JPH0253249A - Magnetic reproducing device - Google Patents

Abstract

PURPOSE:To omit an operation of a tracking volume and to surely obtain a just tracking state by performing a search operation according to timing of a control signal to a switching pulse signal. CONSTITUTION:When a magnetic tape 2 picture-recorded by other different video tape recorder than a video tape recorder 1 is reproduced by the video tape recorder 1, the timing intervals T1 and T2 of the control signal SCTL to the switching pulse signal SWP are detected out. As a result, a starting part of a consecutive picture recording, etc., can be detected based on the detected results T1 and T2. Then, the traveling speed of the magnetic tape 2 is varied in accordance with the detected results T1 and T2, while the signal level of a regenerative signal SRF to be outputted from magnetic heads 3A and 3B is detected out, and based on this detected result, a tracking control is carried out. By this method, the operation of the tracking volume is omitted, and hence the just tracking state can surely be obtained.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Industrial field of application B. Overview of the invention C. Conventional technology Problems to be solved by the invention E. Means for solving the problems (Figs. 1 and 5) F. Effects (Figs. 1 and 5) Figure) G Embodiment (Figures 1 to 6) H Effects of the Invention A Industrial Application Field The present invention relates to a magnetic playback device, and is particularly applicable to a control (CTL) signal obtained from a control track, such as in a video tape recorder. Based on this, it is suitable for application to a magnetic reproducing device that performs tracking control.

B. Summary of the Invention The present invention provides a magnetic reproducing device in which, in accordance with the timing of a control signal with respect to a switching pulse signal,
By performing the search operation, it is possible to omit the operation of the tracking volume and reliably obtain the just tracking state.

C. Prior Art Conventionally, some video tape recorders have been designed to perform tracking control based on a CTL signal recorded on a control track.

That is, during recording, the capstan motor and the rotating drum are driven at a predetermined speed to sequentially form diagonal recording tracks on the magnetic tape at a predetermined track pitch.

At the same time, a CTL signal is recorded on the control track using a fixed head in synchronization with a switching pulse signal whose signal level is inverted at the start of scanning of the magnetic head.

On the other hand, during playback, by controlling the phase of the capstan motor so that the switching pulse signal is synchronized with the CTL signal obtained via the fixed head, the recording time is adjusted to the timing of the start of scanning of the magnetic head. The magnetic tape is run at the same timing as the magnetic tape, so that the magnetic head just tracks the recording track formed on the magnetic tape.

D Problems to be solved by the invention By the way, in this type of video tape recorder,
Due to unavoidable manufacturing variations in the mounting position of the fixed head that records and plays back CTL signals, when playing back magnetic tape recorded with other video tape recorders,
The delay time of the switching pulse signal with respect to the CTL signal is adjusted to ensure compatibility between video tape recorders.

In other words, in a video tape recorder, the delay time of the switching pulse signal relative to the CTL signal is changed by operating the tracking volume provided on the operation panel, and this allows the tracking volume to be controlled. It is designed so that a state of just tracking can be obtained.

Therefore, for the user, the highest signal-to-noise ratio (signal-
It is necessary to operate the tracking volume while visually checking the reproduced video so as to obtain a reproduced video with a good to-noise ratio.

In particular, when playing back magnetic tapes that have been spliced and recorded using different video tape recorders, or when playing back magnetic tapes whose recording mode has been switched from standard recording mode to long-term recording mode during recording, the magnetic Since the period from the start of scanning of the magnetic head to the rise of the CTL signal changes in the middle of the tape, the tracking volume must be adjusted again in the middle of playback, making the adjustment work more complicated. Ta.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a magnetic reproducing device that can obtain a state of just tracking without manipulating the tracking volume.

Means for Solving Problem E To solve this problem, the present invention provides a control signal S for the switching pulse signal SWP.
CTL timings T1 and T2 are detected, and the detection result T
1. The running speed of the magnetic tape 2 is varied according to T2, and after detecting the signal level of the reproduction signal SIF output from the magnetic heads 3A and 3B, tracking control is performed based on the detection result of the signal level. .

By detecting the timings T1 and T2 of the control signal SCTL with respect to the F-effect switching pulse signal SWP, it is possible to detect the start portion of continuous recording based on the detection results T1 and T2.

Therefore, based on the detection results T1 and T2, the running speed of the magnetic tape 2 is varied, and the magnetic heads 3A and 3B are
By detecting the signal level of the reproduced signal S0 output from and performing tracking control based on the detection result,
It is possible to reliably obtain a just tracking state by omitting the operation of the tracking volume.

G example An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, l designates a video tape recorder as a whole, in which a magnetic tape 2 is wound around a rotating drum (not shown) in an Ω shape and runs at a predetermined speed.

As shown in FIG. 2, the rotating drum receives the switching pulse signal swp with the magnetic heads 3A and 3B mounted thereon.
<Figure 2 (A)) is rotated at a predetermined rotational speed in synchronization with the switching pulse signal S.
During the period when the logic level of WP is logic rHJ and rLJ,
The reproduced signal S* is alternately transmitted via the magnetic heads 3A and 3B.
v<(B) in FIG. 2).

The detection circuit 4 receives reproduced signals S, l via the preamplifier circuit 5.
F, the envelope transverse wave signal 5ott of the reproduced signal S□
(FIG. 2(C)) is output to the control circuit 6.

This allows the signal level of the reproduced signal S0 to be detected via the detection circuit 4.

The control circuit 6 is composed of a microcomputer circuit configured to input the envelope transverse wave signal 5DtT via an analog-to-digital conversion circuit, and converts the CTL signal S CTL obtained from the fixed head 7 into a switching pulse signal S.
Take it with WP.

Further, the control circuit 6 outputs a control signal S to the capstan motor drive circuit 8 to control the phase of the capstan motor 9 to control the running speed of the magnetic tape 2.

That is, the control circuit 6 outputs the control signal S when the video tape recorder 1 starts playing, and outputs the CTL signal s c
After the signal level of wt rises, the logic level of switching pulse signal SWP falls to logic rLJ (
That is, the running speed of the magnetic tape 2 is changed so that the period (hereinafter referred to as delay amount) up to the time when the magnetic head 3A or 3B starts scanning gradually changes.

In this way, as shown in FIG. 3, it is possible to change the running timing of the magnetic tape 2 with respect to the scanning timing of the magnetic heads 3A and 3B according to the amount of delay.
As a result, a reproduced signal S□ whose signal level rises to a maximum value according to the amount of delay is obtained.

Therefore, by detecting the delay tDC at which the signal level of the reproduction signal 5IIF is the highest and controlling the running speed of the magnetic tape 2 so that the signal level of the reproduction signal 5IIF becomes the highest, the complicated tracking volume operation at the start of reproduction can be omitted. Just tracking status can be obtained by

Thus, in this embodiment, the control circuit 6 changes the delay amount and at the same time sequentially takes in the envelope detection signal S 11ET, thereby generating the envelope detection signal S Ill!
The delay amount DC at which the signal level of f becomes the largest is detected (hereinafter referred to as a search operation).

Furthermore, the running speed of the magnetic tape 2 is controlled using the delay amount De, thereby omitting the operation of the tracking volume and obtaining a just tracking state.

That is, the control circuit 6 receives the switching pulse signal swp
The delay amount is sequentially switched in the period of , and the logic level of the switching pulse signal SWP rises to the logic rHJ at time t, L, tl-3, and j.
t1, tz-z%tZ-3,..., the envelope yA detection signal S,
□ is quantized and taken in, and the delay amount is thereby switched at one frame period to sequentially detect the signal level of the reproduced signal S□.

Further, the control circuit 6 controls the detection result (El-
+ , El-i , El-3), (Ez-+ , Ez-
z, Et-s> as shown in the following formula % formula % (1), and the addition result (hereinafter referred to as evaluation value) E
The delay cover at which the signal level of the envelope detection signal S□ is the highest is detected based on l, El, . . . .

By the way, if the evaluation values E, , E, , etc. are obtained during the period in which the logic level of the switching pulse signal SWP rises to the logic rHJ in this way,
Playback signal S using only one magnetic head 3A or 3B
The IF signal level can be detected, and the magnetic head 3
Errors in detection results caused by variations between A and 3B can be prevented.

Furthermore, if the envelope detection signal SD4f is taken in multiple times during the period when the logic level of the switching pulse signal SWP rises to the logic rHJ and the signal level of the reproduced signal S1 is detected, the influence of dropout etc. It is possible to detect the signal level of the reproduced signal SIF by reducing the amount of noise, thereby making it possible to reliably detect the delay amount Dc at which the signal level of the envelope detection signal Sotr becomes the largest.

Thus, as shown in FIG. 4, depending on the change in the amount of delay,
Evaluation values whose values change stepwise are obtained.

Furthermore, the control circuit 6 determines the maximum value of the delay amount that yields the largest evaluation value. After detecting X and the minimum value DHIN and obtaining the maximum value DNA expressed by the following formula % formula % (3) and the delay amount which is the average value of the minimum value DHIN, A control signal SC is output to control the phase of the capstan motor.

In this way, if the phase of the capstan motor is controlled by the delay amount DC, which is the center value, based on the maximum value DMAX and the minimum value D□8 of the delay amount that yield the largest evaluation value, the signal of the reproduced signal 5IIF The magnetic tape can be run with the delay amount that maximizes the level.

By running the magnetic tape at the same timing as when recording with respect to the start of scanning of the magnetic head, it is possible to reliably obtain a state of just tracking. A video signal with a good SN ratio can be obtained.

Furthermore, the control circuit 6 includes a counter circuit, and detects the period T from when the logic level of the switching pulse signal SWP rises to the logic rHJ until the CTL signal 5cTL rises for each field synchronization, and based on the detection result. The search operation is repeated.

That is, as shown in FIGS. 5 and 6, when playing back the magnetic tape recorded by the video tape recorder 1,
If the magnetic tape 2 is run so that the CTL signal 5CTL (Fig. 5 (B)) rises at the timing when the switching pulse signal SWP (Fig. 5 (A)) falls, a state of just tracking can be obtained. .

On the other hand, a first video tape recorder different from the video tape recorder 1
When the magnetic tape recorded by the second video tape recorder is played back by the video tape recorder l, the playback signal S
Delay amount Dc+ and Dcz at which the signal level of 0 becomes the maximum value
(Fig. 5(C) and (D)), respectively, the magnetic tape 2
It is necessary to run the .

Therefore, when the magnetic tape 2 that has been spliced and recorded by the first and second video tape recorders is played back by the video tape recorder 1, the start portion of the spliced recording (in this case, the recorded portion is CTL signal S67. in response to the switching pulse signal SWP (consisting of the boundary where the portion recorded by the video tape recorder switches to the portion recorded by the second video tape recorder). The timing changes by a value ΔT from period T1 to period T2.

Therefore, unless the delay amount is reset at the start of spliced recording, the phase of the capstan motor is controlled so that the portion recorded by the second video tape recorder runs with the delay amount DCI, and the SN of the reproduced image There is a problem that the ratio deteriorates.

Therefore, in this embodiment, when the fluctuation continues for a period of several fields, the search operation is performed again and the running of the magnetic tape is reset to the delay amount I)cz.

That is, the control circuit 6 determines that the count value of the counter circuit is
During the period of the predetermined field, when the fluctuation exceeds the predetermined value continuously, the control signal S is outputted, and the running speed of the magnetic tape is varied again to detect the evaluation value.
1 to run the magnetic tape.

In this way, even when playing back a magnetic tape that has been recorded closely, it is possible to omit the operation of the tracking volume and to reliably obtain a just-tracking state.

By the way, in this way, the switching pulse signal SWP
If the search operation is performed by detecting the timing variation of the CTL signal S, □, it can be used not only when playing back a spliced recorded magnetic tape, but also when changing the recording mode from the long-time recording mode in the middle. Just tracking can be achieved reliably when playing back a magnetic tape that has been switched to standard recording mode, or vice versa. .

Furthermore, even if there is an unrecorded portion on the magnetic tape, just tracking can be performed again when the magnetic tape runs to the recorded portion.

In the above configuration, when the video tape recorder 1 starts playing, the control signal S is outputted from the control circuit 6, and the magnetic tape 2 runs so that the delay amount is changed at one frame period.

At this time, the control circuit 6 detects the signal level of the reproduced signal S□ obtained from the magnetic head 3A or 3B multiple times for each frame, and the detection results are added for each frame to obtain an evaluation value. .

Among the evaluation values, the maximum delay amount (I!D1.lAX and minimum value DMIN) that yields the largest evaluation value are detected, and the phase of the capstan motor 9 is controlled with a delay of 1oc, which is the center value. , magnetic head 3A (3B
) The magnetic tape 2 is run at the same timing as during recording with respect to the scanning start timing to ensure a just tracking state.

On the other hand, CTL signals S, 1 . The timing is detected in one field period, and when the timing fluctuates continuously for several fields, the running speed of the magnetic tape changes again and the evaluation value is detected, and the value is reset. delay k
The magnetic tape 2 runs at l D c t.

According to the above configuration, the period from when the logic level of the switching pulse signal SWP rises to logic "L" until the rise of the CTL signal S, □ is detected, and the search operation is restarted based on the detection result. By doing this, even when playing back a magnetic tape that has been continuously recorded, the tracking volume operation can be omitted and a just tracking state can be reliably obtained.

In the above embodiment, a case has been described in which the signal level of the reproduced signal SRF is detected three times during one frame period, but the number of detections is not limited to this and can be freely selected as necessary. Can be done.

Furthermore, in the above embodiment, after the logic level of the switching pulse signal SWP rises to the logic rHJ,
CTL signal S Although the case has been described in which the period until CTL rises is detected, the present invention is not limited to this. For example, if the logic level of the switching pulse signal SWP is a logic "
When detecting the period from when the CTL signal SCTL falls to "I4" to when the CTL signal SCTL rises, the key is to detect the timing of the CTL signal SCTL with respect to the switching pulse signal SWP.

Furthermore, in the embodiment described in -F, the case was described in which the timing of the CTL signal sctt which controls the switching pulse signal SWP is detected and the search operation is performed. Then, when the signal level of the reproduced signal Sat changes significantly, the search operation may be performed.

In fact, in Fig. 6, the reproduced signal SIF is signaled at the splice portion, and the signal . You can reset the amount.

Furthermore, when playing back a magnetic tape whose recording mode has been switched midway through, the switching of the recording mode may be detected and a search operation may be performed based on the detection result.

Furthermore, in the above-described embodiments, a case has been described in which the present invention is applied to a video tape recorder, but the present invention is not limited to a video tape recorder, but is applicable to a data recorder configured to reproduce desired data in place of a video signal. Furthermore, it can be widely applied to magnetic playback devices such as digital audio recorders that play back audio signals.

Effects of the Invention As described above, according to the present invention, the tracking volume can be adjusted even when playing back a magnetic tape that has been closely recorded by performing a search operation according to the timing of the control signal with respect to the switching pulse signal. Just-tracking status can be reliably obtained by omitting operations.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a video tape recorder according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining its operation, and FIGS. 3 and 4 are characteristic curve diagrams for explaining its operation. , FIG. 5 is a signal waveform diagram for explaining the operation when reproducing a magnetic tape recorded on a continuous basis, and FIG. 6 is a characteristic curve diagram for explaining the operation. ■・・・Video tape recorder, 2・・・・・・
Magnetic tape, 3A, 3B...Magnetic head, 4.
...Detection circuit, 6...Control circuit, 9...
...capstan motor.

Claims (1)

[Claims] After detecting the timing of the control signal with respect to the switching pulse signal, and varying the running speed of the magnetic tape according to the detection result, and detecting the signal level of the reproduction signal output from the magnetic head. . A magnetic reproducing device characterized in that tracking control is performed based on the detection result of the signal level.