JPS61145701A - Magnetic recording and reproducing method - Google Patents

Abstract

PURPOSE:To reproduce separately an image signal and a digital signal with a head having azimuth angles different from each other by recording shallowly a digital signal modulated by the heat having a different azimuth angle on a track recorded with an image signal. CONSTITUTION:The deepness of the recording layer of an image signal is 0.25-0.3 times the recording wavelength, and the signal is recorded up to the depth of 0.3-0.8mum in a domestic VTR. Since the thickness of a magnetic layer 27 of a magnetic tape is 2-4mum, an unrecorded layer 27c is present. As the recording and reproduction of a digital signal do not necessitate so high S/N as the recording and reproduction of an analog signal, a digital signal of a wide band is recorded on the shallow part of a recording layer 27b recorded with an image signal to form a digital signal recording layer 27a. When a digital signal is reproduced with 15dB S/N, the code error rat is a value of 10<-5> which approaches the practical value. Accordingly, 20-30dB S/N including an allowance can be satisfactorily secured.

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 and reproducing device, such as a rotating head type video 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 using so-called azimuth recording, in which the azimuth angles of the two rotating heads for recording video signals are different, and information is recorded on almost the entire surface of the magnetic tape. There are almost no gaps. 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 VTR audio signal recording,
A method of recording a frequency-modulated audio signal along with a video signal on a TR video track has been put into practical use (for example, l'-VH3), Ia1i VTRJ, Shuzo Tsumachi et al.
Nahonal Technical Report
.

vol 30, 41 Feb, 1984)
6 The frequency allocation signal in this recording method is shown in Figure 2, and the recording state diagram in the depth direction of the magnetic tape is shown in Figure 3.
As shown in the figure.

In FIG. 2, 22 is a luminance signal containing 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 an azimuth angle different 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.
6b, and the video signal is then recorded on the surface layer 25a of the magnetic layer. Note that 25C 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.

The problem that the invention aims to solve Such conventional VTRs have several problems.

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.

(because it requires a wider band than FM), and because the audio signal is recorded on the low frequency side with a large current, it is impossible to ignore the interference of the audio signal recorded in the deep layer when playing back 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 the audio is recorded later while the video is being played back. So-called after-recording is possible. However, as is clear from FIG. 3, since the audio signal is recorded deeply, if it is erased or re-recorded, the video signal will also disappear, making after-recording impossible.

An object of the present invention is to solve the problems of conventional VTRs, and to provide a PCM signal in which an audio signal is encoded in the shallow part of the analog track where the video signal etc. is recorded. By recording a wideband digital signal in synchronization with the vertical and horizontal synchronizing signals of the video signal, it enables high-density recording in VTRs that can simultaneously play back high-quality video and digital signals. 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 digital signals recorded in shallow layers.

Means for Solving the Problems The magnetic recording and reproducing method of the present invention uses a head having an azimuth angle different from the recording head of the video signal to perform vertical synchronization of the video signal by adjusting the digital signal on the track on which the video signal is recorded. It synchronizes and records signals and horizontal synchronization signals, and enables video and digital signals to be played back using heads with different azimuth angles.

For production use.

The above-mentioned recording and reproducing method enables the reproduction of high-quality signals such as PCM audio signals as well as video 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. .

EXAMPLES Hereinafter, examples 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 for explaining the basic principle of the present invention.

When video signals are recorded on magnetic tape using a rotating head in the conventional manner, the depth of the recording layer is 0.25 of the recording wavelength.
~0.3 times, and current consumer VTRs have o, 3~o
, since the thickness of the magnetic layer 27 of a general magnetic tape is 2 to 4 μm, there is a non-recording layer 27a as shown in FIG. do. The conventional example explained in FIG. 2 and FIG. 3 utilizes a part of this non-recording layer, but due to the nature of wood, only long wavelength (low frequency band) signals 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 digital signals does not require the same S/N ratio as recording and reproducing analog signals, and records broadband digital signals in the shallow part of the recording layer 27b where video signals are recorded. , a digital signal is recorded as a digital signal recording layer 27a. To play digital signals, S/
If N is 1 sdB, the code error rate will be about 10 to 5, which is close to a practical value.
It is sufficient if N can be secured. Therefore, a modulated digital signal to be recorded in a shallow layer may be recorded at a depth such that the S/N satisfies the above value.

If the video signal is to be recorded at the optimum recording current (the recording current value that maximizes the reproduction output), the recording current for the digital signal may be H or less. Naturally, the modulated digital signal is shallowly recorded after the recorded video signal, so the playback output of the video signal decreases, but the extent of this is small because the recording current of the digital signal is small, and the recording current Taking the value as an example, it stays 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, it is less likely to be directly involved in the reproduction of the video signal, and modulation noise is reduced, so the actual S/N drop in the video signal is further reduced. . 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 bit 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, 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 occurs.Therefore, the reproduction output of the video signal rotary head is recorded in the digital signal recording layer 27a. The azimuth angle can be set so that only the video signal is reproduced without picking up the signal, and the reproduction output of the rotary head for digital signals reproduces only the digital signal without picking up the signal of the video signal recording layer 27b. For example, if the azimuth angle of the video and digital heads is set to 3
Practical track width of 1.5 by varying 0'
It is possible to share the bands of both signals over two or more bands.

FIG. 5 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 a disturbing component. However, the deviation scene parts with large interference components are close to each other in frequency modulation carrier frequency, and due to the triangular noise nature of 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, it is possible to record PCM audio signals without expanding the recordable band (PCM audio signals can be recorded, and narrowband consumer V
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. 6 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. The magnetic tape 3o runs in the direction of arrow A, and the rotary cylinder 35 rotates in the direction of arrow B at 30 Hz, so-called rotating two-head helical force type V.
It is TR. In this case, the video signal head 33 contacts the tape before the digital signal head 31, and the video signal head 34 contacts the tape before the digital signal head 32.

For example, the azimuth angles of the video signal heads 33 and 34 are set to ±6°, and the digital head 31
The azimuth angle of and 32 is ±30°. With this configuration, a video signal is first recorded on the track on the magnetic tape, and then a digital signal is modulated and recorded in the shallow layer by another azimuth head. The recording current of each head is set to an optimum recording current for the video signal heads 33 and 34, and a recording current smaller than the optimum recording current for the digital signal recording heads 31 and 32.

FIG. 7(a) shows a part of a video signal composed of vertical and horizontal synchronizing signals, a luminance signal, and a color signal.

Further, examples of digital signals including vertical and horizontal synchronization signals are shown in FIGS. In this example, the repetition length of a group of digital signals, that is, the length of one unit block, is equal to the length of one horizontal section of the video signal, and the horizontal synchronization signal and vertical synchronization signal included in the digital signal are constituent elements of the video signal. Suppose that it is similar to a certain synchronization signal.

Therefore, the basic structural unit lengths of the video signal and the digital signal are the same. The main purpose of synchronizing the video signal and digital signal is to generate a high-energy cross between the respective synchronization signals) −
The purpose of synchronization is to reduce the negative effect that one signal has on the other signal, so the timing of synchronization is as shown in Figure 7 (a) and (
As shown in bl, the synchronization signal of the video signal may be set at a time when no digital signal exists.

In this way, the crosstalk of one synchronization signal with large energy will have a negative effect on the other synchronization signal, but since the synchronization signal originally has a large amount of energy, the deterioration of the synchronization signal due to the negative effect of this other crosstalk will be minimal. This is sufficient for practical use, and the time at which each synchronization signal crosstalks is a blanking period in which nothing other than the synchronization signal exists, so it is unlikely that it will adversely affect signals that exist outside of the blanking period and cause signal deterioration. It has the characteristics of ``na,''. If the video signal and digital signal are not synchronized, but the timing is not appropriate even if the synchronization is applied, and the time relationship between the video signal and digital signal is as shown in Figure 7 (,) and (C). The crosstalk of the synchronization signal included in the video signal degrades the data portion of the digital signal, and the synchronization signal included in the digital signal degrades the luminance signal and color signal of the video signal.

That is, if proper synchronization is not applied between the video signal and the audio signal, both signals will deteriorate.

The present invention can solve this problem of signal deterioration.

FIG. 1 is a block diagram of a main part of an embodiment of the present invention, that is, when the digital signal includes a synchronization signal. In the figure, the video signal shown in FIG. 7(a) is applied to the terminal 5, is amplified by the recording amplifier 7 via the recording side video processing circuit 'e, and is recorded on the magnetic tape by passing through the entire rotary head 3.4. Ru. Here, the recording-side video processing circuit 6 frequency-modulates the luminance signal, converts the carrier color signal into a low frequency band, and converts it into the luminance signal 22 and carrier color signal 230 frequency bands shown in FIG. Next, the audio signal containing the synchronization signal shown in FIG. 7(b) applied to the terminal 9 is code-modulated by the synchronization circuit 8 in synchronization with the vertical synchronization signal or horizontal synchronization signal contained in the video signal. The modulation 1
2, the signal is converted into a signal shown in FIG. 6, 29, further amplified by a recording amplifier 13, and 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 signal is input to the terminal 16, demodulated to the original video signal, and outputted to the terminal 16. 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 PCM audio signal. The FM demodulated digital signal is further decoded by a decoder 19 into an analog signal, that is, an audio signal, and is output to a terminal 21 via the LPF 2o.

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 shallowly records a digital signal modulated by a head having a different azimuth angle from the video signal recording head on a track where the video signal is recorded, in synchronization with the video signal. However, it is possible to reproduce video signals and digital signals separately using heads with different azimuth angles, and is an extremely high-density recording method that can record separate digital signals with almost no deterioration in the quality of the video signal. be. In other words, whether or not the digital signal includes a synchronization signal, the crosstalk of the synchronization signal, which has a large amount of energy, will rarely have a negative effect on the signal that exists at a time different from the time when the synchronization signal exists. This allows for good reproduction of both digital and video signals.

Digital signals recorded in the shallow layer of the magnetic tape in synchronization with the video signal can share the band with the video signal, making it possible to achieve a wide band, and since it is in the shallow layer, it can be erased and rewritten. It has the excellent feature of being easy to use.

Therefore, it is easy to use this digital signal for audio PCM recording, and in that case, the S/N of the audio signal,
Performance such as frequency characteristics, distortion rate, wow, and flutter are significantly improved, and it also becomes possible to perform after-recording, which was impossible with conventional FM audio recording, making it possible to create a VTR with extremely superior sound quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus to which the present invention is applied, FIGS. 2 and 3 are a frequency allocation diagram and a recording state diagram in the depth direction of a magnetic tape, respectively, to explain the conventional example, and FIG. 4 is a diagram of the present invention. FIG. 5 is a diagram showing a frequency allocator according to one embodiment of the present invention; FIG. 6 is a configuration diagram of a magnetic head group used in an embodiment of the present invention; FIG. 7 is a diagram for explaining synchronization between a video signal and a digital signal. 22...FM luminance signal, 23...Low frequency conversion carrier color signal, 27...Magnetic layer, 27a...
...Digital signal recording layer, 27b...Video signal recording layer, 29...Frequency modulated digital signal, 30...Magnetic tape, 31.32...
...Digital signal head, 33°34...
Video signal head, 3.5...Rotating cylinder, 3
6...Horizontal synchronization signal of video signal, 37...
. . . Horizontal synchronization signal of the digital signal, 38 . . . Bright color signal and color signal of the video signal, 39 . . . Data portion of the digital signal. Name of agent: Patent attorney Souo Nakao and 1 other person 2nd
Figure 3 Figure 4 Figure 5 Refrigeration number (MHz) Figure 6

Claims (6)

[Claims] (1) On the track on which the first signal composed of a signal including a synchronization signal is recorded, a second signal is synchronized with the first signal by a recording head different from the recording head of the first signal.
A magnetic recording and reproducing method characterized by overlappingly recording and reproducing signals. (2) The second signal is composed of a signal that includes its own synchronization signal that is synchronized with the first signal, and during playback, the second signal is determined based on the synchronization signal of the reproduced second signal. 2. The magnetic recording and reproducing method according to claim 1, wherein the magnetic recording and reproducing method comprises restoring. (3) The magnetic recording and reproducing method according to claim 1, wherein the first signal and the second signal are recorded and reproduced by heads having mutually different azimuth angles. (4) The magnetic recording and reproducing method according to claim 1, wherein the first signal is recorded before the second signal. (5) The magnetic recording and reproducing method according to claim 1, wherein the first signal is a video signal and the second signal is a digital signal. (6) The magnetic recording and reproducing method according to claim 1, wherein the second signal is a signal obtained by digitizing an audio signal and further in the form of a luminance signal constituting a video signal.