressing a compressed and recorded audio signal using an expansion circuit during playback, we described a method in which the starting point when writing to memory is the leading edge of the playback vertical sync signal. Another method for accurately determining memory write timing during playback without using signals will be described with reference to FIG.

FIG. 6A shows a waveform near the vertical synchronization of the video signal, and ■ indicates the vertical synchronization signal.

6 and 6 are signals FM modulated by the video signal O in FIG. Overlapping recording is performed.

On the other hand, the audio signal is compressed as described above and
For example, a burst signal P made from a clock signal is inserted immediately before this a, and the memory is stored after a certain time (which may be 0) from the end point of this burst signal P during playback. Enables you to start writing to.

The second signal is FM modulated and gated for a wider period before and after the second signal to obtain an FM wave like E. Ho's F
The M wave is added to the mouth FM wave to form a composite signal such as , and the rotating magnetic head records the audio FM signal on a portion of the magnetic tape at a winding angle θ.

An effective method for removing crosstalk interference from adjacent tracks is to reduce the reproduction signal from adjacent tracks by using azimuth recording, which is also used in VH3 VTRs, as shown in Figure 7. . That is, by tilting the inclination angles of the gaps of the rotary magnetic heads HA and HB in opposite directions, it is possible to reduce the crosstalk from the adjacent tracks by taking advantage of the fact that the azimuth recording becomes larger when reproducing the adjacent tracks.

Furthermore, in the above explanation, a specific example was described in which the control signal is recorded at the bottom end of the tape, and the audio signal is compressed and recorded at the top end of the tape. It is also possible to compress the audio signal and record it at the bottom of the tape (depending on the system, a control track may not be necessary). Although the timing relationship in the circuit configuration in this case changes slightly, it can be configured based on the same concept as in the specific example described above. In this case, the extra angle θ of the wrapping angle of the tape in FIG. 2 can be increased by wrapping the tape more toward the head entry side (left side in the figure).

The above has described the case of compressing the audio signal and recording it with a rotary head in a two-head helical force scan VTR. It can be applied to 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.

Furthermore, in the above description, the case where one field of a video signal is recorded on one recording track is explained.
When recording two fields on one track, or one field of one! This method can also be applied to the case where only - (n is an integer) are recorded.

Furthermore, in the above explanation, a method was described for recording a time-compressed audio signal in the overlap recording section.
In TR, it is also possible to record a time-compressed audio signal on an extension of each recording track of a video signal.

Now, in the above explanation, a case has been described in which audio signals are recorded for one channel, but a method for recording audio signals for two channels will be explained with reference to FIG.

In FIG. 9, time-compressed two-channel audio signals are recorded separately on the front and rear extensions of each video track in the video signal recording track area 3, and the two-channel audio signals are recorded on each video track. The time axis is compressed and recorded in units of time length corresponding to the time length of the video signal recorded on the video signal.

Since the specific circuit configuration for recording as shown in FIG. 9 can be realized by combining the circuit configurations described so far, the explanation will be omitted here. Also, the tape running route is the 10th
It is clear that this can be achieved by wrapping the tape around a rotating magnetic head cylinder as shown in the figure, by θ more than the conventional tape winding angle of 180' + 2α on both sides.Generally, video signals are recorded. As for the tape winding angle required for this, it is sufficient to wrap the tape by an extra zero on both sides and record the time-compressed audio signal on that part. 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.

According to the configuration of the present invention shown in FIG. 9, the audio signal recording areas of CH1 and CH2 are recorded at both ends of the track (near the end of the tape) so as not to overlap with the video signal, so that the audio dubbing for each chat p is performed. It is also possible to respond to As described above, according to the present invention, as the density of VTRs increases further in the future, the tape speed will become slower and the tape speed will become slower.
It can record audio signals of channels and has the following characteristics.

1. The audio band of 15 KHz can be secured regardless of the tape speed.

2 Almost unaffected by wow and flutter. In other words, the rotational unevenness of a VTR is extremely small, and the wow and flutter components of tape running are expressed as vt/v, where the tape speed is vt and the rotational peripheral speed of the head is VH.
It becomes H. And normally vt/vH is π7 or less. Therefore, wow and flutter in the audio signal are reduced to a negligible level compared to recording with a rotating head.

3. A fixed head for audio recording and playback is not required, and a rotating head for video recording can be shared.

4 This is a system in which both video and audio signals are recorded and played back using a rotating magnetic head, but it is possible to perform after-recording of separate audio signals. In other words, it is possible to erase the edge of the tape corresponding to the audio recording part with a fixed erasing head and re-record it, or if you re-record on top of the recorded audio signal, the previously recorded signal will be erased. It is erased and a new signal remains. This is possible because the audio signal is modulated at a high frequency and recorded at a short wavelength.

[Brief explanation of the drawing]

FIG. 1A is a side view showing an outline of a conventional video tape recorder, the mouth is a plan view of the same, and FIG. The mouth is the same plan view, FIG. 3 is a block diagram for explaining a specific example for realizing FIG. 2, and FIG.
The figure is a block diagram of a specific example of the time compression (expansion) circuit in Figure 3, Figure 5 is a timing and waveform diagram to explain the operation in Figure 3, and Figure 6 is the writing to the memory circuit during playback. Waveform diagrams for explaining other specific examples of determining timing; FIGS. 7 and 8 are diagrams each showing audio signal recording positions on a magnetic tape; FIG. 9 is a diagram showing a recording pattern of an embodiment of the present invention. 10 are plan views showing essential parts of a tape running system according to an embodiment for realizing FIG. 9. 7...Video signal input terminal, 8, 19...
...FM modulator, 9, 10, 20, 21.24, 25°29.30...Gate circuit, 16...
Audio signal input terminal, 17... River/time compression circuit, 27
, 32...FM demodulator, 33... Song time expansion circuit, HA. HB...Rotating head. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 4 Figure 5 Figure 6 Figure 7! Figure 9 Figure 10

Claims (1)

[Claims] An apparatus for recording a television signal by winding a magnetic tape diagonally around a rotating head cylinder equipped with a plurality of magnetic heads and sequentially forming diagonal recording tracks on the magnetic tape, wherein the video of the television signal is recorded. Signals (video signals) are sequentially recorded as diagonal tracks in the center of the tape, and magnetic heads for recording the video signals are used to record the video signals on the front and rear extensions of each recording track. A magnetic recording/reproducing device characterized in that it is configured to time-compress separate audio signals corresponding to a video signal and record them so that they do not overlap with the video signal.