JPH0981990A - Magnetically reproducing device and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the running of a magnetic tape at a first speed from the timing capable fixing an on-track position predicted by observing the change in a tracking state in the state that the magnetic tape is offset from the first speed to a second speed when the running speed of the magnetic tape is transited to the same first speed as the time at a recording time. SOLUTION: A part surrounded by a broken line is processed by software, and a target value 22 of an ATF error is subtracted 23 from the ATF error digitized by an A/D converter 21 to generate a phase error. Then, a servo operation 24 such as integration and gain adjustment 25 are applied to the phase error. Further, the gap of a capstan FG is measured 26, and after the gap is coverted into a capstan speed, the target value 28 of the capstan speed is subtracted 29 therefrom to generate a speed error. Then, the servo operation 30 such as the integration and the gain adjustment 31 are applied to the speed error. Then, the phase error and the speed error subjected to the servo operation and the gain adjustment are added 32 and imparted to a capstan driver as a capstan control signal. Thus, the capstan control is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reproducing a digital video signal, a digital audio signal, etc. recorded on a magnetic tape, and more specifically, the running speed of the magnetic tape is set to the same speed at the time of recording. ATF when doing
(Automatic Track Finding)
The present invention relates to a technique for shortening the servo pull-in time.

[0002]

2. Description of the Related Art A magnetic recording / reproducing apparatus has been proposed for recording / reproducing an ATF pilot signal (hereinafter simply referred to as a pilot signal) together with an information signal such as a digital video signal or a digital audio signal on a magnetic tape by a rotary magnetic head. .

FIG. 8 shows the relationship between the track pattern, the ATF pilot signal and the magnetic head in such a magnetic recording / reproducing apparatus, and FIG. 9 shows the AT in the track of FIG.
3 shows a frequency spectrum of an F pilot signal.

As shown in FIGS. 8 and 9, the track F1
And F2, ATF pilot signals of frequencies f1 and f2 are recorded. On the other hand, the track F0
In, the notches of the components of the frequencies f1 and f2 are formed. The ATF pilot signal and notch of these frequencies f1 and f2 are added by converting the digital information signal to be recorded and the like into 24-25 in the channel encoder. Then, during reproduction, tracking control is performed so that the crosstalk components of the ATF pilot signals f1 and f2 of the tracks F1 and F2 adjacent to the magnetic head H0 that has scanned the track F0 have the same level.

[0005]

SUMMARY OF THE INVENTION According to the present invention, for example, in the magnetic recording / reproducing apparatus of the above-mentioned format, when the running speed of the magnetic tape is set to the same speed at the time of recording,
The present invention provides a new and useful means for reducing the pull-in time of the TF servo.

[0006]

In order to solve the above-mentioned problems, a magnetic reproducing apparatus according to the present invention comprises means for controlling the running speed and phase of a magnetic tape and means for detecting a tracking state. When transitioning the running speed of the tape to the same first speed as during recording, the change in the tracking state was observed while the magnetic tape was running at the second speed offset from the first speed. The feature is that the timing at which the on-track position comes is predicted from the observation result, and the magnetic tape is controlled so as to run at the first speed from the timing.

In the magnetic reproducing method according to the present invention, when the traveling speed of the magnetic tape is changed to the same first speed as that at the time of recording, the magnetic tape is offset from the first speed at the second speed. It is characterized by observing the change of the tracking state in the state of running at, predicting the timing when the on-track position comes from the observation result, and controlling the magnetic tape to run at the first speed from that timing. It is a thing.

The magnetic reproducing apparatus and the magnetic reproducing method according to the present invention mean an apparatus and a method for reproducing at least a magnetic tape. That is, it includes an apparatus and method for recording / reproducing on / from a magnetic tape.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a main part of a magnetic reproducing apparatus to which the present invention is applied. This magnetic reproducing apparatus includes magnetic heads H0 and H1 for reproducing digital data recorded on a magnetic tape 1,
It is provided with RF amplifiers 2 and 3 for amplifying reproduced signals of the magnetic heads H0 and H1, and a switch SW1 for alternately switching the outputs of the RF amplifiers 2 and 3 to form a time series.

The magnetic heads H0 and H1 are, for example, 150 per second.
1 on the outer circumference of a rotating drum (not shown) that rotates at a rotating speed
They are provided at positions facing each other by 80 degrees and have different azimuth angles. The magnetic head H0 is shown in FIG.
Is controlled so that the magnetic head H1 alternately scans the tracks F1 and F2 in FIG. The switch SW1 is a microcomputer 5 described later.
Is switched in accordance with the rotation of the rotary drum by the head switching signal generated by.

The magnetic reproducing apparatus of FIG. 1 further includes a switch S.
An AT that generates an ATF error from the RF signal that has passed through W1
An F circuit 4, a microcomputer (hereinafter, referred to as a microcomputer) 5 that controls the entire apparatus, a capstan 6, and a motor drive signal according to a speed command signal generated by the microcomputer 5, and a capstan motor (not shown). No.) and a capstan driver 7 for applying the voltage.

The microcomputer 5 generates a capstan control signal from the capstan FG which has detected the rotation frequency of the capstan 6 and the ATF error. Further, the head switching signal described above is generated from the drum PG detecting the rotation phase of the rotating drum and the drum FG detecting the rotation frequency of the rotating drum.

The ATF circuit 4 includes a bandpass filter 11 for extracting a pilot signal component of frequency f1, a bandpass filter 12 for extracting a pilot signal component of frequency f2, and a rectifying circuit 13 for rectifying the output of the bandpass filter 11. A rectifying circuit 14 for rectifying the output of the bandpass filter 12, a subtracting circuit 15 for taking a difference between the output levels of the rectifying circuit 13 and the rectifying circuit 14, and a low frequency component of the output of the subtracting circuit 15 are taken out to generate an ATF error. And a low-pass filter 16.

In this embodiment, in the magnetic reproducing apparatus configured as described above, when the running speed of the magnetic tape 1 is raised from 0 to 1 speed, that is, when the magnetic tape 1 is raised from the stopped state to the same speed as during recording, for example, 0. The change in the tracking state is detected while the magnetic tape is running at 9 times speed, and the timing at which the next on-track position comes next is predicted at the timing when the on-track position or the off-track position is detected. Control to drive at 1x speed.

Before describing the running control of the magnetic tape described above, an ATF error during 1 × speed reproduction will be described. In the following description, the magnetic head H0 is set to CH.
(Channel) 0, and the magnetic head H1 is CH1. As is apparent from FIG. 8, when the magnetic tape is running at 1 × speed, the CH0 ATF error has a center value in the on-tracking state and a positive or negative maximum level based on the center value in the off-tracking state. Becomes Whether it is positive or negative depends on whether the tracks F1 and F2 are present on the left and right of the track F0.
In the middle of the on-tracking state and the off-tracking state, it swings positively or negatively based on the center value at a level according to the amount of deviation from the on-tracking state. on the other hand,
The error of CH1 has a center value in the off-tracking state, and has a positive or negative maximum level based on the center value in the on-tracking state. Whether it is positive or negative changes depending on which of the tracks F1 and F2 is being reproduced. In the middle of the off-tracking state and the on-tracking state, positive or negative swings alternately with a level according to the amount of deviation from the off-tracking state with reference to the center value.

Next, the principle of tracking control in this embodiment will be described. FIG. 2 shows a change in the tracking state when the magnetic tape is run at 0.9 times speed. In this figure, the horizontal axis represents time and the vertical axis represents the deviation from the track center. When the magnetic tape is run at 0.9 times speed, 9 tracks are advanced in 10 times at 1 times speed. Therefore, A of CH0 and CH1
The TF error has a relation that it changes by one cycle during the time of 20 tracks during reproduction.

FIG. 3 is a timing chart showing changes with time of the ATF error detected from the magnetic heads H0 and H1 and the RF envelope when the magnetic tape 1 of FIG. 1 is run at 0.9 times speed. The level on the horizontal axis in these ATF errors is the center value. The thick broken line shown in (A) is the on-track position detected from the ATF error of CH0, and the thin broken line shown in (B) is the off-track position detected from the ATF error of CH1. Then, the thick broken line shown in (C) shows an example of the next on-track position predicted based on the detection output of the position of (A) or (B).

As shown in FIG. 3A, when the magnetic tape is run at 0.9 times speed, the ATF error of CH0 is the same as the center value when the magnetic head H0 crosses the track F0. The polarity level is continuous. Therefore, theoretically, if the magnetic tape is momentarily run at 1x speed at this point, the on-track state can be instantaneously achieved, but in reality it is impossible, and the on-track position comes next. The timing is predicted, and at that timing, the speed of the magnetic tape is increased so that the speed becomes 1 × speed and the on-tracking state is achieved. The position shown in (C) in FIG. 3 is predicted as described above.
An example of the timing when the speed becomes double is shown.

On-track position prediction is CH1 ATF
It can also be based on an error. As shown in FIG. 3B, in the ATF error of CH1, the level of the same polarity with respect to the center value continues at the time when the magnetic head H1 intersects the track F0, that is, at the off-track position. Therefore, this off-track position is detected, and the timing at which the next on-track position comes from there is predicted. Since the time from the off-track position to the next on-track position is almost half the time from the on-track position to the next on-track position, this makes it possible to enter the on-tracking state more quickly. is there.

Next, with reference to FIG. 4, a method for detecting the timing when the levels of the same polarity are continuous will be described. It is also possible to detect that the same polarity level continues, by detecting that a value smaller than or larger than the center value continues, but if it is detected in this way, it is possible to accurately detect when there is an offset due to circuit variation. It may not be detected.

Therefore, here, the sample value of the ATF error for each track is held, the sample value of this time is subtracted from the sample value of the previous time, and the change point of the continuity of the positive and negative polarities of the value is used to turn on. Detect track position or off-track position. Here, the sample value for each track is
For example, samples are made at a plurality of points in one track and the average value is used.

The horizontal axis of FIG. 4 represents time and the vertical axis represents the sampled value of the ATF error. In addition, the positive and negative values shown below the horizontal axis represent the result of subtracting the current sample value from the previous sample value. As shown in FIG. 4, when the sample value of the ATF error takes positive and negative values alternately with respect to the center value, the result of subtracting the present sample value from the previous sample value also takes positive and negative values alternately. . However, if the ATF error sample value continues with the same polarity with respect to the center value,
The same polarity continues in the result of subtracting the current sample value from the previous sample value. That is, the continuity of the polarities of the subtracted values changes. Therefore, the position of (A) or (B) in FIG. 3 can be detected by detecting the change in the continuity of the polarity of the subtracted value.

Next, referring to the flow chart of the microcomputer shown in FIG. 5 and the timing chart shown in FIG.
The tracking control operation will be described. First, the microcomputer 5 gives a predetermined speed command signal to the capstan driver 7 to activate the capstan 6 (step S1).
At this time, the speed of the capstan 6 is, for example, 0.8 times. In FIG. 6, activation is started at time t0.

Next, the continuity of the ATF error polarity is observed (step S2). This may be either CH0 or CH1, but as described above, detecting the off-track position on CH1 allows the on-tracking state to be quickly established. Of course, whichever CH0 or CH1 is selected, the time until the on-tracking state is set can be predicted. In FIG. 6, it is shown that the observation of continuity of the ATF error polarity is started from time t1 and the determination is ended at time t2.

As a result of the observation, if the continuity of the polarities is changed, the next on-track position is run at 0.8 times speed for a certain time in order to perform 1 times speed playback (step S3).
S4). FIG. 6 shows that the vehicle is traveling at 0.8 times speed until time t3.

After a lapse of a certain time, the capstan 6 is set at 1 × speed, ATF phase servo is applied, and reproduction is performed at 1 × speed (steps S5 and S6). In FIG. 6, the capstan is pulled up to the 1 × speed reproduction state from time t3. This immediately locks the ATF phase servo in the on-tracking state.

FIG. 7 shows a speed command signal generation process in the microcomputer 5. Here, the part surrounded by the broken line is a process by software. As shown in this figure, from the ATF error digitized by the A / D converter 21 to the AT
The target value (22) of the F error is subtracted (23) to generate a phase error. Then, the servo calculation (2
4) and gain adjustment (25).

Further, the interval of the capstan FG is measured (2
6) and after converting it into a capstan speed (27), the target value (28) of the capstan speed is subtracted (29) to generate a speed error. Then, this is subjected to servo calculation (30) such as integration and gain adjustment (31).

Then, the phase error and the speed error which have been subjected to the servo calculation and the gain adjustment are added (32) and given to the capstan driver 7 as a capstan control signal. With the above configuration, the capstan control as shown in FIG. 6 can be performed.

Although the above-mentioned embodiment has been described by exemplifying 0.9 times speed and 0.8 times speed, it goes without saying that the present invention is not limited to these speeds. Further, in the above-described embodiment, the control at the time of making a transition from the stopped state to the 1 × speed reproduction state has been described. However, the present invention makes it possible to make a transition from the high speed reproduction state such as cue or review to the 1 × speed reproduction state. It can also be applied. In that case, the on-track position or the off-track position may be detected at a speed of about 1.1 times or 1.2 times, the on-track position may be predicted from that position, and the speed of the capstan may be reduced to the 1x speed.

Although notches having frequencies f1 and f2 are formed in the track on the CH0 side in the above embodiment, the notches may not be formed. Furthermore, the frequency f1
Pilot signals of frequencies other than and f2 may be recorded.

The present invention can be applied to any capstan servo system in which the amplitude of the ATF error changes according to the deviation from the on-tracking state, regardless of the frequency of the pilot signal.

As described above in detail, according to the present invention, the pull-in time of the tracking servo when the magnetic tape is changed from the stopped state, the queue, the review state, etc. to the 1 × speed reproduction state is within a fixed time. Can be Therefore, it is possible to immediately reproduce the video and audio when the transition to the 1 × speed reproduction state is made.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a magnetic reproducing device to which the present invention is applied.

FIG. 2 is a diagram showing a change with time in a tracking state when a magnetic tape is run at 0.9 times speed.

[Fig. 3] A when the magnetic tape is run at 0.9 times speed
6 is a timing chart showing changes in TF error and RF envelope with respect to time.

FIG. 4 is a diagram illustrating a method of detecting a timing at which a magnetic head crosses a track.

FIG. 5 is a flowchart showing a capstan control process of a microcomputer.

FIG. 6 is a timing chart corresponding to a capstan control process.

FIG. 7 is a block diagram showing a process of generating a capstan control signal in a microcomputer.

FIG. 8 is a diagram showing a relationship between a track pattern, an ATF pilot signal, and a magnetic head in a conventional magnetic recording / reproducing method.

9 is a diagram showing a frequency spectrum of a pilot signal in the track of FIG.

[Explanation of symbols]

1 ... Magnetic tape, 4 ... ATF circuit, 5 ... Microcomputer, H
0, H1 ... Magnetic head

Claims (3)

[Claims] 1. A means for controlling a running speed and a phase of a magnetic tape, and a means for detecting a tracking state, wherein when the running speed of the magnetic tape is changed to a first speed which is the same as that at the time of recording, A change in the tracking state is observed in a state where the magnetic tape is run at a second speed that is offset from the first speed, the timing at which the on-track position comes is predicted from the observation result, and the magnetic field is calculated from the timing. A magnetic reproducing apparatus, characterized in that the tape is controlled to run at the first speed. 2. Tracking in a state where the magnetic tape is run at a second speed offset from the first speed when the running speed of the magnetic tape is changed to the same first speed as when recording. Observe the change of state, predict the timing when the on-track position comes from the observation result,
A magnetic reproducing method comprising controlling the magnetic tape to run at the first speed from the timing. 3. The magnetic reproducing method according to claim 2, wherein the timing at which the next on-track position comes next is predicted at the timing at which the off-track position is detected.