JPH01191361A - Device for recording and reproducing control signal - Google Patents

Abstract

PURPOSE:To attain re-writing with a stable and exact timing and to improve the reliability of operation by preparing the various types of timing signals, which are needed when a control signal is re-written, based on a capstan reference signal. CONSTITUTION:A second capstan servo reference signal, which is outputted from a monostable multivibrator 22 for tracking 22, and the front edge pulse of a reproducing control signal, which is reproduced from a control head 29, are controlled so as to be phase-synchronized by a capstan servo circuit. When the back edge of the control signal, which is reproduced from a recorded tape, is re-written, the various types of the timing signals for the re-writing are generated from a record control signal generating circuit 26 based on the capstan servo reference signal which is phase-synchronized with the control signal. Thus, the stable and exact timing signal can be made and exact information can be included in the control signal.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) This invention relates to a video tape recorder.

The present invention relates to a control signal recording and reproducing device that records and reproduces cueing and address information using control signals, and in particular allows cueing and address information to be rewritten on a recorded tape using control signals.

(Prior Art) In a video tape recorder, a control track is provided on the tape and a control signal is recorded therein in order to control the rotary head to accurately trace the recording track. Normally, only the positive edge of a control signal is used for tracking control, and the negative edge is not used, so a circuit has been developed that records cue position information or addresses by changing the position of this negative edge. has been done. This circuit not only records the cue position information from the first recording on the tape, but also allows the cue position information to be written again to the already recorded tape for editing purposes. .

FIG. 4 shows an example of a conventional control signal recording/reproducing circuit incorporated in a VHS video tape recorder, which allows re-recording by changing the position of the negative edge of the control signal. A DC voltage 2 is supplied to one terminal of the control head 1, and a movable contact of a switch 3 is connected to the other terminal. One terminal P of the switch 3 is
A reproducing amplifier 4 for deriving a reproduced load signal.
The output of this regenerative amplifier 4 is supplied to a movable contact of a switch 5 and is also led out to an output terminal 6. The control signal derived to the output terminal 6 is used as a comparison signal in a capstan servo circuit, for example.

One terminal P of the switch 5 is in an open state, and the other terminal R is connected to the timer circuit 7, 8.9. Each timer circuit 7, 8.9 has a different time constant and obtains output pulses b, c, d with different phases. The output pulse b of the timer circuit 7 is supplied to the set inputs of flip-flops 9 and 10, the output pulse C of the timer circuit 8 is supplied to the reset input of the flip-flop 9, and the output pulse d of the timer circuit 9 is supplied to the set inputs of the flip-flops 9 and 10. supplied to the reset input of And the output f of flip-flop 9
is supplied to the other terminal R of the switch 3. Further, the output e of the flip-flop 10 is supplied to the control end of the switch 3, and when the output e is at a high level, the switch 3
selects terminal R, and selects terminal P when it is at low level.

FIG. 5 shows the operating waveforms of the above circuit.

Signals a to g shown in FIG. 5 are signals appearing in portions indicated by the same reference numerals in FIG. 4, respectively.

Now, if we assume that the circuit rewrites the negative edge position of the control signal and writes cue information, we obtain the following operation. First, in order for the control signal to represent "0", the width from the positive edge to the negative edge should be (60±5)% of one cycle, as shown in Figure 6, and to represent "1", the width from the positive edge to the negative edge The width to the edge is one period (27,5±2.
5) Must be %. Therefore, first, the control signal is reproduced and its positive edge (a in FIG. 5) is extracted. From this time tl, a pulse b is output after a period TI, and the flip-flops 9, 10 are set. As a result, the switch 3 is switched to the terminal R side, and a recording current is supplied to the control head 1 (a positive current flows in the control signal). Next, from time point 11 to period T2
After that, pulse C is output. As a result, the flip-flop 9 is reset and the output f becomes low level, so that current flows through the control head 1 in the negative direction. This reversed current in the negative direction causes a negative edge to be written on the control track on the tape. 5 is a signal waveform appearing at the terminal of the control head 1. In FIG.

Here, by switching the time constant of the timer circuit 8 using a switching signal, the period T2 can be changed. In other words, it is possible to write again by varying the negative edge position of the control signal. Further, when a period T3 has elapsed from time t1, a pulse d is obtained and the flip-flop 10 is reset. As a result, the switch 3 is switched to the terminal P side, and the next positive edge of the reproduction control signal is detected. Then, based on this positive edge detection, the timer circuit 7.8.
9 is triggered and the negative edge is rewritten.

(Problems to be Solved by the Invention) As described above, in the conventional control signal recording/reproducing circuit, when rewriting the negative edge of the control signal,
A timing pulse is generated to control the switch 3 and flip-flops 9 and 10, and its reference is the positive edge of the control signal reproduced from the tape.

However, if the positive edge is used as a reference, if noise is mixed into the positive edge part for some reason, or if the positive edge is missing due to noise, it will not be possible to obtain a signal for each square timing at an accurate point in time. . Furthermore, if the phase of the correct edge fluctuates due to factors other than servo disturbances, such as noise, there is a problem in that significant malfunctions occur and accurate cueing information cannot be recorded. The phase fluctuation of the positive edge should originally follow the servo disturbance. Furthermore, since the recording/reproducing circuit described above is a separate system from the normal recording circuit for control signals, the overall circuit scale increases.

Therefore, the present invention eliminates the unstable factor that determines the timing when rewriting the trailing edge (negative edge) of a control signal, makes it possible to include stable and accurate information in the control signal, and reduces the circuit scale. It is an object of the present invention to provide a control signal recording and reproducing device that is effective in reducing the amount of noise.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a method for recording and reproducing a control signal for reproducing a leading edge of a control signal of a videotape and rerecording a trailing edge of the reproduced control signal. When rewriting the trailing edge of a control signal played back from a recorded tape in the apparatus, a means is provided to generate various timing signals for this purpose based on a capstan servo reference signal that is phase-synchronized with the control signal. It is designed to have a simple configuration.

(Operation) According to the above means, since the capstan servo reference signal that determines various timings does not have its phase position disturbed or is lost due to noise, it is possible to create a stable and accurate timing signal. , accurate information can be included in the control signal.

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

FIG. 1 shows an embodiment of the present invention, in which an input terminal 21 is supplied with a capstan servo reference signal (R). This reference signal (R) is supplied to the tracking mono multivibrator 22 and also to one fixed contact RPC of the switch 23. The capstan servo reference signal (R) is a mono multi-by-break 2 for tracking.
2 is triggered, whereby a second reference signal (A)- is obtained from the tracking mono multivibrator 22. This second reference signal (A) is supplied to the fixed contact (PB) of the switch 23, and is also supplied to one input terminal of the phase comparator 24, and the reproduction control signal (
The phase is compared with G). An error signal resulting from this phase comparison result is introduced into the capstan servo circuit via the output terminal 25.

A movable contact of the switch 23 is connected to a recording control signal generation circuit 26. The recording control signal generation circuit 26 generates various timing pulses, which control a recording control signal (C), a timing signal (D) for controlling the recording current control switch 28, and a head mode changeover switch 31. A timing signal (E) for controlling the Schmitt amplifier 33 and a timing signal (F) for controlling the Schmitt amplifier 33 are generated.

The switch 28 sends the recording control signal (C) outputted via the recording amplifier 27 to the control head 29.
It is turned on when the trailing edge (negative edge) of the control signal is written by the timing signal (D). The switch 31 supplies the reproduction control signal reproduced by the control head 29 to the phase comparator 24 via the amplifier 32 and the Schmitt amplifier 33, or
Supply DC voltage from 0.

The timing signal (E) becomes high level at the timing of the leading edge (positive edge) of the playback control signal, and acts to switch the switch 31 to the terminal a side so that the playback control signal can be introduced into the phase comparator 24. During the period, the voltage becomes low level, and the switch 31 is switched to the terminal side so that the DC potential from the DC power source 30 can be introduced into the phase comparator 24.

This embodiment is constructed as described above, and the operation will be described below.[A1 Normal Recording Operation] In the normal operation, the switch 23 selects the terminal. Therefore, the recording control signal generation circuit 26 is triggered by the capstan servo reference signal (A) and generates the recording control signal (C).

Also, at this time, the timing signal (D) becomes high level, the switch 28 is turned on, and the recording control signal (D) is turned on.
C) is supplied to the control head 29. As a result, normal control signals are recorded on the tape.

[B] Normal playback During normal playback, the timing signal (D) becomes low level and the switch 28 is turned off. Therefore, the control signal is not recorded, and the reproduction control signal reproduced by the control head 29 is transmitted to the reproduction amplifier 32. The signal is input to the phase comparator 24 through the Schmitt amplifier 33. The timing signal (E) at this time is always at a high level, and the switch 31 is set to the terminal a side.

[C] When recording, reproducing, and rewriting control signals, the operation timing chart at this time is as shown in FIG.

For example, in order to record cue information, the trailing edge (negative edge) of the control signal is
When rewriting the data, the operating mode is as shown in FIG. (A) to (G) in FIG. 2 are waveforms of signals (A) to (G) shown in each part of FIG. 1.

FIG. 2(A) shows the second capstan servo reference signal output from the tracking mono multivibrator 22, and FIG. 2(B) shows the leading edge pulse of the reproduction control signal reproduced from the control head 29. This is the output of the regenerative amplifier 32. This leading edge pulse and the second capstan servo reference signal are controlled to be phase synchronized by the capstan servo circuit.

At this time, the switch 23 is switched to the terminal (PB) side, so the recording control signal generation circuit 26
It is triggered by the second capstan servo reference signal (A).

When the recording control signal generation circuit 26 is triggered by the second capstan servo reference signal (A), it changes the timing signal (E) to a low level after a period Tl from the trigger time 101. As a result, the switch 31 is switched from the terminal a side to the terminal a side, and a constant DC voltage from the DC power supply 30 is supplied to the regenerative amplifier 32.

Then, after a period T2 from time ②, the timing signal (D
) turns on switch 28. When the switch 28 is turned on, a recording current flows through the control head 29, whereby a recording control signal (C) is supplied to the magnetic head 29. The recording control signal (C) is also generated in synchronization with the trigger timing, for example, in the waveform shown in FIG.

In this case, serial data is supplied from the terminal 261 to the recording control signal generation circuit 26, and the high level period of the recording control signal (C) is switched according to the data. If the input data is "1", the period (Xl) is high from the trigger time t01, and if the input data is "0", the period (X2) is high from the trigger time t21.
) is at a high level.

When the recording control signal (C) becomes low level, a reverse current flows through the control head 29. This time t12 becomes the trailing edge (negative edge) of the control signal and is recorded on the tape. (H) in the same figure shows the rewritten control signal.

Furthermore, after a period T4 from time tol, the timing signal (
E) becomes high level and controls the switch 31 to the terminal a side. As a result, the period including the leading edge of the reproduction control signal reproduced from the control head 29 is transmitted to the reproduction amplifier 32. Phase comparator 2 via Schmitt amplifier 33
4.

Therefore, the phase comparator 24 provides an error output necessary for the capstan servo.

Here, the Schmitt circuit 33 is reset by the timing signal (F) to ensure a reliable output (B) from the regenerative amplifier 32.
) is operated so that the signal (G) rises exactly when the signal (G) is present. In other words, the Schmitt amplifier 33 has the positive side level determination circuit 331. Negative side level determination circuit 332 and flip-flop 3 which is reset/reset by these outputs
35, and during normal playback operation, the playback control signal is set and reset at the leading edge and trailing edge, but when the control signal is rewritten,
At the time when the trailing edge is regenerated, the switch 31 is switched to the terminal side, and the reset operation may not be reliably obtained. For this purpose, a timing signal (F) is applied to the reset terminal of the fringe flop 335 via an OR circuit 334 to ensure Schmitt operation.

[Effects of the Invention] As explained above, the present invention provides stable and accurate timing in order to create various timing signals necessary for rewriting control signals based on a capstan reference signal. Rewriting is possible and operation reliability can be improved. Furthermore, since this circuit generates a recording control signal even when writing a control signal in the normal video signal recording mode, there is no need to provide a separate recording control signal recording circuit, and it is effective in reducing the circuit size. be.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a signal waveform diagram of each part of the circuit of FIG. 1, FIG. 3 is a circuit diagram showing an example of the Schmitt amplifier of FIG. 1, and FIG. 5 is a diagram showing a conventional control signal rewriting circuit, FIG. 5 is a diagram showing a timing signal D, and FIG.
The figure is an explanatory diagram showing an example of data represented by control signals. 22... Mono multivibrator for tracking, 2
3.28.31...Switch, 4...Fil comparator, 26...Recording control signal generation circuit, 27.
... Recording amplifier, 29 ... Control head, 32
...again. Main amplifier, 33... Schmitt amplifier. 3121 tl Figure 4 Figure 5, -7110... Teichino°
°1°'Figure 6

Claims (1)

[Scope of Claims] In a control signal recording and reproducing apparatus that reproduces a leading edge of a control signal of a videotape and re-records a trailing edge of the reproduced control signal, the reproduced control signal is controlled by a capstan servo circuit. A recording control whose falling phase is controlled according to a first timing signal using a capstan servo reference signal that is phase-synchronized with the leading edge of the capstan servo, a second timing signal whose phase is different from the first timing signal, and the content of the input data. means for generating a signal; first switching means controlled by the first timing signal and including a switch for introducing only a leading edge portion of the reproduction control signal into a phase comparator for the capstan servo; A control signal recording/reproducing apparatus comprising: second switching means controlled by the second timing signal and supplying the recording control signal to the control head.