JPH01220213A - Digital signal recording and reproducing system - Google Patents

Abstract

PURPOSE:To prevent unrequired data from being recorded and to detect tracking information with high precision by applying DC free modulation on data to be recorded generally, disturbing the DC free modulation at a certain point on a track, and setting disturbance differently between adjacent tracks. CONSTITUTION:A magnetic head 6 modulates a data string 17 to be recorded in track length by a modulator 4, however, a modulation rule in modulated output 17 is disturbed in periods (19-27). The DSV (Digital Sum Variation) of each block of the modulated output 18 goes to '0' in the periods (19-27), and the modulation rule is disturbed, then, it changes like DSV28, and in the DSV28 and 29, the disturbance of the modulation rule are set differently between the adjacent tracks. At the time of reproduction, a signal is introduced to a demodulator 9 and a filter 14, and the modulator 4 performs a DC free operation almost in all periods, and the DSV changes in extremely limited period. Therefore, different signals between the adjacent tracks can be obtained from the filters 14. In such a way, it is possible to detect a tracking error correctly as holding a recording and reproducing function.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates particularly to digital signal recording and reproducing systems such as helical scan type digital magnetic recording and reproducing systems.

BACKGROUND OF THE INVENTION The need for recording and storing digital information has particularly increased in recent years. Various methods and devices are being considered depending on the nature and purpose of the data being handled.

Therefore, a conventional system in this field will be first explained using a Hercal scan type t-air recording and reproducing device as a recording device for recording video signals digitized as digital information.

FIG. 3 is a block diagram showing a conventional device.

In the figure, 32 is an input terminal, and 33 is an analog-to-digital converter (hereinafter referred to as an A/D converter).
/Dfi converter), 34 is a recording side processor, 36 is a modulator, 36 and 38 are magnetic heads, 37 is a magnetic tape,
39 is a demodulator, 4o is a Kawasaki side processor, 41 is a digital μ
- Analog converter (hereinafter referred to as D/A converter). 42 is an output terminal (also referred to as a D/A converter in the drawings).

A video signal to be recorded is supplied to an A/D converter 33 via an input terminal 32. The A/D converter 33 digitizes the applied analog video signal and sends it to the recording side processor 34.
Send the data to. The recording side processor 34 performs predetermined digital processing on the received digital data. For example, data formatting, error correction encoding, band compression, etc. are performed. The result is digitally modulated by a modulator 36 and transferred to a magnetic tape 37 via a magnetic head 36.
recorded above.

During playback, the signals recorded on the taste tape 37 are read out via the magnetic head 38 and decoded by the demodulator 39. The output of the demodulator 39 is subjected to predetermined digital processing in a reproduction side process d40.

Here, data de-formatting, error correction decoding, band expansion, error correction, error correction, etc. are executed.

The result is inversely converted into an analog signal by a D/A converter 41, and an analog reproduced video signal is sent out via an output terminal 42.

Next, a description will be given with reference to a conventional tape pattern diagram shown in FIG.

FIG. 4 is a tape pattern diagram of the conventional method described above.

In the figure, 43 is a magnetic tape and 44 to 47 (id) racks. In the helical scan type magnetic recording and reproducing device, the magnetic heads 36 and 38 are mounted on a rotating cylinder,
This is a method of recording and reproducing on a magnetic tape 37 that is wound on the surface of this rotating cylinder at a slight inclination, and as a result, the track patterns formed are in a diagonal direction with respect to the magnetic tape 43, such as tracks 44 to 47. .

By the way, if the recording degree is changed, track 44
The magnetic heads 3e and 38, which have very narrow track widths (track pitches) in tracks 44 to 47, are accurately
It becomes difficult to trace the top.

One way to solve this problem is to multiplex record the pilot signal, extract this pilot signal during playback, detect track deviation, and correct the trace, which is practical for analog recording VTRs. has been made into

What is the frequency spectrum of the recording signal in this analog recording VTR in Figure 6? It shows. In the figure, the horizontal axis shows frequency and the vertical axis shows level /I/. 64 is a video signal component, and 60 to 53 are pilot signals. In an analog recording VTR, the video signal is subjected to predetermined processing and then subjected to FM modulation to create the video signal component 64 (home-use VT
In R, etc., the carrier color signal is converted to a low frequency band and recorded, but this is omitted here. ). Further, a spectrum space is created in the low frequency band, and the pilot signals 60 to 63 are frequency-multiplexed and recorded there.

The four pilot signals 50 to 53 are used in a predetermined manner for each track.For example, tracks 44 to 4 in FIG.
7, pilot signals 60-63 are used, respectively. As a result, since the pilot signal frequencies differ between adjacent tracks, if a tracking error occurs during reproduction, a change occurs in the pilot signal, and the tracking state can be detected. Tracking is corrected based on this result.

Problems to be Solved by the Invention However, in the case of digital recording, the above-mentioned pilot signal insertion method cannot be adopted.

FIG. 6 is a frequency spectrum diagram when, for example, NRZ is adopted as the digital modulation method. In the figure, the horizontal axis represents frequency and the vertical axis represents level. 61 is NRZ
The modulation output signal components 57 to 60 are pilot signals. When the modulator 35 in FIG. 3 performs NRZ modulation, if the input data to the modulator 36 is random, energy exists uniformly up to the low frequency band as shown in 61. Here, similarly to the above-mentioned analog recording VTR, the pilot signal 6
If pilot signals 67 to 60 are inserted, mutual crosstalk will occur between pilot signals 67 to 60 and output signal component 61 of modulator 35, which will adversely affect both. As a result, it becomes impossible to detect tracking errors, and even if accurate tracking is possible, the error rate of reproduced data increases extremely.

On the other hand, a case where a modulation method (hereinafter referred to as "DC free modulation") which has no DC component and has very low noise in the low frequency band is adopted as the modulator 36 will be described with reference to FIG.

In the figure, the horizontal axis is frequency, the vertical axis is level, 68 is the output component of the modulator, and 64 to 67 are pilot signals.

Since it is DC free modulation, there is no energy in the low frequency band like the output component 68, and it is thought that the pilot signals 64 to 67 can be frequency multiplexed to this part.

However, in this case, although no crosstalk occurs to the pilot signals 64 to 67, the crosstalk to the pilot signals 64 to S7 does not occur.
As a result, the output waveform of the modulator 36 is recorded as oscillating up and down at a low frequency. As a result, a zero-cross shift or the like occurs at the time of recording, increasing the data error rate.

FIG. 8 is a waveform diagram when a pilot signal is frequency-multiplexed on the DC-free modulated output. In the same figure, the recording current waveform of the magnetic head 6, 7o and 71 are signal waveforms corresponding to pilot signals, 73 to 78 are zero crossing points, and 7
2 has zero level I, and 6469 has modulator 36 of 1010.
The output waveform of the pilot signal 70. Due to Ryo1, it is undulating up and down. As a result, it can be seen that the interval between zero cross points 73 to 780 fluctuates.

As described above, digital recording has a problem in that it is not possible to introduce the pilot signal insertion method used in analog recording VTRs.

In view of this problem, the present invention has developed a digital
The present invention provides a digital signal recording and reproducing method that can accurately detect tracking information without affecting the information in any way.

Means for Solving the Problems To achieve this, in the present invention, DC-free modulation is normally applied to the data to be recorded, the DC-free modulation is disturbed in some places on the track, and the method of disturbance is different between adjacent tracks. By doing so, the spectrum of the low frequency band is made different between adjacent tracks, and during playback, tracking information is obtained according to the state of the spectrum of the low frequency band.

Function: By using this method, there is no adverse effect on the digital (digital) information to be recorded, unnecessary data is not recorded in excess, and tracking information can be detected with high accuracy.

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

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, 1 is a video signal input terminal, 2 is a 0 converter, 3 is a recording side processor, 4 is a modulator, 5 is a modulation side # unit, e
and 8 a magnetic head, 7 a magnetic tape, 9 a demodulator, 1
o is a demodulation controller, 11 is a reproduction side processor, 12 is a D/A converter, 13 is a video signal output terminal, 14 is a p-wave device, 15 is a track error detector, and 16 is a track error output terminal.

A video signal to be recorded is applied to an A/D converter 2 via an input terminal 1 and digitized.

The output of the A/D converter 2 is subjected to predetermined digital processing in a recording side processor 3 and sent to a modulator 4. Modulator 4
performs DC-free modulation, and is composed of, for example, an 8/10 conversion block code. Normally, the output of this modulator 4 is DC-free, and each block has a DC-free output.
S V (Digital SumVation
) is 0. However, in accordance with instructions from the modulation controller 6 during a predetermined period, the modulator 4 outputs output data whose DSV is not O.

The output of the modulator 4 is recorded on a magnetic data differential via a magnetic head 6.

During reproduction, signals recorded on the magnetic tape 7 are read out via the magnetic head 8 and guided to the demodulator 9. The demodulator 9 normally operates normally and demodulates input data. By the way, DSV is Q in some places on the track.
A signal other than O is recorded, and data that deviates from the modulation rule is applied to the demodulator 9. During this period, instructions are issued from the demodulation controller 1o, and correct data is restored by performing irregular demodulation operations. The output of the demodulator 9 is subjected to predetermined digital processing in a reproduction side processor 11, converted to an analog signal by a D/A converter 12, and a video signal is sent out from a video signal output terminal 13.

On the other hand, the output of the magnetic head 8 is also supplied to an F wave generator 14, and components in a low frequency band are extracted.

The low frequency band components extracted by the wave detector 14 are sent to the tracking error detector 15. The tracking error detector 15 detects the tracking error situation based on the spectrum of the applied signal, and sends out the result via the tracking error output terminal 16.

By the way, when digital information is recorded on the magnetic tape 7 as shown in FIG. 4, during reproduction, the reproduction side processor 11 is operated while recognizing which location on the track or what type of data is being reproduced. There is a need. For this reason, it is usual to record in advance some data indicating the start of a track or a synchronization signal indicating the start of each predetermined data block. Naturally, a controller is required to detect such data and synchronization signals and control the processing of the entire regeneration system, but this is omitted in FIG. 1 for the purpose of simplifying the drawing and explanation. Needless to say, the demodulation controller 10 receives the signal from the controller, estimates the period during which the DSV is no longer 0, and informs the demodulator 9 of the period.

Although FIG. 1 shows a case where the demodulation controller 10 controls the demodulator 9, such a demodulation controller 1o is not necessarily required depending on how the demodulator 9 is configured. For example, if a DC-free 8/10 block code is used as the modulation method, the DSV will be
There are 262 patterns of normal codewords where DSV is not 0, and 772 patterns of codewords whose DSV is not 0. That is,
If a code word whose DSv is not 0 is also allocated in advance, even if the modulator 4 adopts a code word whose DSV is not 0, the demodulator 9 can perform normal demodulation without any abnormality.

Now, an example of how to disturb the DSV in the modulator 4 will be explained with reference to FIG. In the figure, 17 is a data string to be recorded in one track length, 18 is an output data string of the modulator 4, 1
9 to 27 indicate periods during which the modulation rules are disturbed, 28 and 29 indicate DSV in block units, and 30 and 31 indicate the state of DSV ridges, respectively. A data string to be recorded in one track length created by the magnetic head 6 in FIG. 1 in one trace (that is, a data string output from the recording side processor 3) 1
7 is modulated by the modulator 4, but the modulation rule is disturbed in the period 19 to 27 shown in the modulation output 18. The modulator 4 is basically DC free modulation, for example 8/1
It is assumed that this is implemented using o block code or the like. In this case, the DSV of each block of modulated output is 0, but
19 to 27-c disturb the Km rule, and the DSV at this timing is not 0 but changes like DSV28. DSVs 28 and 29 each show the DSV state of two adjacent tracks, and the manner in which the modulation rules are disturbed is made different between the adjacent tracks. j) It can be said that the undulations 30 and 31 of the SVs 28 and 29 are components in a low frequency band, and the undulation 31 has a frequency component twice that of 30.

During reproduction, the signal read out via the magnetic head 8 is guided to a demodulator 9 and a filter 14, as shown in FIG.

By the way, the modulation rji4 operates in a DC-free manner for most of the period, and DS■ changes for a very limited period.

Therefore, the output signal spectrum of the modulator 4 has a tendency similar to that shown in FIG. 7 (however, the appearance of the low frequency band is
It depends on how the swell is made. ). Therefore, p-wave device 1
4, different signals are obtained between adjacent tracks. This functions similarly to the pilot signals 50-53 in FIG.

Furthermore, an example of how to disturb the modulation rules will be given below. Assuming an 8/10 block code as DC-free modulation, the DSV of a 10-bit code word is as shown in Table 1. 1 of the modulator output data 18 in FIG.
For periods other than 9 to 27, the code word is converted to a code word whose DSV is 0, and for the period 19 to 27, a code word whose DSV is not 0 may be selected.

The present invention has been described above along with the embodiments, but it goes without saying that the present invention is not limited to helical scan type digital recording VTRs, and can be applied to other scanning methods and information other than video.

Further, the period during which the rules of the modulation method are disturbed is not particularly defined in FIG. The reason is that the effects of the present invention can basically be obtained anywhere. However, in digital recording VTRs and the like, there are various advantages to disrupting the modulation rules during the period of the sync data section. For example, the purpose of the sync data section is to detect a sync, and this section does not transmit any other information. Therefore, any code word whose L)SV in Table 1 is other than 0 can be freely used. Further, the sync data section is arranged regularly, and both sync and pilot information can be transmitted in the sync data section. There are advantages like this.

Furthermore, in addition to the sync data section, it is also possible to use the ampoule data section and the editing gap section.

Furthermore, it is not necessary to always disturb the DSV between adjacent tracks at the same data position as shown in Figure 2, but it is also possible to vary the frequency and length of disturb the modulation rules between adjacent tracks. .

In addition, although the 8/1o block code has been given as an example of DC free modulation, it is not necessary to limit it to this method, and other D.C.
The effects of the present invention are also exhibited in C-free modulation.

Effects of the Invention As is clear from the above explanation, the present invention intentionally inserts another signal in order to detect tracking errors during reproduction.9 However, there is no need for superimposition, and there is no adverse effect on the original recording and reproduction of digital data. It is possible to accurately detect tracking errors while maintaining efficient digital data recording and reproducing functions.

In digital recording VTRs and the like, high-density recording is essential, and naturally the track pitch becomes narrower.

Therefore, tracking in a narrow track pinch is an important key technology, and particularly requires recording/reproducing with a low error rate and the ability to accurately detect tracking errors. Also from this point of view, the present invention exhibits extremely high effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a digital signal recording and reproducing method in an embodiment of the present invention, FIG. 2 is a pattern diagram showing changes in a data string and DSV for explaining FIG. 1,
Fig. 3 is a block diagram showing a conventional example, Fig. 4 is a tape pattern diagram, Fig. 5 is a recording signal frequency spectrum diagram in analog recording VTR, Fig. 6 is a frequency spectrum diagram in digital modulation, and Fig. 7 is FIG. 8 is a frequency spectrum diagram for explaining FIGS. 1 and 3, and FIG. 8 is a recording current waveform diagram when a conventional method is introduced for digital recording. 2.../D converter, 3... Recording side processor, 4... Modulator, 5... Modulation controller, 6.8. ...Magnetic head, 7...Magnetic tape, 9...Demodulator, 1°...Demodulation controller, 11...Reproduction processor , 12...
... D/A converter, 14... Door wave device, 15...
...Track error detector. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 Figure 5 [μm Gae Sanko Figure 6 [Zhou he loses]

Claims (1)

[Claims] The data to be recorded is normally subjected to DC free modulation, and the DC free modulation is disturbed in some places on the track, and by varying the way the DC free modulation is disturbed between adjacent tracks, the A digital signal recording and reproducing method characterized by varying the spectra of frequency bands and obtaining tracking information according to the state of the spectrum of the low frequency band during reproduction.