JPS6126903A - Magnetic recording and reproducing method - Google Patents

Abstract

PURPOSE:To improve the quality of the reproduced sound signal by recording the sound PCM signal on a track of video signals by a head having an azimuth angle different from that of the video signal and so that the track of the sound PCM signal is set on a guard band. CONSTITUTION:The video signals are recorded to a magnetic tape from a terminal 29 via a video signal processing circuit 30 provided at the recording side and through rotary heads 4 and 5. While the sound signals are recorded to the magnetic tape from a terminal 32 via a sound signal processing circuit 33 at the recording side and through rotary heads 6 and 7. The heads 4 and 5 are set at positions at 180 deg. adverse azimuth to each other. While heads 6 and 7 have different azimuth angles from those of heads 4 and 5. The heads 6 and 7 records PCM sound signals on a video track in a long-time mode and then performs recording so that the PCM signal track is set on a guard band between video signal tracks in a standard mode. In a reproduction mode the video signals are reproduced by heads 4 and 5; while sound signals are reproduced by heads 6 and 7. Thus the quality of the sound signals is improved with a magnetic recording/reproducing system.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a rotating head type video tape recorder (hereinafter referred to as V
This relates to magnetic recording and reproducing devices such as TR (referred to as TR).
In particular, it is possible to record and reproduce an audio signal by code modulating C (hereinafter referred to as pay) using a rotary head separately from a video signal.

Conventional Structure and Problems In the conventional VT'H, video signals were recorded by a rotating head, and audio signals were recorded by a fixed head on dedicated tracks on a magnetic tape. However, as VTRs became longer, the tape running speed became slower.
In this case, there is a problem in that the frequency characteristics and S/N of the audio signal deteriorate, and high-quality reproduced sound cannot be obtained. To obtain high quality playback sound even at low tape speeds.

There is a method of modulating and recording an audio signal on a video track of a VTR. This is a method in which the audio signal is frequency-modulated and recorded in the band between the 1-frequency modulated luminance signal and the low frequency-converted carrier color signal, and the audio signal is recorded using the same head as the video signal. There is a method in which audio signals are recorded using a rotating head dedicated to audio. In both cases, the audio signal is recorded in FM, so the S/N ratio is high and the quality is good.In addition, the sound quality does not deteriorate even if the tape running speed is reduced, so it is possible to record the sound of a VTR for a long time. This is one of the most effective recording methods.

However, in recent years, there have been many opportunities to come into contact with high-quality audio sources such as compact discs and audio PCM broadcasts via broadcasting satellites, and there has been a growing consensus that the above-mentioned VTR audio recording system is not fully satisfactory. The main points are that head switching noise occurs, the distortion rate is high, and after-recording is impossible.

In order to eliminate these problems, it would be possible to adopt the audio PCM recording system, but current consumer VTRs do not have the recording density that is sufficient to record a PCM wideband audio signal by adding it to the video signal. It can be said that there is no

A recently developed example is the PCM audio recording system for VTRs. This method uses a broadcast VTR with one rotating head, and as shown in Figure 1, a PCM audio signal track 3 is set in guard band (non-recording base) 2 between video tracks 1, and a separate head is used for recording and playback. be. With this method, wideband PCM audio signals can be sufficiently recorded and reproduced, and high-quality reproduced sound can be obtained.

However, it is difficult to apply the above-described method as is to a consumer VTR that employs the azimuth recording method. This is because the guard band width of the above-mentioned broadcasting VTR is set to be sufficiently large.

This is because an azimuth type consumer VTR basically does not have a guard band as shown in FIG.

Recent consumer VTRs have longer operating hours, and standard mode (
In the case of a VH8-VTR, it is possible to switch between a long-time mode (2 hours) and a long-time mode (also 6 hours), and the rotary head is often used in both modes. This kind of VT
The R recording track pattern (video portion only) is shown in FIGS. 3a and 3b.

"a" indicates standard mode and "b" indicates long-time mode.

For example, in the VH3 system, one track pitch in standard mode is 6Bltm, but in long mode it is only 19.3μm.
It is. - As an example, if the video head width is selected to be 3 oltm, the guard band 12 is approximately 28 μm in standard mode.
．． There are 14. However, in the case of long-time mode, the video head width becomes larger than the trunk pitch, so a guard band cannot be formed. Therefore, although it is theoretically possible to record audio PCM signals using the guard band in the standard mode where guard pan 1' exists, it is not possible to record audio PCM signals in the long-time mode. The problem was that I couldn't do it.

OBJECT OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to solve the problems described above. Another object of the present invention is to provide a magnetic recording and reproducing method that can significantly improve the quality of audio signals by enabling PCM recording and reproducing of audio signals.

Composition of the Invention The magnetic recording and reproducing method of the present invention provides the above-mentioned rotating head type VTR in which a first recording mode in which a guard band does not exist between video signal tracks and a second recording mode in which a guard band exists coexist. In the first recording mode, an audio PCM signal is overlaidly recorded on the video signal track by a head having an azimuth angle different from that of the video signal, and in the second recording mode, the audio PCM signal track is recorded so as to be on the guard band. By this method, the quality of the JVTR reproduced audio signal can be significantly improved in both the above-mentioned modes.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, a method for recording audio PCM in a long-time mode without a guard band will be described. FIG. 4 is a recording state diagram in the depth direction of the magnetic layer for explaining the principle.

When video signals are conventionally recorded on magnetic tape using a rotating head, the depth of the recording layer is 0.26 of the recording wavelength.
~0.3x, and current consumer VTRs have 0.3 to 0
．． Considering that the magnetic layer 18 of a general magnetic tape has a thickness of 2 to 4 μm, there is a non-recording layer 180 as shown in FIG. . 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 shallower part of the recording layer 18b where video signals are recorded. and a digital signal recording layer 18L. In addition, 17 in FIG. 4 shows a base film. For reproducing digital signals, if the S/N is 16 dB, 10
A code error rate of about -5 approaches a practical value. It is sufficient if an S/N of 20 to 30 dB can be secured with a margin. Therefore, the digital signal recorded in the shallow layer is S
It is sufficient to record to a depth such that /N satisfies the above value.

The depth of the recording layer can be controlled by a recording current, and if a video signal is recorded with an optimal recording current (a recording current value that maximizes the reproduction output).

The recording current for digital signals may be in a small chunk.

Naturally, the digital signal is recorded in a shallow layer after the recorded video signal, so the playback output of the video signal decreases, but the extent of this is small because the digital signal recording layer is extremely thin.The above recording current value is an example. It falls within 3 to 6 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 difficult to be directly involved in the reproduction of the video signal, and the modulation noise is reduced, so the actual S/N reduction of the video signal is 2 to 2. It remains at around 3dB. In this way, it is possible to suppress the S/N deterioration of the previously recorded video signal and record a digital signal with a practical code error rate thereon.

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 by filtering, but it is necessary to consider the case where the two signals are close to each other or overlap. For example, 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, a first-order loss L occurs.

However, W Nidraft 2 width λ: recording wavelength Therefore, the playback output of the rotating head for video signals is.

The azimuth is such that only the video signal is played back without picking up the signal recorded on the digital signal recording layer 18L, and the playback output of the digital signal rotary head is set to the digital signal without picking up the signal on the video signal recording layer 18b. Corners can be set. For example, by making the azimuth angles of the video and digital heads different by 300 degrees, it is possible to share the band of both signals over the entire band of 1.5 to 2 MHz or more with a practical track width. As a result, the fifth
As shown in the figure, a frequency-modulated luminance signal 19 and a low frequency-converted carrier color signal 20 are frequency-multiplexed to form a video signal recording layer 1.
8b, and a broadband digital signal 21 within the same band as those signals can be recorded on the digital signal recording layer 1B&. In the case of 0 frequency allocation shown in FIG. 4, the S/N deterioration of the video signal remains at 2 to 3 dB, and a digital signal of about 4 Mft can be recorded.

This means that audio signals can be digitally recorded on PCiMj, and even in long-time mode where there is no guard band, it is possible to record and play back audio signals much better than the audio FM recording explained in the conventional example. It shows what will happen.

As long as the azimuth angles of the video and audio PCM heads are set sufficiently large, the track position of the audio PCM head in the long-time mode can be anywhere on the video track.

Under these conditions.

The position of the audio PCM head is preferably determined by paying attention to the performance of the standard mode V' in which a guard band exists. FIG. 6 shows an example of this. a is a head arrangement diagram on the rotating cylinder 8, and the image heads 4 and 5 are opposite azimuthal to each other.
It is located at 800. The audio PCM signal is recorded by dedicated heads 6 and 7, which are arranged to form an angle ψ with the video heads 4 and 5, and also have a height relative to the reference plane as shown in b. Arrange them so that they are shifted by h. Due to the angle ψ0 and the step in Figure 6.

Since there is a gap between the scanning trajectory of the video head and the scanning trajectory of the audio PCM/throat, it is necessary to set ψ and h appropriately.
In the standard mode, the audio PCM recording heads 6 and 7 can be placed in the center of the guard band as shown in FIG. Figure 0 shows the width of the gutter to the audio PCM: 20μm, ψ=45
This is an example where h=20/1j771. In this case, in the long-time mode, nodes 6 and 7 are placed on the video track to the audio PCM as shown in d.

As already explained, in long-term mode.

Although the audio PCM signal can be recorded on the video track due to shallow recording and azimuth loss, the S/N of the video signal is slightly degraded. However, as explained in the embodiment shown in Figure 6, in the standard mode where a guard band exists, the S/PCM is recorded on the guard band.
No deterioration of N occurs at all.

As described above, by providing a pair of audio PCM grooves that can be used both in the standard mode and the long time mode, high quality audio PCM recording can be realized in both modes.

In addition, in standard mode, the audio PCM recording signal is basically recorded on the guard band of the video signal, so the audio PCM recording signal does not deteriorate the video signal, so the audio PC
There is no problem in making the recording current during iM recording larger than that in long-time mode.

In this way, the S/N ratio when reading the audio PCM signal in the standard mode is improved, and a recording system with fewer code errors can be realized.

Furthermore, although the F width of the audio PCM recording head is set to 20 μm in the embodiment shown in FIG. 6, it can be selected to be smaller than, for example, the video signal track width in the long-time mode. Although the actual S/N drops slightly, this has little effect on the reproduced sound as long as the bit error rate exceeds a desired value. In this case, since there remains an area in the shallow part of the video track where no audio PCM recording is performed, the S/N of the video signal is improved compared to the case of FIG. 6.

Even with this configuration, if the angle ψ and the step are appropriately set, it is possible to arrange the audio PCM rack in the standard mode at approximately the middle of the guard band between the video tracks.

In addition, if the recording current of the audio PCM signal in the standard mode is set near the optimal recording current where the playback output is almost maximum, the signal can be rewritten without the need for a special erasing head, so the audio 7-channel recording function can be used. can be easily realized.

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 29, passes through a recording side video signal processing circuit 30, is amplified by a recording amplifier 31, and is recorded on a magnetic tape through one-rotation heads 4, 6. The recording-side video processing circuit 3o frequency-modulates the luminance signal, performs low frequency conversion on the carrier color signal, and frequency-multiplexes the signal.

Next, the audio signal applied to the terminal 32 passes through the recording side audio signal processing circuit 33, is amplified by the recording amplifier 22, and is recorded on the magnetic tape through the one-rotation head 6.7. The recording side audio signal processing circuit 33 converts the audio signal into code modulation (PCM) L.
, convert the code into a format that is easy to record, and apply, for example, a frequency modulation signal.

Next, the time of reproduction will be explained. The azimuth angle of the video signal and digitized audio signal recorded on magnetic tape was changed.

Playback using each dedicated head.

The video signal is reproduced by rotary heads 4 and 5, and an amplifier 2
After being amplified in step 3, the signal is input to the reproduction side video signal processing circuit 24, demodulated to the original video signal, and output to the terminal 25. The audio signal is reproduced by the rotary heads 6 and 7 and the amplifier 26
After being amplified, the signal is input to the reproduction side audio signal processing circuit 27, decoded into a 1-element audio signal, and outputted to the terminal 28.

Effects of the Invention As detailed above, the present invention records the audio PCM signal in the guard band portion of the video track in the standard mode, and records the azimuth angle of the video track on the video track in the long time mode where no guard band exists. The audio PCiM signal is overlaid recorded using a separate head with a different azimuth angle, and in the standard mode there is no deterioration in the S/N of the video signal, and in the long time mode there is only slight S/N deterioration. PCM of audio signal just by accompanying
Enables recording and playback. Therefore, compared to the reproduced audio signal in a conventional VTR, various performances such as S/N, frequency characteristics, distortion rate, wow and fluff can be dramatically improved. In particular, since PCM recording of audio is possible in both standard mode and long-time mode, it is possible to reduce the thickness of the magnetic layer of the magnetic tape used because it does not require fixed head recording or FM recording, which is the conventional audio recording method. This is an extremely useful method that can also contribute to reducing the cost of magnetic tapes.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the track pattern of a broadcasting VTR [i], FIG. 2 is a diagram showing the track pattern of a conventional and consumer azimuth recording type VTR, and FIG. 3a. b is an enlarged view of an azimuth recording type track pattern at different mode and toe, FIG. 4 is a cross-sectional view of a magnetic tape for explaining the present invention in detail, and FIG. 5 is a frequency allocation diagram, FIG. 6 is a diagram showing the arrangement of heads and the relationship between track patterns and head positions for explaining a magnetic recording and reproducing method according to an embodiment of the present invention, and FIG. 7 is a diagram showing the configuration of the magnetic essential parts. 4.5...Rotary head for video signal, 6,7...
... Rotating head for audio PCM, 11.13...
...Video track, 15.16...Video track, 8...Rotating cylinder, 18...Magnetic layer, 18a...Audio PCM signal recording layer, 18
b...Video signal recording layer, 21...Audio PC
M signal band. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Fig. 2 Fig. 3 (α) /f4 Fig. 4 Fig. 5/q M Kyo tshz) Fig. 6. (η) (b) Figure 7

Claims (5)

[Claims] (1) The first recording mode of a rotary head VTR in which a first recording mode in which a guard band does not exist between video signal tracks and a second recording mode in which a guard band exists coexist is used to record images on video signal tracks. A magnetic recording and reproducing method, characterized in that an audio PCM signal is recorded in an overlapping manner by a head having an azimuth angle different from that of the signal, and in the second recording mode, the audio PCM signal track is recorded so as to be on the guard band. (2) Audio PCM in the first mode and second mode
2. The magnetic recording and reproducing method according to claim 1, wherein the heads for recording signals are the same head. (3) The magnetic recording and reproducing method according to claim 1, wherein the recording current for the audio PCM signal in the second mode is set to be larger than the recording current for the audio PCM signal in the first mode. (4) The magnetic recording and reproducing method according to claim 1, wherein the recording head width of the audio PCM signal is set smaller than the video track width in the first mode. (5) The magnetism according to claim 1, characterized in that the recording current of the audio PCM signal in the second mode is set to approximately the optimum recording current, so that only the audio PCM signal can be after-recorded. Recording and playback method.