JPS61150101A - Magnetic recording and reproducing method - Google Patents

Abstract

PURPOSE:To attain high density recording and high sound quality VTR by recording overlappingly a digital signal of a sound signal to a shallow layer on a track on which an analog video signal is recorded while providing a specific frequency characteristic and recording/reproducing with heads of different azimuth angle. CONSTITUTION:The analog video signal is recorded to a recording layer 27b of a magnetic layer 27 on a base film 28 of a magnetic tape. Then the digital sound signal is recorded to the shallow layer 27a of the layer 27b while a frequency characteristic is given overlappingly so that the recording level changes with the frequency. Since the sound signal is recorded to the shallow layer 27a, a large current giving effect onto the video signal is not required and code modulation (PCM) recording is applied. Thus, the video and sound are recorded with excellent S/N with high density possible for after sound recording and the signal is recorded/reproduced with high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-density magnetic recording and reproducing method that multiplexes analog signals and digital signals on a magnetic layer such as a magnetic tape and enables separate reproduction.

2. Description of the Related Art In a conventional magnetic recording/reproducing device, such as a rotating head type video tape recorder (hereinafter referred to as a VTR), luminance signals and color signals forming a video signal are recorded on a video track, and an audio signal is recorded on a separate audio track. Information is recorded on almost the entire surface of the magnetic tape by so-called azimuth recording, in which the azimuth angles of two rotating heads for recording video signals are different, and information is recorded on almost the entire surface of the magnetic tape. There is very little space available. For this reason, the current state of the industry is to focus on improving recording density by shortening wavelength recording and narrowing tracks.

Recently, with the aim of improving the performance of audio signal recording for VTRs,
A method of recording a frequency-modulated audio signal together with a video signal on a TR video track has been put into practical use (for example, ``VHS Hi-Fi VTRJ, - Tsucho Shuzo et al., Na
tional Technical Report.

-vol, 30. No. 1, Feb. 19
4B4). FIG. 2 shows the frequency allocation in this recording method, and FIG. 3 shows the recording state in the depth direction of the magnetic tape.

In FIG. 2, 22 is a luminance signal including a frequency-modulated synchronization signal, and 23 is a low-band-converted carrier color signal.

24 is a signal obtained by frequency modulating (FM) an audio signal,
The audio signal is recorded in a band between the low frequency conversion carrier color signal 23 and the FM luminance signal 22 by an audio-dedicated head at a different azimuth and angle from that of the video signal head.

As is clear from FIG. 3, the FM audio signal is recorded in the deep layer 2 of the magnetic layer with a large recording current before the video signal.
sb, and the video signal is then recorded on the surface layer 262L of the magnetic layer. Note that 250 is a non-recording layer of the magnetic layer, and 26 is a base film.

In the case of such a conventional example, since the audio signal is recorded in FM, the S/N ratio is high and the quality is good, and the sound quality does not deteriorate even if the tape running speed is slowed down.
It can be said that this is one of the effective methods for recording TR. Moreover, it is noteworthy that it utilizes the deep layer of the magnetic tape magnetic layer, which was not previously used.

Problems to be Solved by the Invention There are several problems with such conventional Vi'H. First, it is necessary to supply a large current to the recording head in order to record the FM audio signal deeply, and the frequency band that can be recorded is limited to a relatively low range due to space loss. .

As a result, it was impossible to develop IF to record changed code 111 (PCM), which has higher quality than FM recording of audio signals.
Since the audio signal is recorded on the low frequency side with a large current, the interference of the audio signal written in the deep layer cannot be ignored when playing the video signal. A large current supply circuit for recording audio signals becomes large-scale, and the large current adversely affects other video circuits.

Second, it is impossible to perform after-recording. Conventionally, in a VTR, video and audio are recorded on separate tracks, so it is possible to record the audio later while playing the video, so-called after-recording. However, as is clear from FIG. 3, since the audio signal is recorded deep, if it is erased and re-recorded, the video signal will also disappear, making after-recording impossible.

The purpose of the present invention is to solve the problems of conventional VTRs, and to provide a wide band signal such as a PCM signal in which an audio signal is encoded in the shallow part of an analog signal track where a video signal etc. is recorded. By giving the recording level of the digital signal a desired frequency characteristic, it is possible to efficiently perform high-density recording on a VTR while suppressing the negative effect on the analog signal in the deep layer. It is an object of the present invention to provide a magnetic recording and reproducing method that makes it possible to erase and re-record only signals.

Means for Solving the Problems The magnetic recording and reproducing method of the present invention modulates a digital signal on a track on which a video signal is recorded using a head having an azimuth angle different from that of the recording head for the video signal, thereby reducing the negative influence on the video signal. Overlapping recording is performed at a recording level with suppressed frequency characteristics, and video signals and digital signals can be reproduced using heads with mutually different azimuth angles.

Operation By using the recording and reproducing method described above, PCtM is recorded along with the video signal.
It is possible to reproduce high-quality signals such as audio signals, and it is also possible to erase and re-record digital signals, so it can be used in many applications as a high-density recording method.

Embodiment' Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 4 is a recording state diagram in the depth direction of the magnetic layer, which does not provide a detailed explanation of the present invention. When video signals are conventionally recorded on magnetic tape using a rotating head, the depth of the recording layer is 0.26 to 0.3 times the recording wavelength, and in current consumer VTRs, the depth is 0.3 to 0. This means that data is recorded to a depth of 8 μm, which is the same as the magnetic layer 2 of a general magnetic tape.
7 has a thickness of 2 to 4 μm, a non-recording layer 270 exists as shown in FIG. The conventional example described in FIGS. 2 and 3 utilizes a portion of this non-recording layer, but essentially only signals with long wavelengths (low frequency band) can be recorded. The shallow layer of the tape magnetic layer is suitable for recording broadband signals, and in fact, video signals are recorded only on the very surface.

The present invention focuses on the fact that recording and reproducing analog signals does not require 87N for recording and reproducing digital signals, and records broadband digital signals in the shallow part of the recording layer 27b where video signals are recorded. .

This is referred to as a signal recording layer 271L. For reproduction of digital signals, 137K has a code error rate of 15 (with IB, the bit error rate is about 10-5, which approaches a practical value.
(It is sufficient if the S/N of IB can be secured.

Therefore, a modulated digital signal to be recorded in a shallow layer may be recorded at a depth such that 8/N satisfies the above value.

The depth of the recording layer can be controlled, for example, by the magnitude and frequency of the recording current. Figure 6 shows a signal of frequency f (
FIG. 5 is a diagram illustrating the reproduction output with respect to the recording current level (ft < f2 < fs in FIG. 5). In the case of a digital signal, for example, if the original signal can be restored when the reproduction output at the level indicated by 30 in FIG. , the original signal can be restored if the IR is 3 or higher. That is, when a recording current having a frequency characteristic as shown by 32 in FIG. 6 is applied, a digital signal is restored. In a conventional VTR, the recording current of the video signal has the frequency characteristic shown in FIG. 6, which is set near the optimum recording current that provides the maximum output at each frequency. If digital signals are recorded while maintaining such frequency characteristics, the recording current for low frequency signals increases and the signals are recorded deeper into the tape magnetic layer, so the low frequency signals are not transferred to the video signal. There are many negative effects. Here, the digital signal has a sixth
When recording with a recording current having the frequency characteristics shown in FIG. 32, the signal is recorded at a shallower depth than the signal having the recording characteristics shown in FIG. , deterioration of the video signal can be further reduced. In this way, by giving the recording level of the digital signal a frequency characteristic, it is possible to reduce the negative effect on the video signal and to record the digital signal and the video signal.
can play two signals.

If a video signal is recorded with an optimum recording current (a recording current value that maximizes the reproduction output), the recording current of a digital signal may be 1 A or less. Naturally, since the modulated digital signal is shallowly recorded after the recorded video signal, the playback output of the video signal decreases, but the extent of this is slight because the recording current of the digital signal is small, and the above recording Taking the current value as an example, it remains within about 2 dB. Moreover, since the noise due to the surface nature of the tape is recorded in the shallow layer of the digital signal, the modulation noise that is difficult to be directly involved in the reproduction of the video signal is reduced, so the actual S/N drop in the video signal is even smaller. Become. In this way, the S of the video signal recorded earlier
It is possible to suppress the /N degradation to a small level and to modulate and record a digital signal having a practical code error rate on top of a video signal.

By the way, if the occupied bands of the video signal and the digital signal are far apart, it is possible to obtain the desired signal from the reproduced signal using a filter, but if we consider the case where the two signals are close to each other or overlap, It is necessary to make the azimuth angle of the rotary head for recording and reproducing video signals different from the azimuth angle of the rotary head for recording and reproducing digital signals. Generally, it is known that if the gap direction of the reproducing head is inclined by θ with respect to the gap direction of the recording head, the following loss will occur.

However, Wnidrack width λ: recording wavelength Therefore, the reproduction output of the video signal rotary head does not pick up the signal recorded on the digital signal recording layer 271L and reproduces only the video signal, and the reproduction output of the digital signal rotary head is The azimuth angle can be set so that only the digital signal is reproduced without picking up the signal from the video signal recording layer 27b. For example, by making the azimuth angles of the video and digital heads different by 30 degrees, it is possible to share the band of both signals over a band of 1.6 to 2 MH2 or more with a practical track width.

FIG. 7 is a frequency allocation diagram of an embodiment according to the present invention. This example attempts to record PCM audio signals while keeping the recordable band of a conventional VTR. In this case, the video signal and the frequency-modulated PCM audio signal are separated by azimuth loss, but if the azimuth angle is small, crosstalk occurs and becomes an interfering component. However, the deviation parts with large interference components are close to the carrier frequency of the frequency modulation, and due to the nature of the triangular noise of the frequency modulation, it is possible to reproduce both the video signal and the PCM audio signal with almost no S/N deterioration. In this case, there is no need to widen the recordable band (it is possible to record PCM audio signals, but it is necessary to widen the recordable band).
It is also fully applicable to TR. Furthermore, since PCM audio signals are recorded with frequency modulation, many characteristics of frequency modulation in magnetic recording are utilized. In the example, the baseband digital signal is amplitude modulated or frequency modulated and recorded in a shallow layer above the track where the luminance signal is recorded, but any other modulation method for the digital signal may be used. It can be applied even if

FIG. 8 is a diagram showing an example of the configuration of a rotary head group for realizing the magnetic recording and reproducing method of the present invention. magnetic tape 3.5
travels in the direction of the arrow M, and the rotating cylinder 4o moves in the direction of the arrow B for 30H! This is a so-called rotary two-head helical type VTR that rotates at a constant speed. In this case, the video signal head 38 contacts the tape before the digital signal head 36, and the video head 39 contacts the tape before the digital signal head 37. For example, the azimuth angles of the video signal heads 38 and 39 are set to ±6°, and the digital head 3
The azimuth angles of 6 and 37 are ±30'. With this configuration, a video signal is first recorded on a track on the magnetic tape, and then a digital signal is modulated and recorded in a shallow layer by another azimuth head. The recording current of each head is set to the optimum recording current for the video signal head 38, 39, and the frequency characteristic shown in FIG. Set to recording current.

FIG. 1 is a block diagram of main parts of an embodiment of the present invention. In the figure, a video signal is applied to a terminal 5, passed through a recording side video processing circuit 6, amplified by a recording amplifier 7, and recorded on a magnetic tape through rotary heads 3 and 4. The recording side video processing circuit 6 frequency-modulates the luminance signal, performs low frequency conversion on the carrier color signal, and converts it into the frequency bands of the luminance signal 22 and the carrier color signal 23 shown in FIG. Next, the audio signal applied to the terminal 8 is subjected to PCM by a code modulator 9, limited to only the required band by a low-pass filter (LPF) 10, converted to the signal shown in FIG. The signal passes through an adjustment circuit, is amplified by a recording amplifier 13, and is recorded on a magnetic tape through rotary heads 1 and 2. Video signals recorded on magnetic tape and frequency-modulated digitized audio signals are played back using dedicated heads with different azimuth angles. The video signal is reproduced by the rotary heads 3 and 4, amplified by the amplifier 14, and then input to the reproduction side video signal processing circuit 16, where it is demodulated to the original video signal and sent to terminal 1.
6 is output. The audio signal is reproduced by the rotary heads 1 and 2, amplified by an amplifier 17, and then demodulated by a demodulator 18 into a baseband PGM audio signal. The FM demodulated digital signal is further decoded by a decoder 19 into an analog signal, that is, an audio signal, and outputted to a terminal 21 via an I and PF 20.

In the case of this embodiment, the digitized audio signal is recorded on the very surface of the magnetic layer, so it can be easily rewritten with a new signal with a weak recording current, and it can also be easily erased. be able to.

If the erasing or re-recording current is set appropriately, it will have almost no effect on the video signal.

Effects of the Invention As detailed above, the present invention enables shallow layer recording by imparting a frequency characteristic to the recording current of a digital signal modulated by a head having a different azimuth angle from the recording head of the video signal on a track where the video signal is recorded. However, the video signal and the digital signal can be reproduced separately by heads having different azimuth angles, and different digital signals can be recorded with almost no quality deterioration of the video signal. In other words, the recording layer in the depth direction of the digital signal magnetic layer is controlled with a recording current that has frequency characteristics that reduce the deterioration of the video signal, and the separation between the two signals is performed using azimuth loss, which is extremely effective. High-density recording is possible.

The digital signal recorded in the shallow layer can share the band with the video signal, and an extremely wide band can be realized.
It has the excellent feature of being easy to erase and rewrite because it is located in a shallow layer. Therefore, it is easy to use this digital signal for audio PCM recording, and in that case,
Performance such as S/N, frequency characteristics, distortion rate, wow and flutter of audio signals has been significantly improved, and conventional FM
After-recording, which was impossible with audio recording, is also possible, and a VTR with extremely excellent sound quality can be realized.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention;
2 and 3 are a frequency allocation diagram and a diagram of the recording state in the depth direction of the magnetic tape, respectively, to explain the conventional example, FIG. 4 is a diagram of the recording state in the depth direction of the magnetic layer, and FIGS. Each figure provides a detailed explanation of the invention t7)7
", Figure 5 is a diagram explaining the relationship between recording current and reproduction output with respect to frequency, Figure 6 is a diagram explaining the frequency characteristics of recording current necessary to obtain the desired reproduction output, and Figure 7 is an example. 8 is a side view of the configuration of a magnetic head group used in an embodiment of the present invention. 22...FM luminance signal, 23...Low frequency conversion transport Color signal, 27...Magnetic layer, 27&...
...Digital signal recording layer, 27b...Video signal recording layer, 35...Magnetic tape, 38.37
...Digital signal head, 38.39...
...Video signal head, 40...Rotating cylinder,
34... Frequency modulated digital signal. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3 Figure 4 Figure 5 Figure 6 Notification Line area Figure 7 Figure 8

Claims (6)

[Claims] (1) A digital signal is set to be lower than the recording level of the analog signal on a track on which an analog signal is recorded, and the recording level of the digital signal is overlaid with frequency characteristics such that it changes depending on the frequency, and is overwritten and reproduced. A magnetic recording and reproducing method characterized by: (2) The magnetic recording and reproducing method according to claim 1, wherein the recording level of the digital signal is controlled by a recording current flowing through a recording head. (3) The frequency characteristic of the digital signal is such that the recording level is almost constant up to a certain frequency, and the recording level gradually decreases in a frequency band higher than that frequency. 2. Magnetic recording and reproducing method described in Section 1. (4) The frequency characteristic of the digital signal is such that the recording level gradually increases up to a certain frequency, and the recording level gradually decreases in a frequency band higher than that frequency. The magnetic recording and reproducing method according to scope 1. (5) The magnetic recording and reproducing method according to claim 1, wherein the analog signal and the digital signal are recorded and reproduced by heads having mutually different azimuth angles. (6) The magnetic recording and reproducing method according to claim 1, wherein the analog signal is recorded before the digital signal.