JPS6231555B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic reproduction device for color video signals between different television standard systems, and more particularly, to a magnetic reproducing device for color video signals between different television standard systems, and in particular, the present invention relates to a device for magnetically reproducing color video signals between different television standard systems, and in particular, the number of horizontal scanning lines differs from each other, and color video signals in a predetermined horizontal period are omitted or overlapped. The present invention relates to a magnetic reproduction device for color video signals capable of compensating for phase shifts of carrier color signals due to various factors.

Typical television standard systems include:
There are NTSC, PAL, and SECAM systems. The NTSC system has a field frequency of 60Hz and the number of scanning lines is 525, while the PAL system and SECAM
The method (these are also called CCIR methods) has a field frequency of 50 Hz and a number of scanning lines of 625. Furthermore, the color signal transmission method is different; in the PAL method, the polarity of the I signal is inverted for each scanning line,
In the SECAM method, the I signal and Q signal are FM modulated and sent alternately (line sequentially) for each scanning line.

Therefore, due to differences in scanning methods, color signal transmission methods, etc., television receivers and recording/playback devices designed for one television standard system cannot, in principle, play back video signals from other systems. Can not. When only a television receiver is used, it is sufficient to have one of the systems of the broadcasting stations that can be received, so the inconvenience caused by the difference in the systems described above is not so much of a problem. However, in recent years, with the spread of general-purpose recording and playback devices (video tape recorders, hereinafter referred to as VTRs), pre-recorded video tapes and video software have become widely available, and many people want to play video software of other formats. This is becoming more and more common. In this case, it would be sufficient to have all the VTRs and television receivers (or monitor receivers) for each television standard format, but for example, in an area where NTSC broadcasting is being carried out, if the PAL format or SECAM
It is very uneconomical to have PAL or SECAM system VTRs, receivers, etc. in terms of usage efficiency, and it is difficult to obtain PAL or SECAM system equipment in such areas.

For this reason, there is an increasing need for a conversion device that converts video signals of different television standard formats from one to the other.

However, such a video signal conversion device is
Currently, there are only large, expensive products for broadcasting stations, and no small, inexpensive products that can be supplied to video software stores, service shops, or even households have appeared on the market. .

SUMMARY OF THE INVENTION In view of these circumstances, it is an object of the present invention to provide a compact and inexpensive magnetic reproduction device for color video signals that can be incorporated into general household or semi-professional VTRs.

Another object of the present invention is to provide a magnetic reproduction device for color video signals in which a phase shift of a carrier color signal does not occur.

Preferred embodiments of the present invention will be described below with reference to the drawings. In this example,
Videotapes recorded in CCIR format can be converted to NTSC.
This figure shows an example of a magnetic reproducing device for color video signals that can be reproduced by a VTR of the same system.

First, the VTR used is one having a two-head helical scan type rotary head device. FIG. 1 is a perspective view showing the rotary head section of this type of VTR.
It has a rotary disk 2 that rotates in the direction. At the upper and lower positions of this rotary disk 2, there are upper and lower drums 3, which are fixed to the chassis of the VTR, etc.
4 is placed. The motor 5 rotates the rotating disk 2 at a frame frequency of 30Hz, which is the frame frequency of the NTSC system.
Rotate and drive. The magnetic tape 6 is wound diagonally around the upper and lower drums 3, 4, etc. over an angular range of just over 180 degrees, and is driven to run in the direction of arrow b.

As shown in FIG. 2, on the rotating disk 2,
Two rotating magnetic heads 7 _A and 7 _B are mounted at an angular distance of 180° from each other. Here, the rotating magnetic heads _7A , _7B are mounted on the head bases _8A , _8B via bimorph plates 9A, _9B , which are electro-mechanical conversion elements, so that the rotating magnetic heads _7A , 7B are arranged in the direction of the rotational axis. It can be displaced in the c direction.

Next, FIG. 3 shows a plan view of the videotape 6, on which a plurality of diagonal recording tracks T (however, only the center line is shown) are formed parallel to each other. There is. During recording in the PAL system, two rotating magnetic heads rotate at 25 Hz, and the recording tracks T are formed at a rate of 50 per second. Furthermore, on one recording track T, video signals for 312.5 horizontal scanning periods are recorded. When playing back such a videotape 6 on an NTSC VTR, the tape running speed is set to the same speed as during recording, and the rotating magnetic head is rotated at 30 Hz. At this time, six tracking trajectories (referred to as reproducing tracks) U of the rotating magnetic head are arranged for the five recording tracks _T1 to _T5 . Here, as mentioned above, the rotating magnetic head 7 is moved in the direction c of the rotation axis in FIG. 2, that is, in the width direction c of the recording track T in FIG.
by displacing the reproduction track U to the recording track T.
Position it correctly on top. In this way, 50 recording tracks T will be played back by 60 playback tracks U per second, and the field frequency will change.
Can be converted to 60Hz. In this case, 5
Any one of the book record tracks T ₁ to T ₅
A book, for example, recording track _T4 , is being reproduced overlappingly by two reproduction tracks _U4 and _U5 .

The reproduced signal obtained in this way is sent to the input terminal 10 in FIG.
As a result, the number of horizontal scanning lines is reduced from 625 in CCIR.
Converted to 525 NTSC. This line number conversion circuit section 11 writes the above-mentioned reproduction signal into a memory such as a CCD (charge coupled device) or a BBD (bucket brigade device), and appropriately selects a clock frequency for reading the signal. At the same time, video signals of 100 non-consecutive horizontal periods out of the 625 horizontal periods are dropped, and the remaining ones are made continuous. Therefore, there are 525 horizontal scanning lines in one frame, that is, 1/30 second, and conversion to an NTSC video signal is performed.

The above is a video signal conversion related to the scanning method, but in the case of a color video signal, it is necessary to further convert the frequency of the color subcarrier and correct the phase shift of the carrier color signal during the above-mentioned missing or redundant reading. be done.

Here, to explain the phase shift of the carrier color signal, for example, in a general VTR, the carrier wave of the color signal is converted to a low frequency and recorded.
This low frequency is not an integral multiple of the horizontal frequency _H , but has a predetermined offset. This is to reduce interference to the luminance signal, and for example, a carrier wave having a frequency such as (44-1/8) _H or (44-1/4) _H is used. Therefore, the phase of the carrier wave at the start of the horizontal period is sequentially shifted by the offset (for example, 1/8 wavelength) as shown in FIG. 5A. In this Figure 5, one horizontal period is (2-
1/8) wavelength. However, when a predetermined horizontal period is omitted or overlapped when converting the scanning method, the order of the shift by the offset is lost, a phase jump occurs at the end of the horizontal period, and the carrier wave becomes discontinuous. That is, in FIG. 5, if each of the horizontal periods . Furthermore, if the horizontal periods are read out overlappingly, the result will be as shown in FIG. 5C, where a phase lead of 1/8 wavelength will occur at the connection point '.

Therefore, these omissions and discontinuities in the phase of the carrier wave of the color signal at the time of redundant reading are corrected to make the carrier wave continuous as shown by the broken lines in FIG. 5B and C. This is the frequency conversion circuit section 12 shown in FIG.
This may be performed when converting the color subcarrier to the frequency of the NTSC system.

That is, the frequency conversion circuit section 12 uses a balanced modulator or the like to mix the frequency signal from the oscillator 13 with the low frequency carrier wave from the line number conversion circuit section 11, and converts the mixture into an NTSC carrier wave frequency. At this time, the phase of the output signal from the oscillator 13 is corrected by the phase correction circuit section 14 at the time of the above-mentioned omission or duplication, resulting in continuous
The NTSC carrier wave is made available to the output terminal 15. Here, a signal corresponding to the above-mentioned missing or duplicate read operation is supplied from the terminal 16 to the phase correction circuit section 14. In addition, the direction of the phase jump (delay or advance direction) when missing and when overlapped.
Since these are opposite to each other, the direction of phase correction in the phase correction circuit section 14 is also opposite.

A more specific configuration for converting such a scanning method and a conveyed color signal will be described with reference to FIGS. 6 to 9. These figures 6 to 9 show color video signals in PAL format.
This shows a conversion device that converts from the NTSC format to the NTSC format.

The aforementioned rotating disk 2, upper and lower drums 3 and 4
The magnetic tape 6 is wound around and guided around a guide drum such as a capstan 17 and a pinch roller 1.
8 in the direction of arrow b. motor 19
drives the capstan 17 to rotate. Furthermore, pulse generators 20 _A and 20 _B that detect the rotation of the rotating magnetic heads 7 _A and 7 _B and generate pulses are provided in relation to the rotating shaft of the rotating disk 2 and the _like . A pulse is obtained when _7B starts tracking on tape 6. Rotating disk 2
Since it rotates at 30Hz, each of these rotation detection pulses is 1/1, as shown in Figure 7A and B.
Since the pulses are obtained at 30 second intervals and the angular interval between the magnetic heads 7 _A and 7 _B is 180° (half a revolution), the time difference between each pulse A and B is 1/60 second.

On the other hand, on one side edge of the tape 6, as shown in FIG.
A square wave signal with a duty of 50% (arrows P _A , P _A
reference. ) is recorded as a control pulse. The upward arrow P _A of the rectangular wave signal in FIG. 3 indicates the rising edge, and the downward arrow P _B indicates the rising edge of the rectangular wave signal. The control head 30 detects this rectangular wave signal and reproduces the rising edge as a positive pulse and the falling edge as a negative pulse, as shown in FIG. 7C. The interval of this reproduction control pulse C is
Since the tape running speed is the same as when recording in PAL format, it is 1/50 second.

Next, a servo system for controlling the rotational speed and tape running speed of these rotary heads, and a control drive system for bimorph plates _9A and _9B for displacing magnetic heads _7A and _7B in the direction of arrow c will be explained.

First, a pulse A obtained from a pulse generator _20A is supplied to a phase comparator 21, where the phase is compared with a 30Hz reference pulse, and the comparison error voltage is supplied to the motor 5 via an amplifier 22. , the rotating magnetic heads 7 _A and 7 _B operate at 30Hz as described above.
It is controlled so that it rotates. Here, above 30Hz
The reference pulse is supplied to the input terminal 13, and can be obtained, for example, by frequency-dividing a clock pulse for reading out a CCD or the like, which will be described later. Further, the pulses A and B from the pulse generators 20 _A and 20 _B are sent to the flip-flop circuit 24.
Supplied to the set side and reset side of the As _shown in FIG.
“0” in the period during which _B tracks on tape 6
, and its inverse pulse shown in FIG. 7E are obtained.

Next, the control pulse C from the control head 30 is frequency-divided by a frequency divider 31 to 1/5 to obtain a pulse having a period of 1/10 second, as shown in FIG. 7F. In addition, the flip-flop circuit 24
The frequency of the pulse D is divided by 1/3 by the frequency divider 25 to obtain a pulse having a period of 1/10 second, as shown in FIG. 7G. These pulses F and G
A phase comparison is performed in a phase comparator 32, and the comparison error voltage is supplied to the motor 19 via an amplifier 33. In this way,
Pulses F and G have a constant phase relationship, and the third
One of the reproduction tracks U shown in the figure, _U1 , is controlled to be correctly positioned on the recording track T.

That is, in FIG. ₃ , diagonal tracks U ₁ , U _{2 ,} .
U ₁ is correctly located on the recording track T ₁ (but at the tracking start point). The remaining reproduction tracks U ₂ , . . . , U ₆ are not correctly positioned on the recording track T. For this purpose, the pulse shown in FIG. 7G from the frequency divider 25 is supplied to the sawtooth wave generating circuit 26, and as shown in _FIG . It becomes zero when tracking starts on ₁ , and head 7 _B starts playing track.
At the time of starting tracking on U ₄ , a sawtooth wave voltage is obtained that instantly changes from the maximum value 1/2V ₀ to the minimum value -1/2V ₀ .

This sawtooth wave voltage H is then supplied to the sampling and holding circuits 27 and 28, where it is sampled and held by pulses A and B, respectively, and stepped sampling and holding voltages are obtained, respectively, as shown in FIGS. 7I and J. It will be done.

Therefore, the sampling _and holding voltages in _{FIG .}
In the period when U ₅ is formed, the regeneration track U ₁ ,
The values correspond to the direction and amount of deviation of U ₃ and U ₅ from the recording tracks T ₁ , T ₃ and T ₄ , respectively.Similarly, the sampling hold voltage in _FIG . ₂ , _U4 , and _U6 , the values correspond to the direction and amount of deviation of the reproducing tracks _U2 , _U4 , and _U6 from the recording tracks _T2 , _T4 , and _T5, respectively.

Then, the voltage V ₀ mentioned above is the amplifier 3
4 and 35 to the bimorph plates 9 _A and 9 _B , the heads 7 _A and 7 _B are controlled to a value such that they are moved by one pitch of the recording track when viewed in the direction opposite to the direction in which the tape 6 is transported. Ru.

Therefore, if sampling and holding voltages I and J are applied to bimorph plates _9A and _9B through amplifiers 34 and 35, the reproduction drug
U ₁ , U ₂ , U ₃ , U ₄ , U ₅ and U ₆ are shifted from the positions of the tracks indicated by the chain lines and are placed on recording tracks T ₁ , T ₂ , T ₃ , T ₄ , T ₄ and T ₅ respectively. will now be positioned correctly.

By the way, during playback, when the transport speed of the tape 6 is the same as during recording and the rotational speed of heads 7 _A and 7 _B is different from that during recording, the inclination of the playback track actually changes. also record track
T ₁ , _{T 2 , . U2} ,...
…U ₆ becomes the playback track. Therefore, even if the sampling and holding voltages I and J are applied to the bimorph plates _9A and _9B , the head _7A or _7B will only be correctly positioned on the recording track at the time when the pulse A or B is obtained. , i.e., the regeneration tracks U ₁ , U ₂ , U ₃ , U ₄ , U ₅ and U ₆
has recording tracks T ₁ , T ₂ ,
It is only located correctly on T ₃ , T ₄ , T ₄ and T ₅ , but it deviates from these as it approaches the end, and at the end it is only 1/6 of one pitch of the recording track as seen in the transport direction a of the tape 6. It deviates from this.

Therefore, the signals D and E from the flip-flop circuit 4 are transmitted to the triangular wave voltage generation circuits 36 and 37.
are supplied from the circuit 36 to the reproduction tracks U ₁ , U ₃ , U ₅ by the head _7A as shown in FIG. 7K.
A triangular wave voltage that linearly changes from zero to 1/6 V ₀ is obtained during the period in which the voltage is formed, and the circuit 37 generates the reproduction track U ₂ , as shown in _FIG .
Similarly, a triangular wave voltage that linearly changes from zero to 1/6V ₀ is obtained during the period in which U ₃ and U ₆ are formed. and,
In the adder 38, the sampling hold voltage I and the triangular wave voltage K are added to obtain a control voltage as shown in FIG. 7M, and in the adder 39,
The sampling hold voltage J and the triangular wave voltage L are added to obtain a control voltage as shown _{in FIG} .

Therefore, the regeneration tracks U ₁ , U ₂ , U ₃ , U ₄ ,
U ₅ and U ₆ are now located correctly on the recording tracks T ₁ , T ₂ , T ₃ , T ₄ , T ₄ and T ₅ from the beginning to the end, and are reproduced as shown in FIGS. 9A and B. be done.

In this way, a reproduced video signal whose field frequency is converted to 60 Hz is obtained. The number of horizontal periods in one frame of this reproduced video signal is 625
, and the horizontal frequency _H ′ is the original horizontal frequency _H
It is 18.7656KHz, which is 625/525 times the frequency. Also, regarding the carrier color signal, 1
The phase is reversed by 180 degrees every horizontal period, and the color subcarrier frequency _c ' is 823.341 KHz from (44-1/8) _H '.

The reproduced signals from the rotating magnetic heads 7 _A and 7 _B thus obtained are switched and extracted by the switch circuit 40 using the signals D and E from the flip-flop 24 and sent to the amplifier 41 . The output signal from this amplifier 41 is sent to the input terminal 10 of the color video signal conversion system. Further, the horizontal synchronization signal included in the output signal from the amplifier 41 is separated by a synchronization separation circuit 43 and sent to a horizontal signal input terminal 44.

Next, the color video signal conversion system will be explained with reference to FIG.

First, a phase inversion control circuit section 45 for restoring the phase inversion of the carrier color signal for each horizontal period of the color video signal supplied to the input terminal 10 inputs the signal to one switching terminal a of the switching switch 51. A signal with the phase of the color signal reversed by 180° is sent, and the input color signal is sent to the other switching terminal b as is (however, the attenuator 5
2) is being sent. Here, the color signal phase inversion means connected to the switching terminal a is as follows:
A balanced modulator 53 is used, and this balanced modulator 5
3 is the frequency 2 which is twice the color subcarrier frequency _c '
The signal _c ' is used as the second input signal. Further, the changeover switch 51 is connected to a D flip-flop circuit 54.
In principle, it is switched every horizontal period by the output signal from the . The carrier color signal of the output signal from the changeover switch 51 is a signal in which continuous subcarriers whose phase inversion for each horizontal period has been corrected are modulated by a chromaticity signal. This output signal is sent to the next-stage crosstalk removal circuit section 46 via a low-pass filter circuit 55 with a cut-off frequency of about 2.2 MHz.

Here, a circuit configuration provided in relation to the color signal phase inversion control circuit section 45 will be described. First, the horizontal signal from the horizontal input terminal 44 is sent to the clock input terminal of the D flip-flop 54, the delay element 56, and the PLL circuit 57 which outputs a signal with a frequency of 240 _H ' which is 240 times higher than the horizontal signal. ing. Further, a part of the output from the balanced modulator 53 is sent to a burst gate circuit 59 via a bandpass filter circuit 58 whose passband is around 2.47MHz of approximately _3c '. The gate control signal of this burst gate circuit 59 is transmitted to the delay element 56.
I'm getting it from The burst output signal from the burst gate circuit 59 is sent to a phase comparator 61 of a type of PLL system 60 that performs an automatic phase control operation. The output error signal of this phase comparator 61 is sent to a VFO 62 whose frequency changes depending on the input signal level.
This VFO62 oscillates at approximately 436.3KHz. The output signal from the VFO 62 is sent to a PLL circuit 57 in a multiplier (or balanced modulator) 63.
A signal having a frequency equal to the sum of these signal frequencies (approximately _4.94MHz≈6c ') is extracted via the bandpass filter circuit 64. Here, the oscillation frequency ₁ of VFO62
and the frequency ₂ of the output signal from the PLL circuit 57 may satisfy the following relationship: ₁ + ₂ ≈6 _c ', and are not limited to the above frequency values. Next, the output signal from the bandpass filter circuit 64 is divided in half by a frequency divider 65 to have a frequency of approximately _2c ', and is then sent to the phase comparator 61 via a phase adjustment circuit 66. The signal is sent and the phase is compared with the burst signal from the burst gate circuit 59. Therefore, the phase of the output signal from the bandpass filter circuit 64 is fixed in a constant relationship to the phase of the burst signal from the burst gate circuit 59, and the carrier color obtained via the balanced modulator 53 is The phase of the carrier wave component of the signal is reversed by 180°. On the other hand, the output signal from the bandpass filter circuit 64 is frequency-divided by 1/3 by the frequency divider 68,
Approximately through the bandpass filter circuit 69
A signal with a frequency of 1.65 MHz (≈2 _c ') is sent to the balanced modulator 53. Further, the error signal from the phase comparator 61 is sent to a tuner 71, and the output of this tuner 71 is sent to an unstable multivibrator circuit 72, so that this circuit 72 has a frequency of 9.383KHz of 1/2 _H '. generates a square wave signal with a duty of 50%. This rectangular wave signal is sent to the D input terminal of the D flip-flop circuit 54.

With the above configuration, the burst signal of the color video signal from the balanced modulator 53 of the phase inversion control circuit 45 is sent to the PLL system 60 via the burst gate 59, and this PLL system 60 responds to the burst signal. Synchronization is achieved with a constant phase relationship, and a constant phase relationship is also maintained with respect to the horizontal signal from the input terminal 44. Therefore, the carrier color signal component of the output signal from the balanced modulator 53 of the phase inversion control circuit section 45 has a phase inversion of 180 degrees with respect to the carrier color signal component of the input signal.

Here, when a color video signal in which the phase of the carrier color signal is reversed by 180 degrees in units of one horizontal period, such as in the PAL system, is input, when the phase reversal occurs, the error output signal of the phase comparator 61 is occurs, and the unstable multivibrator circuit 7 is transmitted via the tuner 71.
2, and the corresponding operating state output is sent to the D input terminal of the D flip-flop circuit 56. Since this D flip-flop circuit 56 uses the horizontal signal from the terminal 44 as its clock, as long as the above phase inversion normally occurs every horizontal period, it will alternately generate outputs of "1" and "0" and switch. The switch 55 is controlled to be sequentially switched from one of the terminals a and b to the other every horizontal period. Therefore, the carrier color signal obtained from the changeover switch 51 via the low-pass filter circuit 55 is a continuous phase signal without phase inversion as described above, that is,
The carrier color signal is similar to the NTSC system.

By the way, for field frequency conversion,
When color video signals for a predetermined field are played back missing or overlappingly, for example, as described above, one recording track T ₄ is played back overlappingly on two playback tracks U ₄ and U ₅ . In some cases (see FIG. 3 and FIGS. 9A and 9B), when these fields are missing or overlap, the phase change for each horizontal period may become discontinuous. Even with such discontinuous phase inversion, the phase comparison circuit 61, the unstable multivibrator circuit 72, and the D flip-flop 54 perform the phase inversion control operation normally, and the low-pass filter circuit 5
The phase of the carrier color signal obtained from 5 is continuous.

Note that the above is the control of phase inversion for each horizontal period of the carrier color signal of a color video signal when converting from the PAL system to the NTSC system, but it also applies when converting a color video signal from the NTSC system to the PAL system. The same can be done, and in this case, the continuous phase carrier color signal may be converted into a carrier color signal whose phase is inverted every horizontal period.

Next, the crosstalk removal circuit section 46 prevents the color signals of adjacent tracks from being mixed in as crosstalk components when the rotating magnetic head 7 tracks the tape, and acts as a comb filter. In other words, the delay line 7 delays a part of the input signal by one horizontal period.
3 and a low-pass filter 74 with a cutoff frequency of approximately 3.3 MHz, and is added to the input signal in an adder 75 to obtain a color signal from which the crosstalk component has been removed.

Next, the line number conversion circuit section 11 sequentially writes the color video signal into the memory 77 in units of, for example, one horizontal period, controls the readout using the memory control circuit 78, and switches the changeover switch 79 so that one field 625 Convert the number of horizontal scanning lines of the book to 525. This corresponds to, for example, 6 out of 25 consecutive horizontal periods of the color video signal shown in FIG. 9C.
This can be done by reading out the 1st, 12th, 18th, and 24th horizontal periods (see Figure 9D), and the read color video signal is read out by omitting the 21st, 12th, 18th, and 24th horizontal periods (see Figure 9E). ).

Here, when a CCD or a BBD is used as the memory 77, the time axis of the output signal can be easily expanded or contracted with respect to the input signal by changing the clock frequency during writing. Also, by switching the changeover switch 79 during reading, it is possible to easily perform missing or duplicate reading.

In this way, 25 consecutive horizontal periods of the input signal are converted to an output signal of 21 consecutive horizontal periods, resulting in 525 horizontal scan lines and a subcarrier frequency of 525. /625 times 690.329KHz, that is, the low-pass converted color subcarrier frequency similar to that used in NTSC magnetic recording.
_c = (44-1/8) _H.

However, the carrier color signal of the color video signal obtained in this way is between the 5th and 6th, between the 10th and 11th, and between the 15th and 16th among the 21 horizontal periods. The phase of the subcarrier of the color signal becomes discontinuous between the 20th and 21st positions. This is because, as described above, since there is an offset of 1/8 wavelength of the subcarrier for one horizontal period, a phase jump occurs by the offset of the missing horizontal period.

Therefore, when converting the color signal carrier wave to the color subcarrier frequency (3.58MHz) of the NTSC system, the above-mentioned phase jump is also corrected at the same time, so that the color signal becomes a color signal modulated with continuous phase color subcarriers. ing.

That is, from the line number conversion circuit section 11, a low-pass filter circuit 81 with a cut-off frequency of about 1.5MHz is transmitted.
The carrier color signal obtained via (the subcarrier is
690.329KHz) is sent to the balanced modulator 82 of the frequency conversion circuit section 12. Approximately 4.27MHz (=3.58+0.69MHz) signals are input to this balanced modulator 82, and these signals are balanced-modulated and
By extracting it through a bandpass filter circuit 83 whose passband is around 3.58MHz,
A carrier color signal is obtained by modulating the 3.58MHz subcarrier of the system. Here, the band pass filter 83
burst gate circuit 84 from a part of the output signal of
The burst signal is taken out via the phase comparator 8.
I am sending it to 5. The phase comparator 85 compares the phase of this burst signal with the reference signal (frequency is 3.579545MHz) from the oscillator 86.
The error output signal is sent to VFO87. this
The VFO 87 oscillates at 3.575515 MHz, and the output signal is sent to a frequency converter 91 such as a balanced modulator of the phase jump correction circuit section 14'. This frequency converter 91 is supplied with a signal of 694.299 KHz=(44+1/8) _H , which is a frequency approximate to the subcarrier wave that is low frequency converted during magnetic recording and reproduction in the NTSC system. The phase of this signal is jumped by, for example, 1/8 wavelength during the above-mentioned missing (or overlapping) readout. This is synchronized with the horizontal signal (8×
When obtaining the (44+1/8) _H signal by dividing the output signal from the PLL circuit 92, which is locked at a frequency of 44+1) _H , into 1/8 using a frequency divider 93 such as an octal counter, For example, the frequency divider 93 If is a counter, by holding only one count,
It is sufficient to perform a phase jump by 1/8 wavelength.

In this way, VFO 87 and frequency divider 93
A signal of 4.2698143 MHz, which is the sum of these signals, is extracted via a bandpass filter 94 and supplied to the balanced modulator 82 of the frequency conversion circuit section 12. There is. Therefore, at the same time that a phase jump occurs in the low-frequency color subcarrier signal obtained from the low-pass filter 81, the phase jump correction circuit 1
Since the phase of the signal obtained from the frequency divider 93 of 4 jumps to the same extent, a signal with a continuous phase can be obtained from the balanced modulator 82 even before and after the jump.

Note that the count hold of the octal counter that is the frequency divider 93 is performed by, for example, outputting the output of the 21-ary counter 95 that counts horizontal signal pulses to the decoder 9.
6, and the decoder 96 sends the count hold signal to the octal counter, which is the frequency divider 93, at the end of the 5th, 10th, 15th, and 20th of the 21 horizontal periods.

As is clear from the above description, the color video signal magnetic reproducing apparatus according to the present invention converts the color video signal of the first television standard format reproduced from the reproduction head into the second television standard format. In the conversion device for converting the color video signal into a color video signal, the memory control means sequentially writes the color video signal of the first method into the memory, and reads out the color video signal of a predetermined number of non-consecutive horizontal periods with omissions or overlaps. and a phase control means for controlling at least the phase of the carrier color signal of the color video signal in accordance with the number of the missing or overlapped horizontal periods when the color video signal is missing or overlapped. There is.

Therefore, the phase jump of the carrier color signal that occurs when the horizontal period is missing or overlapped reading is automatically corrected, and the phase of the color subcarrier of the obtained color video signal is continuous, so that normal color reproduction can be performed.

Next, as another feature of the present invention, when reproducing a color video signal, the carrier color signal of the color video signal is frequency-converted to the lower frequency side. At this time, a means for frequency converting the reproduced carrier color signal is required, and the present invention is characterized in that the phase of the conversion carrier signal supplied to the frequency converting means is controlled by the phase control means.

Still another feature of the present invention is that the frequency conversion means includes an oscillator having an oscillation frequency n times the frequency of the low-band carrier color signal, and an output of the oscillator that is
and a counter configured to step down to n, the counter is held or coded according to the number of horizontal periods that are dropped or overlapped when the color video signal is missing or overlapped, and the counter is held or coded in accordance with the number of missing or overlapped horizontal periods, and the phase of the carrier color signal is A carrier wave signal having a phase variation amount corresponding to the change is formed.

Therefore, phase changes can be corrected accurately with a relatively simple configuration.

Furthermore, another feature of the present invention is that a comb-tooth filter is provided to mix the conveyed color signal with the conveyed color signal of one horizontal period before. Cross strokes from adjacent tracks etc. are greatly reduced.

It should be noted that the present invention is not limited to the above-mentioned embodiments; for example, conversion from the NTSC system to the PAL system can be performed in substantially the same manner as in the embodiments. in this case,
60 to convert the field frequency 30Hz to 25Hz
All you have to do is play back the recorded track of the book with 50 playback tracks (with some parts missing), and you can also
In order to convert 525 horizontal periods to 625, it is sufficient to read out 4 non-consecutive horizontal periods overlappingly for 21 consecutive horizontal periods to obtain a color video signal of 25 consecutive horizontal periods, and these overlapping readings The phase correction may be performed in the phase advance or lag direction opposite to that of the embodiment. Furthermore, the conversion of other methods is also similar. Further, as a video signal recording and reproducing device, in addition to a video tape recorder, the present invention can be easily applied to photoelectric, magnetic, mechanical, etc. video disk players.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a rotary head section of a video tape recorder, FIG. 2 is a perspective view showing the rotary disk 2 of FIG. 1, and FIG.
FIG. 4 is a plan view showing the recording track T and reproduction track U on the magnetic tape 6, and FIG. 5 is a block diagram showing the basic configuration of the main part of the embodiment of the present invention.
C is a time chart for explaining the phase jump of the color subcarrier, FIG. 6 is a block circuit diagram showing a specific example of the servo system of the embodiment, and FIGS. 7A to N
is a time chart showing the waveforms at each point A to N in FIG. 6, FIG. 8 is a block circuit diagram showing a specific example of the circuit in FIG. 4, and FIG. 9 A to E are the circuits in FIG. 8. This is a time chart to explain the operation. DESCRIPTION OF SYMBOLS 1... Rotating head device, 7... Rotating magnetic head, 9... Bimorph plate, 10... Input terminal of color video signal conversion system, 11... Line number conversion circuit section, 12... Frequency conversion circuit section, 14 ,14'...
...Phase jump correction circuit section, 45... Phase inversion control circuit section, 46... Crosstalk removal circuit section.

Claims (1)

[Scope of Claims] 1. A color video signal of a first television standard format including a low frequency conversion carrier color signal recorded on a magnetic medium is converted to a color video signal of a second television standard format. In a magnetic reproducing device for reproducing, a memory for sequentially writing color video signals of the first method reproduced from a reproducing head into a memory, and reading out color video signals of a predetermined number of non-consecutive horizontal periods with omissions or overlaps. a control means, a frequency conversion means for converting the frequency of the low frequency conversion carrier color signal to a high frequency band; and a frequency conversion means for frequency converting the low frequency conversion carrier color signal to a high frequency band; 1. A magnetic reproduction apparatus for a color video signal, comprising: a phase control means for controlling the phase of a color signal carrying the signal by the frequency conversion means. 2. The frequency converting means includes an oscillator having an oscillation frequency n times the frequency of the low-band carrier color signal, and a counter that steps down the output of the oscillator to 1/n. Alternatively, the counter is held or loaded according to the number of missing or overlapped horizontal periods at the time of duplicate reading, and a carrier wave signal having a phase variation amount corresponding to a phase change of the carrier color signal is formed. A magnetic reproduction device for color video signals according to claim 1. 3. The magnetic reproduction device for color video signals according to claim 1, further comprising a comb-tooth filter configured to mix the carrier color signal with a carrier color signal from one horizontal period before.