JPS61144754A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To put the 1st and the 2nd video signals in phase precisely and easily and to perform magnetic reproduction by accumulating a signal corresponding to the phase difference between both signals for a specific time. CONSTITUTION:The 1st video signal I to be recorded newly is processed by vertical synchronous separations 19. Further, the 2nd video signal which is recorded on a magnetic tape 1 is led out of a pulse generator 11 and processed by vertical synchronous separation 27. Those signals are supplied to an exclusive OR circuit 28 to detect their phase difference signal T, and the output signal of an up/down counter 31 corresponding to the detection signal is sent to a counter circuit 21. This circuit 21 counts and accumulates a clock at constant intervals of time and its output signal is latched with the output P of a generator 11 and D/A-converted 24; and the phase error voltage Q is added 39 to the output F of a speed control circuit 34 and the sum is sent to a control circuit 40, which controls the rotation of a drum motor 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording and reproducing device that makes it possible to easily synchronize a video signal recorded on a magnetic tape with a video signal to be newly recorded. It is.

Conventional configuration and its problems In a magnetic recording/reproducing device (hereinafter referred to as VTR), when editing is performed by inserting and recording a new video signal consecutively to a video signal recorded on a magnetic tape, when a new video signal is to be recorded. If the phases of the synchronizing signals of the first video signal recorded on the magnetic tape and the second video signal recorded on the magnetic tape do not match, a time axis error will occur in the video signal at the editing point, causing disturbances in the reproduced image. Become.

To reduce this disturbance, it is necessary to detect the phase difference between the synchronization signals of the first video signal and the second video signal, and to control the phase of the drum motor with the magnetic head so that this phase difference becomes zero. There is. In order to realize such phase control, generally a pulse generator (hereinafter P(r A method has been used in which the drum motor is controlled to make the phase difference between the synchronizing signals zero by delaying the signal (denoted as ) using a variable delay circuit according to the phase difference.

Conventional phase control will be explained below with reference to the drawings. FIG. 1 is a block diagram of conventional phase control, and detects the phase difference between the second video signal 1° and the first video signal 90 already recorded on the magnetic tape 3 reproduced by the magnetic head 1. The signal detected by the circuit 7 is accumulated by the accumulation circuit 8, and input to the variable delay circuit 4 to change the delay amount of the signal of PGl 1. The phase difference between the delayed PGll signal and the first video signal 9 is detected by the phase difference detection circuit 5, and the drum motor 2 is controlled by the drive circuit 6 so that the output of the phase difference detection circuit 7 becomes zero. . In this way, the phases of the first video signal and the second video signal are matched.

However, in this conventional method, a highly accurate variable delay circuit is required to reduce the time axis error at the editing point, and the configuration is complicated.

Furthermore, if the drum motor is controlled to match the phase of the first video signal and the second video signal when the tracking is shifted before the editing point, the tape pattern at the time of recording will be recorded as being shifted from the normal position. Therefore, if editing is repeatedly performed in this state, there is a drawback that deviations in the tape pattern will accumulate.

OBJECTS OF THE INVENTION An object of the present invention is to accurately match the phases of a first video signal and a second video signal without using a high-precision variable delay circuit, and to perform accurate editing even when tracking is out of alignment. An object of the present invention is to provide a magnetic recording/reproducing device that enables the following.

Structure of the Invention In order to achieve the above object, the present invention provides: a signal corresponding to the phase difference between the first video signal and the PG signal, and a signal corresponding to the phase difference between the first video signal and the second video signal. The drum motor is configured to control the phase of the drum motor using the signal obtained by adding the signals obtained by adding the signals. You can match it without having to worry about it.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of the servo control circuit of "/TR" in one embodiment of the present invention, and the circuit is digitally controlled. It is composed of a motor 2, a magnetic tape 3, a speed control circuit 34, a phase control circuit 35, a phase-number circuit 36, and a drive circuit 38. The drum motor 2 has a frequency generator 37 (hereinafter referred to as F) that detects the rotation speed.
and P(rll), and the magnetic head 1 records and reproduces video signals on the magnetic tape 3.The drive circuit 38 has the speed control circuit 3
4 and the phase control circuit 36, and a control circuit 40 that controls the drum motor 2.
It is composed of.

The operation of the servo control circuit of this embodiment configured as described above will be explained below. Figure 3 shows speed control circuit 3
Figure 4 is a waveform diagram of phase control circuit 360, Figure 6 is a waveform diagram of phase control circuit 360.
6 and 6 are waveform diagrams of the phase-number circuit 36.

First, the speed control circuit 34 controls the drum motor 2 to a constant rotational speed. Waveform shaping circuit 1 outputs Fe12
The FC signal B obtained by waveform shaping in step 2 is delayed by a certain amount by a delay circuit 13, and the counter circuit 14 starts counting clocks in response to the obtained start signal C. The overflow signal E at the overflow terminal of the counter circuit 14 is counted a predetermined number n times by the counting circuit 16, and the gate circuit 16 is operated by the obtained gate signal G.
With the launch signal H obtained by gating the signal B, the counter output of the counter circuit 14 is held in the latch circuit 17 as shown in FIG. The digital signal of the latch circuit 17 is converted into an analog signal by the D/A conversion circuit 18,
Obtain speed error voltage F. The speed error voltage F is the drive circuit 38
and controls the speed of the drum motor 2. For example, if the speed of the drum motor 2 decreases, the speed error voltage F increases, the drum motor 2 is accelerated by the drive circuit 38, and the speed is controlled to be constant. The above is an explanation of the operation of the speed control circuit 34.

The phase control circuit 36 controls the drum motor 2 to a constant rotational phase. The first vertical synchronizing signal J is separated from the first video signal signal to be newly recorded by the vertical synchronizing separation circuit 19, and the value m of the preset terminal PI is sent to the counter circuit 21 by the start signal K delayed by the delay circuit 2o. After that, counting of the clock M is started via the gate circuit 22 which is opened at the output of the delay circuit 2e. PGll
The counter output N of the counter circuit 21 is held in the latch circuit 24 by the latch signal P obtained by waveform shaping the signal in the waveform shaping circuit 23. The latch circuit 24 is reset during the "H" level period of the start signal. The digital signal of the launch circuit 24 is converted into an analog signal by the D/A conversion circuit 26, and becomes a phase error voltage Q. The phase error voltage Q is input to the drive circuit 38 to perform phase control of the drum motor 2. For example, when the phase of the drum motor 2 advances as shown by P' in FIG. 4, the phase error voltage Q increases, and the drive circuit 38 accelerates the drum motor 2 and controls the phase to lag. In addition, when the phase of the drum motor 2 advances further or at startup, the counter circuit 2
1's counter output N overflows, an overflow signal 0 is output, and the gate circuit 22 outputs the clock M.
is prohibited, the counter output N is held at the maximum value, and the drum motor 2 is accelerated. Next, when the phase of the drum motor 2 is greatly delayed and the falling edge of the latch signal P reaches the "HI+" level period of the start signal, the latch circuit 24 is reset and the phase error voltage Q becomes zero, causing the drum motor to 2 is decelerated.

Further, in FIG. 4, when the counter output N becomes zero after presetting the counter circuit 21, pulses a and b are output as an overflow signal 0, but a gate signal obtained by delaying the start signal K by the delay circuit 26 is output. “°H”
``Banned for level period.

The above is an explanation of the operation of the phase control circuit 36.

A normal drum servo is performed by a speed control circuit 34, a phase control circuit 36, and a drive circuit 38, and controls the rotation of the drum motor 2. However, during editing, such a drum servo does not have a function to match the phase of the first video signal and the second video signal, so a time axis error occurs in the video signal at the editing point, causing disturbances in the reproduced image. do. As a countermeasure for this, conventional VTRs detect the phase difference between the first video signal and the second video signal, and use the first vertical synchronization signal or PG
The delay amount of the signal ll is changed by a variable delay circuit according to the phase difference to control the rotation of the drum motor 2, and the phases of the first video signal and the second video signal are matched.

In the embodiment of the present invention, a variable delay circuit is not used, and a phase-number circuit 36 is used to prevent disturbances in the reproduced image. The phase-number circuit 36 will be explained below. The vertical synchronization separation circuit 27 separates the second vertical synchronization signal S from the second video signal R on the magnetic tape 3 reproduced by the magnetic head 1 via the video signal reproduction circuit 41, and the second vertical synchronization signal S is separated by the exclusive OR gate 28. As shown in FIG. 6, a phase difference signal T corresponding to the phase difference between the first vertical synchronizing signal J and the second vertical synchronizing signal S is detected.

The counting circuit 29 determines the number of sampling times for phase comparison between the first video signal and the second video signal, and the first vertical synchronizing signal J is sent to the gate circuit 3o every four times predetermined by the counting circuit 29. is operated, and the phase difference signal T is inputted to the enable terminal of the up/down counter circuit 31 as an enable signal U.

Next, the lead/lag phase detection circuit 32 detects the first vertical synchronization signal J.
The leading/delaying phase detection signal V is detected according to the phase lead/lag of the second vertical synchronizing signal S, and if the first vertical synchronizing signal is leading, the level is "H", and if it is lagging, the signal is "L++". Each input of the up/down counter circuit 31 is connected to a switching circuit 42 that is switched by the assemble start signal X.
However, at H level, each switch is switched to the a side, and at L level, each switch is switched to the b side. When the switch 33 is in the OFF state, the preset terminal of the amplifier down counter circuit 31 is at "L" level, and the preset input terminal PIO value is preset. In this embodiment, the preset input terminal P
Since I is connected to ground, the counter output W is reset. To enable the phase-number circuit 36, turn on the switch 33 and turn on the assemble start signal X.
is set to H level, the up/down counter circuit 31 is enabled for counting, and the clock M is counted during the H level period of the enable signal U output from the gate circuit 3o. The up/down counter circuit 31 detects when the leading/lag phase detection signal V is “H”.
” level, it operates as a down counter, and when it is “L” level, it operates as an up counter. The counter output W is input to the preset terminal PI of the counter circuit 21, changes the preset value m, and the phase difference signal T becomes zero. The drum motor 2 is controlled via the phase control circuit 36 and the drive circuit 38 so that the phases of the first video signal and the second video signal match.

As shown in FIG. 6, when the assemble start signal X changes to L level, assemble editing, that is, recording of control signals and video signals is started. At the same time, each switch of the switching circuit 42 is switched to the b side, and the up/down counter circuit 31 is switched to the clock M by the advance/delay phase signal 2.
A clock whose frequency is divided by the frequency dividing circuit 43! is counted, and the counting is stopped when the overflow signal z1 becomes L level.

At this point, the counter output W becomes zero, and normal phase control is performed.

The leading/lagging phase signal 2 is a signal obtained by inverting the most significant bit of the up/down counter circuit 31. When the most significant bit is at H level, the leading/lagging phase signal 2 becomes L level, and the up/down counter circuit 31 becomes an up/down counter. When the most significant bit is at L level, the leading/lag phase signal 2 is at H level, and the up/down counter circuit 31 operates as a down counter.

Furthermore, when returning the counter output W to zero, if the frequency of the clock Y is high, control of the drum motor 2 will be disrupted, so it is necessary to increase the frequency division ratio of the frequency dividing circuit 43.

In this way, in this embodiment, by adding the counter output W corresponding to the phase difference signal T to the phase control circuit 36, the phases of the first video signal and the second video signal can be adjusted without using a variable delay circuit. By pulling the counter output W back to zero after starting recording during assemble editing, even if the phases are matched with tracking deviation before recording, recording can be performed using the regular tape pattern. be able to.

In this embodiment, the counter output W is added to the counter circuit 21, but the same effect can be obtained by adding it to the phase error voltage q. Further, by changing the frequency division ratio of the frequency dividing circuit 43, the return time of the counter output W can be changed.

Effects of the Invention As is clear from the above explanation, the present invention accumulates a signal corresponding to the phase difference between the first video signal and the second video signal at regular intervals, so that it is not possible to An excellent effect can be obtained in that a function to easily match the phases of the first video signal and the second video signal can be achieved without requiring a variable delay circuit that delays the first video signal or the PG times signal. Furthermore, the phase difference signal W is first inputted without going through the variable delay circuit.
Since the phase of the video signal is cumulatively added directly to the phase of the video signal, it is possible to obtain the effect of improving the accuracy of controlling the time axis error.

In addition, in assemble editing, after the start of recording, the up/down counter circuit 31 counts the clock Y and pulls the counter output W back to zero, thereby controlling the drum motor 2.
An excellent effect can be obtained in that a regular tape pattern can be recorded with smooth control transition without disturbing the control.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of conventional phase control, Fig. 2 is a block diagram of phase control in an embodiment of the present invention, Fig. 3 is a waveform diagram of the speed control circuit, and Fig. 4 is a waveform diagram of the phase control circuit. ,
6 and 6 are waveform diagrams of the phase matching circuit. 1...Magnetic head, 2...Drum motor, 3...Magnetic tape, 11...Pulse generator, 19...Vertical synchronization Separation circuit, 21.
...Counter circuit (cumulative circuit), 22...
・Gate circuit, 27... Vertical synchronization separation circuit, 2
8...Exclusive OR gate, 29...Counting circuit, 3o...Gate circuit, 31...
・Up/down counter circuit, 32...Advance/lag phase detection circuit, 34...Speed control circuit, 36...
... phase control circuit, 36 ... phase matching circuit,
3. Frequency generator, 38. Drive circuit, 42. Switching circuit, 43.
...Frequency dividing circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure (H) Figure 4 (M)
-11111-Figure 5Figure 6 Figure 111

Claims (1)

[Claims] A pulse generator that outputs a pulse signal according to the rotational phase of a rotating body having a magnetic head, a first vertical synchronization separation circuit that separates a vertical synchronization signal from a first video signal to be newly recorded, and a recording medium. a second vertical synchronization separation circuit that separates a vertical synchronization signal from a second video signal recorded on the second video signal; and a signal corresponding to a phase difference between the output of the first vertical synchronization separation circuit and the output of the pulse generator. a first phase difference detection circuit that outputs the output of the first vertical synchronization separation circuit;
A second phase difference detection circuit outputs a signal according to the phase difference with the output of the vertical synchronization separation circuit, and during the output period of the second phase difference detection circuit, the first clock is counted and the signal is detected at regular intervals. and a control circuit that controls the rotational phase of the rotating body, adds the output of the first phase difference detection circuit and the output of the accumulation circuit, and based on this addition output, By driving the control circuit, the phase of the rotating body is controlled, and after the start of recording, the second
A magnetic recording/reproducing device configured to set the output of the accumulator circuit to a predetermined value by counting the clocks of the accumulator circuit.