JPS59175054A - Magnetic video reproducer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic recording and reproducing apparatus having a variable speed function by intermittent driving of a magnetic tape.

[Background of the invention]

In a rotating head helical scan type magnetic recording/reproducing device, some kind of synchronizing signal is recorded on the magnetic tag during recording, and the synchronizing signal is reproduced during playback to control the rotational phase of the capstan or rotating head cylinder. Tracking control is performed by a servo circuit so that the rotating head correctly traces the video signal recording track of the magnetic tape.

As a synchronizing signal, a method is used in which a pulse signal having a period of 1/2 of a vertical synchronizing signal, usually referred to as an o~le signal (abbreviated as CTL), is written into the end of the tape. In the method using this control signal, no matter what speed the magnetic tape is running, such as intermittent running, the CTL
The absolute phase with respect to the recording pattern of the magnetic tape when the partner number is detected is uniquely determined.

For this reason, intermittent drive is used to instantly run a magnetic tape that is stopped in a noiseless still state to a noiseless state after one frame, and to perform noiseless a-motion by repeating this operation at appropriate time intervals. In the CTL system, variable speed regeneration could be easily implemented by performing stop control including reverse braking of the capstan motor after a predetermined time delay after detection of the CTL signal.

The method described above was for a method that uses the CTL I,@ number, but in another servo method, a method in which synchronization signals are superimposed on the video track (abbreviated as the pilot method), a jealous signal is used instead of the CTL signal. It is necessary to obtain a tracking error signal from the level of the reproduction by-limit signal during running or stop periods, and use this information to control the intermittent drive of the magnetic tape.

However, if the tracking error signal has a sufficiently large time constant M
Unlike normal playback, in which servo control can be performed on average through a low-pass filter, the tracking error signal information in cases where high-speed response is required, such as in intermittent drive, has a poor S/N ratio and cannot be as noiseless as the conventional CTL method. It was not possible to realize intermittent drive.

[Purpose of the invention]

The object of the present invention is to overcome the drawbacks of the prior art described above by providing a variable speed control system using intermittent drive that can control the stop to a noiseless still state with an accuracy equal to or higher than when using a conventional CTL, even when using a regenerated pilot signal. There is K, which provides a magnetic recording and reproducing device with the following functions.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention is designed to control the intermittent drive of a magnetic tape by using information during the stop period as effectively as possible, by converting a reproduced pilot signal converted into a digital quantity into one frame. The digital integration process is performed over a predetermined plurality of fields during the stop period, and based on all the integrated values, a good signal-to-noise ratio corresponding to the amount of deviation from the normal noiseless stop state is obtained. We adopted a means to generate a stop error signal.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram of a magnetic recording and reproducing apparatus according to an embodiment of the present invention.

In FIG. 1, 1 is a magnetic tape, 2 is a cylinder motor, 3 is a rotary video head, and 4 is an intermittent drive control circuit 16 that detects the rotational phase of the cylinder and includes a servo circuit, and a head switching signal svs.

5 is a capstan motor, 6 is a signal circuit for taking and suspending low-frequency components from the video head output, 7 is a tracking error signal processing circuit using a pilot method, and 8 is the four local circuits described below. a bandpass filter (BpFl) for selectively passing a bimit signal having a frequency of Mf; 9 a mixer for mixing the outputs of the local frequency generator 10 and E p F; 1;
1 and 13 are full-band bass filters CBPFs that selectively pass specific pilot frequency differences and output 5fx errors and hr errors, respectively; -12 and 14 are detectors.

15 is a frequency detector, 17 is an AD (analog tintal) converter, 18 is a subtracter, 19 is an integrator (or accumulator), 20 is a data latch, and 21 is a comparator.

22 is a circuit for generating these stop error signals, and an intermittent drive mode command and a head switching signal 5IV50.
This is a control circuit for controlling based on the timing of .

Next, the operation of an embodiment of the present invention will be described using FIG. 1, a pattern diagram of intermittent driving in FIG. 2, and a signal waveform diagram of each part in FIG.

In this embodiment, four types of pilot frequencies are used as pilot systems: f2 (6b51x) and f2 (Z5ht).
.

The following describes how j's (1a, 5f7z) and h (9, 5fi) are written into a video track field by field in this order. Here, jtr is the horizontal synchronization frequency. In addition, #MJfll of the pilot method regarding normal recording playback
: is well known and will not be described in detail.

In Figure 2, m + , 7't s fs + f'
4. J + I jz is a track on which a pilot signal is pre-recorded, oblique part (A) I (B) , (A) shows the head trajectory with intermittent drive and stopping every time, (IZ) , <b> represents moving by intermittent drive. In addition, in non-embodiments, CA) f (B), C only during playback
A)...I will explain the so-called field steal, which reproduces everything at the same azimuth, but normal frame stills can be considered in the same way.

First, the stop error signal corresponding to the amount of deviation from the normal noiseless state in the stop state CA) is generated by S
Explain that there are many ways to defraud people.

In the intermittent drive mode, the control circuit 22 fixes the local frequency mixed with the regenerated pilot signal plLOT to, for example, h. At the position CA), the error signals obtained from both adjacent tracks during the stop period of the first prisoner, the 5fz error and the jx error, are as shown in FIG. Therefore 5ftt
It is considered that the value obtained by subtracting the difference between the error and the fx error by one point at the center of the 1L' period of 5r3o represents the instantaneous stop error signal. However, as can be seen from FIG. 3, this value has an extremely poor C5N ratio.

Therefore, in this embodiment, sampling and AD conversion (by the AD converter 17) are performed twice during a predetermined time τ (to eliminate the effect of switching) of one field (approximately 16.7 yns) per sampling pulse number, and the subtracter 18 An integrator 19 integrates the difference signal P between the 5fx error and the fx error. Furthermore, the integrated waveform of m field (equivalent to 9 operations because it is integrated only at "Lo" of S1r'5Q) is Q, and finally the control circuit 22 sends the total integrated value to the data latch 2o using the latch pulse signal. The value latched in is the stop error signal E whose S/N ratio is increased by averaging.

The reason why only one half of sw;'so (1L0 in this case) is integrated is to ignore the fact that differences in conditions such as head width imbalance exist between degrees H and L degrees of 5F50. If the noise in the reproduced pilot signal is composed of only random components, the S/N ratio will be W times higher than in the case of an instantaneous stop error signal.

In the embodiment, since le=256 and 7n210, a significant increase of 31 dB is possible.

FIG. 4 shows the amount of tape deviation (normalized by track pitch P) X from the normal noiseless state g (x=o) and the corresponding stop error -S;X. Therefore, the comparator 21 compares E corresponding to the deviation kSK with the reference level data REF (which is 0° in the balance head, allowing initial tracking adjustment when the REF is stopped at a certain degree) and intermittent drive control multiplier C. is output to the intermittent drive control circuit 16.

On the intermittent drive side (# circuit 16, the count value of 1 frequency detector 15 corresponds to a transfer distance that is an integral multiple of 1 field)
If the control signal C is positive, FGo is decreased by a unit amount (several counts), and if it is negative, it is increased by the unit amount to make the front balance positive. Intermittent driving is realized in the direction in which the error signal E approaches 0°.

The above explanation has been made with a configuration using individual logic circuits so that it is easy to understand the hourglass shape during integration, but as in another embodiment shown in FIG.
l Procepiig UrLit) 31. Microcomputer 3 containing pass line 32 on one chip
It is also possible to configure it with 5. In this case, the number of steps of the stopping error must be created using software. The operation shown in FIG. 5 will be explained below using the flowchart shown in FIG. In this example, we will explain the case where the difference between the 5hr error and the fx error is created by the subtracter 34 before AD conversion in order to simulate the number of inputs for AD conversion, but the 5ftr error and jrr error are independently input to the AD converter 30. The same can be considered when inputting information. The advantage of inputting independently is 3 hours.
It is possible to cancel the influence of DC drift of r error and fH error.

Stopping error (In the N-E creation routine, when the number of samplings (It calculations) is set as m for Rufield number in one field, 1 of the counter in the microcomputer is
Each variable is N.

Let it be N1. Further, a value corresponding to REF in FIG. 1 is set with the REF volume 35.

First, set the value of an appropriate memory M to 0°, N1 to °0°, and S
jV'; N only in the period (falling edge) of ILl of 0
'', the output voltage of the subtracter 64 (corresponding to PK in FIG. 3) which has been AD-converted twice is integrated into the memory MVc.

By performing the integration further 77L/2 times (#I=171/2), the stop error signal E is held in the memory H. Therefore, the control signal can be controlled in the same way as shown in Figure 1, depending on the positive or negative value of H.

With the present invention, it is possible to maximize the integrated circuit number 9m/2 by varying it in accordance with the intermittent slow speed.

It can contribute to improving the SN ratio.

The above explanation was for the case where the a-cal frequency was fixed at h, but in this case, the 5fx error is fs in Figure 2.
'h, fx error is j, -f, and due to the differential characteristics of the tape head system, Si of jl, which has the lowest frequency, is slightly unfavorable. Therefore, if necessary, set the stop position fs) rack (currently stopped at h track) and set the local frequency to fs.
, the 5hr error can be set to f2f=, and the ftr error can be set to Moum.

〔Effect of the invention〕

As explained above, according to the present invention, there is no need for a CTL signal, and any method that can obtain a tracking error signal using a pilot signal or the like can be used to achieve slow and still motion by one intermittent drive due to the averaging effect of tintal integration. It is possible to realize variable speed playback with the same or higher accuracy than when using a conventional CTL signal.

[Brief explanation of the drawing]

The first cause is a block diagram of a magnetic recording and reproducing device according to an embodiment of the present invention, FIG. 2 is a pattern diagram of intermittent drive according to the present invention, FIG. 3 is a signal waveform diagram of the valley, and FIG. 4 is a stop error signal. FIG. 5 is a block diagram according to another embodiment, and FIG. 6 is a flowchart for explaining the operation of FIG. 5. 7... Tracking error signal processing circuit 16... Intermittent drive control circuit 17, 30... AD converter 18, 34... Subtractor 19... Integrator 20.
...Data latte 21...Comparator 31--CPU 33...Microcomputers 4 Figure S Figure 6

Claims (1)

[Claims] 1. In a rotary head helical scan type magnetic recording and reproducing device that performs tracking by weight recording pilot signals in a video trunk, means for intermittently driving a magnetic tape and reproducing during a stop period. means for detecting a pilot signal; means for fixing a pilot local frequency mixed with the pilot signal to one specific type for a predetermined period; means for time-integrating; means for performing said integration over multiple fields during a stop period; and means for performing said integration over a plurality of fields during a stop period; means for generating an error signal, and the magnetic tape is driven intermittently in a direction in which the stop error signal approaches zero. - A magnetic recording and reproducing device whose main feature is to record and reproduce images. 2. The magnetic recording and reproducing apparatus according to claim 1, wherein an integral operation is performed only in one of the even-numbered fields and the odd-numbered fields. 68 Tracking machine A means for fixing the pilot local frequency for detecting and mixing error signals to one specific type, and detecting the error obtained from both adjacent tracks during the stop period by using two predetermined types of bandpass filters from the mixed signal. 6. The magnetic recording and reproducing apparatus according to claim 1 or 2, further comprising means for extracting a signal and performing production processing after each of the two types of error signals is converted into digital data. 4. Claims 1 to 4, characterized in that the bi-a-cal cycle number of one specific type of mixture is determined so that the level of the error signal after mixing does not become the lowest. 6. The iφDenM magnetic recording device according to item 6.