JPS6387087A - 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 read, to an external part at the period when 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 to an image memory circuit 16. A writing/reading control circuit 31 receives a rise pulse PG of a head changing-over pulse to occur at a drum servo circuit 27 and operates the completion time of a drop-out period based on this. During the drop-out period, the memory updating off the image memory circuit 16 is prohibited, and namely, a control signal is supplied to the image memory circuit 16 so as to read the old stored data to the external part. Thus, by depending on the setting of a drop-out generating period, the extent of supplement can be freely changed and the optimum supplement can be executed for a 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 and reproducing apparatus I shown in FIG. 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 hepts 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/reproducing device 1 includes magnetic heads 4a, 4 for special reproduction in addition to magnetic heads 2a, 2b for normal reproduction.
b is necessary, which inevitably leads to high costs.Furthermore, even if magnetic heads 4a and 4b are provided for special reproduction, it is not possible to completely banish the noise bars that are associated with special reproduction from the screen; As the number of magnetic tapes increases, the wear of the magnetic tape 3 also increases, which tends to impair 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. The dropout generation period, which is uniquely determined according to the speed ratio during even-numbered speed playback, is set by converting it into the count value of the horizontal synchronization signal that starts counting immediately after the head is switched, and the dropout occurs. During the period when dropout occurs, a write control command is supplied to the image memory circuit to update the stored data, and during the period when dropout occurs, updating of the stored data in the image memory circuit is prohibited, while old data that is not updated is The present invention is characterized in that it is configured by providing a write/read control circuit that supplies a read control command to read the data to the outside.

[Function] The present 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, depending on the speed ratio during even-numbered speed reproduction. The dropout occurrence period, which is determined by , data is written to update the stored data, and during the period when dropout occurs, updating of the stored data in the image memory circuit is prohibited, while old data that is not updated is read out to the outside. Enables double speed playback.

[Examples] Examples of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a schematic circuit configuration diagram showing an embodiment of the magnetic recording/reproducing apparatus of the present invention, FIG. 2 is a circuit diagram of the old read/write control circuit shown in FIG. 1, and FIGS. 3.4 are , respectively, 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.

In FIG. 1, a magnetic recording/reproducing device 11 includes a pair of magnetic heads 2a having different azimuths. 2b is connected via a preamplifier circuit 12 and an amplifier circuit 13 to a demodulator 14 that performs demodulation of the frequency modulated luminance signal and frequency conversion of the low frequency conversion color signal. The demodulator 14 is connected to an AD converter 15 and an image memory circuit 16 that stores video data converted into a digital signal 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 +6. 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
In conjunction with A conversion 417, it operates according to a reference clock at a frequency four times the color subcarrier frequency locked to the horizontal synchronization signal provided by reference transmitter 2H19. In addition to these operating clocks, the output of the reference oscillator I9 is divided into a frame reference signal with a frequency of 30 Hz by a frequency dividing circuit 20, and a phase-locked loop circuit 21 which performs phase control based on this frame reference signal. However, capstan servo circuit 2
The rotation of the capstan motor 23 is controlled via the capstan motor 2. As is well known, the rotation of the capstan motor 23 is controlled by a control head 24 that detects control pulses recorded on the magnetic tape 3, via a preamplifier circuit 25 and a 1/2° frequency divider circuit 26 with an even frequency division ratio. The signal is supplied to the phase-locked loop circuit 2I.

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 it is supplied via the flywheel oscillator 30, the address for writing and reading is updated every 1 lines like a multiplex, and the address is reset at a vertical cycle. Note that even if the horizontal synchronization signal supplied to the synchronization separation circuit 29 is lost, the flywheel oscillator 30 inertially continues the previous oscillation and functions to supplement the lost synchronization signal. A portion of its output is supplied to the vertical reset circuit 28.

31 is a write/read control circuit that controls writing and reading of the image memory circuit, and a horizontal synchronization signal that starts counting the dropout occurrence period, which is uniquely determined according to the speed ratio during even speed playback, from immediately after head switching. During the period when dropout does not occur, a write control command is supplied to the image memory circuit 16 to update the stored data, and during the period when dropout occurs, the image memory circuit 16 While prohibiting updating of stored data, a read control command is supplied to read old data that is not updated to the outside.

Before entering into a description of the write/read control circuit 31, a method for setting the dropout period will be described 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 S1, 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 VS) the moving speed in the direction perpendicular to the rack. Let u1 head width be 1, and let t be the elapsed time since the magnetic head 2a is completely positioned on the track, then 5=So
It becomes u 1 t. 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 it is BoS, Φ=Bo(Soult) Therefore, the magnetic flux density B(=Φ/S
0) becomes Bo(Soult)/So.

For this reason, the reproduction output E (
= vB) is Bov (Soul 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, uTf= (m −
1) The relationship L (m=2. 4. 6 , , ) is established, so Boy (TrS, −(m −1) L 1 t )
/'rrs.

E is expressed as E=Bov t using S o =L I
'rr (m I ) t )/'rr.

Therefore, the peak reproduction output when 1=0 is E. Then, since Ea=Bov, the playback output E is Eo/l/
If t is τ when it decreases to n, then Eo/n = Bov t'rr (m 1 )
r ) / Tr, so r= (n −1) Tr/n (m −1) and E
If Te is the time when = 0, then Te = Tf/ (m
-1) becomes. 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= ((2 to 1) n-1) Tf/n (m-1
)Wk-((2 to -1)n+1)Tr/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
-1)n+1)Tr/n (m-1)TH, and the administrator Rk/TH gives the output timing of the read command,
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 l 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, a 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 horizontal synchronization signal HD supplied from the synchronization separation circuit 29 is supplied to the clock input terminal of the counting circuit 32. When the first dropout period of the I field period arrives, the counting circuit 32 reaches exactly R1/T)I and completes counting. 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/TH, and the counting is completed as shown in Fig. 4 (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 the 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 horizontal synchronizing signal HD.

When the count value reaches a preset value Wl/T'H, the counting circuit 34 outputs a ripple carry signal as shown in FIG. 4(K).

As a result, the output of the inverter circuit 44, which inverts the ripple carry signal of the counting circuit 34, causes the counting circuit 34 to
At the same time, the D flip-flop circuit 42 is cleared via the latch circuit 45. That is, the low level Q output of the D flip-flop circuit 42 is supplied to the image memory circuit 16 as a write command, and this corresponds to the end of the dropout period.

In this way, in quadruple speed high-speed reproduction, the magnetic heads 2a and 2
b is scanned 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 (one field period), the magnetic head 2a and scanning by 2b,
This makes it possible to vary the position at which dropout occurs.

This point is particularly important when the image memory circuit 16 updates the memory contents, and the dropout that occurs during scanning of the magnetic head 2& is caused by the image memory circuit 16 memorizing the last time the magnetic head 2b scanned. 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.

In the above embodiment, the case where the magnetic tape 3 recorded in the 3x mode is played back at double speed is taken as an example, but writing and reproduction can also be performed on a magnetic tape in a recording mode in which guard bands are formed between tracks. It goes without saying that this can be adequately handled by changing the count value setting conditions for the counting circuits 32, 33, and 34 in the readout control circuit 31, and the speed ratio is not limited to 4x, but can also be set to other even numbers. can be expanded to.

[Effects of the Invention] As explained above, the present invention is capable of writing and continuing data to an image memory circuit that updates and stores the reproduction output of a magnetic head and outputs the updated data to the outside at an even multiple speed. The dropout occurrence period, which is uniquely determined according to the speed ratio during playback, is controlled by a write/read control circuit that is set by converting the count value of the horizontal synchronization signal, which starts counting immediately after the head is switched, to prevent dropouts. During the period when dropout does not occur, data is written to the image memory circuit to update the stored data, and during the period when dropout occurs, updating of the stored data in the image memory circuit is prohibited, while old data that is not updated is written to the external device. This causes dropouts that occur due to differences in azimuth with respect to recording tracks during high-speed playback, and dropouts that occur due to track crossing where the magnetic head scans across the girt band between recording tracks. The noise bars that occur in the image memory circuit can be completely eliminated by using the image memory circuit as a dropout complement means instead of the special playback head, and instead of detecting the actual dropout and controlling the image memory circuit. Since control is performed according to the dropout occurrence period that is uniquely determined when the sound speed ratio is determined, the degree of interpolation can be freely changed depending on the setting of the dropout occurrence period, making it possible to perform optimal interpolation for each speed ratio. Therefore, excellent effects such as being able to always provide high-speed reproduction images with clear motion and no noise 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, 31°1.
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 device 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 dropout occurrence period that is uniquely determined according to the speed ratio during even-numbered speed playback. is set by converting it into a count value of a horizontal synchronization signal that starts counting immediately after switching the head, and 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, A magnetic recording and reproducing device is provided with a write/read control circuit that prohibits updating of data stored 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. Device.