JPS5818830B2 - Video signal recording method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal recording method and apparatus, in which the difference in carrier frequency of FM modulated waves recorded on adjacent tracks is set to a frequency that has an interleaving relationship with the video signal. A recording method and method that can reduce interference between adjacent tracks, thereby recording with fewer or no guard bands between each track, and increasing the utilization efficiency of a recording medium for recording and reproducing. The purpose is to provide equipment.

Generally, in a video tape recorder or a cassette type video tape recorder, when a signal of one adjacent rack is played back due to track deviation during playback, beat disturbance occurs on the screen.

Conventionally, guard bands were provided between video tracks on the tape to prevent beat disturbances from occurring on the screen.

For example, in the case of a cassette type, the video track width is 85 μm, and the guard band has a width of 50 μm, and the guard band width is 63 fo compared to the track width, which has the drawback that the efficiency of magnetic tape usage is extremely low. there were.

The present invention eliminates the above-mentioned drawbacks, and each embodiment thereof will be described below with reference to the drawings.

FIG. 1 shows a block system diagram of one embodiment of an apparatus for carrying out the video signal recording method according to the present invention.

In the same figure, the video signal input to input terminal 1 is AGC
A circuit 2 controls the signal to a specified level, and an FM modulation circuit 3 performs FM modulation.

At this time, the frequency shift of the FM modulated wave is the synchronization signal tip (
The sync chip) is set to 2.5 MHz, and the white end (white peak) is set to 4 MHz.

The FM modulated wave is amplified by an F'M recording circuit 4 and recorded on a magnetic tape 6 by a magnetic head 5.

The above system is similar to the conventional recording method.

On the other hand, the FM modulated wave from the FM modulation circuit 3 is supplied to the frequency conversion circuit 7, and the FM modulated wave from the local oscillation circuit 8 is
The frequency is converted using a signal with an oscillation frequency of 55 MHz, and the signal becomes 1.
It becomes an FM modulated wave of 3.955 to 15.455 MHz.

This FM modulated wave is supplied to the frequency conversion circuit 9, where it is frequency converted by a signal with an oscillation frequency of 10.739Hz from the local oscillation circuit 10, and is converted into an F of 3.216 to 4.716MHz.
The output FM modulated wave of the FM modulation circuit 3, which was M modulated wave and had a frequency deviation of 2.5 to 4 MHz, was 0.716 M.
This means that it has been converted to Hz.

This FM modulated wave is amplified by the FM recording circuit 11 and recorded by the magnetic head 12 on the magnetic tape 6 adjacent to the track formed by the magnetic head 5 .

Therefore, there is a difference of 0.716 MHz between the frequencies of the FM modulated waves recorded on adjacent tracks on the magnetic tape 6 by the magnetic heads 5 and 12.

In this case, in this embodiment, the FM modulation frequency supplied to the magnetic heads 5 and 12 is set to an odd number multiple of the horizontal scanning frequency 15.734 KHz of the video signal within approximately the same frequency band, that is, 1 times 2. (0,716MH2).

Note that it is desirable that adjacent tracks have a tape pattern in which the horizontal synchronizing signal portions are aligned on a line perpendicular to the tracks.

Next, in the reproduction system, the magnetic head 5 is moved from the magnetic tape 6.
The FM modulated wave of 2.5 to 4 MHz reproduced by the reproducing amplifier circuit 13 is amplified and supplied to the switching circuit 14 .

On the other hand, 3, 216 to 4. are reproduced by the magnetic head 12.
The 716 MHz FM modulated wave is amplified in the regenerative amplifier circuit 15 and then supplied to the frequency conversion circuit 16, where it is frequency converted with the signal from the local oscillation circuit 10 and becomes 13.95 MHz.
The frequency ranges from 5 to 15.455 MHz.

This FM modulated wave is further supplied to the frequency conversion circuit 17,
The signal from the local oscillation circuit 8 is frequency-converted to 2.5~
The FM modulated wave from the frequency conversion circuit 17 and the FM modulated wave from the regenerative amplifier circuit 13 are supplied to the switching circuit 14, where both FM modulated waves are alternately switched. and becomes one continuous signal.

This FM modulated wave is supplied to the FM demodulation circuit 18 and demodulated into the original video signal.

Now, let us consider a case where the magnetic head 5 or 12 causes a track shift during reproduction, and the - head mixes the FM modulated waves of the adjacent tracks and reproduces it.

At this time, the frequency of the FM modulation wave of the adjacent track is always 0.71 compared to the frequency of the FM modulation wave of the track to be reproduced.
Since there is a difference of 6 MHz, when these two FM modulated waves are demodulated, the FM modulated waves of adjacent tracks are 0.716 MHz.
It is mixed into the video signal as an unnecessary signal component having a single frequency of Hz and becomes a noise component.

However, since this frequency is 0°716 MI (z is an odd multiple of - in this example) of the horizontal scanning frequency as described above, there is an increment-leaping relationship with the video signal, and as a result, the noise component is hardly noticeable on the screen.

Therefore, even if the magnetic head 5 or 12 causes a track shift during scanning, the unnecessary signal component is hardly noticeable on the reproduced screen.

Therefore, the spacing between adjacent video tracks on the magnetic tape 6 used can be reduced to minimize or eliminate guard bands, and the utilization efficiency of the magnetic tape 6 can be increased.

In another embodiment, the output signal of the AGC circuit 2 is supplied to two FM modulation circuits with different frequencies of 0.716'MHz, and the output signal is transmitted onto the magnetic tape by two magnetic heads from each FM modulation circuit. Even if the frequency of FM modulated waves recorded on adjacent tracks is 0.
．． 71.6 MHz difference.

There will be.

FIG. 2 shows a block system diagram of a first part of yet another embodiment.

In this example 11.455MHz and 10.739MHz
A general crystal oscillator is used to obtain the special frequency of MH''z.

In the same figure. 3.57954 from crystal oscillator 25
The oscillation frequency of 5 MHz is supplied to the 115 frequency down-down circuit 26 to become 0.716 MHz, and the oscillation frequency is supplied to the 115 frequency down-down circuit 26 to become 0.716 MHz.
The frequency is 10.7.39 MHz.

Further, the 1.0.739 MHz output signal from the tripler circuit 27 is supplied to the frequency conversion circuit 28 together with the 0.716 MHz output signal from the i-down-down circuit 26.
It becomes 455 MHz.

In this case, the special local oscillators 8 and 10 in FIG.
It can operate more stably and can be constructed at a lower cost.

In addition, in order to reproduce a better quality screen, 0.716M
A method for removing unnecessary signal components of H2 is required, and an example thereof will be described below.

In FIG. 1, the video signal demodulated by the FM demodulation circuit 18 is passed through a 500KHz low-pass filter 9 and a 500KHz low-pass filter 9.
is supplied to a high-pass filter 20.

The video signal is divided into two parts at 500KHz,
The output signal component of the high-pass filter 20 is the comb filter 21
supplied to

The video signal from which unnecessary signal components have been removed by passing through the comb filter 21 is supplied to the synthesis circuit 22 together with the video signal which has passed through the low-pass filter 9, where they are synthesized and sent to the output terminal via the video signal output circuit 23. Taken from 24.

As described above, when the synthesis circuit 22 adds the signal delayed by one horizontal scanning period by the comb filter 21 and the next undelayed signal, frequency components whose phases differ by 180° every horizontal scanning period, that is, interleaved signals, are added. The ping frequency component is canceled to zero, and the unnecessary signal component at 0.716 MHz is removed.

At this time, the video signal component appears as the sum of the signals of the two horizontal scanning periods, but due to the nature of the video signal, one field and the next field have almost the same information, so the visual There is no problem whatsoever.

Note that similar results can be obtained even if a nonlinear amplification circuit such as a crispening circuit is used instead of the comb filter 21.

Further, in each embodiment, the FM modulated waves recorded on adjacent tracks have a frequency difference of 0.716 MHz, but the frequency is not limited to this, and any frequency that can be interleaved may be used. That is, similar results can be obtained if the horizontal scanning frequency is an odd multiple of -.

Furthermore, similar results can be obtained by changing the frequency of the FM modulated wave by switching the element or potential that determines the oscillation frequency of the FM modulation circuit 3 for each track.

Although the present invention has been described above with reference to an embodiment in which two magnetic heads are used to record and reproduce information on a magnetic tape, the present invention is not limited thereto, and may be applied within the scope of the claims. Of course, it includes.

As described above, the video signal recording method and apparatus according to the present invention allows carrier frequencies of FM modulated waves recorded on adjacent tracks to be set to approximately the same carrier frequency within an odd number of the horizontal scanning frequency of the video signal within the same frequency band. The frequency difference between adjacent tracks on the recording medium is such that it can be interleaved with the frequency of the video signal, so when playing back Even if the converter causes a track shift, the frequency difference between adjacent tracks is extracted as an unnecessary signal component, but in practice it is hardly noticeable on the playback screen. The guard bands can be reduced or eliminated so that they are adjacent to each other, and the utilization efficiency of the recording medium can be reduced, for example, by about 4% compared to the conventional method.
The frequency difference between signals recorded on adjacent tracks is extremely small compared to the transmission band, and the transmission band between the two tracks is almost the same, so the frequency band can be increased without expanding the frequency band. It has features such as being able to be used effectively.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of an apparatus for carrying out the video signal recording method according to the present invention, and FIG. 2 is a block diagram of main parts of another embodiment of the apparatus of the present invention. 1...Input terminal, 2...AGC circuit, 3...FM
Modulation circuit, 4, 11...FM recording circuit, 5, 12...
・Magnetic head, 6...Magnetic tape, 7, 9, 16, 1
7゜2B...Frequency conversion circuit, 8,10...Local oscillation circuit, 13.15...Regenerative amplifier circuit, 14...Switching circuit, 18...FM demodulation circuit, 19...Low pass filter, 20... high pass filter, 21... comb filter, 22... synthesis circuit, 23... video signal output circuit, 24... output terminal, 25... crystal oscillator, 26
...115 step-down circuit, 27...3 multiplier circuit.

Claims (1)

[Claims] 1. A carrier frequency of an FM modulated wave recorded on one track of mutually adjacent tracks on a recording medium, and an FM modulated wave recorded on the other track. 1. A video signal recording method comprising recording a video signal with a carrier frequency different from the carrier frequency of the video signal by a frequency corresponding to an odd multiple of 1/2 of the horizontal scanning frequency of the video signal within substantially the same frequency band. 2. FM modulate the human video signal using the FM modulation circuit. means for supplying the FM modulated wave taken out from the FM modulation circuit to a magnetic head forming one of the adjacent tracks after the FM modulation circuit; The carrier frequency of the FM modulated wave recorded on one track and the carrier frequency of the FM modulated wave recorded on the other track are set at a horizontal scanning frequency of the video signal within approximately the same frequency band. 1. A video signal recording device characterized in that a video signal recording device records data with a frequency that is different by an odd number multiple of 1/2 of the video signal recording device. 3. Means for FM modulating a human input video signal in a first FM modulation circuit and supplying it to a magnetic head forming one of the adjacent tracks, and FM modulating the input video signal in a second FM modulation circuit. a carrier frequency of the FM modulated wave recorded on the one track and a carrier frequency of the FM modulated wave recorded on the other track. 1. A video signal recording device for recording video signals in substantially the same frequency band, with the video signals being different by a frequency corresponding to an odd multiple of 1/2 of the horizontal scanning frequency of the video signal. 4. Means is provided for switching the oscillation frequency of the FM modulation circuit for FM modulating the human-powered video signal for each track, and the carrier frequency of the FM modulated wave recorded on one of the tracks adjacent to each other on the recording medium is provided. and the carrier frequency of the FM modulated wave recorded on the other track are recorded so that they differ by a frequency corresponding to an odd multiple of 1/2 of the horizontal scanning frequency of the video signal within substantially the same frequency band; A video signal recording device characterized by: 5. A first recording means for supplying a human-powered video signal to a magnetic head forming one of the adjacent tracks after FM modulating it in an FM modulation circuit, and a 3.579545MH
A crystal having an oscillation frequency of a first frequency conversion means that adds a frequency extracted from the first frequency converter ν stage, and a second frequency that adds a frequency extracted from the first frequency converter ν stage and a frequency extracted from the FM modulation circuit. a converting means, a third frequency converting means which adds the frequency taken out from the frequency multiplication means and the frequency taken out from the second frequency converting means, a second recording means for supplying the video signal to the magnetic head forming the other track, and converts the frequency taken out from the third frequency conversion means and the frequency taken out from the FM modulation circuit. The carrier frequency of the FM modulated wave recorded on one track and the carrier frequency of the FM modulated wave recorded on the other track are set so that the difference corresponds to 91/2 of the horizontal scanning frequency of the video signal. 1. A video signal recording device for recording video signals within substantially the same frequency band with a frequency corresponding to an odd multiple of 1/2 of the horizontal scanning frequency of the video signal.