JPS63249907A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a VTR in which the after-recording function of a voice signal is realized by using a rotary head, by providing a means which records another voice signal shallower than a magnetized area by a video signal on the surface layer part of a magnetic tape. CONSTITUTION:The voice signal inputted from an input terminal 1, after the micro level component of which being enhanced at a noise reduction circuit 2 and the high frequency component of which being enhanced at a pre-emphasis circuit 3, is changed to a signal to be FM-modulated at an FM modulation circuit 4. Afterwards, a signal of desired band is extracted at a BPF5, and is amplified at a recording amplifier 6. Meanwhile, as for an inputted video signal, the luminance signal component of the signal is extracted at an LPF12, and after it is changed to the signal to be FM-modulated at a luminance recording process circuit 13, the component of the band superposed on a low frequency conversion chromaticity signal is eliminated at an HPF14, then, the signal is added on an adder 15. In such a way, it is possible to perform the after- recording of the voice signal on the recording track of the video signal and the voice signal, and to reproduce the voice signal recorded simultaneously with the video signal and an after-recorded voice signal selectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a helical scan type magnetic recording and reproducing device in which a video signal and an audio signal are respectively recorded overlappingly by rotating heads.

[Conventional technology]

In recent years, with improvements in magnetic heads and magnetic tapes, the magnetic recording and reproducing characteristics of video signals have improved. Therefore, the desired S/
The amount of tape required to obtain N is small, and recording density has been improved by slowing down the tape speed.

However, since the audio head of the audio signal is fixed, the band of the reproduced audio output becomes narrower as the tape speed becomes slower, resulting in a deterioration of the S/N ratio. Furthermore, due to the instability of the tape running system, there were also problems with performance such as wow/flutter and distortion.

Therefore, in order to reduce and eliminate the drawbacks of the above-mentioned techniques, a video track recording technique is known. This video track dual-use recording technique is described in, for example, Journal of the Society of Telecommunications, Vol. 39. FM modulated according to the audio signal as shown in No. 4pp, 329-332.
An audio modulation signal is recorded on a track, and then a luminance modulation signal that has been FM modulated according to the luminance signal and a chroma reduction signal that has been reduced and converted are overwritten and recorded on the same track on which the FM audio modulation signal is recorded. be.

First, the FM audio modulation signal is recorded, and then the video modulation signal is overwritten.The FM audio modulation signal is recorded deep into the magnetic layer of the magnetic tape, and then the FM audio modulation signal is recorded on the surface of the magnetic layer. A brightness modulation signal having a higher frequency than the signal is recorded without erasing this FM audio modulation signal.

Such a magnetic recording/reproducing device is called an H4F1 video tape recorder (hereinafter simply referred to as a VTR), and it has a higher dynamic range and wow range than the conventional fixed head that bias-records audio signals. It has far superior characteristics in terms of , flutter, distortion, etc., and plays a major role in improving the reproduction characteristics of audio signals.

Note that such a VTR requires two audio signal recording heads on the rotating drum. Originally, at least two video signal recording heads are required, so the number of heads is at least four, but SP (standard mode) and BP (long time)
When changing the video signal recording head depending on the mode,
Since four video signal recording heads are used, the total number of heads in this case is six.

[Problem that the invention seeks to solve]

The audio signal recording method described above is called the depth recording method, but when recording video and audio signals simultaneously, it is necessary to follow the audio signal even though it has excellent performance characteristics as described above. There was a problem that recording, so-called dubbing, was not possible.

In other words, since the audio signal recording area is located in the deep layer of the magnetic tape and the video signal is recorded on the surface layer,
It is impossible to re-record only the audio.

An object of the present invention is to solve such problems and to provide a VTR capable of realizing an audio post-recording function using a rotating head.
Our goal is to provide the following.

[Means for solving problems]

In order to achieve the above object, the present invention provides means for recording an audio signal in a shallower magnetized region than a magnetized region by a video signal on the surface layer of a magnetic tape.

[Effect]

On a magnetic tape where video signals are recorded in the shallow layer and audio signals are recorded in the deep layer, it is possible to post-record the audio signal without erasing these signals, thus reducing the S/N deterioration of the reproduced video signal. can be pressed, and the audio signal recorded in the deep layer and the audio signal that has been dubbed can be selectively reproduced.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a recording system in an embodiment of a magnetic recording and reproducing apparatus according to the present invention, in which 1 is an audio signal input terminal, 2 is a noise reduction circuit, 3 is a pre-emphasis circuit, and 4 is an FM modulation circuit. circuit, 5 is BPF (band pass filter), 6 is recording amplifier, 7 is switch, 8
is an audio dubbing head, 9 is an audio head, 10 is a magnetic tape, 11 is a video signal input terminal, 12 is an LPF
(low-pass filter), 13 is a luminance recording process circuit,
14 is HPF (bypass filter), 15 is adder,
16 is a recording amplifier, 17 is a switch, 18 is an EP mode video head, 19 is an SP mode video head, 20 is a BPF, 21 is a chromaticity recording process circuit, and 22 is an LPF.

In the figure, a noise reduction circuit 2 emphasizes minute level components of an audio signal input from an input terminal 1.
After the high-frequency components are emphasized by pre-emphasis circuit 3, the F
The M modulation circuit 4 converts the signal into an FM modulated signal. Its carrier frequency is 1.3MHz and 1.7MHz in VH3 standard
(2 audio channels). In addition, when a PCM modulation circuit is used instead of the FM modulation circuit 4, the audio signal is sampled at a sampling frequency of 48 KHz and a quantization bit number of 16 bits.
t, inter-carrier wave number 2M) may be a PCM modulated signal of about Iz (however, in this case, there is no need for something equivalent to the pre-emphasis circuit 3). After that, B
A signal in a desired band is extracted by the PF 5, amplified by the recording amplifier 6, and then supplied to the switch 7.

On the other hand, the video signal input from the input terminal 11 is LPF1
2, the luminance signal component is extracted, and the luminance recording process circuit 1
3, in the case of the VH3 standard, it is converted into an FM modulated signal with a carrier frequency of 3.4 to 4.4 Mllz, and then HPF
At step 14, components in a band overlapping with the low-pass converted chromaticity signal are removed and added to adder I5.

Also, the video signal input from the input terminal 11 is filtered through BPF2.
0, the chromaticity signal component is extracted, and in the chromaticity recording process circuit 21, in the case of VHS standard, 0.629 M
After its subcarrier frequency is down-converted to Hz, the LPF
At step 22, unnecessary components are removed and added to the adder 15. The output signal of this adder 15 is amplified by a recording amplifier 16 and then supplied to a switch 17.

The switch 7 is closed to the N side for normal video and audio simultaneous recording, and to the A side for audio dubbing recording.

The switch 17 is closed to the S side in the SP mode in which recording is possible for 2 hours, for example, and to the E side in the P mode in which the tape speed is reduced to 1/3 and the recording is possible for 6 hours.

The audio dubbing head 8, the audio head 9, the EP mode video head 18, and the SP mode video head 19 are provided on the same rotating drum (not shown).

Although FIG. 1 shows one each of these heads 8.9 and 18.19, it goes without saying that two of each head may be mounted on the rotating drum. Furthermore, the EP mode video head 18 and the SP mode video head 19 may be the same head, and recording and playback of SP and SP modes may be performed using the same head.

The audio head 8 and audio head 9 for dubbing scan the magnetic tape 10 in advance of each video head 18 and 19, and
When simultaneously recording audio, the switch 7 is closed to the N side, and the audio signal is supplied from the recording amplifier 6 to the audio head 9 via the switch 7, and is first recorded on the magnetic tape 10.
recorded in

Further, the video signal is transmitted from the recording amplifier 16 via the switch 17 to the EP mode video head 18 when in the EP mode.
In the SP mode, the SP mode video is supplied to the RAD 19 and recorded in a superimposed manner on the track on which the audio signal is recorded.

The track width of each head is 20 to 25 μm for audio head 9.
, 25 to 30 μm in the EP mode video head 18, SP
Each mode image head 19 selects about 60 μm. The cores of these heads are often made of ferrite.

By the way, when audio signals and video signals are saturated recorded on the magnetic tape 10 (recording is performed by setting the recording current level so that the playback output level is maximized), the recording wavelength is changed in the depth direction of the magnetic tape. Me too. In the VH3 standard, the audio recording signal is λ-4μm, the video recording signal is λ-1,
It is about 4 μm. The recording tracks of these audio signals and video signals overlap each other, and since the audio signals are recorded in advance, as a result, the magnetic tape 1
Magnetization as schematically shown in FIG. 2 remains in the 0 depth direction. Figure (a) is in SP mode, figure (b) is in SP mode.
It is of the mode. In the figure, A is the magnetization region of the audio signal, ■
is the magnetized region of the video signal, T is the width of the recording track of the video signal, and t.

is the width of the audio signal recording track. That is, the depth of the magnetized region V due to the audio signal is a little over 1 μm, but the depth of the magnetized region V due to the video signal is about 0.4 μm.
Since the audio signal is recorded prior to the magnetization caused by the video signal, the magnetization caused by the audio signal is erased in the surface layer and remains only in the deep layer.

Therefore, it is necessary to record the audio signal in sufficient saturation to reach the deep layer of the magnetic tape, and the audio head 9 has a gap length of 0.8 to 1.0 μm so that the temperature of the recording magnetic field is broadly reduced from the gap. It is common to set it as a degree. Note that the gap length of the image head 18°19 is usually
It is about 0.4 to 0.5 μm.

As described above, when recording after-recording on the magnetic tape 10 on which video signals and audio signals are recorded, the switch 7
Close it to side A, and input the audio signal for dubbing to input terminal 1. After this audio signal is processed in the same manner as above, it is supplied to the dubbing audio head 8 via the switch 7.
The signal is recorded on the magnetic tape 10 so as to overlap the recording track of the video signal.

The magnetized area by this post-recording audio head 8 is shown as At in FIG. That is, this magnetized region Af occurs in a part of the magnetized region V due to the video signal in the shallow layer portion.

When recording an audio signal for dubbing in this way, it is necessary to ensure that the video signal reproduced from the magnetized region V hardly deteriorates. To this end, the first step is to make the track width tb (FIG. 2) of the audio dubbing head 8 narrower than the track width T of the video head 18, 19. This is because if post-recording is performed over the entire shallow layer of the magnetized region V by the video signal, a large deterioration of the S/H of the reproduced video signal is unavoidable. Second, the carrier frequency of the audio signal to be dubbed is set higher than the carrier frequency of the video signal. As a result, the audio signal is recorded with a shorter wavelength than the video signal, and as described above, as shown in Figure 2, only the very surface layer of the magnetic tape is rewritten with the audio signal. The previously recorded video and audio signals are almost never erased by the post-recording audio signals. Thirdly, the dubbing signal is recorded in saturation. When performing post-recording on the very surface layer of the magnetic tape 10 as described above, unsaturated recording may seem desirable if one considers it simply. However, the reproduction level of unsaturated recorded signals varies greatly from magnetic head to magnetic head, making it extremely difficult to ensure performance.

In this embodiment, as described above, since the recording wavelength of the after-recording signal is shorter than the recording wavelength of the video signal, even if saturation recording is performed, magnetization only reaches the very surface layer. Therefore, saturation recording is desirable to ensure post-recording performance.

Specifically, when FM recording a normal audio signal, the carrier frequency is 1.3 MI (z and 1.7 MHz), and in the case of dubbing, it is preferable to record at a carrier frequency of 7 to 10 MHz. According to experiments, even when dubbing is performed at such a short wavelength, the S
/N was found to be obtained. Of course, the gap length of the audio head 8 for dubbing is about 0.2 to 0.3 μm, which is selected to be narrower than that of the video head.

When dubbing is performed as described above, there is an advantage that during playback, it is possible to select and output either the deep audio signal or the shallow audio signal, whichever is desired. This is a feature that would have been unimaginable in the conventional post-recording system, which uses linear tracks at the ends of magnetic tapes.

Next, the processing means for audio signals during dubbing as described above will be explained with reference to FIG.

In the figure, between the BPF 5 and the recording amplifier 6, there are resistors R3, Ra, Rs and a switching transistor Q2.
An attenuator is provided. During dubbing,
The level of the control signal input to the input terminal 24 is High
h, and the level of the recording signal is reduced. As mentioned above, dubbing records short wavelengths (high frequencies), so
To achieve saturation recording, the recording level must be lower than normal (as the recording current ′ increases, the playback output level will also rise accordingly, but when the recording current exceeds a certain level, the playback output level will decrease). There is such a characteristic between the recording current level and the playback output level. Saturation recording is recording at the recording current level where the playback output level is maximum, but as the recording frequency increases, the playback (The recording current level with the maximum output level decreases). Further, in the modulation circuit 4, a carrier frequency setting circuit consisting of resistors R, , R2 and a switching transistor Ql is provided in a portion that determines the carrier frequency. In the case of a multi-by-break type FM modulator, this corresponds to a resistor that determines the bias current, and during post-recording, the level of the control signal input to the input terminal 23 becomes High, making the carrier frequency higher than during normal recording. Also make it more expensive.

FIG. 3 is a block diagram showing a recording system of another embodiment of the magnetic recording/reproducing apparatus according to the present invention, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In this embodiment, the EP mode video head I8 is also used for audio dubbing, and the audio head dedicated to dubbing can be omitted.

Therefore, during dubbing, by closing the switch 7 to the A side, the EP mode video head 18 is selected as the audio dubbing head.

In this embodiment, the width T of the magnetized region V due to the video signal in the SP mode in FIG. may become a problem, so dubbing may be possible only in SP mode. At this time, the gap length of the EP mode video head 18 is set as
The thickness should be approximately 0.2 to 0.3 μm. Incidentally, when S/N deterioration of the reproduced video signal is not particularly a problem, dubbing may also be made possible in the SP mode.

FIG. 4 is a block diagram showing a recording system of still another embodiment of the magnetic recording/reproducing apparatus according to the present invention, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In this implementation, the audio head 9 is also used for dubbing, and the audio head dedicated to dubbing and the switch 7 in FIGS. 1 and 3 can be omitted.

Even in this case, unless the track width of the audio head 9 is made extremely narrow (less than 19 μm), the width T of the magnetized region V due to the video signal and the magnetized region V due to the audio signal in FIG. t.

Also, if the width of the audio head 9 is narrowed in this way, the level of the reproduced audio signal will drop and the S/N will deteriorate, so it may be used on the condition that only the SP mode can be used for post-recording.

The gap length of the audio head 9 must be approximately 0.2 to 0.3 μm. As described above, when a ferrite head is used with this gap length, deep saturation recording of audio in simultaneous recording of video and audio becomes difficult. Therefore, by forming the audio head 9 from a metal material with a high saturation magnetic flux density, such as sendust or amorphous, it is possible to achieve both recording and reproduction in both the deep layer and the shallow layer.

In this embodiment as well, if S/N deterioration of the reproduced audio signal is not a problem, post-recording of the EP peach may be allowed.

FIG. 5 is a block diagram showing a recording system of still another embodiment of the magnetic recording/reproducing apparatus according to the present invention, in which 30 is an A/D
(analog/digital) converter, 31.32 is an input terminal, 33 is a memory, 34 is a PCM modulator, and the fourth
Portions corresponding to the figures are given the same reference numerals and redundant explanations will be omitted.

In FIG. 5, an audio signal inputted from an input terminal 1 is converted into, for example, a 15-bit digital signal by an A/D converter 30, and supplied to a PCM modulator 34 via a memory 33 to become a modulated signal.

During post-recording, the frequency of the clock pulse input from the input terminal 31 is set higher when reading from the memory than when writing to the memory, and the timing of starting reading from the memory is set to the video signal based on the head rotation phase signal input from the input terminal 32. Switch for each field. The operation of other parts is the same as that shown in FIG. As a result, the audio signal is time-base compressed for each period corresponding to one field of the video signal, and is recorded on the magnetic tape 10 by the audio head 9.

By making the reading start point of the audio signal from the memory 33 different for each field of the video signal as described above, as shown in FIGS. Recording pattern 4 of an after-recording audio signal compressed in time axis once on a signal recording track 40
1 is formed.

Moreover, the position of the recording pattern 41 is shifted by the length of the recording pattern 41 for each recording track 40 (see FIG. 6(a).
)), do you want to shift it any further (see Figure 6(b))?
are distributed in the width direction.

This provides the following effects.

That is, dubbing is naturally performed while viewing the playback screen, and so-called dubbing monitoring must be possible. During dubbing, since an audio recording signal voltage of 5 volts or more is applied to the audio head 9, the audio recording signal is guided to the playback video signal system and the video head, significantly degrading the quality of the playback image being monitored and making it impossible to monitor. There is an inconvenience that it disappears. Therefore, as in this embodiment, the after-recording signal is dispersed in time, and only when this after-recording signal is read out from the memory 33, the audio head 9
When a recording voltage is applied to the recording voltage, the audio recording signal is only partially guided to the reproduced video signal system and the video head, and the reproduced image can be monitored over the entire screen. Further, since the slight deterioration of the S/H of the reproduced video due to dubbing is temporally dispersed over the entire screen, it also has the effect of becoming almost unnoticeable. Of course, a similar effect can be obtained by simply compressing the time axis and dispersing it on the time axis without dispersing it on the recording track.

FIG. 7 is a block diagram showing a reproduction system for the recording system shown in FIG. 4, in which 50 is a reproduction amplifier, 51a, 51b
is a BPF, 52 is a switch, 53 is a demodulator, 54 is a de-emphasis circuit, 55 is a noise reduction circuit, 5
6 is an output terminal, 57 is a switch, 58 is a regenerative amplifier,
59 is HPF.

60 is a brightness regeneration process circuit, 61 is an LPF, 62.6
3 is an adder, 64 is a chromaticity reproduction process circuit, and 65 is a BP.
F, 66 is an output terminal, and parts corresponding to those in FIG. 4 are given the same reference numerals.

In FIG. 7, the audio signal reproduced by the audio radar 9 from the magnetic tape 10 is amplified by a reproduction amplifier 50 and then supplied to BPFs 51a and 51b. BPF5
] In a, only the audio modulated signal component with a low carrier frequency from the deep layer is extracted, and only the audio modulated signal with a high carrier frequency after dubbing in the surface layer is extracted from the BPF5 lb. The switch 52 is operated by the user, and is closed to the N side when a normal audio signal is required, and to the A side when an after-recorded audio signal is required. The audio signal from the switch 52 is sent to the demodulator 5
3, and is demodulated into a baseband signal by a de-emphasis circuit 54 (not required for PCM modulation).
Processed by the noise reduction circuit 55 and sent to the output terminal 56
Output to.

On the other hand, the playback output of the EP mode video RAD 18 or the SP mode video RAD 19 is selected by the switch 57 according to the recording time mode, amplified by the playback amplifier 58, and supplied to the HPF 59 and the LPF 1a. . H
The FM modulated luminance signal is separated from the PF 59 and sent to the luminance regeneration process circuit G.

The signal is demodulated into a baseband signal and supplied to the adder 62 via the LPF 61. Further, a low frequency converted chromaticity signal is separated from the LPF 63, subjected to jitter correction and frequency conversion in a chromaticity reproduction process circuit 64, and then supplied to an adder 62 via a BPF 65. The output signal of the adder 62 is
It is output from the output terminal 66.

In this manner, in this embodiment, even after dubbing, the audio signal recorded at the same time as the video signal is not erased, and the user can select any audio reproduction output.

It should be noted that although the reproducing system has been illustrated only for the recording system shown in FIG. 4, it goes without saying that it can be constructed simultaneously for other embodiments as well. Further, the numerical values listed above are merely examples, and the present invention is not limited thereto. Furthermore, the embodiment shown in FIG.
Although the normal audio signal and the audio signal for dubbing were recorded and reproduced using the same audio head, they may be recorded and reproduced using separate heads as shown in FIGS. 1 and 3.

〔Effect of the invention〕

As explained above, according to the present invention, video signals and audio signals can be recorded on a magnetic tape on which video signals and audio signals are overlaid, without deteriorating the reproduction characteristics of these video signals and audio signals. An excellent effect can be obtained in that the audio signal can be dubbed over the recording track, and the audio signal recorded simultaneously with the video signal and the dubbed audio signal can be selectively reproduced.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing a recording system of an embodiment of a magnetic recording/reproducing device according to the present invention, and Fig. 2 shows a magnetized area by a video signal as seen in the depth direction of a magnetic tape, and this image Schematic diagrams showing magnetized areas due to audio signals recorded simultaneously with signals and magnetized areas due to post-recorded audio signals, Figures 3 to 5
The figures are block diagrams showing recording systems of other embodiments of the magnetic recording/reproducing apparatus according to the present invention, FIG. 6 is a schematic diagram showing recording tracks on the magnetic tape according to the embodiment shown in FIG. 5, and FIG. 5 is a block diagram showing a reproducing system for the recording system shown in FIG. 4. FIG. 1...Audio signal input terminal, 4...FM
Modulation circuit, 7...Switch, 8...Audio dubbing head, 9...Audio head, 10
...Magnetic tape, 11...Video signal input terminal, 17...Switch, 18...
BP mode video head, 19... SP mode video head, 30... A/D converter, 33.
...Memory, 34...PCM modulator. J3 Figure 1 Figure 2

Claims (1)

[Claims] 1. A video head for recording and reproducing video signals and an audio head for recording and reproducing audio signals, and prior to recording of the video signal by the video head onto a magnetic tape, the audio head In a magnetic recording and reproducing apparatus that records the audio signal, the video signal on the surface layer of the magnetic tape, and the audio signal on the deep layer of the magnetic tape, the audio signal is recorded on the surface layer of the magnetic tape. 1. A magnetic recording and reproducing device comprising means for recording another audio signal shallower than a magnetized region by a video signal. 2. The magnetic recording and reproducing apparatus according to claim 1, wherein the means has a head different from the audio head, and the other audio signal is recorded with the head. 3. The magnetic recording and reproducing apparatus according to claim 1, wherein the means includes the audio head, and the audio head records the other audio signal.