JPS62224173A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a rewound reproducing picture without noise by causing a tape to run at (b) times of the conventional reproducing speed at rewinding reproduction and rotating a cylinder at the (a) times of speed reversely. CONSTITUTION:In applying rewinding reproduction, a cylinder is rotated reversely at the speed being (a) times of the conventional reproducing speed and a capstan motor is driven at the speed reversely being (b) times of the conventional reproduction speed. In selecting a=b=6 for example, an RF signal reproduced from a magnetic head 1 whose time base and polarity are reverse with a frequency being 6 times of that at the conventional reproduction is sampled by using a sampling lock 6fcp at an A/D converter 5 via a reproducing amplifier 3 and a low pass filter 4 and written in a memory 6 by a memory controller 10 in time series. The memory controller 10 reads the digital RF data from the memory 6 at the frequency of the fcp in the reverse order from the stored order and inputted to a reproduction processing circuit via a D/A converter 11 and a low pass filter 12.

Description

[Detailed Description of the Invention] 3.Objectives of the Invention (Field of Industrial Application) The present invention provides a helical scan type magnetic recording and reproducing device (
(VTR).

(Prior Art) Conventionally, in this type of VTR, a field memory for storing video signals for one field is provided, and the decoded video signal @
(Ncho SC News @) is A/D converted and stored in the field memory, and during playback, the stored contents of this field memory are read out and input to the D/A converter,
A system has been developed that enables slow playback or still playback without noise or image shaking by restoring the original composite video signal and sending it to the television monitor (published by Denshi Gijutsu Publishing Co., Ltd.). “TV Technology J, 1
(See November 985 issue).

(Problems to be Solved by the Invention) In the conventional VTR described above, when the tape running speed is slow (including stopping), such as during slow playback or still playback, the scanning locus of the magnetic head and the recording track on the tape are This method takes advantage of the fact that the slopes of the images are almost the same, and performs noise-free slow playback or still playback.

However, for example, when performing rewind playback, the magnetic head scans diagonally across multiple recording tracks, so the track recorded by the head at one azimuth angle is Noise always appears when the head crosses.

For example, when rewinding at a speed six times the normal tape running speed and performing a picture search using forward playback, the cylinder should be Since the rotation speed is controlled and the capstan servo system is controlled so that the phase of the playback control signal is locked to six times the cylinder rotation speed, the envelope of the playback video signal becomes as shown in Figure 15. , a noise bar always appears in the valley of this envelope. Therefore, there is a problem in that it is not possible to obtain a noise-free rewinding reproduced image if this is done as it is.

It is an object of the present invention to solve these problems and provide a magnetic recording main device capable of obtaining noise-free rewinding and reproduction images.

[Structure of the Invention] (Means for Solving the Problems) The present invention rotates a cylinder to which a head is attached at a speed a times the normal playback speed (an integer where a≠1) in the opposite direction to normal playback. At the same time, the capstan motor that runs the magnetic tape is moved b times in the opposite direction to that during normal playback (an integer where b≠1).
a rotation control means for rotating at a speed of , a sampling means for sampling a reproduction signal reproduced from the head with a sampling signal of a predetermined frequency associated with the rotational speed of the cylinder, and a storage means for storing the sampled reproduction signal; The stored playback signal is sampled in the opposite direction of the time relationship at the time of sampling (1 of the signal frequency).
The above object is achieved by providing a reading means for reading at a frequency of /a and outputting it as a video signal.

(Function) During rewind playback, the tape is run at b times the normal playback speed, and the cylinder is also rotated in the opposite direction at a speed a times. Then, the relative angle between the scanning locus of the magnetic head and the inclination of the track becomes smaller than when the tape is run at b times, and noise is reduced. For example, if a=b, the scanning locus of the magnetic head and the inclination of the track will be the same as during normal reproduction, and a rewound reproduced image without noise can be obtained. Also, even with the relationship af:b, the relative angle between the scanning locus and the track inclination becomes small, so if a and b are set in a special relationship, the position of noise within one field can be fixed, and the memory Using this method, it is possible to extract an image from which noise has been removed.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention, which is configured to enable rewind playback at six times the normal playback speed. In the figure, 1 is the magnetic head responsible for the azimuth angle (for simplicity, only one head A is shown;
2 is a rotary transformer, 3 is a reproduction amplifier that amplifies the reproduced video signal, 4 is a low-pass filter, and 5 is a predetermined sampling clock for the reproduced video signal. an A/D converter that samples in synchronization with TCP, converts it to digital data, and outputs it; 6, a field memory that stores data of the sampled reproduced video signal; 7, 3.
58 Oscillator that generates clock signal φ for digital processing of MH2, 8 is 1 which is 4 times the frequency of clock signal φ
4.32 MH7 read sampling clock fcp
9 is a 6-multiplier circuit that forms a write sampling clock 6'rcp of 85.92 MH2, which is the frequency of the read sampling clock fcp multiplied by 6, and 10 is a 6-multiplier circuit from the A/D converter 5. clock 5f
Field memory 6 stores data output in synchronization with Cp.
A memory controller 11 controls writing to and reading from the memory, and a D/A converter 11 converts data read from the field memory 6 into an original video signal.
The A converter 12 is a low-pass filter that removes components of f cp/2 or more contained in the output signal of the D/A converter 11 and inputs it to a reproduction processing circuit (not shown).

Here, the cylinder and capstan (both not shown)
are both 6 times (a=
When rotating in the opposite direction with b = 6>, the A head and B head reliably trace the track on the tape from top to bottom within one field on the screen, in the opposite direction to that during normal playback. The envelope of the reproduced RF signal has a frequency six times the normal frequency as shown in FIG. 2, and its amplitude is constant. In this case, the portion corresponding to the bottom portion of the screen is played first, and the time axis is reversed. In addition, when a sine wave SIN as shown in Figure 3 (a) is recorded, the playback output is proportional to SIN/dt, so when rewinding the playback, the time axis as shown in Figure 3 (C) Both polarities are reversed.

Therefore, the brightness signal (Y-FM signal) during normal playback is 30MH2 (5MH7X 6 ), the low frequency conversion color signal is 4.2MH2 (=700KH2X 6 ), and the audio FM signal is 9.0MH2 (=1.5MH2X6).
Thus, they are respectively reproduced from the magnetic head 1.

Therefore, in order to extract each signal of such a frequency, the rotary transformer 2 is selected to have flat frequency characteristics over a wide band of about 50 MH2.

On the other hand, the frequency band of the reproduced RF signal is normally required for reproduction from 6 to 7 MH7, so the sampling frequency TCP is at least twice that, 14.32 MH.
It is set to l.

Further, the number n of quantization bits of the Δ/[) converter 5 is set to 6 bits. Therefore, the memory capacity ff1M of the field memory 6 is M=fCpXtXn='1.433250X106 bits, and the number of addresses is 2.38875X10'' (=M/n
) memory is used. Specifically, six dynamic memory elements (DRAM) having a memory capacity of 1 bit x 256 are used.

In addition, as for the characteristics of the low-pass filter 4, the sampling clock tcp is 14.32 MB2, and the high-speed playback speed is 6 times higher, so as shown in FIG.
．． A characteristic filter with a cutoff frequency of 96 MHl is used.

In the above preparation, from magnetic head 1 to 6 during normal playback.
After being amplified by the RF double signal reproducing amplifier 3, which has doubled the frequency and reproduced with the time axis and polarity reversed, the low-pass filter 4 extracts only the components below /12.96 MH2 and converts it into A/D. It is input to the device 5. Then, this R
The F-fold signal A/D converter 5 samples the signal using a sampling clock 6fCp having a frequency of 85.92 MHl, and converts it into digital RF data corresponding to the amplitude value at each sampling time. Then, the data is written to the memory 6 in chronological order by the memory controller 10.

In other words, as shown in the memory read/write timing diagram in FIG.
A head and R of 8 heads read by one field.
After the F-fold signal is digitized, ΔO, B1 . Al, 8
2.-A7. The tracks are loaded into the memory 6 chronologically in the order of track B8. While the memory controller 10 performs the operation of writing the digital RF data to the memory 6 in this manner, it reads out the digital RF data stored in the memory 6 at the fcp period in the reverse order of the storage order, /A converter 11. And this D/A
converted into the original analog RF signal in a converter 11,
The signal is input to a reproduction processing circuit (not shown) via a low-pass filter 12. As a result, the Y-FM signal, the low frequency conversion color signal, and the audio FM signal are each demodulated and reproduced as a visible image on TV Tanabata.

In this case, the memory 6 is 1 bit x 256 as described above.
A KX6 with a memory capacity of ff1M can store digital RF data for at least one field, but in order to prevent the RF multiplied signal sent to the reproduction processing circuit from being interrupted, here the 2f[! il dynamic memory element 6
Digital RF data is written into fields A and 6B alternately for each field, and when a write operation is being performed on one of the memory elements 6A and 6B, a read operation is performed on one of the memory elements 6 and 6B. This allows digital RF data for six fields to be read out continuously from one memory element 6A or 6B, and it is possible to reproduce the rewind reproduction image without interruption.

Although the phase of the RF multiplied signal reproduced from the magnetic head 1 is inverted, in demodulating the FM wave, it is converted into a voltage according to the instantaneous frequency, so that a demodulated output having the same phase as that during normal reproduction can be obtained. In addition, the color signal is demodulated by locking the phase of the burst signal to the reference signal fsc, so even if the phase is reversed, as long as the phase difference with the burst signal does not change, demodulation is the same as during normal playback. I get the output.

FIG. 6 is a block diagram showing another embodiment of the present invention,
The difference from the embodiment shown in FIG.
This is because it was constructed from −7.

That is, an extra memory is provided to store digital RF data corresponding to 1/6 field time on the screen, and the data is written to the memory for one field as shown in the read/write timing chart in FIG. At the same time, 1/
Memory data for 6 fields is read out, and continuous playback is continued by reading out data from the other 5 memory elements except for the writing time.

For example, during the 1/6 field period, the playback output of the B1 track goes through the memory elements 6-1 → 6-2 → 6-3 → 6-4 → 6.
-5 → 6-6 → are sampled at a sampling frequency of 5fCp and written for one field, and while the data is being written, the data in the memory element 6-7 is at fcp.
The data is read out in the reverse order from when it was stored, with a period of . Thereafter, the signals are read out in the order of 6-5 → 6-4 → . . . 6-2 at a cycle of fcp, and 5/6 of one field of the screen is demodulated.

Next, while the reproduction output of the B4 track is being reproduced, the memory elements 6-2 → 6-3 → 6-4 → 6-5 → 6-6 → 6
At the same time, one field is written in the order of -7 at a cycle of 6fCp, and at the same time, the signal from the memory 6-1 is read out and demodulated at a cycle of fcp in the reverse order from when it was stored. If such operations are performed cyclically, continuous video signals will be demodulated.

In the case of the embodiments shown in FIGS. 1 and 6, since the signal from the same azimuth head is intermittently received, the demodulated video signal is skewed for only 1/2 horizontal scanning period at the field switching point. occurs.

However, this means that the writing timing is started by shifting the writing timing from T1 to T2 by 1/2 horizontal scanning period as shown in FIG. It is sufficient to alternately apply the track, Al to rack.

By the way, in the above embodiment, when the speed of rewinding and playback is increased, the rotation of the cylinder increases, and the playback frequency and sampling frequency become high, and the memory 6 is required to be a device with a high operating speed. Furthermore, the cylinder rotation speed also increases, which places restrictions on motor specifications and power supply voltage. As a means to solve the above points, as shown in the regeneration envelope diagrams in Figures 9 and 10, the following steps are taken: ■ Reverse the cylinder rotation by 3 times, Reverse the capstan rotation by 6 times, ■ Reverse the cylinder rotation. If you run the tape under conditions such as rotating the tape twice in the opposite direction and rotating the capstan six times in the opposite direction, the playback signal will be output as a signal for one field, either without the noise bar or with the noise bar pushed out onto the screen. It becomes possible to take it out. In other words, the cylinder rotation is set to a rotation speed such that the horizontal periodic signal frequency in the reproduction signal is three times that of normal reproduction (in the case of Fig. 9) or 2 (in the case of Fig. 10), and the rotation speed and Ratio with playback control pulse is 1:2
(in the case of Figure 9) or 1:3 (in the case of Figure 10)
If the noise bar is set so as to curve (in case of (in the case of Fig. 9) and 2 multiplier circuit (in the case of Fig. 10), roughly change the cutoff frequency of LPF4 to 1/2.1/3, and in the case of Fig. 9, A2 → A4
→A8→AIO 1~Rack data in order of memory element 6A and memory element 6B at a sampling frequency of 3tcp
In the case of Fig. 10, B2→B5→B
Data is stored in the memory element 6A in the order of tracks 8→811 at a sampling frequency of 2fCp.

By alternately reading data into 6B and reading in the reverse direction using fcp, noise-free rewind playback becomes possible. In this way, a memory whose operating speed is slow can be used as the memory 6, and it is also possible to lower the rotational speed of the cylinder monitor. On the other hand, the present invention can also be used for slow playback. In other words, to explain 1/4x rewind slow playback as an example, if tracking control is performed by setting the cylinder rotation and capstan rotation to 1/4 times the reverse direction during normal playback, the The RF multiplied signal is reproduced at a frequency of 1/4 with the time axis reversed. In this case, the 6 multiplier circuit 9 is changed to a 1/4 frequency divider circuit, and the cutoff frequency of the LPF 4 is also changed to 1/24.

After sampling the reproduced RF signal at a rate of 1/4 fC, A/D conversion is performed and the data of the AO track for one field is loaded into the memory element 6A in the time equivalent to four fields, and the process ends. Immediately after that, the data is read out in the opposite direction from the time of storage by repeating the data four times for four fields at the clock frequency of fcp.

At the same time, 81 tracks of reproduced RF signals are sampled at 1/4 fcp sampling frequency and A/D converted.
Data is written into the other memory element 6B and read out in the same manner. FIG. 11 shows a timing chart for reading in this case. The signal obtained by D/A converting the data read at this time has the same frequency as that during normal reproduction, and is converted into a video signal by a demodulation circuit. However, in this case as well, since the same field is repeatedly demodulated, a skew of 1/2 horizontal scanning period occurs. For this reason, the read order is controlled as shown in the timing diagram of FIG. 12.

In other words, the data for one field is (1).

(2>, (3)) and alternately inserting or not inserting the equalization pulse data (3) for 1/2 horizontal scanning time into the equalization pulse after the vertical synchronization signal, the horizontal The synchronization signals are continuous, and the intervals between the vertical synchronization signals are also equal, forming a regular interlaced video signal.

By the way, the value of a that determines the cylinder rotation speed is not necessarily an integer. In addition, the rotation of the capstan during normal playback
The value of b to be doubled can also be in the forward rotation direction, in which case considering the value as a negative value, it is possible to phase lock the cylinder rotation and capstan rotation by setting na = mb (m, n are integers). Although this is possible, if b/a>3.b/a<-'l, the noise bar will appear on the screen no matter which field is viewed, so b/a=1 to 3 is desirable.

When the capstan rotation is in the reverse direction and a=-b, it is possible to drive the noise to the top and bottom of the screen. Even if a is large and negative, the noise bar can be reduced more than when only b is negative.

In the above description, the RF multiplied signal state is A/D converted and stored in the memory, but it is also possible to demodulate the video signal at a multiplied frequency and then A/D converted and stored in the memory.

Further, although a DRAM is used as a memory element, similar effects can be obtained by using a charge transfer element such as a COD.

By the way, when demodulating into a video signal, since the time axis of the reproduced RF signal is reversed, it cannot be demodulated using the same concept as a normal demodulation circuit. In other words, when an FM signal is demodulated on the opposite time axis, a voltage proportional to the instantaneous frequency of the FM signal is demodulated, so a video signal with the time axis reversed is obtained.However, in general, the Y signal is FM modulated during recording. Emphasis is applied before de-emphasis, so de-emphasis is applied after demodulation during playback. However, a signal demodulated with the time axis reversed cannot be restored to its original state even if it is passed through a normal de-emphasis circuit. In addition, in the low-frequency conversion color signal whose time axis is reversed, the burst position is immediately before the horizontal synchronization signal, and the burst position is obtained by delaying the horizontal synchronization signal that is synchronized and separated based on the Y signal after demodulation. By converting the signal into a 3.588) 12-band signal using a gate pulse at 3.588), removing crosstalk, and then locking the phase to the reference signal, a reproduced color signal with a reversed time axis is obtained. Therefore, as shown in FIG. 13, the FM demodulated Y signal before de-emphasis and the reproduced color signal are transmitted to two systems of memory controllers 10Y, 10C and memory 6Y, respectively.
6C, the Y signal and the color signal are sampled in the memories 6Y and 6C with a signal of twice the highest frequency of each signal band, and stored after A and /D conversion.
After being read out in the reverse direction at a frequency of /a, the Y signal is passed through the Dien 7122 circuit 20, and the color signal is frequency-converted and mixed in the mixer 21 as it is, thereby obtaining a regular video signal. However, in this case, twice as many eight memories are required.

Therefore, as shown in FIG. 14, the Y signal and color signal immediately after FM demodulation are mixed in the mixer 22, and after A/D conversion, they are stored in one memory 6, and read out in the reverse order of writing. If, after D/A conversion, the Y/C separation circuit 23 separates the Y signal and the color signal, the Y signal passes through the de-emphasis circuit 24, and is mixed with the separated color signal in the mixer 25, the memory can be reduced to half. A regular video signal can be obtained with 8 concave holes. It should be noted that circuits without reference numerals in FIGS. 13 and 14 are well-known circuits, and therefore their explanations will be omitted.

[Effects of the Invention] As explained above, according to the present invention, when rewinding and reproducing the video signal 8 recorded on the tape, the capstan motor is rotated in the opposite direction at a rotation speed b times, and the cylinder motor is The cylinder motor is rotated in the opposite direction at a rotational speed a times as high as that of the cylinder motor, and the video signal obtained in this rotational state is sampled at a sampling frequency of a predetermined frequency associated with the rotational speed of the cylinder motor and stored in the memory. Since the reproduction image symbol is read out at a speed of 1/a in the opposite direction to that at the time of storage to extract the reproduced video symbol, it is possible to obtain a rewound reproduced image completely free of noise when a=b. Furthermore, even in the case of a'=I-b, it is possible to fix the noise bar at a specific position and extract only the noise-free portion, so that a noise-free 12-bit reproduced image can be obtained.

In general, it is possible to obtain a reproduced image without skew even during reverse slow reproduction.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. Figure 2 is a waveform diagram showing the envelope of the playback signal obtained when the rotational speed of the cylinder and the tape running speed are increased six times that of normal playback, and Figure 3 shows an example of the playback output waveform in the case of rewind playback. 4 are diagrams showing the frequency characteristics of the low-pass filter 4 in the embodiment of FIG. 1, and FIG.
FIG. 6 is a flowchart showing the read gate timing of the memory in the embodiment shown in FIG. 1, FIG. 6 is a block diagram showing another embodiment of the present invention, and FIG. 7 is a memory in the embodiment shown in FIG. FIG. 8 is an explanatory diagram for explaining the skew correction method in the embodiments of FIGS. 1 and 6. FIG.
The figure is a waveform diagram showing the envelope of the playback signal when the cylinder rotation speed is tripled and the tape running speed is increased six times.
Figure 0 is a waveform diagram showing the envelope of the playback signal when the cylinder rotational speed is doubled and the tape running speed is increased six times, and Figure 11 is a waveform diagram when performing reverse slow playback at 1/4 the speed of normal playback. Figure 12 is an explanatory diagram for explaining the memory read order when performing skew correction. Figure 13 is a time chart showing the memory readout timing, and Figure 13 shows the Y signal after demodulation and the color signal at low level. FIG. 14 is a block diagram showing a third embodiment of the present invention in which the area conversion is stored in separate memories, and the Y signal is demodulated and the color signal is converted to the regular frequency and both are converted. A block diagram showing a fourth embodiment of the present invention in which the mixture is mixed and stored in one memory. FIG. 15 shows the envelope of the reproduced signal obtained when 6x speed rewinding is performed on a VTR with a conventional configuration. FIG. 1...Magnetic head, 2...Rotary transformer, 3.
...Regenerative amplifier, 4...Low pass filter, 5...
A/D converter, 6...Field memory, 6A, 6B
...Memory element, 7.Oscillator, 8.4 multiplier, 9.6 multiplier, 10.memory controller, 11.D/Δ converter, 12..・Low-pass filter, 6-1 to 6-7...Memory device agent Patent attorney Nori Chika Koichi Uji・≠To-Emu 11? Field Throat - Figure 2 Figure 3 Figure 4 4? ,'lt)M''2 -Acceptance Fig. 8 Fig. 9 1 - 1 fee IV - Fig. 10 Menu name 96B No. 6A
6BFigure 11Figure 12

Claims (1)

[Claims] In a helical scan type magnetic recording/reproducing device, the cylinder with the head attached is operated at a times the normal reproduction speed (a≠1).
rotation control means that rotates the capstan motor for running the magnetic tape at a speed b times (an integer where b≠1) in the opposite direction to that during normal playback, and at a speed b times (an integer where b≠1); and sampling means for sampling the reproduction signal reproduced from the head with a sampling signal of a predetermined frequency associated with the rotational speed of the cylinder;
A storage means for storing a sampled reproduction signal, and a reading means for reading out the stored reproduction signal in a direction opposite to the time relationship at the time of sampling at a frequency of 1/a of the frequency of the sampling signal and outputting it as a video signal. A magnetic recording and reproducing device.