JPH0777448B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording / reproducing apparatus, and more particularly to a magnetic recording / reproducing apparatus suitable for quick reproduction of a magnetic tape recorded in a helical scan type apparatus.

[Conventional technology]

The conventional device has fixed the noise bar generated on the screen at a fixed position as described in JP-A-56-166678. This is the output obtained by dividing the running speed of the magnetic tape during fast-view playback by n times that during recording (n is an integer greater than or equal to 2), and dividing the phase detection output according to the rotary phase of the rotary head and the playback control signal by 1 / n. The rotation of the capstan motor is controlled so that the phases of and become the same. However, in the case of one scan of one rotary head, the position on the television screen is only fixed with respect to the signal loss caused by sequentially reproducing across a plurality of recording tracks.
To remain.

[Problems to be solved by the invention]

The above-mentioned prior art does not consider measures for removing or reducing the occurrence of noise on the TV screen, resulting in an unpleasant reproduced image.

An object of the present invention is to provide a magnetic recording / reproducing apparatus that removes noise on the screen and displays a good screen.

[Means for solving problems]

The above object can be achieved by adding a recording means of image information corresponding to a signal missing portion of a reproduced image and a phase synchronizing means of a horizontal synchronizing signal.

[Action]

The image memory in the present invention stores the previously reproduced image signal and operates to output the signal when the signal is missing. Further, the synchronizing means for the horizontal synchronizing signal constantly generates an image by controlling the head rotation speed at the time of pseudo-generating the horizontal synchronizing signal when the signal is lost and at the time of returning to the state where the signal is reproduced again. A control operation is performed so that the memory and the head rotation (a reproduction horizontal synchronization signal reflecting the head rotation) are synchronized with each other. As a result, it is possible to perform good quick playback without noise.

〔Example〕

An embodiment of the present invention will be described below with reference to the block diagram of FIG. In FIG. 1, 1 is a magnetic tape, 2 and 3 are rotary heads, 4 is an amplifier, 5 is a video signal demodulator, 6 is a drum motor, 7 is a horizontal sync signal detector, 8 is a pseudo horizontal sync signal generator, 9 is a clock signal generator, 10 is an address generator, 11 is an image memory, 12 is a pseudo vertical sync signal generator,
13 is a phase comparator, 14 is a drum rotation frequency signal generator (hereinafter referred to as DFG generator), 15 is a switching signal generator, 16 and 17 are interlocking changeover switches, 18 is a video signal processing circuit, 19 is a TV screen, 20 Is a motor driver, 21 is an analog-digital converter, and 22 is a digital-analog converter. The operation of this embodiment will be described below. First, the rotary heads 2 and 3 reproduce the image signal recorded on the magnetic tape 1. This reproduced signal is amplified by the amplifier 4 and demodulated into a video signal by the video signal demodulator 5. The horizontal sync signal detector 7 extracts the horizontal sync signal from the reproduced video signal.
Here, as will be described in detail later, the pseudo horizontal synchronizing signal generator 8 counts the output of the clock signal generator 9 in the noise portion, and is preset by every cycle of the preset signal generated by itself by running. Then, the cycle is set so as to match the cycle of the horizontal synchronizing signal at the time of fast-view reproduction. Further, the clock signal generator 9 performs an operation of generating a clock signal phase-synchronized with the color subcarrier signal, and is a general one composed of a phase comparator, a voltage controlled oscillator, a smoothing circuit and the like. This general structure is shown in FIG. In FIG. 2, 40 is a phase comparator, 41 is a smoother, 42 is a voltage controlled oscillator, 43 is a counter, 44 is an input terminal, and 45 is an output terminal. When the configuration of FIG. 2 is used as the clock signal generator 9 in the present invention, the color subcarrier signal is applied to the input terminal 44 and the count of the counter 43 is set to an appropriate frequency division ratio. The output signal 45 generated here is used as a sampling clock of the video signal in the overall configuration of FIG. Therefore, the count division ratio of the counter 43 is set to about 3 or 4. As a result, the output clock becomes about 3 or 4 times the color subcarrier signal. Next, the specific configuration and main operation of the address generator 10 will be shown below with reference to the block diagram of FIG. In the block diagram of FIG. 3, 50 and 51 are address generation counters and 5
2 to 54 are signal input terminals, 52 and 54 accept preset (or reset) inputs, and 53 and 55 accept clock inputs. These two counters 50, 51 give two-dimensional (x, y) addresses of information stored in the image memory 11. Here, (x, y) are equal to the positions of the pixels on the television screen. That is, the counter 50 counts the clock signals generated by the clock generator 9 and indicates the horizontal position on the screen, and the counter 51 outputs either the horizontal synchronizing signal detector 7 or the pseudo horizontal synchronizing signal generator 8. The signal is counted to indicate the vertical position of the screen. The storage position of image information in the present invention will be described below. That is, the vertical position is determined by counting the horizontal synchronizing signals in the reproduced video signal, and the horizontal position is determined by an accurate clock signal. As a result, one pixel on the screen is stored and read in correspondence with one element on the memory. Now, operation of the DFG generator 14 and the like will be described. When the magnetic tape 1 is driven in synchronization with the rotation of the drum motor 6 as in the prior art described above, the position of noise on the screen is fixed. Therefore, the noise-caused signal missing portion is reproduced before and replaced with the information stored in the image memory 11. For this reason, the part which becomes noise and the part which is not so are discriminated, and the following processing is performed on each part.

○ Non-noise portion → Stored in image memory and output to screen at the same time (write) ○ Noise portion → Read from image memory

There are several methods for making this determination, but in the embodiment shown in FIG. 1, the DFG generated by reflecting the rotation of the drum.
A configuration has been shown in which the above-mentioned partial discrimination is performed by a signal. That is, the time zone in which the rotary head on the drum is in contact with the magnetic tape corresponds to the scanning time on the television screen, and to know the noise position on the screen, the rotation phase of the drum may be monitored. This situation will be described below with reference to the supplementary explanatory diagram of FIG. Fig. 4 (1) is a playback TV screen, (2) is the rotation of the drum and magnetic tape, and (3) is the DFG.
It is a signal. Now, the head on the drum is A in Fig. 4 (2).
When rotating from the point to the point B, the television screen is scanned for one screen (from A to B). An example of the DFG signal at this time is shown in Fig. 4 (3). Then, when scanning in the middle of the screen (Fig. 4 (1) C), the rotary head moves to the position shown in Fig. 4 (2) C.
This is in the vicinity of C in Fig. 4 (3) when looking at DFG. Although not shown in this example, the DFG on the drum
In addition to the above, a signal generator that indicates the rotation phase of the drum is generally provided, and this and DFG can clearly detect the position of the scanning point on the screen. In this example, for example, the rotary phase signal generator is provided near the point A, reset by the output signal every time, and a counter for counting the DFG signal is used to set the scanning point on the screen to a certain degree (DFG).
It can be detected by stepping. According to the example of FIG. 4 (3), since the DFG of 3 cycles is generated by half rotation of the drum, 3 sections on the television screen of FIG. 4 (1) can be detected. Furthermore, the section of the TV screen point can be freely detected by making the DFG step finer and by adding an appropriate delay circuit to the counter output of the DFG signal. The above is the detection of the section on the screen using the DFG signal, but in addition to this, a method of selecting the above-mentioned two processes (memory writing, reading) or the like depending on the reproduction output level of the rotary head can be considered. . An example of this structure is shown in FIG. In the figure, 60 is an envelope detector, 61 is a constant voltage source, and 62 is a voltage comparator. In this configuration, if the reproduced signal is envelope-detected and compared with the level of the constant voltage source, the reproduced level is low in the noise part and large in the other part, so the level judgment is made according to the output of the voltage comparator. It is possible.

According to the above judgment signals of the noise part and the other part,
Changeover switches 16 and 17 shown in FIGS. 1 and 5 are changed over. The points are as follows: ○ Noise part → Switch 16, 17 on the b side ○ Other part → Switch 16, 17 on the a side Here, the switch 17 is switched between the horizontal sync signal reproduced from the magnetic tape and the pseudo-generated horizontal sync signal. The reason for this is that the horizontal sync signal is disturbed in the noise portion, so that a pseudo horizontal sync signal must be generated by counting an accurate clock from the clock generator 9. Here, FIG. 6 shows a specific configuration example of the pseudo horizontal synchronizing signal generator 8. In FIG. 6, 70 is a counter, 71 is a logic circuit, and 72,7.
3 is an AND gate, 74 is an OR gate, 75 is an inverter, 7
6,77 are voltage signals. The operation of this configuration will be described below.
First, assuming that the output of the switching signal generator 15 or the voltage comparator 62 is high and indicates the reproduction of the noise portion, and the output of the other portion is low, the AND gate 73 is closed when the signal 76 is low,
The output of the horizontal synchronizing signal detector 7 is applied as a preset pulse of the counter 70 via the AND gate 72 and the OR gate 74. At this time, the counter 70 continues counting while synchronizing with the output from the horizontal synchronizing signal detector 7, that is, the horizontal synchronizing signal in the reproduced video signal, while counting the clock from the clock generator 9. Next, when the noise portion is reproduced and the signal 76 is inverted to high, the AND gate 72 is closed and the preset pulse is applied to the counter through the AND gate 73. At this time, the logic circuit 71 operates so as to generate the preset pulse of the counter 70, and repeats the counting operation at the cycle corresponding to the horizontal synchronization cycle. With this operation, the pseudo horizontal sync signal continues even if the noise part is reproduced.
77 can be obtained, and by applying this pseudo horizontal synchronizing signal 77 to the address generator 10, the reading from the image memory can be performed without delay.

Next, the operation of the phase comparator 13 and the like will be described. The above configuration can cover the excessive state of switching from the non-noise portion to the noise portion, but conversely causes some problems in the excessive state of switching from the noise portion reproduction to the non-noise portion. This is because the counter 70 and the logic circuit 71 cyclically repeat the counting operation by themselves, although the cycle is set in advance to the horizontal synchronization signal cycle at the time of fast-view playback, but due to fluctuations in the playback speed, etc. A slight phase shift occurs between the pseudo horizontal sync signal generated by the counter itself and the horizontal sync signal detected when the non-noise portion is reproduced again, and the screen seam is curved. In order to prevent this and to make a normal seam, the motor is controlled via the phase comparator 13 and the motor driver 20 to perform phase matching between the two. FIG. 7 shows a concrete structure of the phase comparator 13, and FIG. 8 shows a waveform diagram of its main part. Here, 80 is a sampling pulse generator, 81 is a trapezoidal wave generator, 82 is a sampling and holding circuit, and 83 to 86 are voltage signals. First, the pseudo horizontal sync signal 83 triggers the trapezoidal wave generator 81 to generate a trapezoidal wave 84. On the other hand, the sampling signal 85, which is triggered by the reproduction horizontal synchronizing signal and shaped into an appropriate pulse width by the sampling pulse generator, is trapezoidal waved by the sampling hold circuit 82.
84 is sampled and held, and signal 86 is output. As a result, when the phase of the reproduced horizontal synchronizing signal 83 is delayed from that of the pseudo horizontal synchronizing signal, the sampling hold output 86 increases. In response to this, the motor driver 20 causes the drum motor to rotate at a high speed and advances the phase of the reproduction horizontal synchronizing signal 83. By this control, the pseudo horizontal synchronizing signal and the reproduced horizontal synchronizing signal have a predetermined phase. In this embodiment, the pseudo horizontal sync signal and the reproduction sync signal are controlled so as to have a constant phase. However, a reference signal obtained by dividing the output of the clock signal generator 9 to the horizontal sync frequency is used. Even if the pseudo horizontal sync signal is controlled to have a constant phase,
Almost the same effect can be obtained.

According to the above control, the configuration of the present embodiment makes it possible to perform noiseless two-headed quick playback using the image memory.

〔The invention's effect〕

According to the present invention, a special reproducing head is replaced with a semiconductor element called an image memory for noise-free fast-reading, which has not been realized by adding a large number of rotary heads in a magnetic recording / reproducing apparatus in the related art, and which requires a great deal of cost. As a result, there is no curvature (distortion) of the screen and it can be realized with a high-quality image, so that there is an effect of improving performance and an effect that cost reduction can be expected.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG.
FIGS. 3 and 6 are block diagrams showing specific configurations of the constituent elements in the embodiment, and FIG. 4 is a supplementary diagram for explaining the embodiment.
FIG. 5 is a block diagram showing another embodiment of the present invention,
FIG. 8 is a waveform chart of essential parts of the components shown in FIG. 7 ... Horizontal sync signal generator, 8 ... Pseudo horizontal sync signal generator, 10 ... Address generator, 11 ... Image memory

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayasu Ito, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd. Home Appliances Research Laboratory, Hitachi, Ltd. (72) Inventor Michio Masuda 292, Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Ceremony Company Hitachi Ltd. Home Appliances Research Laboratory (72) Inventor Yukio Fukushima 1410 Inada, Katsuta City, Ibaraki Prefecture Hitachi Ltd. Tokai Plant (56) Reference JP-A-55-53982 (JP, A)

Claims (1)

[Claims] 1. A helical scan type magnetic recording / reproducing apparatus capable of performing a quick reproduction for obtaining a reproduced image while traveling at a speed higher than a tape traveling speed at the time of recording, and a memory means for reading / writing a reproduction signal, and the memory means. Address generating means for generating a read / write address signal, and the memory means for performing the write operation of the reproduction signal in the noise-free portion of the reproduction signal, and the memory means for the noise-containing portion of the reproduction signal. A first read / write means for performing a read operation, and a first portion for selecting the reproduction signal in a noise-free portion of the reproduction signal, and a signal for being read out from the memory means in a noise portion of the reproduction signal. Selecting means, clock generating means for generating a clock signal, and using the clock as a count clock, the noise of the reproduced signal from the tape In the part without a mark, the preset is synchronized with the reproduction horizontal synchronizing signal from the tape, and in the other part, it is preset with the preset signal generated by counting a predetermined number of the clock signal and synchronized with the reproducing horizontal synchronizing signal. Pseudo-horizontal synchronization signal generating means for generating the pseudo-horizontal synchronization signal, and a reproduction horizontal synchronization signal from the tape is selected in a noise-free portion of the reproduction signal from the tape, and the pseudo-horizontal synchronization signal is selected in other portions. The phase difference between the reproduction horizontal synchronizing signal from the tape and the pseudo horizontal synchronizing signal, the second selecting means serving as the address reference signal of the address generating means, and detecting the phase difference of the rotary head according to the phase difference. A magnetic recording / reproducing device for controlling a rotational phase, and a phase synchronizing means for phase-synchronizing the reproduction horizontal synchronizing signal with the pseudo horizontal synchronizing signal. Location.