JPS6139784A - Magnetic recording and reproducing method - Google Patents

Abstract

PURPOSE:To reproduce a signal of high quality such as a PCM sound signal and to erase and record a digital signal by modulating and recording a digital signal on tracks where a video signal is already recorded through a head which differ in azimuth angle from a recording head for video signals, and reproducing the video signal and digital signal through the heads having different azimuth angles. CONSTITUTION:For example, the azimuth angles of video signals heads 13 and 14 are set to + or -6 deg. and the azimuth angles of digital heads 11 and 12 are set to + or -30 deg.. A video signal is already recorded on tracks on a magnetic tape and a digital signal is modulated and recorded in the shallow layer part through the different-azimuth heads. The video signal is reproduced by the rotary heads 13 and 14, and amplified by an amplifier 23 and then inputted to a reproduction side video signal processing circuit 24 and demodulated into the original video signal, which is outputted to a terminal 25. A sound signal is reproduced by the rotary heads 11 and 12, and amplified by an amplifier 23 and then demodulated by a demodulator 29 into a PCM sound signal of the basic band.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to high-density magnetic recording that allows other digital signals such as code-modulated audio signals to be recorded on tracks on which video signals have been recorded and to be separately reproduced. This relates to a reproduction method.

To 3-7 Conventional configuration and its problems In a conventional magnetic recording/reproducing device, for example, a rotating head video tape recorder (hereinafter abbreviated as VTR), the luminance signal and color signal forming the video signal are transferred to the video track. The magnetic tape used for so-called azimuth recording is structured so that the audio signal is recorded on a separate audio track, and the azimuth angles of the two rotating heads for recording the video signal are different. Almost the entire area is used.

Recently, a method of recording a frequency-modulated audio signal together with a video signal on a video track of a VTR has been put into practical use for the purpose of improving the performance of audio signal recording. FIG. 1 shows the frequency allocation in this recording method, and FIG. 2 shows a diagram of the recording state in the depth and direction of the magnetic tape.

In FIG. 1, 1 is a luminance signal containing a frequency-modulated synchronization signal, and 2 is a carrier color signal that has been low-pass converted. 3 is a frequency modulated (FM) signal of an audio signal, which is recorded in the band between the low frequency conversion carrier color signal 2 and the FM luminance signal 1 by the audio dedicated head at an azimuth angle different from that of the video signal head. .

As is clear from FIG. 2, the frequency-modulated audio signal is transferred to the magnetic layer 4 with a large recording current before the video signal.
The video signal is then recorded on the surface layer 4 of the magnetic layer 4. Note that 5 indicates the base film layer.

In the case of such a conventional example, the S/N ratio of the audio signal/dFM recording is large, the quality is higher, and the sound quality does not deteriorate even if the hand speed is slowed down, so it can be used for a long time. It can be said that this is one of the most effective recording methods for VTRs. Moreover, it is noteworthy that it utilizes the deep layer of the magnetic tape magnetic layer, which was not previously used.

However, the conventional example described above has several problems. Firstly, in order to record FM audio signals deeply, it is necessary to supply a large current to the recording head, which limits the frequency band that can be recorded to a relatively low range. The result is code modulation of higher quality than FM recording of audio signals.

5 Henno (PGM) recording is not possible (because it requires a wider band than FM), and because the audio signal is recorded in the low frequency side with a large current, it is difficult to record the audio signal in the deep layer when playing back the video signal. This may result in non-negligible interference with the recorded audio signal, the large scale of the large current supply circuit for recording the audio signal, and the adverse effects of the large current on other video circuits. Second
However, after-recording is not possible. 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 Figure 2, the audio signal is recorded deep down, so if it were to be erased or re-recorded, the video signal would also disappear, making after-recording impossible.

OBJECT OF THE INVENTION The object of the present invention is to solve the above-mentioned problems of the conventional VTR. A magnetic recording and reproducing method that enables higher recording density in VTRs by recording wideband digital signals such as encoded PGM signals, and also enables erasing and re-recording of digital signals recorded in shallow layers. We aim to provide the following.

Structure of the Invention The magnetic recording and reproducing method of the present invention modulates and overwrites a digital signal on a track on which a video signal is recorded by a head having a different azimuth angle from the recording head of the video signal, The head reproduces video signals and digital signals, which enables high-quality signal reproduction such as PGM audio signals, and also enables erasing and re-recording of digital signals, making it suitable for high-density recording. As a one-sided method, many applications are possible.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 3 is a recording state diagram in the depth direction of the magnetic layer for explaining the present invention in detail.

When video signals are conventionally recorded on magnetic tape using a rotating head, the depth of the recording layer is 0.25 of the recording wavelength.
~0.3 times, which is 0.3 to 0 for current consumer VTRs.
．． Since the recording is made to a depth of 8 μm, and since the thickness of the magnetic layer 6 of a general magnetic tape is 2 to 4 μm, there is a non-recording layer 6C as shown in FIG. The conventional example explained in FIGS. 1 and 2 utilizes this non-recording layer, but essentially only signals with long wavelengths (low frequency band) can be recorded. In fact, the shallow part of the tape magnetic layer is suitable for recording broadband signals.
Video signals are recorded only on the surface.

The present invention focuses on the fact that recording and reproducing analog signals is necessary and powerful for recording and reproducing digital signals.
A broadband digital signal is recorded in the shallow layer portion of the recording layer 6b where the video signal is recorded, to form a digital signal recording layer 6a. Note that 7 in FIG. 3 indicates a base film. For reproduction of digital signals, if the S/N is 15+iB, the code error rate will be about 10, which is close to a practical value. It is sufficient to secure a S/N of 20 to 30 (iB) with a margin. Therefore, a modulated digital signal to be recorded in a shallow layer may be recorded at a depth to the extent that the S/N satisfies the above value. The depth of the recording layer can be controlled by the recording current, and if a video signal is recorded at the optimal recording current (the recording current value that gives the maximum reproduction output), the recording current for the digital signal will be % to % of that. That's fine.

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 recording current Seventy-two with values as examples
It falls to ~5dB.

Furthermore, since the noise due to the surface nature of the tape is recorded in the shallow layer of the digital signal, it is not directly involved in the reproduction of the video signal, and the modulation noise is effectively reduced.

The S/N reduction of typical video signals remains at about 2 to 3 dB. In this way, the S//N deterioration of the previously recorded video signal can be suppressed to a minimum and the code error rate can be reduced to a practical level. It is possible to obtain the desired signal from the reproduced signal using a filter, but if you consider cases where the two signals are close to each other or overlap, it is possible to adjust the azimuth angle of the rotating head that records and reproduces the video signal and the digital signal. It is necessary to make the azimuth angle of the rotating head for recording and reproduction different. 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 rotary head for video signals reproduces only the video signal without picking up the signal recorded on the digital signal recording layer 6a, and the reproduction output of the rotary head for digital signals 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 6b. For example, if the azimuth angle of the video and digital heads is set to 3
1. Practical track width by varying 0F'.
It is possible to share the band of both signals over the entire band of 6 to 2 MHz or more.

FIG. 4 is a frequency allocation diagram of an embodiment according to the present invention. This example enables code modulation (PGM) recording of audio on existing consumer VTRs, and by slightly shortening the gap length of the digital signal recording/playback head, the conventional recordable band is slightly extended toward the high frequency side. ing.

The audio signal undergoes PCM where its fidelity is best preserved. If the audio band of 20 KHz is AD converted with 14 bits, the two channels are combined, and a code error correction bit is added, it can be converted to a bit rate of 2 MB/sea. If this is converted into an NRZ code, the base bandwidth will be about 1 MHz.

FIG. 4 shows a method for recording an audio signal having a base bandwidth of about 1 MHz, which has been subjected to PCM, and frequency-modulated luminance signal 1 and low-frequency converted carrier color signal 2 are frequency-multiplexed to produce a third signal. Recording is performed in a layer including a video signal recording layer 11.7 6b and a digital signal recording layer 6a in the figure. After that, the PCM audio signal is amplitude-modulated and the signal 8 converted to a band of 6 to 8 MHz is recorded on the digital signal recording layer 6a, thereby recording the amplitude-modulated PCM audio signal and the video signal on the same track.
CM audio signals are recorded overlappingly. In this case, the occupied bands of the video signal and the PCM audio signal will partially overlap,
Unnecessary components for mutual reproduction are suppressed by the azimuth loss described above. When viewed from the modulated PCM audio signal, the video signal is an interference component, and its magnitude is greatest in the deviation portion. In the embodiment shown in FIG. 4, the modulated PCM audio signal 8 recorded at a low level can be separated by passing it through a no-pass filter of, for example, 6 MHz or higher. The deviation portion of the signal can be further attenuated, making it easier to reproduce the audio signal. In the case of the frequency allocation shown in Figure 4, the S/N deterioration of the video signal is only 2 to 3 dB, and a digital signal of about 2 MB/Sho can be recorded. This means that it is possible to digitally record audio signals, and this shows that it is possible to record and reproduce audio signals much better than the audio FM recording described in the conventional example of FIGS. 1 and 2. Of course, digital signals can be used for other purposes than PCM audio signals. As for the recordable band, it is also possible to apply this embodiment by extending the band from the conventional band by using a metal tape or the like.

FIG. 6 is a frequency allocation diagram of another embodiment according to the present invention. In this example, the recordable bandwidth remains the same as that of a conventional VTR, but it can be recorded on a PC! This is an attempt to realize audio signal recording. Approximately 1MH with 14PcM difference from the embodiment shown in FIG.
The audio signal having the z band is frequency modulated as shown in 9 and is recorded after the video signal in approximately the same band as the deviation of the luminance signal 1. 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 with each other and becomes a disturbance or harmful 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, the recordable band can be expanded ('PGMPCM audio signals can be recorded, which is fully applicable to narrowband consumer VTRs. Also, since PCM audio signals are frequency-modulated and recorded, Of course, many features of frequency modulation in magnetic recording can be utilized.

In the embodiment, the baseband digital signal is amplitude-modulated and frequency-modulated and recorded in a shallow layer on 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 two-rotation head group for realizing the magnetic recording and reproducing method of the present invention. magnetic tape 10
This is a so-called rotating helical type VTR in which the rotary cylinder 15 rotates in the direction of arrow A at a speed of 30H2. In this case, the video signal head 13 contacts the tape before the digital signal head 11, and the video signal head 14 contacts the tape before the digital signal head 12. For example, the video signal heads 13 and 1
The azimuth angle of the digital heads 11 and 12 is set to ±6, and the azimuth angle of the digital heads 11 and 12 is set to ±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 a separate azimuth head. The recording current of each head is set to the optimal recording current for the video signal heads 13 and 14, and a fraction of the above optimal current is supplied to the digital signal head, and the modulated digital signal is applied only to the shallow layer. Set it to be recorded.

FIG. 7 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 17, passes through a recording side video processing circuit 18, is amplified by a recording amplifier 19,
The information is recorded on the magnetic tape through rotating heads 13, 14. The recording side video processing circuit 18 frequency-modulates the luminance signal,
The carrier chrominance signal is low-band converted to the frequency bands of the luminance signal 1 and the carrier chrominance signal 2 shown in FIGS. 4 and 5.

Next, the audio signal applied to the terminal 20 is subjected to PCM by a code modulator 21, limited to only the necessary band by a low-pass filter (LPF) 27, and frequency-modulated by a modulator 28 to produce a signal shown at 9 in FIG. The signal is amplified by the recording amplifier 22, and recorded on the magnetic tape through the rotary heads 11 and 12.

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 13 and 14, amplified by an amplifier 23, and then input to a reproduction side video signal processing circuit 24, demodulated to the original video signal, and output to a terminal 25. The audio signal is sent from the rotating head 11.
and 12, amplified by an amplifier 26, and then demodulated by a demodulator 29 into a baseband PCM audio signal. FM
The demodulated digital signal is further decoded by a decoder 30 into an analog signal, that is, an audio signal, which is output to a terminal 32 via a low-pass filter (LPF) 31.

In the case of this example, since the digitized audio signal is recorded on the very surface of the magnetic layer, it is easy to rewrite it to a new signal with a weak recording current, and it is also easy to erase it. can be done.

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 modulates and records digital signals in a shallow layer on a track on which a video signal is recorded by a head with a different azimuth angle from the recording head of the video signal, The video signal and the digital signal can be reproduced separately, and as soon as the quality of the video signal is almost degraded, another digital signal can be recorded. That is, the recording layer in the depth direction of the magnetic layer is controlled by a recording current, and separation between both signals is performed using azimuth loss, which can be said to be an extremely high-density recording method.

The digital signal recorded in the shallow layer can share the band with the video signal, making it possible to achieve an extremely wide band, and it also has the advantage of being easy to erase and rewrite because it is in the shallow layer. It also has other features. Therefore, the voice P
It is easy to use this digital signal for GM recording, and in that case, the performance of the audio signal in terms of S/N, frequency characteristics, distortion rate, wow, flutter, etc. will be significantly improved, and conventional FM audio recording will An after-record that was impossible.

This also makes it possible to create a VTR with extremely excellent sound quality.

[Brief explanation of the drawing]

Figures 1 and 2 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 Figure 3 is a diagram in the depth direction of the magnetic layer to explain the principle of the present invention. FIG. 4 and FIG. 5 are diagrams showing the frequency allocation of the embodiment, FIG. 6 is a diagram showing the configuration of the magnetic head group used in the present invention, and FIG. 7 is a diagram showing the magnetic recording and reproducing method according to the present invention. FIG. 2 is a block diagram of main parts of a device using. 1...FM luminance signal, 2...Low frequency conversion carrier color signal, 6...Magnetic layer, 6 &...
Digital signal recording layer, 6b...Video signal recording layer, 10...Magnetic tape, 11.12...
・Digital signal head, 13.14...Video signal head, 16...mark ・Rotating cylinder, 3...
Modulated digital signal, 4... Frequency modulated PCM audio signal. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure/fl Hakan (Tomo ZJ Figure 2 Figure 3

Claims (8)

[Claims] (1) On a track where a video signal is recorded, a digital signal is modulated and overlaid by a head having a different azimuth angle from the recording head for the video signal, and the digital signal is overwritten, and the video signal and the digital signal are reproduced by heads having different azimuth angles. A magnetic recording and reproducing method characterized by: (2) The magnetic recording and reproducing method according to claim (1), wherein the video signal is composed of a frequency-modulated luminance signal and a low-frequency-converted carrier color signal, and is recorded before the digital signal. . (3) The magnetic recording and reproducing method according to claim (1), wherein the digital signal is amplitude-modulated and recorded after the video signal. (4) The magnetic recording and reproducing method according to claim (1), wherein the digital signal is frequency-modulated and recorded after the video signal. (5) The magnetic recording and reproducing method according to claim (1), characterized in that the modulated digital signal is placed on the higher side of the occupied band of the video signal. (6) The magnetic recording and reproducing method according to claim (1), characterized in that the frequency-modulated digital signal is arranged in substantially the same band as the frequency-modulated video signal. (7) The magnetic recording and reproducing method according to claim (1), characterized in that the recording current of the modulated digital signal is set smaller than the recording current of the video signal. (8) The magnetic recording and reproducing method according to claim (1), wherein the digital signal is a signal obtained by code-modulating an audio signal.