JPH038026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing device, and particularly to a helical scan type magnetic recording and reproducing device (hereinafter referred to as
VTR (abbreviated as VTR) has been improved so that the recording seam will not be disturbed on the magnetic tape when recording is paused and then recording is restarted.
Regarding VTR.

FIG. 1 is an illustrative diagram of the recording state of a magnetic tape recorded by a helical scan VTR. In the figure, a video track 2 is normally recorded diagonally in units of one field on a magnetic tape 1.
In addition, control signals 3 are recorded at regular intervals in the tape running direction. This control signal 3 is
It is used to control tape travel so that the video head 5 can accurately scan the video track 2 at the playback position. In the following description, a signal before being recorded on the magnetic tape 1 will be referred to as a recording control signal, a signal recorded on the magnetic tape 1 will be referred to as a control signal 3, and a signal reproduced from the magnetic tape 1 will be referred to as a reproduction control signal J.

Normally, the control signal 3 is created by dividing the vertical synchronization signal of the video signal to be recorded by 1/2. Therefore, during playback, the control head 3
The running state of the magnetic tape 1 is adjusted so that the time when the magnetic tape 11 detects the control signal 3 coincides with the time when the video head 5 comes near the starting end of the video track 2 (that is, the part where the vertical synchronizing signal is recorded). controlled.

By the way, if the magnetic tape 1 is temporarily stopped at an arbitrary time during recording and then started again at an arbitrary timing and starts recording immediately, the recording phase of the video track 2 may differ at the joint, or the track may Because the angle of inclination changes,
There was a problem that the reproduced image of that part was distorted. For example, when the magnetic tape 1 is temporarily stopped, the running trajectory of the video head 5 becomes as shown by the dotted line 4 in FIG.

In order to prevent such disturbances at the joints of images, a circuit as shown in FIG. 2 has been used in conventional home VTRs.

Figure 2 shows a conventional VTR that performs continuous recording.
FIG. In the configuration, input terminal 1
1 is connected to a reference signal generator 12. The input terminal 11 receives a vertical synchronization signal A of the video signal to be recorded.
is given. The reference signal generator 12 divides the frequency of the vertical synchronizing signal A by 1/2 to derive a reference signal B for phase control of the drum servo system 20 and capstan servo system 30.

The drum servo system 20 includes a drum motor 21, a drum speed (frequency) detector 22, a drum speed error detector 23, an input terminal 24, a drum rotation phase detector 25, a phase comparator 26, an adder 27, and a motor drive circuit 28. including. A drum setting speed signal is input to the input terminal 24 .

The capstan servo system 30 includes a capstan motor 301 and a capstan speed (or frequency).
Detector 302, amplifier 303, capstan speed error detector 304, input terminal 305, adder 30
6. Drive circuit 307, input terminals 308 and 30
9. Phase comparator 310, control head 31
1. Recording/reproduction changeover switch 312 (hereinafter referred to as changeover switch), contacts 313 and 314, amplifier 315,
Recording amplifier 316, frequency divider 317, capstan phase comparison signal selection switch (hereinafter referred to as selection switch)
318 and contacts 319 and 320.

Here, the capstan speed error detector 304
is the speed signal (pulse signal proportional to frequency) detected by the capstan speed detector 302
A speed error detection signal D is derived by detecting the deviation between the capstan speed signal C and the capstan set speed signal C applied to the input terminal 305. Adder 306
is for adding the speed error detection signal D and the phase error detection signal I given from the phase comparator 310. The motor drive circuit 307 is for stopping or driving the capstan motor 301 in the reverse direction based on the motor stop command signal E or the motor reverse command signal F. Phase comparator 310
compares the phase comparison signal H selected by the selection switch 318 with the reference signal B derived from the reference signal generator 12, and derives the phase error detection signal I. The control head 311 records or reproduces the control signal 3.
The frequency divider 317 divides the frequency of the speed detection signal to generate a phase comparison signal H during recording.

Next, with reference to FIGS. 1 and 2, the specific operation in FIG. 2 will be explained.

First, the operation of the drum servo system 20 will be described. The drum (not shown) is driven by the rotation of the drum motor 21, and rotates at a constant speed in synchronization with the phase of the vertical synchronization signal A, both during recording and when recording is paused. Driven. However, since the drum servo system 20 is not related to continuous recording, detailed explanation thereof will be omitted.

Next, the specific operation of the capstan servo system 30 will be explained.

Operation during Recording During the recording operation of recording on the magnetic tape 1, the changeover switch 312 is connected to the contact 313 side (that is, the recording amplifier 316 side).
Further, the selection switch 318 is connected to the contact 320 side (ie, the frequency divider 317 side). At this time, the capstan motor 301 is rotationally driven by the drive circuit 307. The rotational speed of the capstan motor 301 is detected by a speed detector 302.
, and is amplified by an amplifier 303 and provided to a capstan speed error detector 304 and a frequency divider 317 as a square wave speed detection signal G. Capstan speed error detector 30
4 detects the deviation between the set speed signal C and the speed detection signal G, and supplies the error detection signal D to the adder 306. At this time, the frequency divider 317 divides the frequency of the speed detection signal G and provides the divided output to the phase comparator 310 via the selection switch 318.
The phase comparator 310 uses the frequency-divided phase comparison signal H as a phase feedback signal, amplifies the phase difference with the reference signal B, and provides the output phase error detection signal I to the adder 306. Adder 306 adds speed error detection signal D and phase error detection signal I, and uses the output to control the phase of drive circuit 307. With this, the capstan motor 301
The rotation speed is controlled by phase control.
Therefore, the magnetic tape 1 is transported at a constant speed during recording.

On the other hand, the reference signal B is used as a recording control signal to control the recording amplifier 316 and the changeover switch 3.
12 to control head 311. Thereby, the recording control signal is recorded in synchronization with the video track of the magnetic tape 1.

Operation when a temporary stop command is issued When a motor stop command signal E is applied to the input terminal 308 and a temporary stop command is generated, the recording operation is immediately stopped. Then, the changeover switch 312 and the selection switch 318 are switched to the contacts 314 and 319 side (ie, the playback side), respectively.

In addition, the motor reverse command signal F is input to the input terminal 30.
9, the motor drive circuit 307 reverses the capstan motor 301. Therefore, the magnetic tape 1 is transported in the opposite direction. Then, after the magnetic tape 1 has been transferred by a predetermined amount, the motor stop command signal E is given, so the capstan motor 301 is stopped again, and the transfer of the magnetic tape 1 in the reverse direction is also stopped, and the magnetic tape 1 enters a standby state.

Operation when the temporary stop command is canceled When the temporary stop command is canceled, the motor drive circuit 307 rotates the capstan motor 301 in the forward direction to start transporting the magnetic tape 1 in the forward direction.
At this time, the changeover switch 312 and the selection switch 320 remain connected to the reproduction side, and the recording operation is not started. Further, the capstan motor 301 is connected to the control head 31.
Phase control is performed using the reproduction control signal J reproduced in step 1 as a feedback signal. This state lasts at least as long as the time required for the playback control signal J to synchronize with the vertical synchronization signal A, that is, the time required for the phase of the previously recorded video track to match the phase of the newly recorded video track. Set.

Then, when the set time has elapsed, both the changeover switch 314 and the selection switch 318 are switched to the recording side, and the recording operation is restarted.
At this time, the output signal of the selection switch 318, that is, the phase comparison signal H of the capstan phase control system is converted from the reproduction control signal J to the frequency divider 317.
(a signal obtained by frequency-dividing the speed detection signal G), the frequency divider 317 is reset by the reproduction control signal J in order to match the phases of both signals at the time of switching.

As mentioned above, so that the joints are not disordered,
A continuous recording will be made. However, in the conventional circuit shown in FIG. 1, after the pause is released, the capstan motor 301 is started and the capstan phase control system is activated until the vertical synchronization signal A and the reproduction control signal J are synchronized. It takes a considerable amount of time to settle (stabilize), and the time required for this establishment usually takes about 1 to 1.5 seconds.
For this reason, the recording operation cannot be resumed until after the temporary stop is released and the required settling time has elapsed, which poses a problem in that the recording operation cannot be resumed promptly.

Therefore, the present invention was made to solve the above-mentioned conventional problems, and it is possible to prevent the recording joints from being disturbed and to quickly resume the recording operation after canceling the pause. The purpose of the present invention is to provide a magnetic recording/reproducing device.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIG. 3 is a circuit diagram of a VTR according to an embodiment of the present invention. This embodiment has the same configuration as the conventional circuit shown in Fig. 2, except for slight changes to the capstan servo system, and corresponding parts are given the same reference numerals and their explanation will be omitted. . The capstan servo system 30A in this embodiment differs from the capstan servo system 30 in FIG. .
Frame forwarding refers to the operation of sending a magnetic tape intermittently, and the video signal recorded on the magnetic tape is sent in one frame (for NTSC television signals, 30 frames per second). , one frame consists of two fields, and in a helical scan VTR, one image track consists of one
The operation of advancing by the amount (constituting the field) is called one-frame advance. The tape feed control that sends one frame at a time (in some cases, several frames may be sent) is called a frame feed operation. Further, depending on the direction in which the magnetic tape is fed, expressions such as forward frame feed and reverse frame feed are used. Here, the start-up command circuit 321 generates a capstan motor start-up command signal L based on the temporary stop release command signal K and the reference signal B applied through the input terminal 322. The control pulse generator 323 controls the frequency divider 31 based on the reference signal B.
This generates a control pulse for resetting 7. The reverse frame feed circuit 324 receives a pause command signal M given via an input terminal 325.
In response to this, the capstan motor 301 is temporarily stopped, and then the magnetic tape 1 is fed at least one frame in the reverse direction using the reproduction control signal J.

FIG. 4 is a time chart of each signal to explain the operation when a temporary stop command is issued.

FIG. 5 is a time chart of each signal when a temporary stop release command signal is received.

Next, the specific operation in FIG. 3 will be explained with reference to FIGS. 3 to 5.

Since the operation of the drum servo system is the same as the conventional one, a detailed explanation thereof will be omitted, and the operation of the capstan servo system 30A will be described below.

Operation during recording During recording, the changeover switch 312 is connected to the contact 313 side (recording amplifier 316 side), and the selection switch 318 is connected to the contact 320 side (frequency divider 317 side). At this time, the capstan motor 301 performs speed control based on the speed detection signal G and transfers the speed detection signal G to the frequency divider 3.
The rotation speed is controlled by phase control using a phase comparison signal H whose frequency is divided by 17. The magnetic tape 1 is being transported at a constant feed speed during recording. Further, the reference signal B is transmitted to the recording amplifier 3.
16 and a changeover switch 312 to the control head 311, and is recorded as a control signal 3 on the magnetic tape 1 at regular intervals along the tape running direction.

Operation when a temporary stop command is issued When the temporary stop command signal M is applied to the input terminal 325, the reverse frame feed circuit 324 performs the following operation. First, the reverse frame feed circuit 324
gives a stop command to the motor drive circuit 307 as a backward frame feed control signal N to temporarily stop the capstan motor 301 (period A in FIG. 4A). At this time, record/playback switch 3
12 and selection switch 318 are both switched to the reproduction side. Thereafter, the reverse frame feed circuit 324 performs a frame feed operation in the reverse direction at least once (or multiple times), and maintains the stopped state until the next temporary stop command is released. That is, the backward frame feed circuit 324 is
During the period shown in FIG.
to reverse the capstan motor 301. The motor drive circuit 307 shifts to coasting operation when the tape running speed (analog signal correlated to the speed detection signal G) shown in FIG. 4b reaches a predetermined value (period shown by c in FIG. 4a). . When the control head 311 detects the control signal 3 (see Figure 4c), the reverse frame feed circuit 323 switches the reverse frame feed control signal N to a braking command (d shown in Figure 4a). . As a result, the motor drive circuit 307
causes the capstan motor 301 to brake.
The braking operation of the capstan motor 301 can be performed by various braking methods, such as electromagnetic braking by short-circuiting the motor windings, or braking by generating reverse torque in the rotational direction.

When performing the above-mentioned operation, if the tape running speed during the coasting period C and the braking torque during the braking period D are always constant during reverse frame-by-frame feeding, the magnetic tape 1 that has stopped after the reverse frame-by-frame feeding operation is The relative position between the upper control signal 3 and the control head 311 is always kept constant no matter what timing the temporary stop command M is derived.

Note that this kind of operation is similar to conventional home use
This can be easily achieved using slow-motion playback and frame-by-frame playback techniques in VTRs, and there is no need to configure a particularly complex system.

Operation when a temporary stop release command is issued When the temporary stop release command signal K shown in FIG. A signal (see Fig. 5 d) synchronized with the rise of the signal (see Fig. 5 b) is internally derived, and from this the time
Motor start start command signal L ( _fifth
(see Figure e) is applied to the motor drive circuit 307.
In response, the motor drive circuit 307 immediately starts activating the capstan motor 301. Therefore, the rotational speed of the capstan motor 301 is
After the start-up time T _R shown in FIG. 5f has elapsed, the constant speed is reached. In the prototype, the required startup time _TR is set to approximately one frame period (approximately 30 m sec). However, since this time uses a practical value, it may be a short time depending on the specifications of the system.

At this time, the magnetic tape 1 is transferred in the forward direction, but both the changeover switch 312 and the selection switch 318 remain connected to the reproduction side.

By the way, in the stopped state before the pause is released, the relative positional relationship between the control signal 3 on the magnetic tape 1 and the control head 311 is as follows.
It is kept almost constant by frame-by-frame feeding in the reverse direction. Therefore, the capstan motor 301
The time T ₂ required for the control signal 3 to pass through the control head 311 after the motor starts starting and reaches a constant speed is always constant. Therefore, the phase of the reference signal B to be recorded, that is, the recording control signal (see Figure 5 i, k), and the previously recorded control signal 3, that is, the reproduction control signal J (see Figure 5 g), is so that it matches,
By setting the delay time _T1 , there is no need to monitor the playback control signal J during the playback operation when the pause is released, and the phase control by the playback control signal J is performed by the capstan motor 301.
There is no need to apply it.

That is, after the pause is released and until recording is restarted, the control pulse output from the control pulse generator 323 created based on the reference signal B (see FIG. 5j) is used as the phase comparison signal H of the capstan phase control system. ), the output I of the phase comparator 310 will have a fixed output phase that does not change at all. As a result, the capstan motor 30
1 operates in a state where only speed control is performed using the speed detection signal G. At this time,
If the phase relationship between the reference signal B and the control pulse is made equal to the phase relationship between the reference signal B and the speed detection signal G established by the capstan phase control system during recording, constant speed can be achieved. The subsequent tape running speed becomes approximately equal to the steady feed speed during recording. By optimally designing a servo system consisting only of such a speed control system,
In general, settling is extremely fast (that is, stabilization is fast), and it is easy to realize the characteristics shown in FIG. 5f.

Resuming recording operation To restart recording operation, press selector switch 3.
12 and selection switch 318 are both switched to the recording side. Therefore, the phase comparison signal H of the capstan phase control system is switched from the control pulse to the output signal of the frequency divider 317. At this time,
In order to match the phases of both signals at the time of switching, the frequency divider 317 is reset by a control pulse immediately before recording is restarted. This means that
This means that the phase control system starts operating only after recording is restarted.

Further, the recording operation may be started after the reference signal B rises after the tape running speed reaches a constant speed, for example, the time T ₃ of about two frame periods after the start of the motor shown in FIG. 5h. You can also start recording after a delay. In this case, the frame advance operation in the opposite direction is performed twice (i.e. 2 times).
If the number of frames is the same, there is an advantage that continuous recording can be realized with almost no double recording of video tracks.

In addition, in the above-mentioned embodiment, the capstan motor starting start command at the time of canceling the pause is set to the reference signal B.
Although this occurs in synchronization with the rotational phase detection signal of the capstan drum or with the head switching signal generated thereby, exactly the same operation can be achieved.

Further, in the above-described embodiments, the timing of stopping recording during a pause, the stopping timing of the capstan motor 301, or the timing of restarting recording are not explained in detail, but for example, any of the above timings can be used as a reference signal or a video head switching timing. By making appropriate settings in synchronization with the signal, it is possible to perform ideal continuous recording without causing any double recording of video tracks or unrecorded bands.

Furthermore, in the above embodiment, the control pulse created from the reference signal B is used as the phase comparison signal during the period from the release of the pause to the restart of the recording operation, but instead, the capstan phase comparison output is used in the control loop. Adder 3 included
06 to create a separate signal equivalent to the phase comparator output when a control pulse is used, and this signal may be input to the adder 306.

As described above, according to the present invention, there is no need to use mechanical means such as turning the pinch roller on or off with respect to the capstan shaft, the recording joint is not disturbed, and the recording operation when the pause is released is We can restart very quickly,
Unique effects such as continuous recording can be performed automatically so that the ideal condition is achieved.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing the recording state of a magnetic tape recorded on a helical scan type VTR. FIG. 2 is a block diagram of a conventional VTR. FIG. 3 is a block diagram of a VTR according to an embodiment of the present invention. FIG. 4 is a time chart for explaining the backward frame-by-frame feeding operation. FIG. 5 is a time chart for explaining the operation after the temporary stop is released, which is a feature of the present invention. In the figure, 1 is a magnetic tape, 20 is a drum servo system, 30, 30A is a capstan servo system,
301 is a capstan motor, 302 is a capstan speed detector, 311 is a control head,
317 is a frequency divider, 323 is a control pulse generator, 3
10 is a phase comparator, 318 is a selection switch, 32
Reference numeral 1 indicates an activation start command circuit, and reference numeral 324 indicates a reverse frame feed circuit.

Claims (1)

[Scope of Claims] 1. A magnetic recording and reproducing device that performs recording and reproduction using a helical scan method, in which control signals are recorded on the magnetic tape at regular intervals in the recording mode, and control signals are transmitted from the magnetic tape in the reproduction mode. A control head for reproducing signals, a capstan motor for rotating a capstan and running a magnetic tape, a speed detection means for detecting the rotational speed of the capstan motor, an output signal and a speed setting signal of the speed detection means. speed error detection means for detecting a speed error of the capstan motor based on a deviation from the magnetic field and controlling the capstan motor to a constant speed based on the speed error detection signal; a phase control means for controlling the rotational phase of the capstan motor using the control signal reproduced from the tape as a feedback signal for phase comparison; The magnetic tape is reversely fed by at least one frame by the push stamp motor, and the control head detects the recorded control signal while the frame is being fed in the reverse direction, and the control signal on the magnetic tape is detected by the control head. reverse direction frame feeding means for stopping the magnetic tape at a position where the magnetic tape has a fixed positional relationship with respect to the control head, and a vertical synchronization signal in the video signal to be recorded when the pause command is released; The apparatus further comprises a start-up command means for starting the capstan motor at a predetermined timing determined based on the output of a reference signal generator originally created, and after starting the start-up, the rotational speed of the capstan motor becomes constant. 1. A magnetic recording and reproducing apparatus, wherein recording is restarted at an arbitrary timing after the recording is performed, but during this period, phase control operation by the phase control means is disabled.