JPS5937784A - Controller for variable speed reproduction of magnetic video recording and reproducing device - Google Patents

Abstract

PURPOSE:To realize a variable speed reproducing function by a small-scale circuit easily, by detecting amplitude variation of a difference frequency component obtained by converting pilot signals of four kinds of frequency on the basis of a pilot of specific frequency and performing tracking control. CONSTITUTION:A reproduced pilot signal P0 is frequency-converted by a frequency converting circuit 31 with a pilot signal P2 from a pilot signal generating circuit 50 and the difference frequency component is outputted to detecting circuits 32 and 33. An amplifying circuit 34 amplifies the difference between outputs E and F of the circuits 32 and 33 and it is phase-inverted alternately according to pulses S from a circuit 15; and the output G is shaped into a rectangular wave signal and a pulse I is outputted every time it rises or falls. The output I is supplied to a frequency discriminating circuit 38, which outputs an error signal corresponding to variation of the pulse I. On the other hand, the output J of a frequency dividing circuit 42 is phase-compared with a reference signal to obtain an error signal, which is added to the error signal from the circuit 38 to supply the sum signal to a capstan motor 5, performing the tracking control.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable speed playback control method and apparatus for a magnetic recording/playback device such as VTIL.

In a conventional rotary head type VTR, when a tape recorded at a standard specified tape speed is played back at a different high speed, for example, 11 times the standard speed (n is an integer), the so-called tape Frequency f when the frequency of the control signal recorded on the control track at the end is the standard speed.

A method is generally used in which the tape running speed is controlled to be n times (~nX7o).

Further, when reproducing at standard speed, this control signal is used for tracking control for correctly scanning the video track recorded on the magnetic tag with the rotary head.

However, in conventional devices that perform tracking control using this control signal, the relative positional relationship between the control head that records and reproduces the control signal and the rotary head must be constant for each device; If the positional relationship between the two devices is different for each device, tracking will not be performed correctly, or if the control head's orientation and height relative to the tape are incorrect, the control signal will not be recorded and played back correctly, resulting in tracking control There were problems with the reliability of the device, such as instability.

In order to improve this, instead of using a control signal (eliminating the control head and control track), a so-called pilot signal is multiplexed with the video signal on the video track, and the adjacent tracks on the right are recorded at different frequencies. When reproducing this at standard speed, there is a method of tracking control by controlling the tape running speed so that the amount of crosstalk of pilot signals reproduced from both adjacent tracks is approximately equal to tl. has been adopted.

However, this method using Pyrobe No. 8 has the problem that it is not necessarily compatible with the conventional variable speed playback function that relies on control signals. An important issue was how to make this happen.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a servo control device that uses a conventional pilot method to easily realize a variable speed regeneration function with a small-scale circuit.

The present invention detects the amplitude change of the difference frequency component obtained by converting the frequency of a pilot signal that has been repeatedly recorded and played back at four different frequencies based on the pilot signal of a predetermined frequency7, and the frequency becomes constant. Tracking control is performed so that the data can be played back at any variable speed.

EMBODIMENT OF THE INVENTION Hereinafter, the case where the present invention is applied to a rotary two-head type VTR will be explained in detail with reference to an embodiment thereof.

t41 is a diagram showing a tape pattern of a video track formed by multiplexing a pilot signal according to the present invention with a video signal and recording at a standard specified tape speed.

FIG. 2 is a diagram showing an embodiment of a servo control device for reproducing and controlling tracking.

In FIG. 1, tracks A%B are recorded with video signals and pilot signals multiplexed by rotating magnetic heads 21 and 22 having mutually different azimuth angles in FIG. and formed.

Track A corresponds to the pilot signal fI or fs, and track B corresponds to the pilot signal f2 or f4, so that the signals f+, f2, f-, and f4 are sequentially and repeatedly recorded for each track. These pilot signals fI
, f=, fs, f- are determined, for example, as follows, where fTI is the horizontal synchronization frequency of the video signal.

The operation when tracking control is performed based on the pilot signal recorded after video signal pressure multiplexing as described above will be explained using a second practical example.

The magnetic tape 1e is driven to run by the cab stan motor 5. The rotary magnetic heads 21 and 22 are mounted on the disk 2 at an angle of 180 degrees to each other and rotate around the disk.
24 to rotate together with the disk 2. A magnet 3 is attached to the disk 2, which is detected by a tack head 13 to generate a pulse tack head 13 synchronized with the rotation of the magnetic head 21. The pulses from the tack head 13 are phase-adjusted by a phase adjustment circuit 14 so that the magnetic heads 21, 22 and the magnetic tape 1 are in a predetermined relative positional relationship, and then supplied to a pulse forming circuit 15. From this pulse forming circuit 15, a data ratio of 50 is synchronized with the rotation of the magnetic head 21, 22.
The first pulse S is output.

A 10-digit reference signal generation circuit generates a reference signal with a frequency approximately equal to the frame frequency of the video signal. The pulse S from the pulse forming circuit 15 is phase-compared with the reference signal from the reference signal generation circuit 10 in the phase comparison circuit 11, and a phase error signal corresponding to the phase difference between the two is outputted from the phase ratio comparison circuit 11. be done. This phase error signal is supplied to the disk motor 4 via the disk servo circuit 12, and as a result, the pulse S is servo-controlled to be phase-synchronized with the reference signal. It is rotated at a number of revolutions equal to the frequency. The video signal and pilot signal that are alternately reproduced field by field from the magnetic deso 1 by the magnetic heads 21 and 22 whose rotation is controlled in this manner are transmitted to the reproducing circuit 20 and reproduced field by field by the pulse S from the pulse forming circuit 15. The reproduced video signal is outputted to the terminal 100, and the reproduced pilot signal Pu is supplied to the frequency conversion circuit 51.

When playing magnetic tape 1 at standard speed, switch 5
1,52,53 are switched to the terminal X side.

Reference numeral 50 denotes a pilot signal generation circuit, in which the magnetic heads 21 and 22 alternately scan the magnetic tape 1 in response to pulses S from the pulse forming circuit 15. During the scanning period, the pilot signal f1 or f= is sent, and during the period when the magnetic head 22 scans the tape, the pilot signal f2 or f4 is sent.
And, fl, f-1f-f4 are repeatedly generated in this order.

This pilot signal P1 is supplied to the frequency conversion circuit 31 via the X-side terminal of the switch 51.

The frequency conversion circuit 31 performs frequency conversion according to the regenerated pilot signal Po from the regeneration circuit 20 and the pilot signal P1 from the pyro signal generation circuit 50, and the difference frequency component between the two is outputted by the frequency conversion circuit 31. The signals are supplied to detection circuits 32 and 35 which are composed of tank circuits (or bandpass filters) having resonance frequencies fm and 3fH, respectively, and a circuit for envelope detection of the output thereof. The output E from the detection circuit 32 is sent to the frequency conversion port wS51.
When the difference frequency component of the output from the frequency conversion circuit 31 is fTI, the output F of the detection circuit 33 becomes maximum when the difference frequency component from the frequency conversion circuit 31 is sfm.

In FIG. 1, first, during a period in which the magnetic head 21 scans the track Ag on which the pilot signal fI is recorded, the pilot signal generating circuit 50 generates the pilot signal f.
1 is output. When the magnetic head 21 causes a tracking deviation from the scanning center of track A5 and deviates toward one adjacent track fJs, crosstalk (Po and P
The components of f1 to f = = fE increase as the difference frequency component of l, and conversely, the other adjacent track B! If it shifts to the side, the components of crosstalk f1 to f4=sfn increase.

During the period in which the magnetic head 22 continues to scan the next track mountain on which the pilot signal f= is recorded, the pilot signal r2 is output from the pilot signal generation circuit 50, and the pilot signal r2 is output from the scanning center of the track Rs to one adjacent track A4 side. If the deviation occurs, the crosstalk of the pilot signal output from the frequency conversion circuit 31 is 1゛! ~fm=
When the component of 5fn increases and shifts toward the other adjacent track 85, the components of crosstalk f2 to f1=fH increase.

In the amplifier circuit 34, in response to the pulse S from the pulse forming circuit 15, during the period when the magnetic head 21 scans the tape, the f11 component which is the output from the detection circuit 32 and the 3fH component which is the output from the detection circuit 53 are generated. The difference numerator n-
During the period when 5fH is amplified and the magnetic head 22 scans the tape, the 3fH component output from the detection circuit 33 and the f> output from the detection circuit 32 are calculated as the difference between the 3fH component, which is the output from the detection circuit 33, and f>, which is the output from the detection circuit 32, with the polarity opposite to the above. 5fu-fu is amplified, and the output G from this amplifier circuit 54 is passed through a low-pass filter 55 and a switch 5.
2. Via the addition circuit 36 and motor drive amplifier circuit 37,
It is supplied to the capstan motor 5.

As a result, for each track, the crosstalk components from both adjacent tracks, fH and 5fH, are approximately equal.
That is, tracking control is performed so that the scanning center of the track is scanned correctly.

A frequency generator 6 is attached to the capstan motor 5 and generates a signal with a frequency corresponding to the number of revolutions of the capstan motor 50, and this signal is supplied to the frequency discrimination circuit 38 via a switch 53. Ru. The frequency discrimination circuit 3 discriminates the frequency of the signal from the frequency generator 6 and outputs an error signal corresponding to the variation in the rotation speed of the capstan motor 5. This error signal is supplied to the capstan motor 5 via the adder circuit 36 and the motor drive amplifier circuit 57.

As a result, the capstan motor 5 is servo-controlled to rotate at a constant speed, and the tape 1 is run at a predetermined standard speed.

The above is an explanation of the operation of the servo control system when the magnetic tape 1 is reproduced at the standard speed.

Next, the operation of the servo control system during variable speed playback according to the present invention will be explained using the waveform diagram shown in FIG. explain.

In FIG. 2, when performing high-speed reproduction in the reverse direction, the rotation direction of the capstan motor 50 is reversed and the switches 51, 52.
551: Switched to terminal Y Ill. The pilot generation circuit 50 generates pilot signals f1f2, f5 . f
=, for example, the pilot signal f2, is selected and continuously outputted from the pilot signal generation circuit 50. This pilot signal P! is the frequency conversion law via the terminal Y of the switch 51, @! 51.

40 is a rectangular wave shaping circuit, 41ti frequency doubling circuit 42
These are a ij frequency divider circuit and a 43-digit phase comparator circuit.

Figure 1 shows the magnetic head 2 when playing in the reverse direction at 3x speed.
The scanning trajectory of the magnetic head 22 on the tape 1 is indicated by the broken line, and the scanning trajectory of the magnetic head 22 is indicated by the broken line B.

FIG. 3 is a diagram showing the reproduced waveforms of each part at this time.
-') indicates the reproduced output waveform U from the tape, and N indicates the portion where the reproduced output level is minimum and observed as a noise band on the reproduced screen.

(Il) shows the waveform of the pulse S from the pulse forming circuit 15. During the period when the pulse S is at a high level, the head 21 scans over the track A, and during the period when the pulse S is at a low level, the head 22 scans over the track B. scan.

Therefore, as shown in <b> of FIG. 3, during the period of scanning A, tracks B4, A4, . In the period of scanning B in the order of Bs and As, tracks B5, A5, and J are scanned.
, 32, A2, and the mountain, and then the same material is sequentially scanned.

That is, in the case of reverse high-speed playback, two successive tracks or ranks are repeatedly scanned twice in the reverse order to the tonk order during SL recording, and instead of head scanning. (In the example of FIG. 1, when the amount of scanning from person to B is small, ■ jitter, [3i%As is scanned twice.) Therefore, from the reproduction circuit 20, the pilot signal PO
are in the order of J4, f5, J2, and Jol, and when the head scan is performed with a small amount, two pilot signals (in the example of FIG. 1, pilot 7 signals f2 and fl) are repeatedly reproduced twice. This regenerated pilot signal Po is frequency-converted from the pilot signal pt (frequency f-) from the pilot signal generation circuit 50 in the frequency conversion circuit 31, and the difference frequency components that are the output thereof are expressed as f1 to f==fH. That is, the track As where the pilot signal f1 is recorded
, Ai, A's..., the maximum output is obtained from the detection circuit 32. Tracks Aa, ha, As, etc. that are farthest from these tracks
When scanning . . . , the output of the detection circuit 52 becomes minimum. Therefore, the output E from the detection circuit 52 is
A continuous waveform is obtained as shown in FIG. 3(d).

Similarly, the output F from the detection circuit 55 has a waveform similar to that of the output E from the detection circuit 32, except for the polarity, as shown in FIG. 3(#).

In the amplifier circuit 34, the difference between the outputs E and F from the detection circuits 32 and 33 is amplified, and the phase thereof is alternately inverted according to the pulse S from the circuit 15.

That is, during the period when the pulse S is at a high level (scanning period of A), the difference (EF) between the two is amplified, and during the period when the pulse S is at a low level (scanning period of B), the difference (E-F) is amplified with the opposite polarity to the above. F
-E) is amplified.

As a result, the output G1-1 from the amplifier circuit 34, FIG.
As shown in 1), the phase discontinuity of the outputs E and F is removed, resulting in a continuous waveform.

As is clear from the figure, the repetition frequency of the output G from the amplifier circuit 34 is equal to 2.5 times the frequency of the pulse S (ie, the frequency approximately equal to the frame frequency).

In general, the frequency fn of this output G is given by the following equation when the frequency of the pulse S is fs when high-speed reproduction is performed n times in the opposite direction to the standard speed (n is an integer a).

fn −f s X (n+2) / 2 --=
(2) The output G from the amplifier circuit 34 is sufficiently amplified by the rectangular wave shaping circuit 40 and shaped into a rectangular wave signal H as shown in FIG. 5(g).

The frequency of the rectangular wave signal H from the rectangular wave shaping circuit 40 is doubled in the frequency doubling circuit 41, and a pulse (Fig. 3 (A)) is output every time the signal H rises and falls. be done. The frequency doubled pulse I is divided into 1/(L1+2) (115 when 1dn=5 in the example) in the frequency dividing circuit 42, and the output pulse J (fsS diagram (I) ) is supplied to the phase comparison circuit 45.

As is clear from the above explanation, the frequency doubling circuit 41
The frequency of the output ■ from the frequency divider circuit 42 is equal to fs X (n+2), and the frequency of the output J from the frequency divider circuit 42 is equal to fs.

The output (2) from the frequency dividing circuit 7+1 is supplied to the frequency discrimination circuit 3 via the switch 53, and an error signal corresponding to the frequency fluctuation of the pulse (2) is outputted from the frequency discrimination circuit 58.

On the other hand, the phase comparison circuit 43 compares the phase of the output J of the minute one revolution w542 Kerr et al. with the reference signal from the reference signal generation circuit 10, and outputs an error signal according to the phase difference between the two. Ru. This error signal and the error signal from the frequency discrimination circuit 38 are added together in an adding circuit 36 and then supplied to the capstan motor 5 via a motor drive amplifier circuit 37.

As a result, the tape running speed is controlled so that the frequency fn of the output G from the amplifier circuit 54 becomes a constant value determined by the above equation (2), and the frequency fn of the output G from the frequency dividing circuit 42 is controlled.

The pulse J is controlled to be phase-synchronized with the reference signal from the reference signal generation circuit 10, while the pulse S is servo-controlled to be phase-synchronized with the reference signal from the reference signal generation circuit 10. Tracking control is performed so that the pulse S and the output G from the amplifier circuit 54 are phase-synchronized, and as a result, stable high-speed playback is performed with the noise band N appearing on the playback screen fixed at a fixed position. .

In the above example, playback is performed in the reverse direction at a high speed that is an odd number (n-3) of the standard speed, but when playback is performed in the reverse direction at a high speed that is an even number, for example, playback is performed at double speed (n = 2). The waveform diagrams of each part corresponding to FIG. 3 in the case are shown in FIG. 4 (II) to (A
). If n is an even number (n=2m%m is an integer),
The frequency fn of the output G is given by the following equation from equation (2).

fn = fs X (m+ 1)−−−・−・−(
3) Therefore, in this case, the frequency doubling circuit 41 shown in FIG. Output J (Figure 4 (A)) which is directly supplied to J and divided into 1/(m+1)
may also be supplied to the phase comparator circuit 43, and tracking control similar to that described above can be performed.

In the embodiment shown in FIG. 2, the frequency doubling circuit 41
The output H from the rectangular wave shaping circuit 40 may be supplied to the frequency discrimination circuit 38 instead of the output (2) from the square wave shaping circuit (2). Furthermore, during high-speed reproduction, the output from the frequency generator 6 may be supplied to the frequency discrimination circuit 58 as in the case of standard-speed reproduction, without using the above output H%I. For example, even if the S/N ratio of the reproduced pilot signal is not sufficiently high, it is possible to stably control the running speed of the tape.

In addition, since the reference signal from the reference signal generation circuit 10 and the pulse S from the pulse forming circuit 15 are combined in phase synchronization, the reference signal from the four quasi-signal generation circuit 10 is input to the phase comparison circuit 430 as a reference signal input. Instead, the pulse S from the pulse forming circuit 15 or the like may be supplied.

As described above, according to the present invention, the variable speed reproduction function, which has been a problem in the conventional pilot system, can be easily realized with a relatively small-scale circuit. According to the method of the present invention, it is possible to fix the noise band and reproduce it at any variable speed, and in addition to the advantages of the Byron method,
It is possible to improve the reliability and functionality of the device.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a tape pattern of a video track on which a pilot signal is recorded according to the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 43 is a waveform diagram of each part thereof, and FIG. The figure is a waveform diagram of each part based on another embodiment. 50... Pilot signal generation circuit 31... Frequency conversion circuit 32. 35... Detection circuit 34... Amplification circuit 40... Rectangular wave shaping circuit 41... Frequency doubling circuit 42... Frequency division Circuit 43...phase comparison circuit

Claims (1)

[Scope of Claims] A magnetic recording and reproducing device that sequentially multiplexes four-frequency pilot signals with a video signal in a predetermined order every scanning period of the magnetic head, records and reproduces the same using a rotating magnetic head, means for separating the pilot signal multiplexed thereon from the reproduced video signal when reproducing the tape in the reverse direction at a tape speed different from that during recording; and a predetermined predetermined signal equal to any one of the reproduced pilot signals from the means. a frequency conversion circuit that converts the frequency of the regenerated pilot signal based on the pilot signal from the pilot generation circuit; and a frequency conversion circuit that detects an amplitude change in the output from the frequency conversion circuit. It has a detection circuit, and an amplifier circuit that alternately phase-inverts and amplifies the output from the detection circuit every scan period of the nuclear magnetic head, and the output from the amplifier circuit is connected to the tape so that the output from the amplifier circuit is phase-synchronized with the rotation of the nuclear magnetic head. A control device for variable speed playback of a magnetic recording and playback device that controls the speed very finely.