JPS5910113B2 - PAL color video signal recording/playback method and recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording/reproducing method and a recording apparatus for PAL color video signals.

A recording/reproducing machine that records video signals on magnetic tape, the so-called V
Generally, as shown in FIG. 1, in a TR, two rotating magnetic heads HA and HB are installed with an angular spacing of 1800 degrees, and a tape 1 is disposed obliquely on a tape guide drum 2 over a range of approximately 1800 degrees. The head H
Rotate so that A and HB rotate once in one frame,
Diagonal tracks are alternately formed in each field by the heads HA and HB.

The running speed of the tape 1 is selected so that a so-called guard pad is formed between the tracks formed by the heads HA and HB.

In such a recording/reproducing device, the amount of information that can be recorded on one tape is limited to about one hour, although this depends on the length of the tape and other factors. However, programs such as movies and sports are
When recording such programs, which often last for more than an hour, it is desirable to be able to record as long as possible on a tape of limited length.

For this reason, a method of recording without forming a guard band, ie, so that each track is in contact with each other, can be considered.

When such a recording method is adopted, crosstalk from adjacent tracks becomes a problem during reproduction, and therefore it is required to eliminate or reduce this crosstalk by some method. A method to solve this problem has already been proposed. That is, when two rotating magnetic heads HA and HB are used as described above, the inclinations of the air gaps GA and GB of the heads HA and HB are made to be different from each other, as shown in FIG. Since video signals are generally recorded by angle modulation, for example, FM modulation, when the heads HA and HB are configured in this way, the tracks TA and TB formed by the heads HA and HB are in contact with each other.
That is, even if the tape speed is selected to be slow so that there is no guard band, the gap GA between the heads HA and HB during playback is
Due to the so-called azimuth loss due to the difference in the slopes of GB and GB, the crosstalk is significantly reduced.

Therefore, since the track pitch can be reduced, the recording amount can be increased.

However, although this method is effective when the video signal is a black and white video signal, it is inconvenient when the video signal is a color video signal. That is, when recording a color video signal,
Generally, the luminance signal is angularly modulated, for example, FM modulated, so that it occupies the high frequency side of the recordable band, and the carrier color signal is subjected to wave number conversion so that it occupies the low frequency side, and then recorded.

Therefore, by configuring the heads HA and HB as described above,
When recording at a high density as described above, the frequency of the luminance signal is raised, so the azimuth loss increases as described above and crosstalk decreases, but the carrier chrominance signal Since the frequency is kept low, azimuth losses are not increased and therefore crosstalk is not reduced.

In view of this point, the present invention provides a recording/reproducing method and a recording apparatus that particularly reduce crosstalk of carrier color signals.

Conventionally, the above-mentioned dark wave number conversion of the carrier color signal has been performed using a frequency conversion signal having a constant frequency and a constant phase.

In contrast, in the present invention, the phase of the frequency conversion signal is shifted by a constant phase every two horizontal intervals, and
A field in which a second track TA should be formed;
A constant relationship is maintained in the phase shift between the remaining every other track TB and the field to be formed.

That is, the frequency conversion signal from the station wave number conversion signal generation circuit, which will be described later, has a phase shift of 2 horizontal intervals in the field where the track TA is formed, and a phase shift of 2 horizontal intervals in the field where the N track TB is formed. l for each section! The phase is shifted by N. 5-M has the following relationship with M.

Here, the direction of phase shift is the advancing direction when N and M are positive;
When negative, the direction is slow. For example, N=3,
Assuming M=-6, in the field where the track TA is formed, the phase is advanced by π, that is, by 120, in two horizontal intervals, and in the field where the track TB is formed, the phase is advanced by - every two horizontal intervals.
Conversion of the carrier color signal to the original station wave number during reproduction in which the phase is delayed by π, that is, by 60, is also performed using a completely similar frequency conversion signal.

Hereinafter, a PAL color video signal recording and reproducing apparatus to which the present invention is applied will be specifically explained.

FIG. 3 shows an example of the overall circuit configuration of this recording/reproducing machine, in which 11 is an input terminal for color video signals to be recorded;
2 are output terminals for reproduced color video signals, HA and HB.
1 is a rotating magnetic head, which is spaced at an angular interval of 180 as shown in FIG. 1. For example, as shown in FIG. 2, the inclinations of the respective air gaps GA and GB are made different from each other. 1
Reference numerals 3 to 16 indicate recording/reproduction changeover switches, which are respectively switched to the contact R side during recording and switched to the contact P side during playback.

17 and 18 are pulse generators, which are provided in a relationship 180 in relation to the rotation axes of the heads HA and HB;
Frame phase pulses are obtained at predetermined rotation angle positions of A and HB, respectively.

First, let's explain the case of recording.

The color video signal from the input terminal 11 is passed through the low pass filter 2.
0 and extracts the luminance signal, which is sent to the AGC
Circuit 21. Subcarrier trap circuit 22, clamp circuit 2
3. The signal is sequentially passed through a pre-emphasis circuit 24 and a clip circuit 25 and then supplied to an FM modulator 26 for FM modulation.
The modulated luminance signal is supplied to a synthesizer 29 via a high-pass filter 27 and a recording amplifier 28.

The color video signal from the input terminal 11 is also supplied to a bandpass filter 30 to extract a carrier color signal, which is supplied to a frequency converter 36 through an ACC circuit 31 and frequency-converted to the lower frequency side. This frequency conversion is performed using a frequency conversion signal whose phase is shifted as described above. This frequency conversion signal is generated by a frequency conversion signal generation circuit having the following configuration. P.A.
When frequency converting the carrier color signal of an L system color video signal to the lower frequency side, the carrier frequency FL of the converted carrier color signal is generally selected to have a 100 line offset relationship, and for example, be done. Therefore, the frequency Fc of the frequency conversion signal is the carrier frequency of the original carrier color signal Fs
(=4.43MHz), the relationship is as follows.

In this example as well, if you are selected as the opening clerk,
40 is a so-called AFC circuit for forming a signal with a frequency of 44 fH; an oscillation signal from a variable frequency oscillator 41 with an oscillation center frequency of 44 fH is supplied to a frequency divider 42 and divided by one; The brightness signal is sent to the horizontal synchronizing signal separation circuit 43 through the contact R side of the switch 15.
The horizontal synchronizing signal is extracted from the phase comparator 4.
4, this horizontal synchronizing signal and the output signal of the frequency divider 42 are phase-compared, and the comparison error voltage is passed through the low-pass filter 4.
5 to a variable frequency oscillator 41, from which a signal with a frequency of 44 fH is obtained.

Then, a signal of 44fH(7) frequency from this oscillator 41 and a signal of 1fs'-18fH(7) from another oscillator 51.
The frequency signal is supplied to the frequency converter 52, and a signal having the frequency of the sum of the respective frequencies, that is, the frequency of Fc expressed by equation (3) is formed.

This Fc frequency signal is passed through the bandpass filter 5.
3 to the phase switching circuit 61, while frame period pulses obtained from the pulse generators 17 and 18, respectively, are supplied to the set side and the unset side of the flip-flop circuit 62, so that the head HA forms the track TA. A pulse signal whose state is inverted in the field where the field to be output and the head HB should form the track TB is formed, and this pulse signal and the horizontal synchronization signal obtained from the horizontal synchronization signal separation circuit 43 are supplied to the switching signal formation circuit 63. . The switching signal obtained from the switching signal forming circuit 63 is supplied to the phase switching circuit 61, and the phase of the frequency conversion signal of the frequency of Fc is shifted every two horizontal intervals as described above.

That is, in the field where the track TA is formed by the head HA, the phase is shifted by r every two horizontal sections, and the field where the track TA is formed is shifted by r every two horizontal sections.
In the field where track TB is formed by l! every two horizontal sections. The phase is shifted step by step. And this phase shift MO
The frequency conversion signal is supplied to the frequency converter 36, and the carrier color signal is shifted to the lower frequency side, that is, the carrier frequency signal is
So that L=Fc-Fs=(44-18)f'H,
Frequency converted.

Therefore, as the frequency conversion signal is phase-shifted, the phase of the carrier wave of the frequency FL of the low-frequency converted carrier color signal is also shifted every two horizontal intervals, and a track TA is formed. In the field, the phase is shifted by r every two horizontal intervals,
In the field where track TB is formed, l! every two horizontal sections! The phase shifts by M.

This carrier color signal is supplied to a synthesizer 29 through a low-pass filter 37 and a recording amplifier 38.

Then, a composite signal of the FM-modulated luminance signal and the carrier color signal that has been low-frequency converted using the special method described above, obtained from the synthesizer 29, is supplied to the heads HA and HB through the contacts R side of the switches 13 and 14. The tracks TA and TB are recorded at high density on the tape 1 with no guard band formed between the respective tracks TA and TB. Among the above-mentioned circuits, circuits 40, 51 to 57, and 61 to 63 constitute a frequency conversion signal generation circuit. The recording system is as described above. Next, let's talk about playback.

During reproduction, tracking servo is applied so that the head HA scans the track TA and the head HB scans the track TB, as in a normal recording/reproducing machine.

The playback output of heads HA and HB is controlled by switch 13.
and 14 are supplied to switch circuits 73 and 74 through regenerative amplifiers 71 and 72, respectively,
The pulse signal obtained from the above flip-flop circuit 62 turns on the switch circuit 73 in the field where the head HA reproduces the track TA, and turns on the switch circuit 73 in the field where the head HB reproduces the track TB.
4 is turned on, and the reproduced signals obtained from both switch circuits 73 and 74 are combined by a combiner 75.

This synthesized reproduction signal is supplied to a high-pass filter 81 to extract an FM-modulated luminance signal, which is supplied to an FM demodulator 82 through a limiter 81 and demodulated, and the demodulated luminance signal passes through a low-pass filter 83. The signal is supplied to a combiner 89 through a de-emphasis circuit 84.

The synthesized reproduced signal is also supplied to a low-pass filter 90 to extract a carrier color signal that has been low-pass converted using a special method as described above, and is supplied to a frequency converter 92 through an ACC circuit 91. converted to the original frequency. This same wave number conversion is performed using a same wave number conversion signal whose phase is shifted in exactly the same way as in the case of recording. That is, the reproduced luminance signal from the synthesizer 89 is transmitted to the switch 15.
is supplied to the horizontal synchronizing signal separation circuit 43 through the contact P side of the F
Of) A signal of the number of station waves is supplied. Then, this phase switching circuit 61 is controlled in the same way as in the case of recording, and FOO)
The phases of the frequency conversion signals having the same wave number are shifted every two horizontal intervals as described above. That is, in the field where the track TA is reproduced by the head HA, the phase is shifted by 11 every two horizontal intervals, and in the field where the track NTB is reproduced by the head HB, the phase is shifted by 1J every two horizontal intervals.

Then, this phase-shifted frequency M wave number conversion signal is supplied to the frequency converter 92, and the carrier color signal is frequency-converted so that the carrier frequency becomes Fs=Fc-FL. Ru.

The carrier color signal returned to its original frequency is supplied to a C-comb filter 94 through a bandpass filter 93.

The filter 94 is a delay circuit 9 having a delay time of 2 horizontal periods.
5 and a subtracter 96, and the carrier color signal from this filter 94 is supplied to a combiner 89. and output end 1
2, a reproduced color video signal is derived.

Note that the carrier color signal obtained from the C-shaped comb filter 94 is supplied to the burst gate circuit 54 through the contact P side of the switch 16 and a burst signal is taken out. The signals of the reference subcarrier frequency Fs are phase-compared, and the comparison error voltage is passed through the low-pass filter 57 to the oscillator 5.
1 to control its oscillation frequency, the so-called A
A PC circuit is configured.

When using the above recording/reproducing method, adjacent tracks T
Even when high-density recording is performed without forming a guard band between A and TB, the crosstalk of the carrier color signal is reduced to a substantially negligible level during reproduction.

Let me explain why.

Since the carrier frequency of the original carrier color signal is Fs=view I, the original carrier color signal recorded on the track TA is 81n [ω8t+θ1] in any n-th horizontal section.
...(5-1), and in the n+2th horizontal section after that, Sin[ωs(t+2τ)θA}...(6-
1), respectively.

However, τ is one horizontal period. Similarly, as shown in FIG. 4, the original conveyed color signal recorded on the track TB has a recording position in the mth horizontal section adjacent to the recording position of the nth horizontal section on the track TAO. , and the two subsequent recording positions are track TA (7
)n + m+ adjacent to the recording position of the second horizontal section
In the second horizontal interval, they are respectively represented by .

In the field where the track TA is recorded, the phase of the frequency conversion signal supplied to the frequency converter 36 advances by f every two horizontal intervals (delays when N is negative). , the frequency conversion signal is represented by in the n-th horizontal interval and by in the n+2-th horizontal interval two subsequent horizontal intervals.

However, a is an integer. Similarly, in the field where track TB is recorded, the phase of the frequency 2π wave number conversion signal supplied to the frequency converter 36 advances by -i every two horizontal intervals (when M is negative, it is delayed). from)
The frequency conversion signal is, in the m-th horizontal section,
In the (m+2)th horizontal section after that, the following are respectively expressed.

However, b is an integer. Therefore, in the n-th horizontal section, the low-frequency converted carrier color signal actually recorded on the track TA is a signal expressed by equation (5-1) and (5-2).
), the angular frequency is ωL = ωc - ωs, and this is expressed as (6 Among those obtained as the product of the signal expressed by equation (1) and the signal expressed by equation (6-2), the angular frequency is ωL=ωo−ωs, which is expressed by .

Similarly, the low-band converted carrier color signal actually recorded on the track TB is (7-1) in the m-th horizontal section.
) and the signal expressed by the equation (7-2)}Yo, the angular frequency is ωL=ωo−ωs. This is expressed as (8-1
) of the signal expressed by equation (8-2) and the signal expressed by equation (8-2), the angular frequency is ωL=
ωc−ωs, which is expressed as ωc−ωs.

FIG. 4 shows these recorded signals.

When the track TA is reproduced during reproduction, in the field where the track TA is reproduced, the phase of the frequency conversion signal supplied to the frequency converter 92 is the same as during recording. Since the phase advances by increasing in each interval (when N is a page, N is delayed), the frequency conversion signal is, in the horizontal interval where the signal of the n-th horizontal interval is reproduced, and after that, the signal for frequency conversion is The horizontal section in which the signal of the (n+2)th horizontal section of is reproduced is expressed as, respectively.

However, k is an integer. In this case, when the head HA reproduces the signal of the n-th horizontal section of track TA (7), it simultaneously receives the signal of the m-th horizontal section of the adjacent track TB (7) as crosstalk. The signal taken out from the filter 93 in the section is (5-3
) and the signal expressed by equation (5-4), the main signal whose angular frequency is ωs, the signal expressed by equation (7-3), and the signal expressed by equation (5-4).
4) It is the sum of the crosstalk components whose angular frequency is ωs, which are obtained as the product of the signals expressed by the equation.

Similarly, when the head HA reproduces the signal of the track TA(7)n+2nd horizontal section, it simultaneously picks up the signal of the adjacent track TB(7)m+2nd horizontal section as crosstalk. →・The signal extracted from the filter 93 in the horizontal section is the main signal whose angular frequency is ωs, which is obtained as the product of the signal expressed by equation (6-3) and the signal expressed by equation (6-4). One of the signals obtained as the product of the signal expressed by (8-3) and the signal expressed by equation (6-4),
It is the sum of crosstalk components whose angular frequency is ωs.

Therefore, the carrier color signal finally obtained from the C-comb filter 94 in any n+-2 horizontal section during which track TA is reproduced is expressed as:

and the original subcarrier frequency This is because it is selected due to the line offset relationship.

Also, since there is a relationship between N and M as shown in the formula, it follows.

Therefore, becomes.

That is, in the comb filter 94, the adjacent track T
Crosstalk components from B are canceled out.

In this way, crosstalk of the carrier color signal is eliminated by phase-shifting the frequency conversion signal by the opening factor mentioned at the beginning and inserting the C-shaped comb filter 94 in the reproduction system. As an example, as described above, if N=3 and M=-6, track TA may be advanced by 1200 every two horizontal sections, and track TB may be delayed by 600 every two horizontal sections. Fig. 4 shows the phase state of the carrier wave of the frequency conversion signal in this case, and therefore of the low frequency converted carrier color signal to be recorded, as a vector, and arrow 3 indicates the track. This is the direction in which TA and TB are formed.

The slopes of the air gaps GA and GB of the heads HA and HB do not have to be different.

That is, as a countermeasure against the crosstalk of the luminance signal, another method, for example, the following method may be used. this is,
During recording, for example, by changing the DC bias in the FM modulator 26 between the field where the track TA is formed and the field where the track TB is formed, the luminance signal is changed as shown by straight line 4 in FIG. 5 for the track TA. FM modulation is performed according to the characteristics, and on the other hand, in track TB (
11+゛-2) FH only (l=0.1.2...
・) FM modulation is performed according to the characteristics shown by the shifted straight line 5.

Therefore, the modulation frequencies interleave each other between tracks TA and TB, and the crosstalk components during playback have opposite phases when viewed between adjacent horizontal sections, and the crosstalk of the luminance signal is They are visually offset and become less noticeable on the playback screen. As described above, according to the present invention, when recording a PAL color video signal, crosstalk of a carrier color signal can be removed by a simple power method.

Therefore, PAL color video signals can be recorded with high density, and the recording time can be greatly increased compared to the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a rotating magnetic head mechanism of a PAL color video signal recording/reproducing apparatus to which the present invention is applied, FIG. 2 is a diagram showing an example of the state of the magnetic gap of the rotating magnetic head, and FIG. The figure is a system diagram of an example of a recording/reproducing apparatus according to the present invention, and FIGS. 4 and 5 are diagrams for explaining the same. 36 and 92 are frequency converters, 61 is a phase switching circuit, 9
4 is a C-shaped comb filter.

Claims (1)

[Claims] 1. During recording, the phase is shifted by 2π/M every two horizontal sections in the period corresponding to every other track, and the phase is shifted every two horizontal sections in the period corresponding to the remaining every other track. 2π/
A frequency conversion signal whose phase is shifted by M (however, (1/N) - (1/M) = 1/2, and the direction of the phase shift is such that the above N and M are correct). The high frequency carrier color signal is frequency-converted into a low frequency carrier color signal (when it is in the leading direction, and when it is negative, it is in the slowing direction), and during playback, the above low frequency conversion is performed in the opposite manner to that during recording. By frequency-converting the low-band carrier color signal to the original high-band carrier color signal and passing the converted high-band carrier color signal through a comb filter, crosstalk of the carrier color signal between the tracks is eliminated. A method for recording and reproducing PAL color video signals, which removes . 2 During recording, the phase is shifted by 2π/N every two horizontal intervals in the period corresponding to every other track, and the phase is shifted by 2π/N every two horizontal intervals in the period corresponding to the remaining every other track.
A frequency conversion signal whose phase is shifted by M (however, (1/N) - (1/M) = 1/2, and the direction of the phase shift is such that the above N and M are correct). The high frequency carrier color signal is frequency-converted into a low frequency carrier color signal (when it is in the leading direction, and when it is negative, it is in the slowing direction), and during playback, the above low frequency conversion is performed in the opposite manner to that during recording. By frequency-converting the low-band carrier color signal to the original high-band carrier color signal and passing the converted high-band carrier color signal through a comb filter, crosstalk of the carrier color signal between the tracks is eliminated. A recording device used in a method for recording and reproducing color video signals of the PAL system, which removes color video signals, the recording device comprising: at least a frequency conversion circuit for converting the frequency of the high frequency carrier color signal into a low frequency carrier color signal; and a frequency conversion signal generation circuit that generates a signal, and by supplying the frequency conversion signal generated by the generator to the frequency conversion circuit, the frequency conversion of the high frequency carrier color signal to the low frequency carrier color signal is provided. A recording device for a PAL color video signal, which is characterized by converting the video signal.