JPS60143079A - Slow motion reproduction servo-system - Google Patents

Abstract

PURPOSE:To execute smoothly transition to still reproduction from intermittent feeding by setting a phase comparing means at the operation center value of phase comparison and by releasing the set operation at the time of terminating intermittent feeding. CONSTITUTION:A phase comparing means 8 is set at the operation center value of phase comparison by a head switching signals S5 during intermittent feeding. Then, at the time of terminating intermittent feeding, that is, for the still reproduction period, the set operation is released. When intermittent feeding terminates, a correction circuit 6 of the speed servo is also released the correction operation. Thus, reverse corresction of the speed servo by the phase servo can be suppressed. Therefore, transition from intermittent feeding to still reproduction can be executed smoothly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a slow-motion reproduction servo system for a magnetic recording and reproducing apparatus that enables slow-motion reproduction of a system that repeats intermittent V and still reproduction.

Conventional Structure and Problems A method of repeating intermittent forwarding and still playback has been adopted as a method for slow motion playback in a magnetic recording/reproducing apparatus (VTR). The configuration and operation of conventional slow motion playback will be briefly explained below.

FIG. 1 shows an operational waveform diagram of intermittent feeding during conventional slow-motion playback, and FIG. 2 shows a tape playback pattern during slow-motion playback.

In FIG. 1, Sl is a capstan motor current waveform, S2 is a head switching signal waveform, S3 is an intermittent command signal waveform, S4 is a control signal waveform, S5 is a slow tracking signal waveform, and S6 is a flake signal waveform.

As shown in FIG. 1, the control of the capstan motor during intermittent feeding, that is, the tape transport, consists of three steps: acceleration, constant speed, and deceleration, and the stop periods before and after these steps are still playback. Since the intermittent feed period is approximately 2 frames (4 fields), variable speed slow motion playback is possible by arbitrarily setting the stop period. Now, rotation 2 of azimuth recording method
Taking a head VTR as an example, the video track pattern shown in FIG. 2 is recorded and formed on two opposite azimuths arranged at 186 on a rotary cylinder using nodes A and B. (The track pattern is shown in a different shape from the actual pattern - perpendicular to the longitudinal direction of the tape, to make the operation easier to understand.

) And when playing the same trunk multiple times,
For each head A, H, auxiliary throat A' with the same azimuth at the 1SO position.

A configuration is adopted in which a main head and an auxiliary head are combined. Here, there are two types of slow motion playback VC: frame slow playback and field slow playback. In contrast to the zero screen, which is unstable, the latter field throw is configured to reproduce either the odd field or the even field, and the screen is stable. Figure 1.

FIG. 2 is an example of the latter.

In Figure 2, the scanning angle during normal recording and playback is 90
0, and the still playback scanning angle at the time of stop when the tape does not move in the direction of the arrow is as shown by the dotted line.0Here, in order to make one section easier to see, the playback pattern shows only the center line of the scanning locus.

During the stop period, the main head B-auxiliary head B' performs still playback of the recording track B, and the main head B moves to the playback intermediate position a,
That is, the midpoint a of the L'' level period of the head switching signal S2
generates an intermittent command signal S3 and gives an acceleration command to the cab stan motor.

When tape transport is started in response to an acceleration command, the scanning trajectory gradually shifts from a still playback trajectory to a normal playback trajectory, with one section a-b being played back by the main head B, and a section b-c being played back by the auxiliary head B'. - When the acceleration period in which the auxiliary head B' reproduces the vicinity of point C ends, the speed servo of the capstan motor enters constant speed control and the reverse azimuth recording track is reproduced by the auxiliary head A' close to normal reproduction. Section c on the scanning trajectory
-Play d.

The tape speed during this constant speed period is set to about 0.8 to 0.9 times that of normal playback for one field slow playback.
Also, during this constant speed period, the control signal S4 is regenerated, a slow tracking signal S5 is generated, a brake signal S6 for deceleration is created, and the deceleration by the brake signal SsK is started from the time when the auxiliary head A' reproduces the vicinity of point d. , and the next recording track B is reproduced by the auxiliary head B'. When deceleration begins, the trajectory gradually shifts to a still reproduction trajectory, and the section d-e is reproduced by the auxiliary head B', and the section e-f is reproduced by the main head B. Then, at the time when the main head B reproduces near point f, the stoppage of the capstan motor is detected - the brake signal S6 and the intermittent command signal $3 are stopped, the intermittent feed period ends, and the stop period starts again. Do the following. Thereafter, the same operation is repeated by setting this stop period arbitrarily.

For the slow motion playback described above, the cab's tongue servo system for transporting the magnetic tape and the rotary head servo system for controlling the rotation of the rotary head are constructed as follows. The capstan servo system uses only the speed servo and the phase servo as well. At this time, instead of the phase error output of the -phase servo, a method is adopted in which the voltage is switched to a voltage equal to the center voltage during operation. On the other hand, the rotary head servo system is KOI for both speed servo and phase servo, and rotation control is performed so that the relative speed of the tape and head during still playback matches the relative speed during normal angular playback (or recording).
During intermittent feeding, the relative speed is corrected by adding correction to the /8: speed servo that involves relative speed changes. At this time,
If correction is applied only to the speed servo, the phase error output of the phase servo will change and a reverse correction command will be issued. Therefore, the phase of the reference signal is shifted in response to the periodic change of the head switching signal S2 of the one-rotation head. The configuration is such that no change in phase error occurs. However, with such a phase shift method, it is difficult to correct the phase of the reference signal on a 1:1 basis by exposing the periodic change in the head switching signal S2, and the circuit configuration becomes complicated, so the average This is a simple configuration that performs a fixed amount of correction. Therefore, screen shaking during intermittent feed is reduced.1. However, it is not possible to reduce the change in phase error to zero, making it impossible to perform correction using only one speed servo, and when canceling phase shift correction when transitioning from intermittent feed to still playback, the change in phase servo becomes impossible. There were problems such as the synchronization pull-in was not performed smoothly and the still screen did not stabilize immediately due to transient response.

OBJECTS OF THE INVENTION The present invention solves the conventional problems and eliminates the change in the phase error of the rad servo system phase servo during rotation during intermittent feed, and can smoothly transition from intermittent feed to still playback. The object of the present invention is to provide a slow motion playback method.

Structure of the Invention The present invention is a slow motion playback method that repeats intermittent feed and still playback, and at least during a period including the intermittent feed period, the phase comparison means of the phase servo of the rotating head servo system is activated by a head switching signal. The set operation is set at the center value of the phase comparison operation, and the set operation is canceled during other periods, and the phase comparison means is configured with a binary counter, and corresponds to the center value of the phase comparison operation. The invention is characterized in that the setting operation is performed by presetting the binary counter to a count value.

DESCRIPTION OF EMBODIMENTS FIG. 3 shows an embodiment of the slow-motion reproduction servo system of the present invention. A and B are main heads with different azimuth angles, and they are arranged on a rotating cylinder at a distance of 186 degrees from each other. Approximately 18cm 3 rolls A'' record or reproduce signals on the running magnetic tape 1. A/ and B/ are auxiliary heads with the same azimuth as the main heads A and B, and are used for the main heads. The cylinder motor 3, which drives the rotating cylinder, is a frequency generator that detects the number of rotations of the cylinder motor 2. Machine (FG)
, 4 is a speed comparison means that detects the speed error S2 from the FO signal S1 detected by the FG3, 5 is a mixing circuit that mixes the speed error 82 and the phase error 87, and 611-1 is the output S3 of the mixing circuit 6 and the intermittent command signal. S4 is a human-powered correction circuit that corrects the relative speed during intermittent feeding; 7 is a drive circuit that receives the output of the correction circuit 6 as an input and drives the cylinder motor 2; 13 to 3 constitute a speed servo. 8 is a phase comparison means which inputs the phase error output S7 to the mixing circuit 5 of the speed servo to constitute a phase servo. The phase comparison means 8 is composed of a digital circuit, and its constituent elements are a pulse generation circuit (L, P, G) 9, a pulse generation circuit (L, P, G) 9,
J set pulse generation circuit (jP, G) 1o, gate circuit 11. Digital phase comparison circuit (D, P, C) 1
2. Internal reference signal generation circuit (RoS, G) 13.

In the above configuration, during slow motion playback, both the speed servo and phase servo are set so that the relative speed during still playback is approximately equal to the relative speed during normal recording or playback, and during intermittent feed, the intermittent command signal S4 is used. The correction circuit 6 is activated to correct the speed servo so that the relative speed does not change. On the other hand, the phase servo has a phase error of 87
In order to avoid applying reverse correction to the speed servo due to a change in
The configuration is such that the set operation is canceled when the missing feed is completed.

Once the intermittent feeding is completed, the speed servo correction circuit 6 also cancels the correction operation. - By repeating the above operations during slow motion playback, stable slow motion playback is possible.

The present invention provides novelty to the phase comparison means 8 of the phase servo. The configuration and operation of the phase comparison means 8, which is a main block of the present invention, will be explained below with reference to the waveform diagram of FIG.

L, P, and G9 include a head switching signal S6, a clock pulse S6, and an intermittent command signal S4 for selectively switching and extracting the reproduction output of the rotary heads A, A, A', and B' obtained by detecting the rotation of the rotary cylinder. is input, and the intermittent command signal S is generated in advance of the latch pulse S8 in terms of timing.
Preset pulse S9 is output during the period in which 4 is occurring.
Then, a prohibited clock 810 is created in which the clock pulse S6 is prohibited during the latch operation period. P, P, G10 have clock pulse S6 and internal reference signal S1 of R, S, G13.
3 to create a preset pulse S11. The gate circuit 11 has 1. P, G9 preset pulse S
9 Input the preset pulses S11 of to-p, p, and Gio, and obtain a logical sum (OR) output 512. D.jol
2, a latch pulse S8, a preset pulse S9, and an inhibit clock 810 are input. In a normal phase comparison operation, the binary counter comprising n, p, and G12 is preset to the initial counting value NP by the preset pulse S11, and a trapezoidal wave signal of any number of songs, such as the one shown in FIG. Form. Then, the trapezoidal wave signal S1 is generated by the latch pulse S8.
4 is sampled, that is, latched, and the phase is compared, and the phase error 87 is calculated by one person). Here, T1 of the trapezoidal wave signal 814
T2 is the first half period and T2 is the second half period, indicating a phase-locked steady state.

If T2 is set to a fixed value and T1 can be arbitrarily set by switching NP, the relative speed during still playback can be made to match the relative speed during normal recording or playback. By the way, the internal reference signal S13, P, 01
By tecoding the count output of 2 with l't, S, and G13, a pulse is generated at the end of the second half period T2, and jjGlo creates a preset pulse S11 to preset NP, and then T+, T2 again. A closed loop is formed by repeating.

During still playback, the cycle of the head switching signal S6 coincides with one cycle T+-1-Tz of the internal reference signal S1s, but during intermittent feed, it is necessary to correct the speed servo and perform relative speed correction. The period of the switching signal S6 is T
does not match i+T2, and the sampling position is trapezoidal wave signal 8
The phase error 87 changes as the center position of the inclined portion of No. 14 moves away from the center of operation, that is, the center of operation. Therefore, in the present invention, during the period of intermittent feeding, the count value with respect to the center of operation value of the phase comparison is The configuration is such that NO is preset, so that the phase error 87 does not change during this period and becomes the value at the center of the operation, thereby eliminating reverse correction of the speed servo and smoothing the transition from still playback to intermittent feed. . Further, after the intermittent feed, the preset operation for the count value NG is canceled and the preset operation for still playback is restored, thereby making the transition from intermittent feed to still playback smooth.

As explained above, in the present invention, the phase comparison means 8 is set to the operation center value of the phase comparison (count value NCK preset) by the head switching signal 86 during the intermittent feed period, and the above-mentioned setting is set during the other periods (still playback period). By configuring the operation to be canceled, the reverse correction of the speed servo caused by the phase servo can be eliminated, and the transition from intermittent feed to still playback (the same goes for the transition from still playback to intermittent feed) can be made extremely smoothly. The set operation mentioned above may be performed as long as it includes intermittent feed, and may be performed immediately after the transition from intermittent feed to still playback. Of course, it is also possible to cover the entire period of slow-motion playback if it is sufficient for only the slow-motion playback.

However, the above-mentioned phase comparison means 8 is not limited to the configuration shown in FIG. 3, but may include a set function for setting the operation center count value NO, which has a higher priority than the preset function for presetting the initial value NP. For example, preset value switching of NP and NO in D and jCl 2 and the gate circuit 11 can be made unnecessary.

Furthermore, it goes without saying that a configuration in which the preset function is modified can also be applied.Furthermore, the present invention can also be applied to a phase servo of a capstan servo system, and by performing an operation center setting operation over the entire period of slow motion playback. The speed servo can be operated stably.

Effects of the Invention As is clear from the above explanation, in the present invention, the phase comparison means of the rotating head servo system is set to the operation center value of the phase comparison by the head switching signal during the period including intermittent feed during slow motion playback. However, since the set operation is canceled during other periods, the reverse correction to the speed servo can be eliminated, and the transition from intermittent feed to still playback and from still playback to intermittent feed can be made smooth and stable. Slow motion playback can be made into a town, and the practical effect is a dog.

[Brief explanation of drawings]

FIG. 1 is an operating waveform diagram of a conventional slow motion control reproduction method, FIG. 2 is a conventional slow motion reproduction tape pattern diagram, and FIG. 3 is a block diagram showing the basic configuration of the slow motion reproduction method of the present invention. FIG. 4 is an operational waveform diagram of the main blocks of the present invention. 1... Magnetic tape, 2... Cylinder motor, 3... Frequency generator, 4... Speed comparison means, 5... Mixing Circuit, 6...
Correction circuit -7... Drive circuit -8... Phase comparison means, 9... L, P, G (latch pulse generation circuit) -10... p, p, c,
(preset pulse generation circuit), 11...gate circuit, 12...D. p, c (titeral phase comparator circuit), 13...
RoS, G (internal reference signal generation circuit), M, B...
...Rotating main head, AI, B/...Rotating auxiliary head. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2-A-1-B-→-A-→-B-→-4-Figure 3

Claims (3)

[Claims] (1) In a slow motion playback state in which intermittent feed and still playback are repeated, at least during the period including the intermittent feed period, the phase comparison means of the rotating head servo system phase servo is set to the operating center value of the phase comparison by a head switching signal. A slow motion playback servo method characterized in that the set operation is canceled during Seriton and other periods. (2) A patent claim characterized in that the phase comparison means is constituted by a binary counter, and the setting operation is performed by presetting the binary counter to a count value corresponding to the operation center value of the phase comparison. The slow motion reproduction servo method described in item 1. (3) In a slow motion playback state in which intermittent feed and still playback are repeated, at least during the period including the intermittent feed period, the head switching signal causes the phase comparison means of the rad servo system phase servo to rotate to the operating center value of the phase comparison. In other periods, the set operation is canceled, and during slow motion playback, the capstan servo system phase servo phase comparison means of the phase servo is controlled by the capstan motor rotation detection signal. A slow motion playback servo system characterized by setting the operation center value.