JPS6237875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic reproducing device for color video signals between different television standard systems, and in particular, the field frequencies are different from each other, and for a first color video signal, color reproduction for a predetermined field is performed. The present invention relates to a color video signal magnetic reproducing device that controls the phase of a carrier color signal when reproducing video signals with omissions or overlaps, and converts the carrier color signal into a second color video signal.

Typical television standard systems include:
There are NTSC, PAL, and SECAM methods. The NTSC system has a field frequency of 60Hz and the number of scanning lines is 525, whereas 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 color video signal magnetic reproducing device that can be reproduced on 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 obliquely around the upper and lower drums 3 and 4 within 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 7A, 7B are mounted at an angular distance of 180° from each other. Here, the rotating magnetic heads 7A, 7B are connected to head bases 8A, 8B.
On top is a bimorph plate 9 which is an electro-mechanical conversion element.
By attaching it via A and 9B, it can be displaced in the direction of arrow c, which is the direction of the rotation axis.

Next, FIG. 3 shows a plan view of the videotape 6, on which a plurality of parallel oblique recording tracks T (however, only the center line is shown) are formed on the tape surface. 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 tracking locus U of the rotating magnetic head (this is called a playback track) is set to the same speed as the recording speed. Six tracks will be arranged for 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 reproduction signal to 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. , 100 non-consecutive horizontal periods out of 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 above-mentioned 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 repeated 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, in each horizontal period,...
If the signal is read out without being read out, the result will be as shown in Figure 5B, where a phase delay of 1/8 wavelength will occur at the connection point. Furthermore, when the horizontal period is repeated and read out, the result is as shown in FIG. 5C, where a phase advance of 1/8 wavelength occurs 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. Further, pulse generators 20A and 20B that detect the rotation of the rotating magnetic heads 7A and 7B and generate pulses are provided in connection with the rotating shaft of the rotating disk 2, etc., and the rotating magnetic heads 7A and 7B move over the tape 6. A pulse is obtained when tracking starts. Since the rotating disk 2 rotates at 30 Hz, these rotation detection pulses are obtained at 1/30 second intervals, as shown in FIGS. 7A and 7B, and the magnetic heads 7A,
Since the angular interval of 7B 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 _B
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 falling edge.

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 between the reproduction control pulses C is 1/50 second since the tape running speed is the same as that during PAL recording.

Next, a servo system for controlling the rotation speed and tape running speed of these rotary heads, and a control drive system for bimorph plates 9A and 9B that change magnetic heads 7A and 7B in the direction of arrow c will be explained.

First, the pulse A obtained from the pulse generator 20A is supplied to the 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 the amplifier 22. As mentioned above, the rotating magnetic heads 7A and 7B are
Controlled to rotate at Hz. Here, above 30
The Hz reference pulse, which is supplied to the input terminal 13, can be obtained, for example, by frequency-dividing the readout clock pulse of a CCD or the like, which will be described later.

Further, pulses A and B from pulse generators 20A and 20B are supplied to the set side and reset side of the flip-flop circuit 24. As shown in FIG. 7D, this flip-flop circuit 24 outputs "1" during the period when the magnetic head 7A is tracking the tape 6, and outputs "0" during the period when the magnetic head 7B tracks the tape 6. A pulse, 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 above the playback track U4, and the maximum value becomes 1/2 when head 7B starts tracking above playback track _U4 .
We have obtained a sawtooth wave voltage that changes instantaneously from V 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 _.
During the period when U ₃ and U ₅ are formed, the regeneration track
Recording tracks T ₁ , T ₃ , T ₄ of U ₁ , U ₃ , U ₅ respectively
The value corresponds to the direction and amount of deviation from
Similarly, _the sampling _and hold voltages in FIG _.
In the period in which the regeneration tracks U ₂ , U ₄ ,
The values correspond to the direction and amount of deviation of U ₆ from recording tracks T ₂ , T ₄ , and T ₅ , respectively.

Then, the voltage V ₀ mentioned above is the amplifier 3
4 and 35 to the bimorph plates 9A and 9B, the heads 7A and 7B are controlled to such a value that the heads 7A and 7B 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.

Therefore, if sampling and holding voltages I and J are applied to bimorph plates 9A and 9B through amplifiers 34 and 35, the reproduction track
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 reproduction, when the transport speed of the tape 6 is the same as during recording and the rotational speed of heads 7A and 7B is different from that during recording, the inclination of the reproducing track is actually the same as that of the recording track.
T ₁ , _{T 2} , _. …
…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, that is, when the reproduction is completed. 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 24 are transmitted to the triangular wave voltage generation circuits 36 and 3.
7, from the circuit 36 as shown in FIG. 7K, the reproduction tracks U ₁ , U ₃ ,
A triangular wave voltage that linearly changes from zero to 1/6V ₀ is obtained during the period in which U ₅ is formed, and from the circuit 37, as shown in FIG.
Similarly, the period from zero to 1/6 during which U ₂ , U ₃ , and U ₆ are formed
A triangular wave voltage that varies linearly with V ₀ is obtained.
Then, 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. As a result, 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° every horizontal period, and the color subcarrier frequency _C ′ is (44−1/8) _H ′,
It is 823.341KHz.

The reproduced signals from the rotating magnetic heads 7A and 7B thus obtained are switched and extracted by the switch circuit 40 using the signals D and E from the flip-flop 24, and are 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 D
A clock input terminal of the flip-flop 54, a delay element 56, and a PLL circuit 57 that outputs a signal of 240 times the frequency of 240 _H ' in synchronization with this horizontal signal.
is being sent to. 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, which is approximately 3 _C '. A gate control signal for this burst gate circuit 59 is obtained from the delay element 56. 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
VFO whose frequency changes depending on the input signal level
62, and this VFO 62 oscillates at approximately 436.3KHz. The output signal from the VFO 62 is multiplied by the output signal from the PLL circuit 57 in a multiplier (or balanced modulator) 63, and a signal with a frequency of the sum of these signal frequencies (approximately 4.94 MHz = 6 _C) is converted into a bandpass signal. It is taken out via the filter circuit 64. Here, the oscillation frequency ₁ of the VFO 62
The frequency ₂ of the output signal from the PLL circuit 57 only needs to satisfy the relationship ₁ + ₂ = 6 _C '.
It is not limited to each of the above frequency values. Next, the output signal from the bandpass filter circuit 64 is passed through the frequency divider 6
The frequency is divided into 1/2 by 5, and the frequency becomes approximately 2 _C ', and the signal is sent to the phase comparator 61 via the phase adjustment circuit 66, and then sent to the burst gate circuit 59.
The phase is compared with the burst signal from 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 and passed through the bandpass filter circuit 64 to approximately 1.65MHz.
A signal with a frequency of (=2 _C ′) is sent to the balanced modulator 5.
It has been sent to 3. 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.
This circuit 72 has 1/2 _H ′
Generates a square wave signal with a duty of 50 at 9.383KHz. 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 section 45 is transmitted to the PLL system 60 via the burst gate 59.
This PLL system 60 is synchronized with a constant phase relationship with the burst signal, and also maintains a constant phase relationship with 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 inverted by 180 degrees in units of one horizontal period, such as in the PAL system, is input, the error output of the phase comparator 61 is The signal is generated and sent to the astable multivibrator circuit 72 via the tuner 71, and the corresponding operating state output is sent to the D input terminal of the D flip-flop circuit 56. This D
Since the flip-flop circuit 56 uses the horizontal signal from the terminal 44 as its clock, as long as the above-mentioned phase inversion normally occurs every horizontal period, it will sequentially generate outputs of "1" and "0" alternately, and the changeover switch 51 is controlled by sequentially switching from one of 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 case (third
See Figures and Figures 9A and B. ), when these fields are missing or overlap, the phase change for each horizontal period may become discontinuous. Even for such discontinuous phase inversion, the phase comparator circuit 6
1. The phase inversion control operation is normally performed by the astable multivibrator circuit 72 and the D flip-flop 54, and the low-pass filter circuit 55
The phase of the carrier color signal obtained from 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 is done by reading out the 21st, 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 into an output signal of 21 consecutive horizontal periods, resulting in 525 horizontal scanning lines and a subcarrier frequency of 525/ Multiplied by 625 to 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 of 3.58MHz in the NTSC system, the above phase jump is also corrected at the same time, so that the color signal is obtained by modulating color subcarrier waves of continuous phase. .

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 to 3.58MHz.
By extracting it through a bandpass filter 83 whose passband is nearby, the 3.58MHz NTSC system
A carrier color signal is obtained by modulating the subcarrier. Here, a burst signal is extracted from a part of the output signal of the bandpass filter 83 via a burst gate circuit 84 and sent to a phase comparator 85.
In this phase comparator 85, this burst signal and
Reference signal from oscillator 86 (frequency is
3.579545MHz) and the error output signal is sent to VFO87.

This VFO 87 oscillates at 3.575515 MH, 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 having a frequency of 694.299KHz≈(44+1/8) _H , which is approximately the frequency of 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 done by dividing the output signal from the PLL circuit 92, which is locked at a frequency of (8×44+1) _H , into 1/8 using a frequency divider 93 such as an octal counter in synchronization with the horizontal signal. , (44+1/8) _H
When obtaining the signal, between the 5th and 6th, between the 10th and 11th, between the 15th and 16th, and between the 20th and 21st, where the omission occurred among the 21 horizontal periods, For example, if the frequency divider 93 is a counter, the phase jump may be performed by 1/8 wavelength by holding only one count.

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 92 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 feature of the color video signal conversion device of the present invention is that one field of the color video signal having the first field frequency corresponds to one recording track, and a plurality of recording tracks are converted. When reproducing a recording medium in which a predetermined field is recorded using a magnetic head, the color video signal of a predetermined field is omitted from the plurality of tracks or the recorded track is redundantly reproduced to reproduce a second color video signal.
means for converting the color video signal into a color video signal having a field frequency of , and controlling the color video signal read out from the magnetic head in the conversion means for each phase unit horizontal period of the carrier color signal of the first type to convert the color video signal into a color video signal having a field frequency of means for converting the signal into a second type of carrier color signal;
means for detecting the phase of the carrier color signal of a missing or overlapping portion of a predetermined field of the color video signal, modulating the input carrier color signal based on the detected phase, and defining the state of the carrier color signal converting means. That's what happened.

Here, the means for regulating the state of the phase inversion control circuit section 45, which is the carrier color signal conversion means, refers to a circuit section consisting of, for example, a PLL loop system 60, an unstable multivibrator circuit 72, and a D flip-flop circuit 54. .

Therefore, the phase inversion control of the carrier color signal is
The phase of the carrier color signal is controlled not only as a simple repeating operation for each horizontal period, but also when the above simple repeating changes, such as when a predetermined field is missing or is reproduced repeatedly. . Therefore, color component conversion when converting the television standard system can be performed normally, and a good color video signal can be converted without color shift or hue variation.

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, in order to convert the field frequency from 30Hz to 25Hz, it is only necessary to play back 60 recorded tracks with 50 playback tracks (with some parts missing), and also convert the horizontal period of 525 in one field to 625. Therefore, for 21 consecutive horizontal periods, 4 non-consecutive periods
25 horizontal periods may be read out repeatedly to obtain a color video signal of 25 consecutive horizontal periods, and the phase correction at the time of these repeated readings may be performed in the phase advance or lag direction opposite to that in the embodiment. Furthermore, the same applies to conversions of other methods. Furthermore, the present invention can be applied to video disc players and the like other than video tape recorders.

[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)

[Claims] 1. When reproducing a recording medium on which one field of a color video signal having a first field frequency corresponds to one recording track and forming a plurality of recording tracks, a predetermined number of fields are played by a magnetic head. means for converting a color video signal having a second field frequency by reproducing the color video signal missing from the plurality of recording tracks or duplicating the recording track; means for converting a first type of carrier color signal into a second type of carrier color signal by controlling the phase of the carrier color signal of the color video signal every unit horizontal period; A magnetic reproducing device for a color video signal, comprising means for detecting the phase of the carrier color signal in the missing or overlapping portion, modulating the input carrier color signal based on the detected position, and defining the state of the carrier color signal converting means.