JPH03147554A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To perform accurately reproducing tracking even when a CTL signal is unobtainable at the time of reproducing by forming a false control signal which is equivalent to the CTL signal based on an FG (frequency generation) signal for detecting the rotation of a capstan. CONSTITUTION:As for a down counter 8 set at a preset value 36, when a down counting operation from this preset value is performed one time, since one of outputs is changed to be at a high level to bring an output of a NOR circuit 11 back to be at a low level, a pulse P is formed by the output of the NOR circuit 11. Since the value 36 is reset upon completion of down counting to zero by the down counter 8, the pulse P outputted from the NOR circuit 11 turns up in the same period with a regenerative CTL signal. Consequently, the false CTL signal (e) is outputted by the NOR circuit 11, and a capstan servo circuit is controlled by this signal via a switch 5. By this method, even in the case of lack of the CTL signal (b) from a control head 2, the reproducing tracking can be performed by the false CTL signal (e) formed based on the FG signal (a) from a capstan motor.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention uses CTL signals recorded on a magnetic tape to
The present invention relates to a magnetic recording/reproducing device that controls a video head and a capstan motor.

(Prior Art) In a two-head helical scan video tape recorder (hereinafter referred to as VTR), in order to obtain a correct playback screen, the video head and capstan motor are servo-controlled during recording and playback, respectively.

During recording, the head servo controls the rotational frequency and phase of the head based on the vertical synchronization signal of the video signal. During playback, the head servo controls the rotational frequency and phase of the head based on the vertical synchronization signal of the video signal. During playback, the head servo controls the rotational frequency and phase of the head based on the vertical synchronization signal of the video signal. The rotational frequency and phase of the head are controlled by synchronizing with the signal.

During recording, the capstan servo uses the C-FG signal from the frequency generator (FG coil) attached to the capstan rotating shaft and the C-FG multiplied signal frame frequency of 29.97.
The speed and phase of the capstan motor are controlled by a signal frequency-divided into a Hz signal, and the reproduction CTL signal detected by the control head during reproduction is phase-synchronized with the output of the reference transmitter. The switching pulse indicating the rotational phase of the head drum and the reproduction CTL signal are locked to a constant phase, the capstan motor is controlled, and accurate reproduction tracking is achieved.

In this way, conventional VTRs perform playback tracking servo using the playback CTL signal as one phase alignment signal, so if the playback CTL signal is lost due to scratches on the magnetic tape, the capstan motor cannot be controlled. , accurate tracking will no longer be possible.

(Problems to be Solved by the Invention) As explained above, conventional VTRs use CT images recorded on tape for tracking using a capstan servo.
Since the L signal is used, there is a drawback that accurate tracking cannot be obtained if the CTL signal is lost.

An object of the present invention is to solve the above-mentioned problems and provide a magnetic recording and reproducing apparatus that can perform accurate reproduction tracking even when a CTL signal cannot be obtained.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a control head that records a vertical synchronization signal in a recording video signal on a magnetic tape as a CTL signal, and a capstan motor that controls the rotational speed during recording. Detected FG
A signal creation circuit that creates a tracking pseudo control signal equivalent to the above CTL signal based on the low signal, a detection circuit that detects the presence or absence of the playback CTL signal from the control head during playback, and a detection result of this detection circuit. Accordingly, the present invention is characterized by comprising a switch for using the reproduced CTL signal and the pseudo control signal as a reference signal for tracking servo.

(Function) With this configuration, a control signal similar to the CTL signal is generated based on the FG low signal that detects the rotation of the capstan, so even if the CTL signal cannot be obtained during playback. , allowing accurate playback tracking.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the components of an embodiment of a magnetic recording/reproducing apparatus according to the present invention.

In this figure, 1 is a capstan FG coil,
This capstan FG coil 1 outputs pulses according to the rotation of the capstan motor, and generates, for example, 360 pulses in one rotation. As a result, the FG coil 1 generates a low FG signal of 1080 Hz when the capstan rotates 3 times per second in the standard (SP>mode).

The FG coil 1 is used to switch tape speeds via a transmitter 6 that doubles the FG low signal frequency. The second input terminal a of the switch 7 is connected to the first input terminal a of the switch 7 to be
Connected directly to the input terminal. The switch 7 selects the signal from the second input terminal in the standard speed mode, and selects the signal from the multiplier 6 in the double speed mode (LP) and the triple speed mode (EP).

The output terminal of the switch 7 is connected to the count input terminal φ of the down counter 8. Down counter 8 is 0
When counted, all outputs become all low levels, and these outputs are input to the NOR circuit 11, respectively. The output of the NOR circuit 11 is led to the first input terminal a of the switch 5. The down counter 8 is preset operated by a signal from an OR circuit 9, and its preset value is supplied from a preset value control circuit 10.

The preset value control circuit 10 includes a switch 103 and preset value memories iol and io2.
03 is switched and controlled depending on whether the reproduced CTL signal is normally obtained or not, and the preset value memory i
Selectively output preset values from ol, io2
do. Further, the preset value memory 102 selectively outputs different preset values depending on the speed mode. The OR circuit 9 receives the output of the NOR circuit 11 and the CTL signal from the control head 2, and forms a preset operation signal for presetting the down counter 8.

Here, in the preset value control circuit 10, 144 is prepared in the memory 101 and 36.24 is prepared in the memory 102 as preset values for the down counter 8. 36 written in the preset value memory 102 is a value selected in the standard speed mode and double speed mode, and 24 in the same memory 102 is a preset value in the triple speed mode. this is,
This is to generate signals of respective frame frequencies by dividing the frequency of the FG times signal by 1/36 in the standard speed mode, by dividing the frequency by 1/24 in the double speed mode, and by dividing the frequency by 1/12 in the triple speed mode. 144 is a common multiple of 36 and 24, and although it may be at least 37, a margin is provided in order to reliably detect the presence or absence of a CTL signal dropout.

2 is a control head. control head 2
The CTL signal from is guided to the second input terminal of the switch 5, and also to the set terminal St of the RS flip-flop 3. The output of the NOR circuit 11 is led to the reset terminal R of the RS flip-flop 3.

The output of the RS flip-flop 3 switches and controls the switch 5.

The output terminal of switch 5 is connected to the capstan servo circuit.
It is connected to the output terminal 4 from which the TL signal is derived.

The operation of such a magnetic recording and reproducing apparatus during standard mode reproduction will be explained using the timing chart shown in FIG. In FIG. 2, T1 indicates a normal period in which a CTL (H signal) is obtained, and T2 indicates a period from detecting a loss of the CTL signal to switching the control signal during playback tracking to the pseudo control signal according to the present invention. , T3 indicate the control period by the pseudo control signal after switching.

In addition, Fig. 2 (a) shows the F'G signal from the capstan FG coil 1, (b) shows the CTL signal, (C) shows the counter value of the down counter 8, and (d) shows the RS flip-flop. (e) shows the pseudo control signal, and (f) shows the output signal of switch 5.

First, during standard mode playback, the FG multiplied signal a) has a frequency of 10
It becomes a pulse signal of 80 Hz, and when the CTL signal (b) is obtained normally, it becomes a pulse signal of frequency 29°97H2. During the period T1 in which the reproduced CTL signal is normally obtained, the RS flip-flop 3 is at a high level (set state). As a result, preset value control circuit 1
0 is controlled so that the switch 103 outputs the preset value 144 from the memory 101, and the down counter 8 is controlled so that the preset value 144 is output from the control head 2 by the output from the OR circuit 9.
It is preset at the cycle of the L signal.

The down counter 8 is set to FG from the preset value 144.
Count down the double signal a). FG double signal a) is 3
When 6 pulses are counted and the counter value (C) reaches 108, the down counter 8 is preset to 144 again by the output of the OR circuit 9. By repeating the above operation, the counter value 8 produces a high level signal in one of the outputs, and the NOR circuit 11
Outputs a low level signal from. With this, R8
The 7-rip 70 knob 3 maintains a high-level output, and the switch 5 outputs an output signal (f) that selects the reproduced CTL signal (b) from the control head 2. In this way, the capstan servo circuit performs playback tracking based on the playback CTL number.

As shown by the dotted line in FIG. 2(b), when the reproduced CTL signal is missing, the down counter 8 is not preset at a cycle of 36 counts, but continues to count down toward O beyond 108. When the count value reaches 0, all the outputs of the down counter 8 become low level, so that a high level signal appears at the output of the NOR circuit 11. With this rising of the high level, the output of the RS flip-flop 3 changes to low level. This low level signal is transmitted to the down counter 8 by switching the switch 5 to the first input terminal a side and switching the switch 103 of the preset value control circuit 10 to the preset value memory 102 side to set the down counter 8 in the standard speed mode. So, 36
(boundary between periods T2 and T3).

The down counter 8 to which the preset value 36 is set is
When the down-count operation is performed once from the preset value, one of the outputs changes to high level, so the NOR circuit 1
Return the output of 1 to low level.

As a result, the output of the NOR circuit 11 forms a pulse P. When the down counter 8 counts down to O, it is set to 36 again, so that the pulse P output from the NOR circuit 11 appears at the same period as the reproduced CTL signal.

Therefore, the NOR circuit 11 has a pseudo CT of 29.97H2.
An L signal (e) is output, and this signal controls the capstan mobo circuit via the switch 5. In this way, even if the CTL signal from the control head 2 is missing, reproduction tracking can be performed using the pseudo CTL signal (e) formed based on the FG signal (a) from the capstan motor.

In addition, in the case of double speed mode, capstan FG coil 1
The FG signal from is 540Hz, and the period is twice as high.
By switching and connecting the switch 7 to the first input terminal a side, the frequency is doubled by the multiplier circuit 6, and a signal having the same frequency as in the standard mode is input to the down counter 8. Therefore, the operation in this case is the same as in the standard speed mode poem.

In the case of the triple mode, the FG signal q from the capstan FG coil 1 is 3601-1 z. At this time, the switch 7 remains connected to the first input terminal a, and the 720 Hz signal from the multiplier 6 is input to the down counter 8. This frequency is 2
Since the frequency of the pseudo control signal (e) is 29.97Hz, the frequency of the pseudo control signal (e) is 29.97Hz. :Become.

As mentioned above, in standard speed mode and double speed mode,
In the 4th frame period after the reproduction CTL signal pulse is lost, and in the 3x speed mode, in the 6th frame period,
Reproduction tracking can be performed by generating the same magnetic CTL signal as the reproduction CTL signal.

In this way, in this embodiment, a pseudo control signal equivalent to the CTL signal is formed based on the FG signal that detects the rotation of the capstan, so that during playback, CTLM@ is tq
Accurate playback tracking is possible even if the

Note that various modifications can be made to the configuration of the embodiment for forming the pseudo CTL signal.

[Effects of the Invention] As described above, according to the present invention, accurate playback tracking is possible by substituting a pseudo control signal even when a CTL signal pulse is not obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the magnetic recording/reproducing apparatus according to the present invention, and FIG. 2 is a timing chart illustrating the operation of the magnetic recording/reproducing apparatus. 1... Capstan FG coil, 2... Control head, 3... SR flip-flop circuit, 4...
・Output terminal, 5, 7...switch, 6...multiplier,
8... Down counter, 9... OR circuit, 10...
- Preset value control circuit, 11...NOR circuit.

Claims (1)

[Claims] At the time of recording, a control head records the vertical synchronization signal in the recording video signal as a CTL signal on the magnetic tape, and a control head that records the vertical synchronization signal in the recording video signal as a CTL signal, and a control head that records the vertical synchronization signal in the recording video signal as a CTL signal, based on an FG signal that detects the rotational speed of the capstan motor, which is equivalent to the CTL signal. a signal generation circuit that generates a pseudo control signal for tracking; a detection circuit that detects the presence or absence of a reproduction CTL signal from the control head during reproduction; 1. A magnetic recording and reproducing device comprising: a switch for using a pseudo control signal as a reference signal for tracking servo.