JPS62110381A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce a noise due to a crosstalk component that appears on a reproduced picture by providing a carrier frequency switching means and switching carrier frequency that FM modulates video signals band compressed by subsampling of M number of times (M is natural number) to make them differ by specified horizontal synchronizing frequency at every track. CONSTITUTION:Carrier frequency that FM modulates video signals is switched to differ by [n+(1/2M<+1>)fH (n is 0 or positive integer, fH is horizontal synchronizing frequency)] at every track. For instance, in the case where video signals band compressed by subsampling of M=1 number of times are FM modulated and recorded, the amount of shifting of a carrier shifting circuit 18 is set to (n+1/4)fH. When the frequency spectrum of the video signal at that time is recorded in a track A, video signals deviated by (n+1/4)fH are recorded in a track B. Accordingly, even when video signals obtained by restoring by band elongation FM demodulated signals are image-displayed, the crosstalk component becomes oblique checkered pattern and is not conspicuous visually.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a magnetic recording and reproducing device that performs FM modulation on a luminance signal and records and reproduces it on a magnetic tape using a guard panless method, such as a video tape recorder (VTR). .

[Technical background of the invention and its problems] Conventionally, a magnetic recording and reproducing device (hereinafter referred to as V
TR), in order to reduce crosstalk interference from adjacent tracks, the recording FM carrier frequency is set to the horizontal synchronization frequency f II of (n+l
/2) A method is adopted in which recording and reproduction are performed with different fH values. This method will be briefly explained below.

First, looking at the frequency spectrum of the luminance signal above, the fourth
As shown in the figure, a large energy component is generated at the horizontal synchronization frequency f I+ interval. Therefore, a modulated signal obtained by FM modulating this luminance signal also has a spectrum as shown in the figure.

Here, the tape pattern of the helical scan guard bandless method will be explained with reference to FIG.

In the figure, 11 is a magnetic head, and 2 is a magnetic tape, AI.

A2. BO and Bl indicate track patterns. Assuming that the A1 track is being reproduced now, the A1 track reproduction signal contains crosstalk components from the BO and B1 tracks. At this time, if the FM luminance signals of the BO and B11 racks adjacent to the A1 track are frequency-shifted by (n+1/2)fi+ as described above, the At track playback signal will be as shown in FIG. (shown by the solid line in the figure) and the crosstalk component (shown by the dotted line in the figure) have a frequency interleaving relationship. In addition, FIG. 6 shows that the FM luminance signals recorded on the adjacent tracks BO and Bl are AI, and the FM luminance signals recorded on the A2 track are
The frequency spectrum is shown when the frequency of the M luminance signal is shifted by +1/2fl+.

Therefore, the crosstalk components appear as diagonal checkered stripes on the screen where the Al track reproduction signal is reproduced. Such a diagonal plaid is visually unobtrusive. In other words, in a guard panless type VTR, deterioration in image quality is prevented by making the FM luminance signals differ by (n+1/2)fH between adjacent tracks.

By the way, high-definition imaging has been proposed for television broadcasting, and has recently entered the practical stage.

In this high-definition television broadcasting system, in order to increase the bandwidth of the video signal, the video signal is subsampled during transmission to compress the bandwidth. The frequency spectrum of the video signal subjected to this subsampling is as shown in FIG. 7, in which the main signal (indicated by a solid line in the figure) and the folded signal (indicated by a dotted line in the figure) are interleaved. Therefore, when a conventional VTR is used to record and play back a video signal whose bandwidth has been compressed by subsampling, the track playback signal will be mixed with crosstalk components from adjacent tracks as described above, resulting in repeated playback signals. A crosstalk component due to the main signal of an adjacent track overlaps the signal frequency, and a crosstalk component due to the folded signal of the adjacent track overlaps the main signal frequency of the reproduced signal, making it impossible to extract and remove the crosstalk component. When a video signal obtained by expanding the band of such a reproduced signal and then displaying the video signal as an image is displayed, crosstalk components appear as vertical stripes, and the quality of the reproduced image deteriorates significantly.

[Purpose of the Zukomei] This invention was developed to improve the above-mentioned problems, and when recording a video signal band-compressed by subsampling using the guard panless method11),
Even if a crosstalk component from an adjacent track is mixed into the playback signal, the noise due to the crosstalk component that appears on the playback screen can be made relatively inconspicuous, and this makes it possible to display a good +1 raw image. The purpose of the present invention is to provide a magnetic recording/reproducing device that can perform the following functions.

[Summary of the Invention] That is, the magnetic recording and reproducing apparatus according to the present invention performs helical scanning on a magnetic medium by FM modulating a video signal band-compressed by ~1 subsampling (M is a natural number).
In the case of recording using the guard bandless method, the carrier frequency for FM modulating the video signal is set for each track as (n + M + l) f I ((where n is O or a positive integer, and f II is the horizontal synchronization frequency). The present invention is characterized in that it includes a carrier frequency switching means for switching the carrier frequency so that the carrier frequency is different.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows the configuration of a recording section of a VTR to which the present invention is applied. A video signal band-compressed by the above-mentioned subsampling is supplied to an AGC (automatic gain control) circuit 14 via an input terminal 13. , the amplitude is adjusted to a certain level. Then, a YC (luminance/color) separation circuit 15 separates the luminance signal Y and a color signal C, and the luminance signal Y is subjected to signal processing such as pre-emphasis, dark clip, and white clip in the signal processing circuit 16. , is FM modulated by the FM modulation circuit 17. At this time, the FM modulation circuit 17 uses the carrier shift circuit 18 to transmit 1/4 fl of the FM carrier wave for each track in the A track recording period and the B track recording period! It is shifted and interleaved.

Here, the FM-modulated luminance signal is filtered through a bypass filter (H
PF) 19 attenuates the lower sideband of the FM signal, a band below about IMIIZ for inserting the low frequency conversion color signal, and is amplified by the amplifier 20. The luminance signal Y' obtained in this way is mixed with the low-frequency converted color signal C' converted into a low-frequency signal by the YC mixing circuit 21, and then sent to the magnetic heads (A head, B head) via the recording amplifier 22. 23 and recorded on a magnetic tape 24 using a helical scan guard bandless method.

In the figure, reference numeral 25 denotes an adder, and the adder 25 frequency-multiplexes a time base collector pilot signal S from an oscillator (not shown) onto the FM modulation signal. This time base collector pilot signal S is a reference signal for time base correction during reproduction.

The operation of the above configuration will be described below with reference to FIGS. 2 and 3. Here, a case will be described in which a video signal compressed in 11 areas by M=1 subsampling is recorded.

The video signal band-compressed by one subhumbling is F
When recording with M modulation, the carrier shift circuit 18
Set the shift amount to (n+1/4)fit. The frequency spectrum of the video signal at this time is as shown in the diagram ':j Ru. Therefore, when the A track is reproduced, the frequency spectrum of the A track reproduced signal becomes as shown in FIG. That is, in FIG. 2, the solid line is the main signal, the dotted line is the return signal, and the dashed line is B l-
It shows crosstalk components due to the main signal from the rack and the folded signal. Even when this FM reproduction signal is FM demodulated, its frequency spectrum remains unchanged. Therefore, even when the video signal restored by band-expanding the FM demodulated signal is displayed as an image, it becomes a crosstalk component or a diagonal checkered pattern, which is visually unnoticeable. In other words, deterioration of reproduced image quality can be prevented.

As for the actual circuit configuration, the conventional circuit configuration can be used as is, so the carrier shift amount of the carrier shift circuit 18, which conventionally switches the FM carrier frequency of the adjacent track by a head switching pulse (vertical synchronization pulse), can be changed. (n + 1/2) full to (n +
1/4) f II l It is only necessary to change it so that it can be switched. Also, during playback, the FM demodulated signal is (n + 174) f 1 between adjacent tracks.
Since there is a DC potential difference equivalent to 1 minute, this D
It is necessary to cancel the C'% difference, but this is also conventional (n+1
/2) The shift return amount of the carrier shift return circuit that canceled the DC potential difference corresponding to the full amount is (n + l/4
) Just change it to f It. The above can be considered in the same way when the number of subsamplings is 2 or more M times, so the explanation thereof will be omitted.

Next, when recording the pilot signal S for the time base collector by frequency multiplexing on a signal obtained by FM modulating the video signal band-compressed by two series of subsampling, the frequency is set as (n+l/ 4) Set to fj. According to this, the crosstalk component of the pilot signal that appears in the reproduced signal is extracted at the same frequency as during recording, so it does not affect the main signal and the folded signal from the reproduced track.

Furthermore, considering the case where a video signal whose band has been compressed by sampling M times is recorded, M folded signals are included between the main signals in the frequency spectrum of this video signal. Therefore, if the shift amount of the carrier shift circuit 18 is set to (n+M+l)fH,
Crosstalk components due to the main signal and aliased signal from adjacent tracks do not overlap with the main signal and aliased signal from the reproduction track. Furthermore, when frequency multiplexing the pilot signal, by setting the frequency to (n+H+1) f H , the crosstalk component of the pilot signal will not overlap with the main signal and folded signal of the reproduced signal.

Therefore, even if the magnetic recording and reproducing device configured as described above records a video signal whose band has been compressed by subsampling, the crosstalk component from the adjacent track does not overlap with the information component of the reproduced signal, so the image quality deteriorates significantly. It is possible to play videos with a small number of images.

[Effects of the Invention] As detailed above, according to the present invention, when a video signal band-compressed by subsampling is recorded and played back using the guard panless method, crosstalk components from adjacent tracks are mixed into the playback signal. However, it is possible to make the noise caused by the crosstalk component appearing on the reproduction screen relatively inconspicuous, thereby providing a magnetic recording and reproducing apparatus that can display a good reproduced image.

[Brief explanation of drawings]

1 and 2 are for explaining one embodiment of the magnetic recording and reproducing apparatus according to the present invention, and FIG. 1 is a block diagram showing the configuration of the recording section of the magnetic recording and reproducing apparatus to which the present invention is applied. 2 is a characteristic diagram showing the frequency spectrum characteristics of the reproduced signal of the same embodiment, FIG. 3 is a diagram for explaining another embodiment of the present invention, and FIG. 4 is a diagram showing the frequency spectrum characteristics of the reproduced signal of the same embodiment. Characteristic diagram showing the frequency spectrum. Figure 5 is a diagram to explain the helical scan guard bandless method of the magnetic recording and reproducing device. Figure 6 is the frequency of the reproduced signal when recorded using the method shown in Figure 5. Characteristic diagram showing spectral characteristics,
FIG. 7 is a characteristic diagram showing the frequency spectrum characteristics of a video signal band-compressed by one subsampling. 11...Magnetic head, 12...Magnetic tape, 13.
...Input terminal, 14...AGC circuit, 15...Y-
C separation circuit, 16... signal processing circuit, 17... FM
Modulation circuit, 18... carrier shift circuit, 19.・・・
・Bypass filter, 20...Amplifier, 2I...Y
-C mixing circuit, 22...recording amplifier, 23...magnetic head, 24...adder, Y...luminance signal, C...
- Color signal, Y'... Luminance FM modulation signal, C... Color low-pass conversion signal, S... Pilot signal for time base collector. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 3

Claims (1)

[Scope of Claims] A magnetic recording and reproducing device that performs FM modulation on a video signal band-compressed by M times (M is a natural number) of subsampling and records the video signal on a magnetic medium using a helical scan guard bandless method. FM modulated carrier frequency for each track (n+1/[_2M+1]) fH (where n is 0 or a positive integer, and fH is the horizontal synchronization frequency)
1. A magnetic recording and reproducing device comprising carrier frequency switching means for switching the carrier frequency to be different.