JPH0455034B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention is applicable to popular home VTRs and 8mm videos, where a color video signal is not a luminance signal.
The carrier color signal is FM modulated and brought to the high frequency side, and the carrier color signal is frequency-converted to the low frequency side, and the phase of its subcarrier is controlled and recorded. During playback, a comb filter is used to extract the carrier color from the adjacent track. The present invention relates to a color video signal processing device in a color video signal reproducing device that is capable of removing crosstalk components from the signal.

Background technology and its problems In the case of popular home VTRs and so-called 8mm video VTRs that are integrated with a camera, the luminance signal is FM modulated and kept in a relatively high band when recording color video signals. Therefore, the carrier color signal is frequency-converted to the lower frequency side and recorded.

By the way, when recording and reproducing PAL video signals using this VTR, it must be noted that one modulated color signal of the PAL carrier color signal is inverted every horizontal section. That is,
The carrier color signal of the PAL color video signal is the first
As shown in the figure, in every other horizontal section, F ₊ = (E _B − E _Y ) + j (E _R − E _Y ), and in the remaining every other horizontal section, F _- = (E _B −E _Y )−j(E _R −E _Y ), the phase of the modulation signal of the red color difference signal is inverted every horizontal interval, and the signal For F ₊ , a burst signal B ₊ with a phase advanced by 135° with respect to the B-Y axis is inserted, and a signal F _-
, a burst signal B _- whose phase is delayed by 135 degrees with respect to the BY axis is inserted.

When performing color demodulation of this PAL system color video signal, when the color video signal reproduced from the VTR is supplied to the television receiver, it is necessary to correctly perform color demodulation for each horizontal section as described above. The phase of one of the modulated color signals, that is, the red color difference signal, must be inverted every horizontal interval.

During normal playback on a VTR, the continuity of the inversion of the modulated color signal is taken into consideration without any problem, but when the rotating head scans across multiple tracks during high-speed playback or slow-motion playback, etc. In this case, the continuity of this reversal for each horizontal section may be impaired.

That is, FIG. 2 shows an example of a track pattern of a β-format VTR compatible with PAL color video signals, in which every other track TA ₁ ,
TA ₂ ... is the track recorded by one of the two rotating heads HA,
TB ₁ , TB ₂ ..., the other azimuth angle is the head HA
The arrows in the figure indicate the phase of each horizontal interval (1H) of the burst signal in the recorded carrier color signal. There is. In addition,
In order to eliminate the crosstalk of the carrier color signal between adjacent tracks, the actually recorded signal is such that in tracks TA ₁ , TA ₂ . and the remaining every other track TB ₁ , TB ₂
In ..., the subcarrier is recorded as it is in phase, so it does not indicate the phase of the burst signal on the actual recording pattern, and during playback, the track
The case is shown in which the phase is restored for TA ₁ , TA ₂ . . . .

By the way, in this tape pattern, since the horizontal alignment is 1H, the color alignment of the PAL color video signal is not taken.
Therefore, in the high-speed reproduction mode, when the rotary head HA traces and scans a locus as shown by the broken line in _{FIG .}
Hejump. Looking at the phase of the burst signal in the reproduced signal obtained by this high-speed reproduction,
As shown in FIG. 3A, at time point a of this track jump, the continuity of inversion of the burst signal for each horizontal section (hereinafter referred to as burst signal sequence) is reversed. Therefore, if an attempt is made to reproduce the video by supplying the PAL color video signal thus obtained to a monitor receiver, correct color reproduction will not be performed on the screen.

The above explanation was about recording and playing back PAL video signals using a Beta-type VTR, but the so-called 8mm video standard also requires horizontal alignment of 1H or 2H, so color alignment is not taken. A similar problem occurs.

Therefore, a carrier color signal processing device as shown in FIG. 4 was proposed.

That is, this example is for an 8 mm video, and during recording, the carrier color signal is recorded with the subcarrier shifted by 90 degrees every horizontal section, and the remaining one Every other track is one in which the subcarriers are recorded with the same phase.

In this example, in order to correct the reversal of the continuity of reversal for each horizontal section of one modulated color signal (red color difference signal) of the PAL signal, it is necessary to convert the low-frequency carrier color signal to the original carrier color signal. This is done by switching the frequency conversion signal used for frequency conversion to the difference signal between the sum of the low subcarrier frequency _L and the original subcarrier frequency _SC .

In FIG. 4, the signals reproduced by the two rotating heads are supplied to a reproduction amplifier 2 through an input terminal 1, and the output of this amplifier 2 is passed through a high-pass filter 3 to extract an FM-modulated luminance signal. , this is FM demodulated and played back.

The output of the amplifier 2 is also supplied to a low-pass filter 4 to extract a carrier color signal that has been low-pass converted and is supplied to a frequency conversion circuit 5. On the other hand, a variable frequency oscillator ₁₁ is provided that generates a signal with a frequency equal to the low subcarrier frequency _L of the carrier color signal that has been converted to a low frequency. The signal is supplied to the frequency conversion circuit 14 after being phase-controlled as described below.

On the other hand, the subcarrier frequency _SC of the original PAL signal (=
An oscillation signal from a reference oscillator 15 (4.43MHz) is supplied to this frequency conversion circuit 14, from which a signal with a frequency of _SC + _L and a signal with a frequency of _SC - _L are obtained. And these are the band pass filter 16
A and 16B respectively. And these band pass filters 16A and 16B
A signal is selectively taken out by the switch circuit 17 and supplied to the frequency conversion circuit 5.

In this frequency conversion circuit 5, the frequency _SC
+ _L signal minus the low-converted subcarrier frequency _L , so the original subcarrier frequency _SC =
A signal returned to 4.43 MHz is obtained and taken out via bandpass filter 6.

In this case, the phase of the subcarrier is determined by the frequency conversion circuit 5
In this step, the phase of the frequency conversion signal is changed by the phase control circuit 12, so that the phase shifted during recording is returned. That is, a control signal is supplied to the phase control circuit 12 through a terminal 13, and the phase is shifted by 90 degrees for each horizontal section, and the phase is shifted by 90 degrees for each horizontal section. An operation is performed to shift the phase of the signal from the frequency oscillator 11 by 90 degrees, thereby restoring the phase of the subcarrier.

Incidentally, although the output of the bandpass filter 6 still contains crosstalk components from adjacent tracks, this is removed through the C-shaped comb filter 7 consisting of a delay circuit and a subtraction circuit for two horizontal sections, and the output is A crosstalk-free carrier color signal is derived at terminal 8.

In this case, the variable frequency oscillator 11
APC is applied so that the reproduced signal frequency has a constant relationship with the output frequency of the reference oscillator 15. That is, a part of the signal passed through the comb filter 7 is supplied to the burst gate circuit 21 and a burst signal is taken out, which is sent to the phase comparator circuit 24.
and the frequency from the reference oscillator 15
The phase is compared with _{the SC} signal, and the comparison error voltage is supplied to the variable frequency oscillator 11 through the low-pass filter 25 to control its oscillation frequency.

In this signal processing device, as described above,
The sequence of burst signals is corrected as follows.

That is, the output signal from the comb filter 7 is supplied to the burst signal sequence detection circuit 30, and it is detected that the burst signal sequence has been reversed in the following manner.

FIG. 5 shows an example of this sequence detection circuit 30, in which a signal passed through the comb filter 9 is supplied to a phase detection circuit 32 via a burst gate circuit 31 (which may also be used as the burst gate circuit 21). On the other hand, reference oscillator 3 with frequency _SC = 4.43MHz
The signal from the switch circuit 34 is supplied to one input terminal of the switch circuit 34, and is also phase-inverted and supplied to the other input terminal. And this switch circuit 34
is alternately switched between one input terminal and the other input terminal every horizontal section by a signal that inverts the state of "1" and "0" at the time of the horizontal synchronizing signal HD from the flip-flop circuit 36, The output of this switch circuit 34 is supplied to the phase detection circuit 32.

For example, the phase of the signal from the reference oscillator 33 matches the -(R-Y) axis as shown in FIG. 6, and therefore the phase of the output signal from the switch circuit 34 is as shown in FIG. 3B. It comes to show. Therefore, when the sequence of the burst signal is correct, a positive output signal is obtained from the phase detection circuit 32 at the time of the burst signal as shown in FIG. 3C, and the sequence is reversed at point a as described above. In such a case, a negative polarity output signal is obtained from the phase detection circuit 32. The output DS of the phase detection circuit 32 obtained in this way is transmitted to the low pass filter 3.
7 to the level comparison circuit 38, and is compared with the reference voltage E _R. When the output of the detection circuit 32 is lower than the reference voltage E _R , that is, when a negative detection output is obtained, the output becomes “1”. A signal rising to "1" is obtained from this comparator circuit 38, and the flip-flop circuit 39 is inverted by this rising of "1". The output signal SW obtained from the flip-flop circuit 39 is supplied as a switching control signal to the switch circuit 17.

Therefore, from the moment the burst signal sequence becomes reversed, the switch circuit 17 is switched to the opposite side, and the state where the sequence is reversed is corrected.

The principle of inverting the subcarrier with respect to the BY axis by switching this frequency conversion signal will be explained below.

Now, if the angular frequency of the low-frequency subcarrier is ω ₁ , the angular frequency of the original subcarrier is ω ₂ , and the phase of the reproduced carrier color signal is θ, then the frequency conversion signal is a signal of ω ₂ +ω ₁ When using , the output of the frequency conversion circuit 5 (therefore, the output of the bandpass filter 6) is as follows.

ω ₂ +ω ₁ −(ω ₁ +θ)ω ₂ −θ Next, when using the signal ω ₂ −ω ₁ as the frequency conversion signal, ω ₂ −ω ₁ +(ω ₁ +θ))ω ₂ +θ So, in the reproduced carrier color signal, θ=0 is B-
Considering the Y axis, by switching this frequency conversion signal, the phase of the signal obtained by frequency conversion is inverted with respect to the BY axis.

Note that when the frequency conversion signal is switched in this way, the following problems occur.

In other words, it is a change in the phase lock point of the APC loop.

The APC circuit works so that both input signals of the phase comparator circuit 24 have a phase difference of 90 degrees, but for the reasons described later, this lock point is the same as that of the oscillator 15, which is one of the input signals shown in FIG. If the reference phase of the signal from the input signal is 0°, there are two cases: phase point A, where the phase of the other input signal is delayed by 90°, and phase point B, which is advanced by 90°. become.

That is, for example, if there is a phase error Δθ in the low-pass conversion carrier color signal, and if the frequency is converted by ω ₂ +ω ₁ as a signal for frequency conversion, then ω ₂ +ω ₁ −(ω ₁ +Δθ)ω ₂ −Δθ When the frequency conversion signal is converted by ω ₂ −ω ₁ , ω ₂ −ω ₁ +(ω ₁ +Δθ)ω ₂ +Δθ, and the phase error thereof becomes an opposite phase.

Since the APC circuit works to eliminate phase errors at the output, the output of the variable frequency oscillator 11 is ω ₁ +
If Δθ, the frequency conversion circuit 5 converts (ω ₂ +ω ₁ +Δθ) − (ω ₁ +Δθ)ω ₂ or (ω ₂ −ω ₁ −Δθ) + (ω ₁ +Δθ)ω ₂ so that the phase error disappears. Become. In other words, the variable frequency oscillator 11 corrects its oscillation output in the same direction regardless of the switching of the switch circuit 17, and therefore the output of the phase comparison circuit 24 also follows in the same direction. On the other hand, when the frequency conversion signal is changed by switching the switch circuit 17 at the input of the phase comparison circuit 24, the phase error direction is in the opposite direction. The lock point is set to A by switching.
There are two points, point and B, and the lock phase is
A 180° change, that is, a reversal.

This will not cause any problems unless processing such as phase detection is performed in the subsequent circuit when handling the signal at terminal 8, but normally an automatic color killer circuit is provided in the subsequent stage, and this circuit uses Since a detection method is used, it is inconvenient that the phase of the signal obtained at the output terminal 8 is inverted. Therefore, in this example, a switch circuit 22 is provided between the burst gate circuit 21 and the phase comparison circuit 24, and the burst signal from the burst gate circuit 21 is supplied as is to one input terminal of the switch circuit 22, and the phase Inversion circuit 2
3 to the other input terminal, and in synchronization with the switching of the switch circuit 17, the output SW of the sequence detection circuit 30 outputs this switch circuit 22.
are switched so that there is only one lock point.

Note that this phase inversion processing circuit may be provided between the connection point between the comb filter 7 and the burst gate circuit 21 and the output terminal 8, or may be provided in the signal path supplied from the oscillator 15 to the phase comparison circuit 24. It may be provided. Furthermore, it may be provided between the phase comparison circuit 24 and the variable frequency oscillator 11.

By the way, in the above-described correction of the continuity of inversion of the burst signal, the cancellation of crosstalk from adjacent tracks regarding the carrier color signal component was not considered a problem in the above example. However, the crosstalk from adjacent tracks may not be correctly canceled during the delay time of the comb filter, resulting in the following drawbacks.

That is, when a discontinuity in the burst signal sequence occurs at point a of the track pattern described above as shown in FIG. This is done from the time of the burst signal delayed by a horizontal period or more.

In the case of Fig. 8 A, 2H from the discontinuity point a
(1H is one horizontal interval) The switch circuit 17 is activated at the delayed time point b, and the inversion process is performed. 8A is the output of the band pass filter 6, but the output of the band pass filter 6 still contains crosstalk components. This is shown in FIG. 8B. In the illustrated example, in order to make the explanation easier to understand, it is shown that the crosstalk component can be removed by addition in the comb filter. In this case, if the periods before and after the inversion point b are considered separately, crosstalk cancellation by shifting every 90 degrees is performed correctly. However, from the discontinuity occurrence point a to the switching reversal point b,
Because it is a period of just over 2 hours, immediately after the reversal, the
Since the uninverted signal from 2H before is used, the crosstalk component remains without being removed. That is, FIG. 8C shows the comb filter 9.
represents the phase of the burst signal of the carrier color signal from the track to be scanned in the output signal of the 2H delay line of
Figure D shows crosstalk components from adjacent tracks. Therefore, as the output signal of the comb filter 9, the original carrier color signal will be in the correct state as shown in FIG. 5E, but the crosstalk component will be as shown in FIG. In Figure F, the circle indicates that the crosstalk has been canceled, and as is clear from this figure, the crosstalk component remains without being canceled for a little over 2H from the point of reversal. Then, with respect to the phase of the reference signal of the phase detection of the sequence detection circuit 30 (G in the same figure), the original signal becomes as shown in E in the same figure, even though the continuity of the phase inversion of the burst signal is correctly connected. First, this crosstalk component is phase-detected and is erroneously detected as a sequence reversal, and this detection output results in a detected pulse being obtained again after reversal at time a, as shown in Figure H. Therefore, as shown in the figure, the output signal of the flip-flop circuit as a switching signal is inverted, and as a result, the switch circuit 17 is also switched, and as a result, the original signal sequence is reversed again. I get used to it. Then, the sequence detection circuit 30 detects this reversal again, and this reversal occurs alternately and consecutively, resulting in a so-called oscillation, and the signal system becomes unstable.

In the above, one modulation color signal peculiar to PAL signals is 1.
This is when considering the continuity of the sequence, which is reversed every horizontal period, but even in the case of NTSC signals, the phase of the burst signal itself is reversed due to VTR skew, etc. A similar situation occurs in the burst ID circuit that detects the occurrence of phase inversion.

That is, FIG. 9 has this burst ID circuit.
This shows a processing circuit for the carrier color signal of a VTR playback device, in which the reproduced NTSC color video signal through the input terminal 1 is supplied to the low-pass filter 43 through the amplifier 42, and the carrier color signal that has been low-pass converted is extracted. This is supplied to the frequency conversion circuit 44. Then, like the PAL signal, a signal with a frequency equal to the sum of the original subcarrier frequency _SC and the low subcarrier frequency _L is supplied to this frequency conversion circuit 44, and from this, the subcarrier frequency is changed back to the original frequency.
A carrier color signal is obtained which is returned to _{the SC} , and is taken out via a bandpass filter 45. This crosstalk component is removed through a C-shaped comb filter 48 consisting of a delay circuit 46 for one horizontal period and a subtraction circuit 47, and the output terminal 4
It is taken out at 9.

The signal for frequency conversion is subjected to APC and is formed as follows.

That is, the variable frequency oscillator 5 with a free-running oscillation frequency _L
0 is set. The color signal carried through the comb filter 48 is then supplied to a burst gate circuit 51 to extract a burst signal, which is then supplied to a phase comparator circuit 52. On the other hand, a signal with a frequency _SC from the reference crystal oscillator 54 is supplied to this phase comparison circuit 52, and the phases of the two are compared.The comparison error output is supplied to the variable frequency oscillator 50 through the low-pass filter 53, and its oscillation frequency is It is designed to lock to the phase of the reproduced signal. The signal from the variable frequency oscillator 50 is then supplied to the phase control circuit 55, and during recording, the phase of the subcarrier is inverted every horizontal section, and during reproduction from every other track recorded. , phase inversion processing is performed for each horizontal section. and,
The signal from the phase control circuit 55 is supplied to the frequency conversion circuit 56, and the reference signal from the oscillator 54 is supplied to the frequency conversion circuit 56.
From this, a signal with a frequency _SC + _L is obtained, which is taken out via a bandpass filter 57.
The signal passed through the bandpass filter 57 is supplied as it is to one input terminal of the switch circuit 58, and is also supplied to the other input terminal of the switch circuit 58 through the inverter 59. This switch circuit 58 is controlled by the detection output of a burst ID detection circuit 60, which will be described later, and when the burst signal phase is reversed by 180 degrees, the switching state is reversed.

The burst ID detection circuit 60 is configured as follows. That is, the burst signal from the burst gate circuit 52 is supplied to the phase comparison circuit 61, while the oscillation signal from the reference oscillator 54 is phase-shifted by 90 degrees by the phase shifter 62, and then the phase comparison circuit 61
supplied to Then, the phase comparison error outputs of both are supplied to the level comparison circuit 64 through the low-pass filter 63 and compared with the reference voltage ER', and when the output of the low-pass filter 63 becomes lower than the voltage ER', the comparison output The state of flip-flop circuit 65 is inverted. The output of this flip-flop circuit 65 is then transferred to the switch circuit 58.
is supplied as a switching control signal.

FIG. 10 is a diagram for explaining the burst ID circuit, and A in the figure shows the phase of the burst signal in the carrier color signal reproduced and restored from the original track. That is, at point e in the figure, the phase of the burst signal is inverted due to the influence of skew or the like. The crosstalk from the adjacent track at this time, which is in the case of β format, is inverted every horizontal section, as shown in FIG. 2B. Therefore, the signals obtained by delaying these signals by one horizontal interval become as shown in C and D in the same figure, and the signal output through the comb filter 48 becomes as shown in E and F in the same figure. In this case, the reference phase of the reference signal from the 90° phase shifter 62 is expressed as −
When the phase coincides with the (B-Y) axis, the output of the phase comparator circuit 61 is as shown in H in the same figure, and the output of the flip-flop circuit 65 is in a comb shape than at time e as shown in the figure. A discontinuous detection output is obtained at a time delayed by the delay time of the filter 48, and the switch circuit 58 is thereby inverted.

Therefore, after switching 1 in FIG. 10A, the burst signal returns to the correct phase state, but when switching in this way, crosstalk components may remain without being removed. That is, as shown in B, D, and F in the same figure, when switching occurs, the signal before switching is used to cancel crosstalk, so this does not become a continuous signal and crosstalk is removed. In other words, it remains. When this happens, this crosstalk component is again regarded as an erroneous burst phase and detected by the burst ID detection circuit 60, and the flip-flop circuit 65 inverts again at the time of detection, so the switch circuit 58 returns to the original switching state. state, and the burst phase changes again. Therefore, in this case too,
The state of the switch circuit 58 will become unstable, just like the situation in the case of the burst signal sequence of the PAL signal.

In the above example, the arrows for each phase shown in FIGS. 8 and 10 schematically show the phase at the time of the burst signal, and are different from the phase of the actual carrier color signal. is slightly different. Therefore, since the inversion point is immediately after the detection output of the phase of the burst signal is obtained, it is unrelated to the horizontal synchronization signal, and in reality, the phase of the burst signal is inverted between certain horizontal intervals. In this case, the portion of the carrier color signal after the burst signal in the horizontal section will be correctly corrected.

In other words, the diagram only shows the phase at the time of the burst signal to simplify the explanation.

Purpose of the Invention In view of the above points, the present invention uses the above-mentioned method in the case of correcting the continuity of phase inversion for each horizontal section of a modulated color signal of a PAL color signal, or in a burst ID circuit of an NTSC reproduced color video signal. The aim is to provide something that prevents false positives from occurring.

Summary of the Invention In the present invention, when reproducing a color video signal recorded in a low-band conversion carrier system, correction of phase inversion for each horizontal section of one modulated color signal of a burst signal in the case of PAL system and NTSC color When switching the phase inversion of the burst signal by the signal burst ID circuit, the correction operation and switching operation are prevented by preventing the correction operation and switching operation from the correction time and the switching time by the delay time of the comb filter. The aim is to prevent this from happening.

Embodiment FIG. 11 shows an embodiment of this invention.
This is an example showing an example in which the present invention is applied to the above-mentioned sequence detection circuit 30 in a PAL color signal reproduction system.

In FIG. 11, 61 is an input terminal to which a horizontal synchronization signal SA (FIG. 12A) is supplied, and this horizontal synchronization signal SA is converted into a phase-inverted signal SB (FIG. 12B) via an inverter 62. This is supplied to one input terminal of AND gate 63. On the other hand, the sequence detection signal DS from the comparison circuit 38 (C in the same figure)
is supplied to the other input terminal of this AND gate 63. And the output SD of this AND gate 63
(D in the figure) is supplied to the set terminal of the flip-flop circuit 64. This flip-flop circuit 6
The D terminal of 4 is grounded, and when an input pulse is supplied to the clock terminal, its output SE (E in the same figure) drops to low level.
When a pulse is supplied to the set terminal while SET is at a low level, its output SE (E in the figure) rises to ``1''. Therefore, this flip-flop circuit 64 rises to "1" at the first pulse of the sequence detection output SC. However, after that, it remains at "1" unless a pulse is supplied to the clock terminal.

On the other hand, the horizontal synchronization output SA through the terminal 61 is supplied to one input terminal of the AND gate 65. The output of the flip-flop circuit 64 is supplied as a gate signal to the other input terminal of this AND gate 65, and during its high level period, this AND gate 65
5, the output SF (FIG. 5F) in which the horizontal synchronizing signal SA is gated is obtained. Therefore, the output SF of the AND gate 65 becomes in a state of gating the horizontal synchronizing pulse from the time when the comparison output DS of the sequence detection output is obtained. The output SF of this AND gate 65 is supplied to the clock terminals of flip-flop circuits 67 and 68 forming a counter 66. This flip-flop circuit 6
7 and 68 are D-type flip-flop circuits. The counter 66 also includes an AND gate 69, and the Q outputs SG and SH (G and H in the figure) of the D-type flip-flop circuits 68 and 67 are supplied to the input terminal of the AND gate 69. In this case, the flip-flop circuits 67 and 68 each produce signals that divide the signal SF by 1/2, but their phases differ by 180 degrees, so the output SI of the AND gate 69 is As shown in FIG. 12, the signal becomes a low level for two horizontal periods. This signal SI is then supplied to the clock terminal of the flip-flop circuit 64.

As shown in the figure, this signal SI rises at the leading edge of the horizontal synchronization signal two horizontal periods after the beginning of the next horizontal period in which the first pulse of the sequence detection output comparison output DS is obtained. This results in a signal that rises approximately three horizontal periods after the first pulse of the comparison output DS is obtained. Since this rising edge is supplied to the flip-flop circuit 64 as a clock signal, the output SE of the flip-flop circuit 64 is
After about 3 horizontal periods from the first sequence detection comparison output DS, it falls to low level.
The state is set again by a subsequent pulse of the comparison output DS. Therefore, the flip-flop circuit 64 is not inverted even if there is a pulse DS for about three horizontal periods from the first pulse of the comparison output DS.

The output of this flip-flop circuit 64 is
The flip-flop circuit 39 is inverted by the rise of SE, and this becomes the detection output SW of the sequence detection circuit 30 as the above-mentioned switch switching signal.

Thus, according to the circuit of FIG. 11, once the first pulse of a sequence of discontinuous detection pulses occurs, that detection pulse is inhibited for at least two horizontal periods thereafter, even if it is obtained during that time. Therefore, even if false detection occurs in these two horizontal sections due to crosstalk components from adjacent tracks of the carrier color signal due to the influence of the delay time of the comb filter as described above, This eliminates the possibility of erroneous switching conditions.

In the embodiment shown in FIG. 11, the comparative output pulse DS is gated by the horizontal synchronizing signal using the gate circuit 63 because the output time of the pulse DS overlaps with the horizontal synchronizing pulse for some reason. If this occurs, this first horizontal synchronizing pulse will be counted by the counter 66, so the period during which the pulse DS is inhibited may not be approximately 3 horizontal intervals but less than 2 horizontal intervals. This was provided to prevent this.

In the above example, the case of a PAL color signal was explained, so the period to be inhibited was two horizontal periods, but when applied to a burst ID circuit for an NTSC signal, this may be at least one horizontal period. This is because the delay time of the comb filter is one horizontal period.

When applied to this burst ID circuit, a circuit similar to that shown in FIG. 11 (however, the inhibiting period may be two horizontal periods) may be provided between the comparison circuit 64 and the flip-flop circuit 65.

Note that the circuit that inhibits the sequence detection output by at least the delay time of the comb filter is not limited to the configuration using a counter as described above, but can also be configured by using, for example, a monostable multivibrator to form a wind pulse. Of course it's good too. However, when configured as described above, there is an advantage that stable operation is possible without the influence of noise when configured with a monostable multivibrator.

Effects of the Invention According to the present invention, when it is detected that the sequence of the burst signal is incorrect or that the phase of the burst signal of the NTSC signal has occurred,
When each of them is controlled to be corrected, it is possible to eliminate the influence of crosstalk components that occur during the delay time of the comb filter from the time of control, and stable correction operations can be performed.

[Brief explanation of drawings]

Figure 1 is a diagram for explaining a PAL color video signal, Figure 2 is a diagram for explaining that discontinuity occurs in the burst signal sequence of a PAL signal,
FIG. 3 is a diagram for explaining the same, and FIG. 4 is a block diagram of an example of a circuit for correcting sequence discontinuity.
5 is a block diagram of an example of the main part of the circuit in FIG. 4, FIG. 6 is a diagram for explaining FIG. 5, FIG. 7 is a diagram for explaining FIG. 4, and FIG. 8 is a diagram for explaining FIG. 4 is a diagram for explaining the disadvantages of the circuit, FIG. 9 is a block diagram of an example of an NTSC color video signal reproducing device, FIG. 10 is a diagram for explaining the same, and FIG. 11 is a diagram of the circuit of this invention. A block diagram of an example of the main part, and FIG. 12 are waveform diagrams for explaining the same. 30 is a burst signal sequence detection circuit;
60 is a burst ID detection circuit; 5 and 44 are frequency conversion circuits for returning the low frequency converted carrier color signal to the original subcarrier frequency signal; 18 and 58 are for correcting the sequence and correctly correcting the burst signal phase. 64 is a flip-flop circuit for inhibiting the sequence detection pulse by at least the delay time of the comb filter. 66 is a counter for forming the inhibiting period.

Claims (1)

[Claims] 1 The luminance signal is FM modulated and the carrier color signal is
During playback of an FM-modulated luminance signal that is frequency-converted to the lower frequency side and recorded, and the phase of the subcarrier is shifted by a predetermined amount at a predetermined timing, the carrier color is A frequency conversion circuit for converting the subcarrier frequency _L of the low-band carrier color signal to the original subcarrier frequency _SC is provided in the signal reproduction system, and the frequency conversion circuit converts the subcarrier frequency L of the low band carrier color signal back to the original subcarrier frequency _SC . The carrier color signal is passed through a comb filter to remove crosstalk components from adjacent tracks. A circuit is provided to detect a change in the phase continuity of the burst signal in the subsequent carrier color signal and the continuity of inversion with respect to a specific phase axis, and the detection output causes the frequency conversion signal to change to the frequency _SC. Processing of a color video signal in which the signal is switched to a signal of the sum and difference of and _L , and the switching is prohibited even if the detection output is generated for at least a period corresponding to the delay time of the comb filter from the point of switching. Device.