JPS6319942B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic editing phase matching device in a magnetic recording and reproducing apparatus (hereinafter referred to as VTR) equipped with a capstan servo system, and in particular, the present invention relates to an electronic editing phase matching device in a magnetic recording and reproducing apparatus (hereinafter referred to as VTR) equipped with a capstan servo system, and in particular, from an electronic editing standby mode, which is a playback mode, to a recording mode. The present invention provides a new method for reducing phase synchronization disturbance in the capstan servo system when switching to

Normal VTRs use a capstan servo system to improve tracking during playback.

In a VTR equipped with a capstan servo system, during recording, the phases of the capstan rotational phase detection signal and a reference signal are compared, and the servo system is operated so that the phase difference between the two signals is constant, and the reference signal is It is recorded on the control track of the magnetic tape as a control signal. During reproduction, the phase of the reproduction control signal from the control track is compared with the reference signal, and the servo system is operated so that the phase difference between the two signals is constant. A tracking monomulti is used for the capstan servo system playback mode mentioned above, and the phase of the playback control signal is adjusted (usually by adjusting the amount of delay) using the tracking monomulti, which is a delay means.
(Used in the FIXed state), this realizes a tracking servo.

Equipped with a capstan servo system like the one above.
When performing electronic editing on a VTR, when switching from electronic editing standby mode to recording mode, the compared signal is switched from the playback control signal to the rotational phase signal, so if the phases of both signals are not matched, phase lock will occur. It comes off. For this reason, the capstan motor becomes phase locked while being accelerated or decelerated, and since the magnetic tape is recorded in a speed-modulated form, there is a problem that tracking cannot be achieved at the joints of electronic editing.

In order to solve this problem, conventionally, the rotational phase of the capstan motor and the phase of the reference signal are matched in phase during electronic editing.

A conventional example will be explained below with reference to the drawings.

FIG. 1 is a block diagram of a phase matching method for phase comparison signals in conventional electronic editing, and FIG. 2 is an operational waveform diagram of FIG. 1. In FIG. 1, 1 is a phase comparator, 2 is a switching circuit, 3 is a frequency converter, and 4 is a control signal generator. The operation will be explained based on FIGS. 1 and 2.

A rotation detection signal b that detects the rotation of the capstan motor is input to the frequency converter 3. The frequency converter 3 outputs a converted signal c obtained by converting the rotation detection signal b to a frequency of 1/n (where n is a natural number) so as to be equal to the frequency ( _b /n) of the reference signal e. Therefore, the rotation detection signal b has a frequency _b and is converted by the frequency converter 3 into a converted signal c having a frequency _b /n, and the converted signal c becomes one input of the switching signal 2. The other input of the switching circuit 2 is the control signal a reproduced from the control track of the magnetic tape. The output g of the switching circuit 2 is configured to be a control signal a in the electronic editing standby mode and a conversion signal c in the electronic editing recording mode, depending on the mode command signal d.

The output g of the switching circuit 2 is input as a phase comparison signal to the phase comparator 1, where a phase comparison is performed with the reference signal e, and the phase comparator 1 outputs a phase difference signal h.

The control signal generator 4 inputs the mode command signal d and the reference signal e, stops the operation of the frequency converter 3 at time _t4 when the mode command signal d is switched from standby mode to recording mode, and generates the next reference signal. At time _t5 when e occurs, a control signal f is generated to start the operation of the frequency converter 3 again. The frequency converter 3 restarts its operation at time _t5 by the control signal f, but is configured to generate the conversion signal c when the first rotation detection signal b after time _t5 is input at time _t6 . There is. Therefore, when the mode command signal d switches from standby mode to recording mode at time _t4 , the phase difference between the phase comparison signal g and the reference signal e is given by _t6 - _t5 , and its range is O. <t ₆ −t ₅ ≦1/ _b , and the maximum is 1/ _b .

The larger the phase difference between the phase of the phase comparison signal g and the phase of the reference signal e, the longer the time required for phase matching between the rotational phase of the capstan motor and the phase of the reference signal during electronic editing. Therefore, it is not desirable for a VTR.

Therefore, it is possible to reduce the phase difference between the phase comparison signal g and the reference signal e, and to shorten the time required for phase matching between the rotational phase of the capstan motor and the phase of the reference signal during electronic editing. There must be.

The present invention provides an electronic editing phase matching device that can further reduce phase shift compared to conventional phase matching systems.

FIG. 3 is a block diagram of the configuration of the present invention, and FIG. 4 is an operational waveform diagram of FIG. 3.

The configuration and operation of the present invention will be explained based on FIGS. 3 and 4. In Fig. 3, 1 is a phase comparator, 2 is a switching circuit, 3 is a frequency converter consisting of a counter, etc., and 5 is a delay circuit consisting of a preset circuit 6 and a counter 7, which is used to switch from standby mode to recording mode. phase comparison signal g
This shows a configuration in which the phase difference with respect to the reference signal e is set to ±1/2 _b or less.

However, _b is the frequency of the rotation detection signal.

A rotation detection signal b for detecting the rotation of the capstan motor is input to the frequency converter 3.

The frequency converter 3 generates a converted signal c having a frequency _{b /} n equal to the frequency of the reference signal e from the rotation detection signal b having a frequency b.

In addition, in standby mode, the frequency converter 3 is activated at time t ₀ , by the reproduction control signal a.
The rotation detection signal b after being reset at t ₃ is frequency-converted and converted signals c at times t ₁ and t ₄ are output. The switching circuit 2 receives the reproduction control signal a and the conversion signal c of the frequency converter 3 as input, and according to the mode command signal d, the output i of the switching circuit 2 outputs the reproduction control signal a if it is in standby mode before time _t5 . However, in the recording mode after time _t5 , the configuration is such that the converted signal c is output.

The output i of the switching circuit 2 is input to a preset circuit 6. A preset circuit 6 presets a counting start value in a counter 7 using the output i of the switching circuit 2. The counting start value is switched by the mode command signal d, and in standby mode, the counting start value N _P0 is given, and in the recording mode, the counting start value is given.
Give N _P1 . The counter 7 stops counting when it reaches a predetermined value NF, and the delay time τ _d is calculated by equation (1).

τ _d = (NF−N _P )/ _CK (1) The relationship between the above counting start values N _P0 and N _P1 is expressed by equation (2).

N _P1 = N _P0 ± _CK / _b (M-1/2) (2) However, in equations (1) and (2), _CK is the frequency of the clock pulse l of the counter, N _P is N _P0 or N _P1 , and _b is The frequency M of the rotation detection signal b is the value when the Mth rotation detection signal b after being reset in the reproduction control signal a is used as the conversion signal c, and in the above explanation, since it is immediately after, M=1. It is. Further, the sign ± is + if the counter is an up counter, and - if the counter is a down counter.

The second term in equation (2) is for correcting the phase difference between the reproduction control signal a and the conversion signal c.

In other words, since equation (2) is obtained by subtracting 1/2 _b from the conventional phase shift of 0 to 1/ _b , the phase shift is ±1/2.
It can be less than or equal to _b . This is 1/2 of the conventional example
It is.

As described above, the phase comparison signal g delayed by the delay circuit 5 is compared in phase with the reference signal e in the phase comparator 1 as in the conventional example, and a phase error output h is obtained.
This is the control signal for the capstan servo system.

According to the present invention, when recording from the standby mode, which is the playback mode, to the electronic editing recording mode, the counting start value of the presettable counter, which is the delay means, is changed, and the amount of delay is changed, thereby eliminating the phase shift in response to the mode change. The period of the rotation detection signal is less than 1/2 of 1/f _b , and the phase matching operation can be performed extremely easily and smoothly.
Furthermore, by configuring the delay means with a counter, it is possible to easily set the delay amount, and it is also possible to correct variations in the delay amount due to variations in circuit elements. Furthermore, the counter serving as the delay means can also be used as the above-mentioned tracking monomulti, which has been conventionally used for tracking in the capstan servo system reproduction mode.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a phase matching method in conventional electronic editing, FIG. 2 is an operation waveform diagram of FIG. 1, FIG. 3 is a block diagram of an embodiment of the phase matching method of the present invention, and FIG. 4 is an operation waveform diagram of FIG. 3. FIG. DESCRIPTION OF SYMBOLS 1... Phase comparator, 2... Switching circuit, 3... Frequency converter, 4... Control signal generator, 5... Delay circuit, 6... Preset circuit, 7... Counter.

Claims (1)

[Claims] 1. A frequency conversion means for converting the frequency of a rotation detection signal of a capstan motor; and a switching means for outputting a playback control signal in an electronic editing standby mode according to a mode command signal and outputting the output of the frequency conversion means in a recording mode. , a delay means for delaying the output of the switching means, a comparison means for comparing the phases of the reference signal and the output of the delay means, resetting the frequency conversion means by the control signal in the standby mode, and resetting the frequency conversion means in the recording mode. and a reset means for canceling the reset, the delay means comprises a counter whose counting start value can be preset by the output of the switching means, and the counting start value is switched by the mode command signal. Edit phase matching device.