JPS6387088A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain the even number double speed reproduction without a noise by prohibiting the updating of the memory data of an image memory circuit and reading the old data, which are not updated, to an external part while a drop-out occurs. CONSTITUTION:A reproducing output demodulated by a demodulator 14 is made into a digital signal by an A/D converter 15 and successively updated and stored into an image memory circuit 16. A writing/reading control circuit 31 counts a false horizontal synchronizing signal HD supplied from a flywheel oscillator 30, sets a drop-out period and outputs it to an image memory circuit 16, based on a pulse PG to show the rise of a head change-over pulse to occur at a drum servo circuit 27. The drop-out detecting period prohibits the updating and storing of an image memory circuit 16 and the old data already stored are read to the external part. By making variable the setting of the drop-out period with the double speed ratio, the optimum supplement can be executed for the double speed ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording and reproducing apparatus that uses an image memory circuit and enables high-quality even-numbered multiple speed reproduction.

[Prior Art] A magnetic recording/reproducing apparatus 1 shown in FIG. 5 has a pair of magnetic heads 2a and 2b having different azimuths arranged opposite each other at a position that divides a head drum 2 into two. This figure shows the basic structure of a helical scan method in which a pair of magnetic heads 2a and 2b diagonally cross a magnetic tape 3 running in contact with it and alternately scan it while recording or reproducing video signals. In this type of helical scan type magnetic recording/reproducing device, normal playback is performed in preparation for special playback such as so-called high-speed playback, in which a desired scene is searched for while running the magnetic tape 3 at a tape speed several times that of recording. Two magnetic heads 4a and 4b for special reproduction prepared outside the magnetic heads 2a and 2b for special reproduction are arranged at positions determined with consideration to achieve optimal scanning, and the reproduction envelope that is inherent in special reproduction is It is common to configure the structure to suppress noise generation due to reduction.

[Problems to be Solved by the Invention] The above-mentioned conventional magnetic recording and reproducing apparatus l has magnetic heads 4a and 4 for special reproduction in addition to magnetic heads 2a and 2b for normal reproduction.
Since b is necessary, the cost is inevitably high.
Moreover, even if the magnetic heads 4λ and 4b are provided for special reproduction, it is not possible to completely eliminate the noise bars that are inherent in special reproduction from the screen; There were drawbacks such as increased wear and a tendency to reduce durability.

[Means for Solving the Problems] The present invention solves the above-mentioned problems, and allows a pair of magnetic heads with different azimuths to alternately perform diagonal scanning to record signals on a magnetic tape. A magnetic recording and reproducing device that performs even-numbered speed playback by running the tape at a speed that is multiplied by an even-numbered speed ratio, which updates and stores the playback output of the magnetic head and also outputs the updated data to the outside. an image memory circuit that separates the horizontal synchronization signal included in the reproduction output of the magnetic head, and an output of the synchronization separation circuit that is supplied with A flywheel oscillator that outputs a pseudo-horizontal synchronization signal of the same period based on the horizontal synchronization signal that was being supplied to the It is set by converting the dropout occurrence period, which is uniquely determined according to writing/reading control that supplies a write control command so as to prevent data from being updated in the image memory circuit during a period in which dropout occurs, and supplies a read control command to read old data that is not updated to the outside; The present invention is characterized in that it is configured by providing a circuit.

[Operation] This invention uniquely writes and reads data to and from an image memory circuit that updates and stores the reproduction output of a magnetic head and outputs the updated data to the outside according to the speed ratio during even-numbered speed reproduction. The dropout occurrence period, which is determined by On the other hand, data is written to update the stored data, and during the period in which dropout occurs, updating of the stored data in the image memory circuit is prohibited, and by reading old data that is not updated externally, it is possible to generate even numbers without noise. Enables double speed playback.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a schematic circuit diagram showing an embodiment of the magnetic recording/reproducing apparatus of the present invention, FIG. 2 is a circuit diagram of the write/read control circuit shown in FIG. 1, and FIG. 3A and 3B are a diagram showing a reproduction locus during quadruple speed high-speed reproduction and a signal waveform diagram of each part of the circuit shown in FIG. 2, respectively.

In FIG. 1, a magnetic recording/reproducing device 11 has a pair of magnetic heads 2a and 2b having different azimuths, demodulates a frequency-modulated luminance signal, and performs frequency conversion of a low-frequency conversion color signal through a preamplifier circuit 12 and an amplifier circuit 13. It is connected to the demodulator 14 which performs the following. The demodulator I4 is connected to an AD converter 15 and an image memory circuit 16 which stores digital video data in units of fields and is capable of writing and reading at any time. This image memory circuit 16 plays an important role in compensating for dropouts during even-numbered speed reproduction, and its output is converted into an analog signal by a DA converter 17 and output to the outside.

Reference numeral 18 denotes an address control circuit that specifies addresses necessary for writing and reading data stored in the image memory circuit 16. In this embodiment, the write address is updated for each line of the video signal, and reset at vertical intervals. be done. This address control circuit 18 is connected to the AD converter 15 and D
Together with the A converter 17, it operates in accordance with a reference clock supplied from a reference oscillator 19 and having a frequency four times the color subcarrier frequency. In addition to these operating clocks, the output of the reference oscillator 19 is also supplied to a frequency dividing circuit 20, and is divided into a frame reference signal having a frequency of 30 Hz. A phase-locked loop circuit 21 that performs phase control based on this frame reference signal controls the rotation of a capstan motor 23 via a capstan servo circuit 22. As is well known, the rotation of the capstan motor 23 is caused by the rotation of the magnetic tape 3.
The signal is supplied to the phase-locked loop circuit 21 from a control head 24 that detects control pulses recorded in the control head 24 via a preamplifier circuit 25 and a 1/2° frequency divider circuit 26 with an even division ratio.

By the way, the address control circuit 18 receives a vertical reset signal from a vertical reset circuit 28 connected to a drum servo circuit 27 that controls the rotation of the head drum 2, and a horizontal synchronization signal separated by a synchronization separation circuit 29 connected to the demodulator 14. Since the signal is supplied via the flywheel oscillator 30, as described above, the address for writing and reading is updated every line, and the address is reset in a vertical cycle. The flywheel oscillator 30 outputs a pseudo-horizontal synchronization signal of the same period based on the previously supplied horizontal synchronization signal even after the supply of the horizontal synchronization signal from the synchronization separation circuit 29 is cut off. It is. Therefore, the magnetic head 2a.

Even if the horizontal synchronization signal included in the reproduced output of 2b is missing, the oscillation up to that point continues inertia, and the missing synchronization signal can be complemented. Note that a part of the output of the flywheel oscillator 30 is supplied to the vertical reset circuit 28.

Reference numeral 31 denotes a write/read control circuit that controls writing and reading of the image memory circuit, and counts pseudo horizontal synchronizing signals supplied from the flywheel oscillator 30, and also counts pseudo horizontal synchronizing signals supplied from the flywheel oscillator 30, and also calculates unique signals according to the speed ratio during the even speed reproduction. It is set by converting the dropout occurrence period, which is determined by is supplied, and during a period in which dropout occurs, updating of the data stored in the image memory circuit 16 is prohibited, while a read control command is supplied to read old data that is not updated to the outside.

Now, before starting to explain the write/read control circuit 31, a method for setting the dropout period will be explained with reference to FIG.

The magnetic tape 3 shown in FIG. 3 is recorded in 3x mode, and there are no guard bands between tracks. Now, the contact area between one magnetic head 2a and a track whose azimuth matches is 81, and the head area of the magnetic head 2a is 80, and the moving speed of the magnetic head 2a in the track direction is vl, and the moving speed in the direction perpendicular to the track is vl. If the u1 head width is 1 and the elapsed time from when the magnetic head 2a is completely positioned on the track is t, then 5=So
Becomes ult. Furthermore, assuming that the magnetic flux density B0 on the magnetic tape 3 is constant, the magnetic flux Φ penetrating the magnetic head 2a is
Since B o S, Φ=Bo(So ult
) Therefore, the magnetic flux density B(-Φ/S
0) becomes Be(Soult)/So.

Therefore, the reproduction output E (
= vB) is nov (so −ul t ) /S
.

The reproduction output E is a linear function of time t.

Here, if the field period is Tf and the track width is L, then in m-times speed playback, uTr= (m-1)
The relationship L (m=2.4.6.,) is established, and therefore Bov ('rrso-(m-1) L lt )
/TfS.

Using S o-L 1, E = B6v t'rr (m 1 ) t )
/ Tf. Therefore, if the peak reproduction output at t-0 is Eo, then Eo''B, v, so if t is τ when the reproduction output E decreases to 1/n of Eo, Eo/n = Bov r' rr-(m-1)r)
/Tr, so r=(n-1)Tf/n (m-1) Also, if the time when E-0 is Te, then Te-Tf/
(m −1). Then, after the time Te has elapsed, when a further time Te-τ elapses, the playback output E becomes l of Eo.
/n, and this process is repeated thereafter, so the start time Rk and end time Wk of the dropout period are Rk= ((2k -1) n -1) Tf/n (
m −1) Wk−((2k −1) n+1 ) Tf
/n (m −1). However, k=1.2,
3. ,.

Therefore, the field period Tr is defined as the horizontal synchronization period T
When converted to the number of write or read clocks equal to H, each of the above timings becomes ((2 to 1)n-1)Tr/n(m-1)T! 1((
2 to -1)n+1)Tf/n (m-1)T.

The former Rk/TH gives the output timing of the read command, and the latter Wk/To gives the command timing of the write command.

By the way, as shown in FIG. 2, the write/read control circuit 31 controls the start timing R1 of the dropout period in the summer field period in, for example, quadruple speed playback.
Three counting circuits, namely counting circuits 32 and 33 that respectively instruct R2, and counting circuit 34 that instructs end time Wl and W2, constitute the main part, and their specific configuration and operation will be explained in the fourth section. This will be explained along with the figures.

First, the pulse PG indicating the rising edge of the head switching pulse supplied from the drum servo circuit 27 is applied to the first stage D.
The D flip-flop circuit 35, which is supplied to the clock input terminal of the flip-flop circuit 35 and whose data input is always at a high level, is set. Then, by the Q output of this D flip-flop 35, the AND gate circuit 3 of the next stage is
6 opens, and the pseudo horizontal synchronization signal HD supplied from the flywheel oscillator 30 is supplied to the clock input terminal of the counting circuit 32. The counting circuit 32 calculates, at the time when the first dropout period of the l field period arrives,
The count value just reaches R1/To and the counting is completed.

A ripple carry signal outputted simultaneously with the completion of counting is supplied to the latch circuit 38 via the inverter circuit 37, and is also supplied to the load input terminal of the counting circuit 32 itself. As a result, the counting circuit 32 is loaded with a preset initial value, and the D flip-flop circuit 35 is cleared by the pull-carry signal via the latch circuit 38, as shown in FIG. 4(D).

On the other hand, the counting circuit 33 is loaded with an initial value by the Q output of the D flip-flop circuit 35, and the counting circuit 33 is loaded with an initial value by the Q output of the D flip-flop circuit 35.
Counting starts in synchronization with the rise of the ripple carry signal. Then, counting is completed when the counting output reaches the predetermined count value R2/T)l, and as shown in FIG.
As shown in Fig. G), the ripple carry signal is supplied to the latch circuit 40 via the inverter circuit 39, and is also supplied to the load input terminal of the counting circuit 33 itself via the AND gate circuit 41.

The outputs of the latch circuits 38 and 40 are used as clock inputs of another D flip-flop circuit 42 via a NOR gate circuit 49, so the D flip-flop circuit 42 whose data input is always at a high level receives each ripple carry signal. At the rising edge of , the Q output becomes high level. This high-level Q output serves as a read command to the image memory circuit 16, and corresponds to the start of the dropout period at times R1 and R2. Further, the Q output of this D flip-flop circuit 42 opens the gate of the AND gate circuit 43 at the next stage, and the counting circuit 34 starts counting the pseudo horizontal synchronizing signal HD. The counting circuit 34 is
When the count value reaches a preset value Wl/T)l, a ripple carry signal is output as shown in FIG. 4(K). As a result, the initial value is loaded into the counting circuit 34 by the output of the inverter circuit 44 that inverts the ripple carry signal of the counting circuit 34, and
The D flip-flop circuit 42 is cleared via the latch circuit 45. That is, the D flip-flop circuit 42
The low level Q output of is supplied to the image memory circuit 16 as a write command, which corresponds to the end of the dropout period.

In this way, in 4x high speed reproduction, the magnetic head 2a
and 2b scan across four tracks in one scan, but as a result of the difference in the scan start track and scan end track in one scan (L field period), the magnetic heads 2a and 2b scan across four tracks in one scan. By scanning by 2b, the dropout occurrence position can be made different.

This point is particularly important when the image memory circuit 16 updates the memory contents, and dropouts that occur during scanning of the magnetic head 2a are stored in the image memory circuit 16 when the magnetic head 2b scanned last time. Furthermore, dropouts that occur during scanning by the magnetic head 2b can be supplemented by data stored in the image memory circuit 16 when the magnetic head 2a scanned last time.

As mentioned above, the magnetic recording/reproducing device 11 eliminates noise bars caused by dropouts caused by differences in azimuth with respect to recording tracks during high-speed reproduction.
This can be completely eliminated by using the image memory circuit 16 as a dropout supplement means instead of the special playback head. Furthermore, the image memory circuit 16 is not controlled by detecting dropouts that actually occur, but is controlled according to the dropout occurrence period that is uniquely determined when the speed ratio is determined, so the dropout occurrence period cannot be set. Since the degree of interpolation can be freely changed and optimal interpolation can be performed for each speed ratio, it is possible to always provide high-speed playback images with smooth motion and no noise. Furthermore, the counting circuits 32, 33, and 34 in the write/read control circuit 31 that control the image memory circuit 16,
Pseudo horizontal synchronization signal HD from flywheel oscillator 30
The magnetic head 2a operates based on the magnetic head 2a.

Even if the horizontal synchronization signal during reproduction output of 2b is lost, stable operation can be guaranteed.

In the above embodiment, even when reproducing a magnetic tape in a recording mode in which guard bands are formed between tracks, the count value setting conditions for the counting circuits 32, 33, and 34 in the write/read control circuit 31 are changed. As a result, it is possible to perform high-speed playback with no noise bars caused by differences in azimuth or noise bars caused by track crossing, and the speed ratio is not limited to 4x, but can also be played using other even numbers. It can be freely expanded to double the size.

[The effects of the invention include noise bars that occur due to dropouts that occur due to differences in azimuth with respect to recording tracks, and dropouts that occur due to track crossing where the magnetic head scans across the girt band between recording tracks. , it is possible to completely eliminate dropouts by using the image memory circuit as a supplementary means to replace the special playback head, and instead of controlling the image memory circuit by detecting dropouts that actually occur, the speed ratio is Since control is performed according to the dropout occurrence period that is uniquely determined at a fixed point in time, the degree of interpolation can be freely changed depending on the setting of the dropout occurrence period, and optimal interpolation is possible for each speed ratio. It is possible to always provide smooth, high-speed playback images with no noise, and the write/read control circuit that controls the image memory circuit operates based on the pseudo horizontal synchronization signal supplied from the flywheel oscillator. Even if the horizontal synchronization signal during the reproduction output of the magnetic head is lost, stable operation can be guaranteed, and other excellent effects are achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit diagram showing an embodiment of the magnetic recording/reproducing apparatus of the present invention, FIG. 2 is a circuit diagram of the write/read control circuit shown in FIG. 1, and FIG. A diagram showing a reproduction locus during 4x high-speed reproduction, a signal waveform diagram of each part of the circuit shown in FIG. 2, and FIG. 5 are a schematic configuration diagram showing an example of a conventional magnetic recording and reproducing apparatus, respectively. 2a, 2b, ..., magnetic head, 3. ,,Magnetic tape,
11. ,,magnetic recording and reproducing device, 16. ,. Image memory circuit, 29. ,, synchronous separation circuit, 30°1.
Flywheel oscillator, 31. ,,Write/read control circuit.

Claims (1)

[Claims] Magnetic recording and playback that performs even-numbered speed playback by running a magnetic tape on which signals are recorded by alternately obliquely scanning a pair of magnetic heads with different azimuths at a tape speed that is the tape speed at the time of recording multiplied by an even-numbered speed ratio. The apparatus includes an image memory circuit that updates and stores the playback output of the magnetic head and also outputs the updated data to the outside, and a synchronization separation circuit that separates a horizontal synchronization signal included in the playback output of the magnetic head. The output of this synchronization separation circuit is supplied to a flywheel oscillator that outputs a pseudo horizontal synchronization signal of the same period based on the previously supplied horizontal synchronization signal even after the horizontal synchronization signal supply is cut off. Then, the pseudo-horizontal synchronization signal supplied from this flywheel oscillator is counted, and the dropout occurrence period, which is uniquely determined according to the speed ratio during the even-numbered multiple speed playback, is determined by the counted value of the pseudo-horizontal synchronization signal after head switching. During a period in which dropout does not occur, a write control command is supplied to the image memory circuit to update the stored data, and during a period in which dropout occurs, the stored data in the image memory circuit is while prohibiting the update of
A magnetic recording/reproducing device comprising a write/read control circuit that supplies a read control command to read old data that has not been updated to the outside.