JPS63229648A - Rotary head type digital signal recording and reproducing system - Google Patents

Abstract

PURPOSE:To always perform a stable tracking without damaging a tracking state even in the case of the occurrence of drop-out or the like by sampling and holding a difference signal using a just before sampling pulse which is free from drop-out or the like. CONSTITUTION:Lengths of a synchronizing signal fs included in two ATF signals reproduced from an ATF signal recording section on the recording track terminal side at the first time of rotary head scanning and reproduced from that on the recording track start side at the second time of rotary head scanning are decided, and the decided result is a reference signal. After third and fourth rotary head scanning are finished, this reference signal is compared with the synchronizing signal fs included in two ATF signals reproduced from the ATF signal recording section on the recording track terminal side at the first time of rotary head scanning and reproduced from that on the recording track start side at the second time of rotary head scanning; and only when the lengths of the synchronizing signal fs coincide with each other, this synchronizing signal fs is used to update an error signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a method for recording a recording track formed by a rotary head on a magnetic tape in a certain period from the beginning of each recording track and in a certain period just before the end of each recording track. For automatic tracking detection (A
Automatic Track Finding (hereinafter referred to as TF) signal, as well as a recording function that records digital audio signals in the middle part of the other tracks, and a recording function that records the recorded signals of the recorded magnetic tape in a good manner. The present invention relates to a rotary head type digital signal recording and reproducing method having a reproducing function.

(Prior Art) Among digital audio tape recorders (DAT) that can record PCM audio data obtained by pulse code modulation (PCM) of analog audio signals on magnetic tape and play it back, a rotary head is used. At DAT,
The magnetization pattern recorded on the magnetic tape is recorded with adjacent tracks having different azimuth angles and without guard bands between each track. AT for each part
Record the F signal and record the PCM in the middle of the other tracks.
Audio data is recorded in a predetermined signal format and played back.

PCM audio data has at least two modes: sampling frequency 48K, 2 channels.

Standard mode of straight line with 16 bits for mother and child, sampling frequency 32kHz2, 2 channels, 12 bits for quantization
There is a bit-nonlinear long-time mode (also called half-way mode). In reality, the sampling frequency is further 44.1kHz.
, mode, sampling frequency 32kl-1, 4 channels, quantization bit number 12 bits non-linear mode, etc., but these modes have the same recording and playback time as the standard mode.

In the half-speed mode, the rotational speed of the rotating drum and the tape running speed are each ten times that of the standard mode, and the digital signal (to be exact, 8r [signal, clock pulse for generating PCM audio data)] is also standard. As the frequency is multiplied by that of the standard mode, the overall operating speed of II is multiplied by that of the standard mode, except for the interconversion part between the analog audio signal and the digital signal.

Standard mode data rate is 48kHz x 2 x 16 = 1536 bits/
The data rate in sec half speed mode is 32k H, x 2 x 12 = 768 bits/
sec. Therefore, in half-speed mode, the sound quality is slightly inferior to that in standard mode, but by making the operating speed of the entire device twice that of standard mode, it takes twice as long for the same magnetic tape as in standard mode. Recording and playback possible.

(Problems to be Solved by the Invention) It is desirable to realize a multifunctional AT by configuring a rotary head type DAT that can operate in a standard mode so as to be able to operate in a half-speed mode. However, this method has the following problems, which cause high costs, technical difficulties, and quality deterioration.

■Since the ATF signal frequency and the carrier frequency of PCM audio data are twice as high as those in standard mode, during playback, AT
Of the signal processing circuit for F signal frequency and PCM audio data, the analog filter circuit and the PLL (phase-locked loop) circuit for data reading can be operated by switching their respective operating frequencies, or by using two sets (standard It is necessary to prepare one for mode and one for half-time mode and switch between them.

■The connection between the rotating head attached to the rotating drum and the recording amplifier and playback amplifier is normally done via a rotary transformer, but in half-speed mode the signal frequency is twice that of standard mode, so low-frequency The bond deteriorates.

■If the C/N during playback is optimized in standard mode, the relative linear velocity between the tape and head will be twice that of standard mode.In half-speed mode, the playback head output voltage will be 1/2 times that of standard mode. Therefore, the C/N deteriorates.

■Both the drum motor and capstan motor meet the specified performance (drum rotation jitter and phase synchronization with the electric circuit, capstan motor rotation unevenness, etc.) at two types of rotation speed corresponding to standard mode and half speed mode, respectively. ).

Therefore, in Japanese Patent Application No. 61-209243 entitled "Rotary Head Type Digital Signal Reproducing Apparatus", the present applicant set the rotary head at a constant speed in both the standard mode and the half speed mode, and changed only the magnetic tape running speed. Above■
We have proposed a device that solves all of the problems related to reproduction described in (1) and (2), and a part of each of the problems described in (1) and (2) above.

The present invention further improves this proposal.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention uses a rotary head type digital signal recording and reproducing method to obtain F)0M for a certain period of time obtained by pulse code modulating an audio signal. In the first mode, a multiplexed signal consisting of audio data and a tracking detection signal time-division multiplexed before and after the PCM audio data for a predetermined period is sequentially formed into tracks one by one on the magnetic tape by a rotating head. or the amount of data per unit time is approximately twice that of the first mode, and the rotational speed of the rotary head and the running speed of the magnetic tape are approximately the same as those of the first mode. In a rotary head digital signal recording and reproducing method for reproducing the recorded signal of the recorded magnetic tape recorded in the second mode, which is twice the recorded signal of the recorded magnetic tape recorded in the second mode, During playback, the running speed of the recorded magnetic tape is set to be approximately the same speed as that of the second mode, the rotational speed of the rotary head is set to be approximately the same speed as that of the first mode, and the rotating head is Therefore, a total of 4 per two adjacent recording tracks of the recorded magnetic tape.
Among the reproduction signals obtained by scanning at a ratio of 1 to 3 times, the first tracking detection signal reproduced from near the end of one recording track obtained by the first scanning, and the first tracking detection signal obtained by the second scanning. Tracking control is performed based on the second tracking detection signal reproduced from immediately after the starting end of the one recording track.

(Example) The rotary head type digital signal recording and reproducing method according to the present invention has the same rotational speed of the rotary head in the standard mode (first mode), but the magnetic tape running speed is half that of the superior mode. During playback in the fast mode (second mode), the rotary head scans each two adjacent recording tracks four times, and the ATF signal at the end of the recording track obtained from the first scan is The ATF signal (first tracking detection signal) reproduced from the recording section and the ATF signal (second tracking detection signal) reproduced from the recording section of the ATF signal on the start end side of the recording track obtained by the second scan. After the third and fourth rotation head scans are completed, the result of determining the quality of the synchronization signal fs included in each ATI' signal is used as a reference signal.
Using this reference signal, the rotating head scans the next two adjacent recording tracks four times, starting from the ATF signal recording section on the #i end side of the recording track obtained by the first scan. The reproduced ATF signal (first tracking detection signal) and the AT reproduced from the ATF signal recording section on the start end side of the recording track obtained by the second scan.
The signal lengths of the synchronization signals fs included in each ATF signal are compared based on the F signal (second tracking detection signal), and only when the lengths of the synchronization signals fs match, this synchronization signal fs is By updating the error signal using
Even if a disturbance occurs, reproduction can always be performed in a good 1~racking state. Hereinafter, even when the rotary head scans four times per two adjacent recording tracks, the same tracking control as described is performed.

Fig. 1 is a block diagram of an embodiment of ATF signal detection which is the main part of the method of the present invention, Fig. 2 is a time chart of signals of each part of the structure shown in Fig. 1, and Fig. 3 is a half-speed diagram of the method of the present invention. FIG. 4 is a block diagram of the DAT to explain the method of the present invention; FIG. 5 is a diagram showing part of the TF track pattern (4-track complete type); It is.

In Fig. 4, 1 is a rotating drum, 1a and lb are rotating heads, 2 is a regenerative amplifier, 3 is AT T' (i detection circuit (ATF block)), and 4 is a low-pass filter (LPF).
, 5 is an envelope detection circuit, 6.7 is a sample hold circuit (S/old, S/82), 8 is a subtracter, 9 is an equalizer (EQ), 10 is a comparator, ・11 is an ATF signal detection circuit (5YNC detection), 12 is a changeover switch, 1
3 is an adder, 14 is a motor drive circuit, 15 is a capstan motor, 16 is a frequency generator (FG), 17 is a capstan, 18 is a drum motor, 19 is a drum servo circuit, 20 is a phase comparator (PC) , 18a is a sensor, 21.
22 is a frequency dividing circuit (1/m, 1/n), 23 is a frequency-voltage conversion circuit (F-V), and T is a magnetic tape.

A rotating head 1a and another rotating head 1b opposite thereto are fixedly attached to the rotating surface of the rotating drum 1. The magnetic tape T is wound obliquely around the rotating drum 1 over an angle range of 90 degrees, and is further held between a capstan and a pinch roller and made to run in the direction of the arrow. The rotating heads la and 1b have a gap with opposite azimuth angles, and are wider than the recording track (
For example, it has a width of 1.5 times) and is rotated together with the rotating drum 1. A rotating shaft 18C of the drum motor 18 is fixed to the center of the rotating drum 1. A rotating head 1a and another rotating head 1b opposite thereto are fixedly attached to the rotating surface of the rotating drum 1.

The ATF signal detection circuit 3 is supplied with the reproduction signal obtained from the rotary head 1a (1b) via the reproduction amplification grave 2, and the reproduction signal is supplied to the ATF signal detection circuit 11 via the equalizer 9 and the comparator 10. Here, the ATF signal is detected from the reproduced signal and a sampling pulse SP1 is generated.

Output Sr1. Sampling pulse SP1 is supplied to sample hold circuit 6, and sampling pulse SP2 is supplied to sample hold circuit 7.

Further, the above-mentioned reproduced signal is supplied to the envelope detection circuit 5 via the low-pass filter 4, and after being envelope-detected there, this detection signal is applied to the sample-hold circuit 6, where it is applied at the timing of the sampling pulse SP1. The sample is held. This sampled and held signal is supplied to one terminal of the subtracter 8. Further, the detection signal from the envelope detection circuit 5 is supplied to the ten terminal of the subtracter 8. The subtractor t3 unit 8 outputs a difference signal obtained by subtracting the sampled and held signal level from the detected signal level. This difference signal is supplied to the sample hold circuit 7,
Sample and hold is performed at the timing of sampling pulse SP2. In this way, from the block hold circuit 7 to A
A TI'i difference signal (tracking detection signal) is output.

This ATF signal is supplied to the PB terminal of the changeover switch 12, and applied to one terminal of the adder 13 via its movable contact, where the signal from the frequency-voltage conversion circuit 23 applied to the other terminal is The capstan motor 15 is supplied to the capstan motor 15 to run the magnetic tape T at half speed.
Speed 1 for 7! ti control.

The frequency generator 16 generates a frequency signal according to the rotation of the capstan 17, and this frequency signal is divided into 1 by the frequency dividing circuit 22.
/n and then applied to the frequency-voltage conversion circuit,
Here, after being converted to a voltage level according to the frequency, it is applied to the other terminal of the adder 13. Capstan servo is thus performed.

Sen) t18a generates a frequency signal according to the rotation of the rotary drum 1, and this frequency signal is supplied to one input terminal of the drum servo circuit 19, and a reference signal is supplied to the other input terminal.

During reproduction in the half-speed mode, the rotational speed of the rotary head 1a (Ib) is the same as in the standard mode (2000 rpm), and the running speed of the magnetic tape T is selected to be double the speed in the standard mode.

The magnetic tape T recorded using the above-described DAT shown in FIG. 4 has an ATF track pattern (four-track complete track pattern) formed thereon as shown in FIG.

The center of each track (e.g. B head even frame, C head
B) ODD FRAME ADDRESS ) ) records PCM signal audio data, and also tracks part A of a certain section from the start end of each track (bottom right in the figure).
An ATF signal is recorded in TF1 and a certain section of the track TF2 immediately before the end of each track (top left in the figure).

FIG. 3 is a diagram illustrating a head scanning locus when a track formed during half-speed mode recording according to the present invention is reproduced in half-speed mode.

The rotational speed of the rotary heads 1a, 1b during half-speed mode (second mode) reproduction is twice that of half-speed mode recording, and the running speed of the magnetic tape is the same as during recording.

Therefore, the scanning trajectory of the rotary heads la, 1b during reproduction does not match the scanning trajectory (recording track pattern) during recording, and as shown in the figure, the scanning trajectory of the rotary heads la, 1b does not match the scanning trajectory (recording track pattern) during recording.

1B, 2A, 2B, . . . have scanning trajectories and tracking offsets Δθ of the rotary heads 1a and 1b.

That is, the rotary heads Ia and tb rotate the two adjacent tracks I
For A and IB (2A, 2B), scan trajectories are drawn at a rate of 4 times. Here, tracks 1A, 28 (18, 2B
) indicates a track recorded by a rotary head 1a (Ib) having a gap of a positive (negative) azimuth angle, for example,
There is no guard band between adjacent tracks.

Reproduction signals of a frequency higher than a predetermined value that are alternately reproduced from the two rotary heads la and lb are signals reproduced from a recording track having a magnetization pattern with the same azimuth angle as the reproduction rotary head due to the well-known azimuth loss effect. and
Further, the reproduction signal level is approximately proportional to the sliding width of the recording track of the rotary head.

Of the four scans performed by the rotary head on two adjacent tracks 1^11B, the level of the reproduction signal reproduced from tracks 1A and IB by the first and second scans is higher than that of the third scan. and track I by the fourth scan.
This is higher than the reproduction signal level reproduced from A and IB.

As described above, the ATF signal (tracking detection signal) is recorded in a predetermined section immediately after the beginning of each track and in a predetermined section immediately before the end of each track. Also ATF
The signal consists of a synchronization signal fs for timing control of sample and hold of the ATF detection output, and a pilot signal fp.

The synchronization signal fS is a relatively high frequency signal that has an azimuth loss effect (for example, a frequency signal recorded on one of 62 adjacent tracks).
S is 522kHz2, fs recorded on the other side is approximately 784
kH7), whereas the pilot signal t
o is selected to be a low frequency (for example, 133kllZ) that has little azimuth loss effect, that is, is reproduced as crosstalk from adjacent tracks.

The ATF signal section of each track is a synchronization signal recording section in which the synchronization signal fs is recorded for a certain period of time, and a period of approximately 1.57H provided after this section for erasing the previous signal.
It consists of a Hz erasure signal recording section, and a pilot signal recording section in which a pilot signal fp is recorded for a certain period of time next to this section, and the pilot signal recording section of the next track is the erasure signal recording of the immediately preceding track. The pilot signal recording sections are arranged adjacent to each other, and pilot signal recording sections and synchronization signal recording sections are not arranged adjacent to each other between adjacent tracks.

A track in which the ATF signal having the above configuration is recorded is played back at twice the recording speed using a rotary head having a gap of the same azimuth angle as the recording speed.

In this case, the first scan of the rotary head causes the rotary head 1a to scan across the entire track 1^.

Hereinafter, by the second scan of the rotary head, the rotary head 1b
scans across approximately half of each of tracks IA and 1B,
By the third scan of the rotary head, the rotary head 1a scans over a part of the track 1^, the whole of the track 1B, and a part of the track 2, and by the fourth scan of the rotary head, the rotary head 1b scans over a part of the track 1^, the whole of the track 1B, and a part of the track 2. A part of track 1B and most of track 2A are scanned.

As mentioned above, the synchronizing signal fs for timing control of sample and hold of the ATF detection output is reproduced only when reproducing with a rotary head having a gap of the same azimuth angle as the recording track, and the pilot signal fp is reproduced when the recording track and the same azimuth angle gap are used. Of course, when the signal is reproduced by a rotary head having a gap of the same azimuth angle, the signal is reproduced, and it is also reproduced from adjacent tracks as crosstalk.

As described above, the scanning trajectory of the rotary heads la, lb during reproduction does not match the recording track pattern of the rotary heads la, 1b during recording, and there is a tracking offset Δθ. That is, there is a tracking offset of +Δθ in the ^TF signal recording section on the start end side of the track, and a tracking offset of -80 in the ATF signal recording section on the end side of the track.

Therefore, when the two ATF-detected error signals of tracking offset +Δθ and tracking offset −Δθ are averaged, the influence of the tracking offset becomes zero.

Therefore, as will be described later, the present invention reproduces data from an ATF signal recording section at the end of the recording track during the first scanning of the rotary head, and from a ^TF signal recording section at the beginning of the track during the second scanning of the rotary head. 2 ATFs
The result of determining the length of the synchronization signal fs included in each signal is used as a reference signal, and after the third and fourth rotation head scans are completed, this reference signal and the first rotation are again used. A at the end of the recording track when scanning the head
The synchronization signal [S included in the two ATF signals respectively reproduced from the TF signal recording section and the ATF signal recording section on the track start end side during the second rotary head scan are compared, and the synchronization signal fs is determined. Only when the lengths match, the error signal is updated using this synchronization signal fs.

Figure 1 is a block configuration diagram of an embodiment of signal detection, and Figure 2 is a time chart of signals in each part of the configuration shown in Figure 1. Same configuration as described above. The same reference numerals are given to the parts, and the explanation thereof will be omitted.

In the same figure, 24 is a bandpass filter (BPF), 25
26 is a comparator, 26 is an ATF signal selection and extraction circuit, 27 is a wave number counter, 28 is a signal length determination circuit, 29 is a shift register (RGI, RG2), 30 is a timing signal generator, 31 is a sample pulse generator, 32. 36 is D-F
F circuit, 33 is an EX-NOR circuit, 34 is a HAND circuit, and 35 is a Lt IIIVEIIIT-NOR circuit.

The shift register 29 is a two-stage serial-in/parallel-out shift register.

The reproduced signals TA(n), TB(n), .

At the same time, it is also supplied to a low-pass filter 4 to separate the pilot signal fp. The reproduction synchronization signal taken out from the bandpass filter 24 is applied to the inverting input terminal of the comparator 25, where it is compared with a predetermined voltage level applied to the non-inverting input terminal, and then output to the ATF signal selection and extraction circuit 26. be done. The ATF signal selection and extraction circuit 26 selectively extracts the ATF signal that is being outputted as a reproduction synchronization signal, and uses it as a selected ATF signal.

The location of this selected ATF signal is the ATF point shown in FIG. That is, the reproduced signal T reproduced from the recording track of the magnetic tape T during the first scanning of the circulation head 18
A(n), the ATF signal recording section on the terminal side of TA(n+1), and the reproduction signal TB(n) reproduced from the recording track during the second scanning of the rotary head 1b.

It shows the positions of two ATF signals respectively reproduced from the ATF signal recording section on the start end side of TB(n+1).

The selected ATF signal is supplied to the wave number counter 27, which outputs a count number corresponding to the signal length (block length) of the selected ATF signal to the signal length determination circuit 28. The signal length determination circuit 28 determines whether the signal length of the selected TF signal is "1" or "1" according to the count supplied from the wave number counter 27.
This determination signal is supplied to the next stage shift register 29.

The shift register 29 temporarily stores this discrimination signal in synchronization with the signal (2) supplied from the timing signal generator 30, and outputs parallel output signals RGI and RG2. Signals RGI and RG2 are supplied to two input terminals of the HAND circuit 34, and signal RG4 is supplied to one input terminal of the EX-NOR circuit 33.

The timing signal generator 30 is the ATF signal selection and extraction circuit 2
Select ATF signal from f10.6, signal f10. fll and clock signals are supplied, and signals 03T, IT, 2
T.

12T, signal 5TCK, and signal RGCL are output.

Now, ■ the second one that does not have detection failures such as dropouts.
In the “good condition” shown in the figure, the discrimination signal is two selection ATs.
Output in synchronization with the F signal. As a result, since the state of the output signal r of the D-FF circuit 32 remains unchanged, the sample pulse generator 31 receives the output signal r from the signal length determination circuit 28.
1" or "Hide" signal length, the sampling pulse SP1. Output Sr1. The sampling pulse SP2 outputs a pulse synchronized with the rise of the signals RGI and RG2.

Note that the sample pulse generator 31 is supplied with signals 03T and 2T from the timing signal generator 30.

(2) In the "defective state" shown in FIG. 2 where detection failure such as dropout occurs, the discrimination signal is not the same as the discrimination signal described above. As a result, the state of the output signal fail of the t)-FF circuit 32 changes from the above state, the sample pulse generator 31 outputs the predetermined sampling pulse SP1, and the sampling pulse SP2 is synchronized with the rising edge of the signal RGI. Outputs only pulses.

That is, when a correct discrimination signal cannot be obtained due to a dropout or the like, a new sampling pulse SP2 is not generated, and the sample and hold circuit 7 uses the previous sampling pulse SP2 in which no dropout or the like has occurred to generate a subtracter. The differential signal supplied from 8 is sampled and held.

In this way, even when a dropout or the like occurs from the sample hold circuit 7, the ATrfi difference signal without any dropout or the like immediately before is output and stable tracking can always be performed. .

(Effects of the Invention) As described above, the rotary head type digital signal recording and reproducing method according to the present invention does not impair the tracking state even when a dropout occurs during so-called half-speed mode reproduction, and always maintains a stable l. - Since racking can be performed, extremely high quality PCM audio data can be continuously reproduced for a long time.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of ATF signal detection, which is the main part of the method of the present invention, and Fig. 2 is a time chart of the signals of each part of the structure shown in Fig. 1. FIG. 4 is a block diagram of the DAT to explain the method of the present invention, and FIG. 5 shows a part of the ATF track pattern (4-track complete type). FIG. 1... Rotating drum, 1a, 1b... Rotating head, 2
... Regenerative amplifier, 3... ATF signal detection circuit, 4.
...Low-pass filter, 5...Envelope detection circuit, 6
．． 7... Sample hold circuit, 8... Subtractor, 9
...Equalizer, 10...Comparator, 11...AT
F signal detection circuit, 12... changeover switch, 13...
Calculator, 14... Motor drive circuit, 15... Capstan motor, 16... Frequency generator, 17... Capstan, 18... Drum motor, 18a... Sensor, 19. ...Drum servo circuit, 20...Phase comparison mixture, 21.22...Frequency division circuit, 23...Frequency voltage conversion circuit, 24...Band filter, 25...Comparator, 26... - ATF signal selection and extraction circuit, 27... Wave number counter, 28... Signal length determination circuit, 29... Shift register, 30... Timing signal generator, 31
...Sample pulse generator, 32.36...D-F
F circuit, 33-EX-NOR circuit, 34-HAND times m
, 35, -INVERT-NOR circuit, T-m air tape.

Claims (1)

[Claims] A multiplexed signal consisting of PCM audio data for a certain period obtained by pulse code modulating an audio signal and a tracking detection signal that is time-division multiplexed before and after the PCM audio data for a predetermined period is transferred onto a magnetic tape by a rotating head. Either tracks are sequentially formed one by one and recorded in the first mode, or the amount of data per unit time is approximately 1/2 that of the first mode, and the rotation of the rotary head is In a rotary head type digital signal recording and reproducing method for reproducing previously recorded signals on a recorded magnetic tape recorded in a second mode in which the speed and magnetic tape running speed are approximately 1/2 that of the first mode. , when reproducing the recorded signal of the recorded magnetic tape recorded in the second mode, the running speed of the recorded magnetic tape is set to be approximately the same speed as that of the second mode, and the rotation of the rotary head is Of each reproduced signal obtained by scanning two adjacent recording tracks of the recorded magnetic tape with the rotary head at a rate of four times in total at a speed substantially the same as that of the first mode, A first tracking detection signal reproduced from near the end of one of the recording tracks obtained by the first scan, and a second tracking detection signal reproduced from immediately after the start of the one recording track obtained by the second scan. A rotary head type digital signal recording and reproducing method characterized in that tracking control is performed based on a tracking detection signal.