JPS6112181A - Control circuit for slow motion reproduction - Google Patents

Abstract

PURPOSE:To attain noiseless pattern on a slow motion reproduced picture plane by detecting the deviation of stop position of a magnetic tape by the generating phase of noise, and controlling the stop timing of the magnetic tape depending on the generated phase. CONSTITUTION:The magnetic tape 1 divides a head switching signal by a frequency divider 16, and driven intermittently by the output signal of an FF18 risen in synchronizing with the leading edge of a frequency division output and descended in synchronizing with a trailing edge of a delay output delayed by a reproduced control signal with a monostable multivibrator 17. In such a case, the trailing edge of the drive pulse is controlled by switching the delay amount of the monostable multivibrator 17 according to the relation of phase of a noise (dropout) signal at the delay time control circuit 30. Thus, the sequential stop position of the tape 1 is controlled to a position not generating noise on the reproduced automatically picture plane thereby attaining automatically noiseless slow motion.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a one-rotation head type videotape recorder (hereinafter referred to as V
This invention relates to a slow-motion reproduction control circuit used in a TR.

[Background of the invention]

Conventionally, as a slow motion reproduction method for a VTR, there is a method in which the magnetic tape is moved intermittently, and the same video track on the magnetic tape is repeatedly scanned multiple times by a rotating head during each stop period. First, such a conventional slow motion reproduction method will be explained using FIGS. 1 and 2. In FIG. 1, 1 is a magnetic tape.

2 is a cylinder motor %3, 4 is a video head for rotating and scanning the magnetic tape 1, 5 is a tack head for detecting the rotational phase of the video head 3.4, 6 is a flip-flop, and the 7 flip-flop 6 is a tack head. Based on the output of the head 5, a well-known head switching signal for alternately switching the reproduction signal of the video head 3.4 is created.

7 is a reference signal generator, 8 is a phase comparator, 9 is a drive amplifier for the cylinder motor 2, and these are the video head 3.4
This constitutes a head servo system that controls the rotational phase of the head.

10 is a capstan motor; 11 is a control head that reproduces a control signal for tracking control recorded on the lower end of the magnetic tape 1; 12 is an amplifier;
14 is a phase comparator, and 14 is a drive amplifier for the capstan Tanabata 10, which constitute a capstan servo system that controls the 100-rotation phase of the capstan motor.

15 is a switch for switching between normal playback and slow motion playback, and has a contact N for normal playback and a contact S for slow motion playback. 16 is the clip 70
A divider that divides the head switching signal from the knob 6 by 17N, 17 is a JILi constant multivibrator (mono multi) that delays the control signal from the amplifier 12. %18 is set to the output of the 1 frequency divider 16, and These splitters 16 . Nanano Multi 17, Clip 7
The zero shift 18 constitutes an intermittent drive system for the capstan motor 10 during slow motion playback.

During normal reproduction, the head switching signal 19 shown in FIG. along with alternately switching.

The signal is also input to the phase comparator 8, and the phase is compared with the output of the reference signal generator 7. Based on the comparison output, the cylinder motor 2 is driven via the drive amplifier 9, and the rotation of the video heads 3 and 4 is controlled. Phase is controlled.

On the other hand, the control signal reproduced by the control head 11 is input to the phase comparator 13 via the amplifier 12, where the phase comparison with the output of the reference signal generator 7 is performed, and the comparison output is sent to the normal reproduction contact. The signal is supplied to the drive amplifier 14 via the changeover switch 15 which is switched to the N side, and the rotational phase of the capstan motor 10 is controlled.

During normal playback, the rotary head 5.4 correctly tracks the video track on the magnetic tape 1 and maintains a stable state. A playback screen is now available.

Now, during slow motion playback, selector switch 15
is switched to the contact S side, and the capstan motor 10 is intermittently driven by the output of the 7 lip 70 gear 18. This operation will be described in detail below.

The splitter 16 divides the frequency of the head switching signal 19 (output of the flip-flop 6) shown in FIG. 2(a) by 17N, and the divided output 2° shown in FIG. 2(b) is obtained as the output. (In the illustrated example, the head switching signal 19 is
The case where the frequency is divided into four is shown. ) This rising edge of the branch output 20 sets the flip-flop knob 18, and the set output is sent to the switch 15. The capstan motor 10 is started via the drive amplifier 14. As a result, the magnetic tape 1 starts running, but after the start of running, the control signal 21 shown in FIG. 2(C) is reproduced from the control head 11, and the control signal 21 is
The signal is inputted to the monomulti 17 via the amplifier 12.

The monomulti 17 has a delay waveform 22 shown in FIG. 2 (tL).
is output and the flip-flop 18 is reset at the falling edge, so the drive signal to the capstan sweater 10 disappears and the magnetic tape 1 eventually comes to a stop. During this stop period, the video head 3.4 repeatedly scans the same video track on the magnetic tape several times. Thereafter, at the next rising edge of the frequency divided output 20 from the frequency divider 16, the 7 lip 70 knob 18 is set again, and the above-mentioned starting and stopping operations of the magnetic tape 1 are sequentially repeated, and the magnetic tape 1 is , will be sent intermittently in predetermined amounts.

Flip-flop 1 during such intermittent operation
8, that is, the drive pulse waveform of the capstan motor 10 and the speed change waveform of the capstan motor 10 due to the drive pulse waveform are shown in FIG. 2 (-), respectively.
.

The waveforms shown in (j) are as shown in waveforms 25 and 24.

Here, the stop position of the magnetic tape 1 for each intermittent feeding operation is determined by the delay time of the monomulti 17.

That is, when the delay time is T1 shown in FIG. 2 (tL), the magnetic tape 1
After being reproduced, it moves by the amount of movement wJ corresponding to the shaded area S in FIG. 2(f) and then stops.Similarly,
When the delay time of the monomulti 17 is Tt ((r, ), it moves by the amount of movement corresponding to the shaded portion S, and then stops.

(FIG. 2V), since the horizontal axis is time and the vertical axis is capstan speed, the shaded area S1. of the waveform 24. S
It should be noted that each t represents the amount of movement of the magnetic tape after the control signal 21 is reproduced. )
Therefore, if the delay time of the monomulti 17 is not properly adjusted, the magnetic tape 1
4 stops at a position where the video track cannot be traced correctly, resulting in noise on the playback screen. To prevent this, it is necessary to adjust the delay time of the monomulti 17 and control the stop position of the magnetic tape 1 with high precision. Conventionally, such control of the stop position of the magnetic tape has been performed by the user. This operation was very troublesome because it had to be done manually and moreover, it had to be done every time the tape to be played changed.

[Purpose of the invention]

The object of the present invention is to eliminate the drawbacks of the above-mentioned prior art.

When the magnetic tape is intermittently driven to perform slow motion reproduction on a VTR, the sequential stop positions of the magnetic tape can be controlled automatically to positions where no noise is generated on the reproduction screen.

The present invention provides a control circuit for slow motion playback.

[Summary of the invention]

In order to achieve this object, the present invention detects a deviation in the stop position of the magnetic tape based on the generation phase of noise generated by this deviation, and sequentially controls the stop timing of the magnetic tape in accordance with this generation phase. , is characterized by a noiseless slow motion playback screen.

[Embodiments of the invention]

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

FIG. 3 is the basic principle of the invention. This is a diagram for explaining the correlation between the tape stop position and the noise generation phase of the playback screen, and FIGS. 2A to 2D show examples of four different stop position states of the magnetic tape 1. In these figures, a video track t"' recorded on a magnetic tape 1
s bsc, tL . . . , and the stopping positions of the magnetic tape relative to the rotating head in each state are indicated by arrows below the magnetic tape. Further, the reproduction scanning locus of the rotary head in each of these stop position states is shown by a broken line. Now, suppose we want to stop the magnetic tape 1 to play back video track b after running it in the direction of arrow X.
is the desired position), B is the stopped state at the desired position, and C is slightly before the desired position.

Also, D indicates a state in which it has gone far too far and has stopped. Here, since the magnetic tape 1 is stopped, the reproduction scanning trajectory by the rotary head has a tilt angle different from that of the video tracks a-tL.As is clear from FIG. The intersecting state of the intersecting state differs depending on the state of each stop position of the magnetic tape 1. Further, video tracks a to d are recorded using the azimuth recording method as usual. Therefore, the video track area that can be played back by the one-rotation head at each stop position of the magnetic tape 1 is different, as shown by diagonal lines in FIG. As a result, the reproduction output level (FM video signal level) of the rotating head increases or decreases.

This increase/decrease state of the reproduced output level is shown as a waveform 25 in FIGS. 3A' to 3U, respectively. This playback output level waveform 25
becomes below the level indicated by the dashed line.

Noise will occur on the playback screen (demodulated output of the FM video signal), but this noise (described below).

Koneo dropout signal, abbreviated as DO double signal c) Figure 3 is the waveform! ~μ are shown by waveforms 26, respectively.

As is clear from the figure, the DO signal 26 is transmitted to the magnetic tape 1.
If the stop position is state A, it occurs immediately before each inverted edge of the head switching signal 19, and if it is a slipper C, it occurs after each inverted edge. Also, magnetic tape 1
If the stop position of the magnetic tape 1 is in the state, a reproduction output of a predetermined level or higher cannot be obtained, and the DO signal 26 is constantly generated during the entire period, while the stop position of the magnetic tape 1 is at the desired stop position. In state BK, a sufficiently high level of reproduction output is always obtained, so no DO double signal is generated. Note that the DO double signal generation state when the magnetic tape 1 is not being fed significantly enough is the same as the state. In this way, magnetic tape 1
There is a certain correlation between the stop position of the DO signal 26 and the presence or absence or generation phase of the DO signal 26. Therefore, the presence or absence of the Do signal 26 is detected when the magnetic tape 1 is stopped, and when the DO signal 26 is detected, the phase relationship between its generation phase and the head switching signal 190 phase is checked. For example, since the stop position of the magnetic tape 1 at that time is estimated, it is possible to use the result to perform KIIdJa so that the stop position of the magnetic tape 1 becomes a desired stop position sequentially.

Next, a fourth embodiment of the present invention incorporating such a principle will be described.
This will be explained using FIGS. In Figure 4, 27
is an amplifier for the reproduced FM video signal obtained from the one-rotation heads 3 and 4; 28 is a W signal detector; 29ij, I)O
A phase comparator 30 that compares the phases of the signal and the head switching signal is a delay time control circuit that receives the output of the phase comparator 29 and switches the delay amount of the monomulti 17.

Here, the monomulti 17 corresponds to the monomulti 17 in FIG. 1, and, as already explained, determines the stop position of the magnetic tape 1 according to the amount of delay. Further, since the other components in FIG. 4 are the same as those shown in FIG. 1, the same components are given the same reference numerals as in FIG. 1, and their explanations will be omitted. Note that the reference signal generator 7 and phase comparators 8, 13, . . . shown in FIG. A head servo system such as the drive amplifier 9, a capstan servo system, etc. are not directly related to the gist of the present invention, and are therefore omitted in the embodiment shown in FIG.

Next, the operation of the embodiment shown in FIG. M4 will be explained using the operation waveform diagram shown in FIG. In this embodiment, similar to the conventional example shown in FIG.
The drive pulse waveform 32%, that is, the head switching signal 19 is divided by υ by the frequency divider 16, and the reproduction control signal 21 rises in synchronization with the rising edge of the frequency-divided output 2o.
Delayed output waveform 3 delayed by 'i% no multi 17
Flip-flop 1 falls in synchronization with the falling edge of 1.
In this case, the falling edge of the drive pulse waveform 32 is intermittently driven by the output signal of D.
Depending on the phase relationship of the o signal 33, the delay time control circuit 30
This is controlled by switching the delay amount of the monomulti 17, thereby controlling the stop timing of the magnetic tape 1.

That is, if the drive pulse waveform 32 of the capstan motor 10 rises at time t0 and the delay time of the monomulti 17 at this time is T shown in FIG. 5(d), then the drive pulse The waveform 52 falls at a time T after the control signal 21 is reproduced. It moves by the amount of movement corresponding to the hatched portion S of the speed change waveform) and comes to a stop at time t1. This stopping position is the state shown in FIG. 3A.

That is, if the stop position is a little too far from the desired stop position, the dropout detector 28, as explained in FIG. ), a Do signal 33/ (corresponding to the Do signal 2611C in FIG. 3) is generated.

The added signal 33' is input to a phase comparator 29, where the rising edge of the first pulse is compared in phase with the head switching signal 19 output from the seven lip-flop 6. Since the correct Do times signal cannot be obtained while the magnetic tape 1 is running, the phase comparator 29 performs the phase comparison operation only during the stop period of the magnetic tape 1, but this will be described later. . Now, as a result of the first phase comparison, the phase comparator 29 detects that the stop position of the magnetic tape 1 has gone too far, and this detection output causes the control circuit 30 to
T decreases the delay time 1 ri of the monomulti 17 by a predetermined constant time ΔT.

shall be. Therefore, the magnetic tape 1 has the drive pulse waveform 3
2, the delay time of the monomulti 17 is -Tt.
(<Ts), the magnetic tape 1 is
After reproducing the control signal 21, it moves by a movement amount S smaller than the previous movement amount S and stops at time t3.

After repeating this operation several times, when the dropout detector 28 no longer detects all DO signals, the delay time of the monomulti 17 will not change from then on, and the magnetic tape 1 will be moved to the desired stop position one after another. In other words, the playback screen will be stopped at a position where no noise will occur.

Here, the stop position of the magnetic tape at which noise does not occur on the playback screen should be a position where the generated noise is caught within the vertical retrace period of the video signal. Therefore, in the above-mentioned stepwise control of the magnetic tape stop position, the amount of change in the stop position per step (within the above tolerance range) is made small. By setting the amount of change in delay time ΔT, it is possible to ensure that the magnetic tape 1 is stopped within the above-mentioned allowable range after several control operations.

Also, depending on the initial activation conditions of the magnetic tape 1.

Or due to some other cause, if the stop position of the magnetic Q-Goo is in the state shown in Figure 3C, that is, the stop position is a little short of the desired stop position,
Since the dropout detector 28 outputs a Do signal 33'' (corresponding to the DO signal 26 in FIG. 3d) which occurs immediately after each inverted edge of the head switching signal 19, in this case the phase comparator 29 , detects an insufficient feeding amount of the magnetic tape 1, and based on the detection output, the control circuit 30 increases the delay time of the monomulti 17 by a predetermined amount ΔT.
shall be. Therefore, the magnetic tape 1 restarted at time t4 moves by the increased movement amount S3 after the control signal 21 is reproduced, and comes to a stop at time t. Thereafter, such operations are repeated until the magnetic Qi-Goo stops at a position where no noise is generated on the playback screen. In addition, the stop position of the magnetic Qi-Goo is in the state shown in the third diagram), and the dropout detector 28 is always set to D.
o When outputting a scratch signal, head switching signal 1
9, the phase comparator 29 is configured to generate an output that increases the delay time of the monomulti 17, as will be described later. The sequential stop positions of 1 are controlled so that the desired stop position state is achieved through the state shown in FIG. 3C.

The operations of this embodiment described above are summarized in the flowchart of FIG. States A to DFi in the same figure, Fig. 3 A
-D corresponds to the magnetic tape stop position state. It is now assumed that slow motion playback is fully started and the magnetic tape is stopped at a certain stop position due to the first intermittent feeding.

In this state, it is determined from the FM video signal reproduced by the rotary head whether or not the DO signal 33 is generated.

When the DO signal 33 is generated, the phase of the DO signal 33 with respect to the head switching signal 19 is detected. In state A, that is, when the magnetic tape 1 has been fed too far, the delay time of the monomulti 17 is reduced, and the end of running of the magnetic tape 1 is waited for during the next intermittent feeding using this delay time. State C1, that is, the magnetic tape 1 is not being fed enough, or state D1, that is, the feeding of the magnetic tape 1 is significantly excessive (also when the magnetic tape 1 is not being fed sufficiently). For the same), increase the delay time of Mono Multi 17,
In the same way as above, the user waits for the magnetic tape 1 to finish running. When the magnetic tape 10 has finished running, the Do signal 33 is activated again.
The determination of whether or not this occurs is repeated. As a result of the determination, in a state in which the DO signal 33 is not generated, that is, in state B, the delay time of the monomulti 17 is not changed, and the tape waits for the end of tape running in the next intermittent transmission operation.

Next, the phase comparator 29 and delay time control circuit 30 in FIG.
The structure and operation of this will be explained in more detail with reference to FIGS. 7 and 8.

In FIG. 7, 34 is a count pulse crt: a counter used as a counting input. 35 is a reset pulse generation circuit for resetting the counter 34, and 37 is a counter 5.
68 is a latch pulse generation circuit that supplies 2y pulses to the latch circuit 57, 39 is a switch, and 40 is a control pulse generation circuit that controls switch 39f on and off. It consists of a 29ft phase comparator.

41 is a determination reference signal generator; 42 is a magnitude determination circuit that determines the magnitude of the determination reference signal from 41 and the signal output from the latch circuit 37 of the phase comparator 29; 441-j, the magnitude determination circuit 42; Based on the output, the monomulti 17
An up/down signal generator 36 switches the up/down operation of the counter 43 for setting the delay time of the DO.
A 7 flip-flop 45 for detecting the presence or absence of a double signal is a switch that is controlled on and off by the output of the flip-flop S6, and these are switches that are controlled by the delay time control circuit 3.
It consists of ゜. Note that %46 is an input terminal for the control signal, 47 is an input terminal for the I)0 signal, and %48 is a drive pulse input terminal for the capstan motor.%49 is an input terminal for the head switching signal.

As described above, the phase comparator circuit 29 compares and detects the Do times signal generation phase with respect to the head switching signal, and its operation is as follows. That is, when the head switching signal 19 shown in FIG. 8 (5) is input from the terminal 49, the reset pulse generating circuit 35
generates a reset pulse 54 shown in FIG. 8(ri) at each rising edge and falling edge (inverted edge).
The counter 34 that counts the clock pulses 53 is reset every time the reset pulse 54 is generated. Therefore, a count output as shown in FIG. 8 is obtained from the counter 34, and this count output is input to the latch circuit 37.

On the other hand, the Do signal 33 shown in Figure #L8 is input to the latch pulse generation circuit 3B via the switch 39.
At the rising edge of the first pulse, a latch pulse 58 shown in FIG. The output is a value representing the DO multiplied signal generation phase based on the inverted edge of the head switching signal 19.Here, as described above, the control pulse generation circuit 4o controls the stop period of the intermittent magnetic tape. For this reason, the control pulse generation circuit 401C outputs the drive pulse 32 of the capstan motor input from the terminal 48 [FIG. 8(A)]. terminal 4
The head switching signal 19 from 9 is input, and as shown in FIG. (after two cycles of switching signal 19)
When the next drive pulse 32 rises, a control pulse 56 is generated which becomes a low level and a bell level.

The switch 39 is turned on only during the high level period, that is, during the period when the magnetic tape is stopped. Therefore, the latch pulse generation circuit 38 is supplied with the DO signal 33 from the terminal 47 only during the stop period of the magnetic tape, and the 5 phase comparator 29 is supplied with the DO signal 33 from the terminal 47.
When the 0 phase comparison operation is performed, it becomes K.

Now, the output of the phase comparator 29, that is, the latch circuit 37
The output is input to the magnitude determination circuit 42 of the delay time control circuit 300, and the magnitude relationship with the output of the determination reference signal generator 41 is determined. That is, the determination reference signal generator 41
Median value α of count output waveform 55 of counter 34 [Fig.
f)], the magnitude determination circuit 42 is configured to generate a reference value of a level corresponding to the latch circuit 57.
It is determined whether the output level of is larger or smaller than the median value α. This is nothing but determining whether the high phase of the DO signal 33 is located in the first half or the rear of the inversion period of the head switching signal 190, and as a result, from the magnitude determination circuit 42, A determination output corresponding to the state of excess or deficiency in magnetic tape feeding as shown in C is obtained. In addition, when the magnetic tape feed stops after traveling far too far as shown in the third diagram, the switch 39 is turned on as the magnetic tape feed stops, and at the same time the DO double signal is input to the latch pulse generation circuit 38. Therefore, in this case, 1) 0
The generation phase of the signal is located at the start point of the inversion cycle of the head switching signal 19, that is, in the first half of the inversion cycle, and therefore, the magnitude determination circuit 42 provides a determination output similar to the state shown in FIG. 3C.

The determination output of the magnitude determination circuit 42 is input to an up/down signal generator 44, which generates a . The counter 43 for setting the delay time of the monomulti 17 determines whether to perform an up-count operation or a down-count operation. Here, the monomulti 17 receives the control signal 21 from the terminal 46.
8(C)] is input to its reset terminal R.

It is also input to the counting input terminal of the counter 43 via the switch 45. Therefore, the monomulti 17 starts up every time the magnetic tape is intermittently fed and the control signal 21 is supplied from the terminal 46, and at the same time the count value of the counter 43 increases every time the playback control signal 21 is input. , increases or decreases by a fixed number in accordance with the output of the up-down signal generator 44, and the falling point (delay time) of the monomulti 17 is determined in accordance with this count value. As is clear from the foregoing, the output of the up-down signal generator 44 is obtained by determining the excess or deficiency of the stop position state during each stop period before each intermittent start time of the magnetic tape. ,in the end. counter 43
The count value is.

Each time the magnetic tape is moved intermittently, the stop position is increased or decreased by a predetermined number in order to eliminate excess or deficiency in the stop position.
The delay time of the monomulti 17 is changed in accordance with this increase/decrease, and the stopping position of the next magnetic tape is sequentially controlled. That is, for example, the first magnetic tape stop position is the third magnetic tape stop position.
If it goes a little too far as shown in FIG. Conversely, if the first stop position of the magnetic tape is in the states shown in FIG. 3C and D, the count value of the counter 45 will increase sequentially.

Such operations are repeated until the Do signal 33 from the input terminal 47 is no longer obtained. D.

In the state where the signal 33 is no longer obtained, that is, in the state shown in FIG. 3B, the switch 45 is turned off by the operation of the flip 70 knob 36 that detects its presence or absence, so that the count value of the counter 43 is changed thereafter. Not done, mono multi 17
operates with a constant delay. The operation of the flip-flop 36 for detecting the presence or absence of the DOO number 33 is as follows.

That is, the flip-flop 36 is connected to the control input terminal 4B.
It is reset each time one intermittent feeding of the magnetic tape is stopped by the rising edge of the drive pulse 32 from , and is set by the DOO signal 33 from the terminal 47 generated during the next stop period.

Therefore, as long as the DOO signal 33 is generated during the stop period of the magnetic tape, the output of the flip-flop 36 will always be at a high level during the feeding period of the primary magnetic tape, but the %Do signal 33 will not be generated. It remains at a low level. The above-described on/off control of the switch 45 is performed by the output of the flip-flop 36.

Next, the specific configuration and operation 1r of the monomulti 17 will be explained.
: This will be explained with reference to FIGS. 9 and 10. In Figure 9, %
60 is a clock pulse input terminal, 62 is an AND gate, 63 is a counter, 64 is a coincidence circuit, and 71 is a small power terminal. The attached 46 is the input terminal for the control signal, 4
5 is a switch, 43 is a counter, and these correspond to those explained in FIG. 7, respectively.

Now, before the time t0 shown in FIG. 10, the count value 69 of the counter 63 [FIG. 10 (-)] and the count value 59 of the counter 43 [FIG. 10 (d)] match. The output cuff a of the matching circuit 64 that detects the matching of the counted values of
(fglcl(f), l is at a low level and the AND gate 62 is closed.

In this state, the capstan motor drive pulse 3
2 [FIG. 10(a)] When the running of the magnetic tape is started by the start-up shell and the control signal 21 [FIG. 10(C)] is input from the terminal 46 at time t0, the control signal is As explained in FIG. 7, 21 is also the reset terminal RCf of the counter 63 and the reset terminal R of the monomulti 17 in FIG. ), and is also input to the counting input terminal of the counter 43 via the switch 45. As a result, the counted value of the counter 63 is reset and no longer matches the counted value output of the counter 43, so that the output of the minus number circuit 64 is converted to a high level, and the AND gate 62 is opened. therefore.

Clock pulse 66 from terminal 60 [Figure 10 (h)]
is supplied as the counting input of the counter 65, and the counter 6
3 counting operation is started. On the other hand, control signal 2
The counting operation of the counter 43 by 1 is the same as described above, and for example, as shown in FIG. 10(d), every time the control signal 21 is input.

It is assumed that the count value 59 decreases by a constant number.

At time t1, when the count value 69 of the counter 63 again matches the count value 59 of the counter 43, which has been decreased by a certain number, the output cuff 0 of the minus number circuit 64 returns to low level, the AND gate 62 closes, and the counter 63 counting operation stops. Thereafter, the same operation is repeated every time the control signal 21 is input, and as a result, the output of the minus number circuit 64 is 0.
As shown in FIG. 10(f), the waveform has a high-level period that decreases in sequence in response to the count value 59 of the counter 43 that decreases by a constant number, and the output cuff 0 is the output of the monomulti. It is output from terminal 71 as . As mentioned above, this output is supplied to the reset terminal trap of the flip-flop 18 (FIG. 4), and as a result, the fall timing of the capstan motor drive pulse 320, that is, the stop timing of the magnetic tape is controlled. It is shi.

It goes without saying that when the count value of the counter 43 increases by a fixed number, the high level period of the output signal KVi of the matching circuit 64 increases by a predetermined width.

〔Effect of the invention〕

As explained above, according to the present invention, the magnetic f −7′
When performing slow motion playback of a VTR by intermittent drive, the sequential stop positions of the magnetic tape are automatically moved to positions where no noise occurs on the playback screen. IIJaL automatically performs noiseless slow motion playback. In addition, it is possible to provide a control circuit for slow motion playback that has excellent functions while eliminating the drawbacks of the prior art described above.

[Brief explanation of drawings]

Figure 1 is a block diagram for explaining the conventional slow motion playback method in a VTR, Figure 2 is its operating waveform diagram, Figure 3 is the next diagram for explaining the basic principle of the present invention, and Figure 4 is for explaining the basic principle of the present invention. Figure 5 is a block diagram showing one embodiment of the present invention.
6 is a flowchart for explaining the operation of the embodiment shown in FIG. 4. FIG. 7 is a block diagram showing a specific configuration example of the phase comparator and delay time control circuit in FIG. 4. 8 is an operating waveform diagram, and FIG. 9 is a block diagram showing a specific configuration example of the monomulti in FIG. 4.
FIG. 10 is a diagram of its operating waveforms. 16... Frequency divider 17... Mono multi 1
8...Flip-flop 28-...DO (dropout) signal detector tail 1
Zu brother Z Zu Akira 3 Zu Kun 4 Kuchi Akira! 5 Figure"' j+ tz t3 t
4 tr ehL'5嶌Ra Bo≧ 7 times 18 Figure~S'7

Claims (1)

[Claims] The magnetic tape is activated intermittently using a activation signal obtained by frequency-dividing the head switching signal of the rotary head, and a signal obtained by appropriately delaying a control signal for tracking control reproduced from the magnetic tape after each activation. In a rotary head type video tape recorder in which the magnetic tape is stopped at a predetermined position, the magnetic tape is intermittently fed, and the same video track is repeatedly scanned multiple times by the rotary head during each stop period to perform slow motion playback. , means for detecting a drop in the level of a video signal reproduced from the rotating head during the stop period to a predetermined value or less, a phase comparison means for comparing the phase of the output of the detection means and the head switching signal, and the phase and a delay time control means for controlling the delay time of the control signal in accordance with the output of the comparison means to control the stop position of the magnetic tape, so that the magnetic tape is automatically moved to a position where noise does not occur in the slow motion playback image. 1. A control circuit for slow motion playback, characterized in that it is configured to be able to stop automatically.