JPS62250778A - Search noise eliminating device - Google Patents

Abstract

PURPOSE:To prevent a search nosie and a switching noise from appearing in the screen image as a whole even in the visual search mode by outputting a video signal stored in a memory for a part of the tape from which a reproducing head can obtain no output for reproduction. CONSTITUTION:When a VTR control part is operated, as long as a rotary magnetic head selected by a selecting circuit 9 outputs an electrical signal, the electrical signal is converted to a video signal by an FM modulation circuit 10, converted to a digital signal by an A/D converter 11, and stored in a specified address of a memory 14 specified by an address selector 13. On the other hand, during the time when the rotary magnetic head selected by the selecting circuit 9 does not output an electrical signal, the digital signal stored in the memory 14 is converted to a video signal by a D/A converter 15, and displayed as an image on the screen by a picture circuit. The image thus displayed on the screen does not include noise bars.

Description

Detailed Description of the Invention [Technical Field] The present invention aims to prevent search noise from occurring in the image on the screen even when an FM signal related to an image recorded on a magnetic tape is played back at high speed (visual search). The present invention relates to a search noise removal device.

"Prior Art and its Problems" Usually, a magnetic recording and reproducing bag M (
Hereinafter, it will be referred to as a VTR. ) has a visual search mode that allows you to quickly find the video you want to watch.

When the visual search mode is set, the traveling speed of the magnetic tape becomes faster, so that the reproducing head provided on the rotating magnetic head has an azimuth shift as shown by numerals 5 and 6 in FIG. Since the trace will be traced across a number of different tracks, there will be parts where no playback output can be obtained from the playback head, and the screen of the TV connected to the VTR will show a section corresponding to the track for which no playback output can be obtained. The part that is displayed will be displayed as a noise bar.

This is called search noise.

This search noise occurs in multiple irregularities on the screen, causing the image on the screen to become distorted and making it difficult to find the image you want to see.
As a countermeasure for this, conventionally, in order to reduce this search noise as much as possible, a playback head for search noise prevention, which has the same head azimuth angle as the playback head that is paired with the playback head, is installed near the playback head. ,
These two heads are alternately switched each time a track is crossed, and the azimuth of the track being played back and the output of the playing head that is being played back are output as playback outputs.

However, in a VTR that increases the number of playback heads to prevent search noise from occurring, it is obvious that by adding a head to prevent search noise, the number of rotating magnetic heads increases. This complicates the structure and increases costs. Furthermore, when switching between the normal playback head and the search noise prevention playback head, the FM signal between the images becomes discontinuous, causing a problem in that switching noise appears on the image on the screen.

``Object of the Invention'' The present invention has been made to solve the problems of the conventional art as described above. By outputting the video signal stored in the memory to the portion where the playback head cannot obtain a playback output, search noise and switching noise are eliminated from the screen image as a whole even in the visual search mode. The purpose is to prevent it from appearing.

"Summary of the Invention" In the present invention, a video signal stored in a memory is output to a portion where the playback head cannot obtain a playback output, and the video signal is recorded on a magnetic tape at a predetermined frame frequency. In a magnetic recording/reproducing device having a function of reproducing an FM signal related to a video with a rotating magnetic head at a speed multiple times the frame frequency, the FM signal related to the video is
a high-speed reproduction signal generating means for outputting a signal to reproduce the reproduction speed of the M signal at an even multiple of the frame frequency; a second head: a control signal generating means for outputting a signal at a frequency corresponding to the signal when the signal is output from the high speed reproduction signal generating means; and a second head based on the signal output from the control signal generating means. head selection means for selecting the first head and the second head; storage command means for outputting a storage command signal based on the signal output from the control signal generation means; Storage means for storing, as digital data, an electric signal output from either the first head or the second head selected by the head selection means while the command signal is being output; and: the control signal generation means. D/A converting means for converting digital data stored in the storage means into an electrical signal based on a signal output from the control signal generating means; A signal for converting the digital data stored in the storage means into an electrical signal is outputted to the /A converting means, and the electrical signal outputted from the D/A converting means and the signal selected by the head selecting means are outputted. and a switching means for switching an electrical signal output from either the first head or the second head.

Therefore, as shown in FIG.
When a signal to increase the playback speed of the magnetic tape is output from 6, a signal of a predetermined frequency is output from control signal generating means 17 to storage command means 3, head selection means 9, and switching means 12. Based on the signal, the head selection means 9 periodically switches to select the first head 5 or the second head 6 which has already outputted the electrical signal, and the storage command means 13
The switching means 12 issues a command to store the digital data between the electric signals output from the head selection means 9 in the storage means 14 in synchronization with the head selection means 9; electrical signal and storage means 1
The electric signal outputted from D/A conversion means 15 from D/A conversion means 15 is switched at a predetermined period.

The switching means 12 inputs the electric signal when the head selection means 9 outputs the electric signal, and inputs the electric signal when the head selection means 9 does not output the electric signal. The electrical signal input path is switched so that the electrical signal outputted from the means 14 via the D/A converting means 15 is input.

As a result, even in the visual search mode, search noise is not generated in the image on the screen.

“Embodiments of the invention” The invention will now be described with reference to the illustrated embodiments.

FIG. 2 shows a schematic configuration diagram of a VTR control unit equipped with a search noise removal device according to the present invention. As shown in the figure, a capstan 2 connected to a motor (not shown) controlled by a tape running control circuit 1 drives the magnetic tape 4 in a predetermined direction by compressing the magnetic tape 4 with a pinch roller 3. do. The FM signal that is connected to the video recorded on the magnetic tape 4 is sent to the rotating magnetic head 5 as a first head that comes into sliding contact with the tape 4 and the second rotating magnetic head.
The signal is converted into an electrical signal by a rotating magnetic head 6 serving as a head. The rotating magnetic head 5 has a preamplifier 7.
However, a preamplifier 8 is connected to each rotating magnetic head 6, and the preamplifier 7F3 and preamplifier 8 amplify the weak electrical signals output from the respective heads. Further, the preamplifier 7 and the preamplifier 8 are connected to a fixed contact 9a and a fixed contact 9b of a selection circuit 9 as head selection means, respectively, and the movable contact 9
C includes an FM demodulation circuit 10 that converts the FM signal into a video signal.
is connected. The demodulated electrical signal output from the preamplifier 7 or preamplifier 8 selected by the selection circuit 9 is input to the FM demodulation circuit 10 via the movable contact 9C, where it is FM demodulated and converted into a video signal. Roughly speaking, the FM demodulation circuit 10 is connected to an A/D converter 11 for converting the video signal into a digital signal, and a fixed contact +2a of a switching circuit 12 as a switching means. The A/D converter 11 is connected to a memory 4 connected to an address selector 13 as a storage command means, and the digital signal output from the A/D converter 1 is
The data will be stored at a predetermined address of the memo I 14, which serves as storage command means, designated by the address selector 13. Further, a D/A converter 15 connected to the fixed contact 12b of the switching circuit]2 is connected to the memory 14, and the digital signal stored in the address of the memo 1 to 14 specified by the address selector 13 is connected to the memory 14. is D/A
The converter 15 converts the signal into a video signal again. In addition, the control switch 16 as a high-speed reproduction signal generation means for specifying the video reproduction speed, etc. includes a control signal generation means for comprehensively controlling the tape running control circuit, the selection circuit 9, the memory 14, and the switching circuit 12. A control signal generator 17 is connected thereto. The signal output from the control signal generator 17 is transmitted to the tape running control circuit 1.
The running speed of the magnetic tape 4 is set to a specified speed through the A/D converter of the memory 14, and the switching period of the movable contact 9c of the selection circuit 9 is set to a period corresponding to the running speed of the magnetic tape 4.
The writing period of the digital signal output from the magnetic tape 4 and the reading period of the digital signal to the D/A converter 15 are set to correspond to the running speed of the tape 4, and the switching period of the movable contact +2c of the switching circuit 12 is set to the period corresponding to the running speed of the tape 4. Each is controlled so that the cycle corresponds to the traveling speed of the vehicle.

On the other hand, FIG. 3 shows the recording state of information related to the video recorded on the magnetic tape 4 at a predetermined frame frequency, and the rotating magnetic head 5 and Rotating magnetic head 6
The trajectory is shown.

As shown in the figure, the information included in the video signal is magnetically recorded on a track at a certain angle with respect to the running direction A of the magnetic tape 4. In addition, the rotating magnetic head 5
and the rotating magnetic heads 6 are arranged at different angles θ (head azimuth angle) 18 with respect to the direction perpendicular to the rotation direction of the rotating magnetic heads 5. ing.

The VTR control section configured as described above operates as follows. The operation will be explained in detail below with reference to FIGS. 2 to 6.

First, when the regeneration switch of the control switch 16 is pressed, the control signal generator 17 outputs a signal to the switching circuit 2 to connect the movable contact 12c to the fixed contact 12a, and the signal to connect the movable contact 12c and the fixed contact 12a is output. When the connection is established, a signal to drive the magnetic tape at a normal speed is output to the tape running control circuit 1, and the magnetic tape 4 is
It is driven at normal speed by the capstan 2 and pinch roller 3. When the magnetic tape 4 is driven, the selection circuit 9 selects tracks a+, a2 . When tracing a3...a, the movable contact 9c is connected to the fixed contact 9a, and the rotating magnetic head 6 traces tracks b+, b2°b3...b, which have the same head azimuth angle. In this case, the movable contact 9c is connected to the fixed contact 9b. That is, the rotating magnetic heads 5, 6 are alternately switched at the same frequency as the frame frequency so that the reproduction output of the rotating magnetic head tracing the magnetic tape 4 can be obtained. And the electrical signals output from each preamplifier 7.8 are FM? Jij tone circuit] O converts the video signal into a video signal, and this video signal is output to an image circuit (not shown) via the switching circuit 12, so that a continuous video image is displayed on the screen.

On the other hand, when the visual search switch of the control switches 16 is pressed, this switch signal causes the control signal generator 17 to output a signal to the tape running control circuit 1 to drive the tape at, for example, six times the normal speed. The magnetic tape 4 is driven by the capstan 2 and the pinch roller 3 at six times the normal speed.

Then, the control signal generator] 7 sends the selection circuit 9 to the selection circuit 9 as shown in FIG.
A) A digital signal having the same frequency as the frame frequency is output, and the level of this digital signal is
When the digital signal is L or Hl, the movable contact 9C is connected to the fixed contact 9a, and conversely, when the digital signal is L◯, the movable contact 9c is connected to the fixed contact 9b. When the selection circuit 9 is controlled in this way, the rotary magnetic head 5 and the rotary magnetic head 6 trace the magnetic tape 4 as shown in the trajectory 5.6 in FIG. As shown by the shaded area in FIG. 5(b), no electrical signal is inputted only to the area traced on the track having the same head azimuth angle as each magnetic head 5.6 (the shaded area). Therefore, in this case, the image obtained on the screen by the rotating magnetic head 5 via the FM demodulation circuit 10 and the image circuit is a portion S (hatched area) where the reproduced image exists, as shown in FIG. 4(a). and a portion N (white portion) where a noise bar appears are mixed. Similarly, the image obtained on the screen by the rotating magnetic head 6 is a mixture of reproduced images and noise bars, as shown in FIG. 8 (8).

Further, the A/D converter 11 converts the video signal output from the FM demodulation circuit 10 into a digital signal, and this digital signal is output from the control signal generator 17 as shown in FIG.
Based on a storage command signal as shown in C), the data is stored at a predetermined address in the memory 14 designated by the address selector ]3. Further, this stored digital signal is output to the D/A converter 15 based on the storage command signal. That is, when the level of the storage command signal is HI, the movable contact 12c is connected to the fixed contact 12a, and conversely, when the level is LO, the movable contact 12c is connected to the fixed contact 2b. The frequency of the signal output from the control signal generator 17 to the memory 14 and the switching circuit 12 is 1nl-1 times the frame frequency, where n is the playback speed, and in the above example, the playback speed is 6 times. Therefore, the frequency of the signal is five times the frame frequency.

As described above, when the VT sub-control unit is operated, when the rotating magnetic head selected by the selection circuit 9 has finished outputting an electrical signal, the electrical signal is converted into a video signal by the FM demodulation circuit 1o, and this electrical signal is converted into a video signal by the FM demodulation circuit 1o. The video signal is output to the image circuit via the fixed contact 12a and the movable contact 12c of the switching circuit 12, and is displayed as a video on the screen, and the video signal is converted into a digital signal by the A/D converter 11, This digital signal is the address selector 1
The data is stored at a predetermined address in the memory 14 designated by 3.

On the other hand, when the rotating magnetic head selected by the selection circuit 9 is not outputting an electrical signal, the fixed contact 12b and the movable contact 12c of the switching circuit 12 are connected, and the digital signal stored in the memory 14 is The signal is converted into a video signal by the A converter 15, and displayed as a video on the screen by the image circuit. The image projected on the screen in this way becomes an image that does not include noise bars as shown in FIGS. 6(a) and (1)). In the figure, the video obtained based on the video signal output from the FM demodulator 10 is the shaded area indicated by C in the figure.
The video obtained based on the video signal output from the D/A converter] 5 is the vertical line portion shown in the figure.

"Effects of the Invention" As explained above, according to the present invention, when a video signal is being output from the rotating magnetic head, the video signal causes the video V! to be displayed on the screen. At the same time, this video signal is stored in the memory, and when the video signal is not output from the magnetic head, the video is projected on the screen using the video signal stored in the memory, so that even when playing at high speed, Even if there is a search noise (noise bar), no search noise (noise bar) appears on the screen, and switching during video signal selection is performed by the video signal system, so no switching noise appears on the screen. Roughly,
Since the memory built into the VTR can be used for still playback and slow playback, the memory can be used effectively, and there is no need to provide a search head as in the past, which reduces manufacturing costs. This has the advantage of being able to avoid such problems.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a search noise removing device according to the present invention, FIG. 2 is a schematic block diagram of a VT sub-control unit equipped with a search noise removing device according to the present invention, and FIG. 3 is a block diagram of a search noise removing device according to the present invention.
Figures 4(a) and 4(b) show the recording pattern of the magnetic tape and the trajectory of the magnetic head when played back at twice the speed. Figure 5 (a) shows the resulting playback screen.
), (b), and (c) are waveform diagrams of important parts in the control section shown in FIG. FIG. 7 is a diagram showing a playback screen obtained during high-speed playback. 2...Main jabukun, 3...Pinch roller, 4.
...Magnetic tape, 5.6...Rotating magnetic head, 7
．． 8... Preamplifier, 9... Selection circuit, 9a,
9b, 12a, 12 b...Fixed contact, 9c, 12
c...Movable contact, 12...Switching circuit, A...
・Magnetic tape running direction, B... Rotating magnetic head rotation direction, θ... Head azimuth angle, C... Image portion obtained by the rotating magnetic head, D
...The video part obtained by the digital signal output from the memory. Patent applicant: Kako Kogyo Co., Ltd. Figure 1 Figure 4 Figure 5 Figure 6

Claims (3)

[Claims] (1) In a magnetic recording/reproducing device having a function of reproducing an FM signal related to a video recorded on a magnetic tape at a predetermined frame frequency using a rotating magnetic head at a speed multiple times the frame frequency, the FM signal related to the video is High-speed reproduction signal generation means for outputting a signal to be reproduced at an even number multiple of the frame frequency;
A first head and a second head that take out the FM signal related to the video and convert it into an electric signal; and a control signal that outputs a signal at a frequency corresponding to the signal when the signal is output from the high-speed reproduction signal generating means. Generating means: Based on the signal output from the control signal generating means,
head selection means for selecting the first head and the second head; storage command means for outputting a storage command signal based on the signal output from the control signal generation means;
storage means for storing, as digital data, an electrical signal output from either the first head or the second head selected by the head selection means while the storage command signal is being output from the storage command means; : D/A conversion means for converting the digital data stored in the storage means into an electrical signal based on the signal output from the control signal generation means; and: the signal output from the control signal generation means. Based on this, the D/A conversion means outputs a signal to convert the digital data stored in the storage means into an electrical signal, and
A search characterized by comprising a switching means for switching between an electrical signal output from a converting means and an electrical signal output from either the first head or the second head selected by the head selecting means. Noise removal device. (2) In claim 1, the storage means stores one of the electrical signals obtained by demodulating the FM signal related to the video.
A search noise removal device using a memory that stores a field or one frame as digital data. (3) In claim 1, the frequency at which each of the storage command means, the D/A conversion means, and the switching means is operated is based on the playback speed set by the high-speed playback signal output means as n. , the search noise removal device is |n|-1 times the frame frequency.