JPH02292990A - Video signal format conversion circuit and disk player containing the conversion circuit - Google Patents

Abstract

PURPOSE:To prevent the color slurring by delaying a luminance signal by a prescribed time when converting a color video signal of an NTSC system into another one of a PAL system. CONSTITUTION:An NTSC color video signal (a) is directly supplied to a subtractor 2 and an adder 3 via an input terminal IN as well as to an 1H delay circuit 1. At the same time, the signal (a) is supplied to a switch control signal generating circuit 9 of a digital shifter 40. Then a PAL system converting signal (c) is produced by an adder 42. The chroma signal component obtained by the subtractor 2 is converted into a frequency of the component corresponding to a color video signal of a PAL system and supplied to a BPF 6 and a gain control circuit 50. Then a processed signal component (e) is supplied to an adder 10 together with a signal obtained by delaying the luminance signal obtained by the adder 3 by a delay circuit 51 by a prescribed time. Both signals are synthesized together for prevention of the color slurring.

Description

TECHNICAL FIELD The present invention relates to a signal format conversion circuit for video signals and a disc player equipped with the signal format conversion circuit.

Background Art A color video signal based on the NTSC system (hereinafter referred to as NTSC)
(referred to as a color video signal), the number of scanning lines is 5.
The field frequency is 60 Hz, and the color subcarrier frequency is 3.58 MHz. In addition, color video signals based on the PAL system (hereinafter referred to as P
In the AL color video signal), the number of scanning lines is 625, the field frequency is 50 Hz, and the frequency of the color subcarrier is 4.43 MHz.

There is a demand for a PAL video playback device such as a television receiver that plays video using PAL color video signals to be able to obtain video recorded on a disc on which NTSC color video signals are recorded. It has been considered to provide a video disk player with a format conversion circuit as shown in FIG. 13, which pseudo-converts a color video signal into a PAL color video signal.

In Figure 13, the NTSC read from the disk
The color video signal a is sent to the subtracter 2 via the input terminal IN.
and is directly supplied to the adder 3, and after being delayed by IH (one horizontal scanning period) by the IH delay circuit 1, it is supplied to the subtracter 2 and the adder 3. In the subtracter 2, the luminance signal component is canceled and only the color signal component is output.
In the adder 3, the color signal component is canceled and only the luminance signal component is output. The color signal component output from the subtracter 2 is supplied to a multiplier 4 and multiplied by the output of an oscillator 5.

The oscillation frequency of the oscillator 5 is equal to the difference between the frequency of the color subcarrier in the PAL color video signal (4.43MHz) and the frequency of the color subcarrier in the NTSC color video signal (3.58MHz), that is, 8
The frequency is 54kHz. Therefore, in the multiplier 4, a signal obtained by converting the frequency of the color signal component from the subtracter 2 from 3.58 MHz to 4.43 MHz is formed.

The 4.43 MHz color signal component outputted from the multiplier 4 is transmitted to the phase shifter 7.8 and the fixed contact B1 of the changeover switch SWI via the band pass filter 6 whose passband center frequency is 4.43 MHz. be provided.

The phase shifter 7 is configured to shift the phase of the supplied signal by +45°. Further, the phase shifter 8 is configured to shift the phase of the supplied signal by -45°. The outputs of these phase shifters 7.8 are supplied to each of the fixed contacts A1 and C1 of the changeover switch SW1. In addition, the changeover switch SW1
The fixed contact D1 is grounded.

The output of the switching control signal generation circuit 9 is supplied to the control input terminal of the switching switch SW+. Changeover switch SW,
is the movable contact E. is configured to contact one of the fixed contacts A1 to D1 according to the switching control input.

For example, the switching control signal generation circuit 9 uses a horizontal synchronizing signal in the NTSC color video signal a to detect a period T1 in which a color burst exists in each horizontal scanning period and a period other than this period T1 in which a video information signal exists. During period T1, movable contact E alternately contacts fixed contacts A1 and C1 every IH, and during period T2, movable contact E1 alternately contacts fixed contacts B1 and D1 every IH. The structure is such that it generates a signal to control the

The signal led to the movable contact E1 of the changeover switch SW1 is supplied to the adder 10, and is added and combined with the luminance signal component output from the adder 3 to form a color video signal. The output of this adder 10 is supplied to an output terminal OLIT and sent to a PAL video playback device (not shown).

In the above configuration, the NTS as shown in FIG. 14(A)
When the C color video signal a is co-fed to the input terminal IN,
During the period T1, the movable contact E1 of the changeover switch SW1 receives a signal obtained by phase-shifting the color signal component frequency-converted to 4.43 MHz by +45'', and a signal obtained by shifting the color signal component by +45''.
A signal obtained by shifting the phase by 45" is output alternately every IH, and during period T2, the color signal component and a signal with zero amplitude are alternately output every IH. Therefore, the changeover switch SW+ The color signal component d output from the movable contact E1 becomes a signal as shown in FIG. The color video signal b output from the adder 10 is as shown in FIG. 14(C).

This color video signal b is transmitted to a PAL video playback device (
In this PAL video reproducing apparatus, the color video signal b is supplied to a demodulation circuit as shown in FIG. 15.

In FIG. 15, color video signal b is supplied to a Y/C separation circuit 20 and a sync separation circuit 21. In FIG. The Y/C separation circuit 20 separates the color video signal b into a luminance signal component and a color signal component, and the luminance signal component is supplied to a picture tube drive circuit (not shown) that drives the picture tube.

Further, the color signal component is passed through an ACC (automatic color saturation control) circuit 22 to a burst phase discrimination circuit 23. IH delay line 2
4, supplied to the polarity inversion circuit 25 and adder 26.

The ACC circuit 22 includes a variable gain amplifier 22a that amplifies the color signal component, a burst gate circuit 22b that separates the color burst signal from the color signal component, and a burst gate circuit 22b that responds to the level of the color burst signal separated by the burst gate circuit 22b. Generates ACCi pressure with variable gain 1} Amplifier 2
2a as a gain control signal.
c, and is configured to control the gain of the variable gain amplifier 22a so that the level of the color burst signal is constant.

In the burst phase discrimination circuit 23, the color burst signal is separated from the color signal component, and the subcarrier generation circuit 23 separates the color burst signal from the color signal component.
A rese note signal is generated every time the phase of the color burst signal supplied to the output signal 3 reaches a predetermined phase. This reset signal is supplied to T-type flip-flop 34.

A horizontal synchronizing signal separated from the color video signal by the synchronization separation circuit 22 is supplied to the trigger input terminal of the T-type flip-flop 34, and the T-type flip-flop 34 is inverted every IH.

On the other hand, in the IH delay line 24, the color signal component is delayed by IH and is supplied to adders 26 and 27.

In the adder 26, the color signal component and this color signal component are
The signal obtained by delaying by H is added. In this adder 26, the PA whose phase is inverted every IH
The R-Y components in the L color video signal are canceled and the B-
Although only the Y component is output, in the color video signal b, as shown in FIG. 14(C), the color signal component exists only in the period T2 every IH, The color signal component existing in the period T2 of every IH is also output in the period T2 of the next IH, and the color signal component is output for each H.

Further, in the adder 27, the opposite phase component of the color signal component and the signal obtained by delaying the color signal component by IH are added. In this adder 27, the B-Y component in the PAL color video signal is canceled and only the R-Y component whose phase is inverted every IH is output, but it is similar to the adder 26. Also, the adder 27 outputs a color signal component for each H.

The outputs of these adders 26 and 27 are sent to the synchronous detection circuit 28.
29. The synchronous detection circuit 28 is supplied with color subcarriers generated by the subcarrier generation circuit 33 and shifted by 90° by the phase shifter 35. Further, the synchronous detection circuit 29 receives the color subcarrier generated by the subcarrier generation circuit 33 and a signal obtained by shifting the phase of this color subcarrier by 180° by a phase shifter 35 through a changeover switch 36.
It is supplied alternately every H. These synchronous detection circuits 2
The B-Y signal and the R-Y signal are demodulated by 8.29 and supplied to an image receiver drive circuit (not shown) via a low-pass filter 31.32 with a cutoff frequency of 1.3 MHz to reproduce a color image. be done.

When the color video signal b whose format has been converted by the conventional signal format conversion circuit as shown in FIG. 13 is input to the demodulation circuit as shown in FIG. 15, the amplitude of the color signal component of the color video signal b becomes zero. During the period, only the pre-IH color signal component supplied to the adder 26.27 via the IH delay line 24 is supplied to the synchronous detection circuit 28.29, and during the period when the amplitude of the brown signal component does not become zero. Only the color signal components co-fed to the direct adders 26 and 27 are supplied to the synchronous detection circuits 28 and 29 to reproduce a color image.

However, the horizontal synchronization frequency of color video signal b is N
The delay time of the IH delay line 24 is equal to the horizontal synchronization frequency of the TSC system, whereas the delay time of the IH delay line 24 is set to IH in the PAL system, that is, 64 μs. and IH delay line 2
There is a problem in that the position of the color on the screen of the color signal component that does not pass through 4 is different in the horizontal direction, resulting in color shift.

Summary of the Invention The present invention has been made in view of the above points, and includes:
It is an object of the present invention to provide a signal format conversion circuit for a video signal that can prevent color shift, and a disc player equipped with the signal format conversion circuit.

In the signal format conversion circuit for a video signal according to the present invention, a color video signal according to the NTSC system is separated into a color signal component and a luminance signal component, and the frequency of the color signal component is changed to the frequency of the component corresponding to the color video signal according to the PAL system. While converting the amplitude of the color signal component to a predetermined value or less for a predetermined period every horizontal scanning period, the luminance signal is converted to a predetermined value or less for a predetermined period of time, and then combined with the luminance signal component. The feature is that a delay means is provided for delaying by .

In addition, a disc player equipped with a signal format conversion circuit according to the present invention includes a pickup that reads an NTSC color video signal recorded on the disc, and a horizontal synchronization signal that is separated from the color video signal output from the pickup. A phase comparison is made with a reference horizontal synchronization signal to generate an error signal according to the phase difference between the two signals, and the relative speed between the information reading point of the disk and the pickup is controlled according to this error signal. , converts the frequency of the color signal component of the color video signal output from the pickup into the frequency of the component corresponding to the PAL color video signal, while changing the amplitude of the color signal component to a predetermined value over a predetermined period every other horizontal scanning period. When converting the signal format by lowering the frequency of the reference horizontal synchronization signal to PAL
It is characterized by having the same frequency as the horizontal synchronizing signal in the color video signal according to the system.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 12.

In FIG. 1, an IH delay circuit 1, a subtracter 2, an adder 3
, multiplier 4 and bandpass filter 6 are connected in the same way as in the device of FIG. However, in this example, the multiplier 4 is supplied with the output of the bandpass filter 41. The bandpass filter 41 is configured so that the center frequency is equal to 854kHz. The output of a multiplier 42 is jointly supplied to this bandpass filter 41 . The multiplier 42 is supplied with the output of the digital phase shifter 40 and the output of the oscillator 43. The oscillator 43 is
It is configured to generate a reference signal "2" having the same frequency as the frequency of the color subcarrier of a video signal according to the NTSC system.

The output of the oscillator 44 is supplied to the digital phase shifter 40 . The oscillator 44 is configured to generate a reference signal rl having a frequency four times that of the color subcarrier of the PAL video signal. Digital phase shifter 40
, the reference signal r1 is frequency-divided by a frequency divider 45 to 1/4, and is supplied directly to the clock input terminal of a D-type flip-flop 47, and also to the clock input terminal of a D-type flip-flop 46 via an inverter 48. be shared. The output of the frequency divider 45 is a D-type flip-flop 46.
is supplied to the D input terminal of the switch SW1.
is supplied to the fixed contact C1. Further, the Q output of the D-type flip-flop 46 is supplied to the D input terminal of the D-type flip-flop 47 and also to the fixed contact B of the changeover switch SW+. In addition, the Q output of the D-type flip-flop 47 is connected to the fixed contact A of the changeover switch SW1.
1 is supplied. Further, the fixed contact D1 of the changeover switch SW1 is grounded. The output of the switching control signal generation circuit 9 is supplied to the switching control input terminal of the switching switch SWl, as in the case of the device shown in FIG.

Further, the color signal component output from the bandpass filter 6 is supplied to one input terminal of the adder 10 via the gain control circuit 50. The gain control circuit 10 includes a means for detecting a period T1 in which a color burst signal exists, for example, by the output of the switching control signal generation circuit 9, and generating a gain reduction command signal, and a means for reducing the gain in accordance with this gain reduction command signal. It consists of a variable gain amplifier. The other input terminal of the adder 10 is supplied with a time T by a delay circuit 51.
A luminance signal component which is the output of adder 3 delayed by D is provided. The adder 10 adds and combines the color signal component and the luminance signal component to form a color video signal. Note that the delay time TD in the delay circuit 51 is
IH in NTSC system and IH in F'AL system
The time corresponding to 1/2 of the difference between
The value is set to be equal to the sum of the delay time ΔD (=250 ns+ΔD).

The output of the adder 10 is supplied to an amplitude suppression circuit 52 and a vertical synchronization separation circuit 53. In the vertical synchronization separation circuit 53, a vertical synchronization signal is separated from the color video signal output from the adder 10, and is supplied to a monostable multivibrator (hereinafter referred to as MMV) 54. MMV54 is
It is configured to generate a pulse that is triggered by a rising edge of the output of the vertical synchronization separation circuit 53 and exists over a period T3 from the disappearance of the vertical synchronization signal to the end of the vertical blanking period. This output pulse of the MMV 54 is fed to an amplitude suppression circuit 52. The amplitude suppression circuit 52 is configured to limit the instantaneous level of the input signal to a level vA or less, which is slightly higher than the vedestal level, depending on the output pulse of the MMV 54, for example.

The output of this amplitude suppression circuit 52 is supplied to the output terminal OUT.

In the above configuration, as shown in FIG. Frequency divider 4 that divides the frequency by 1/4
The output of 5 is as shown in FIG. 2(D). The output of this frequency divider 45 is fed to the D input terminal of the D-type flip-flop 46 as a phase-shifted signal fsc3 having the same frequency as the color subcarrier in the PAL system, and also to the fixed contact C1 of the changeover switch SW1. be done.

Since the reference signal r1 is supplied to the clock input terminal of the D-type flip-flop 46 via the inverter 48, the phase shift signal fsc3 is stored and held in the D-type flip-flop 46 by the falling edge of the reference signal r1. The O output of the D-type flip-flop 46 is shown in FIG.
), the signal is obtained by advancing the phase of the phase-shifted signal fsc3 by 45°. The Q output of this D-type flip-flop 46 is supplied as a phase shift signal fsc2 to the D input terminal of the D-type flip-flop 47, and is also supplied to the fixed contact B1 of the changeover switch SWI.

Since the reference signal r1 is directly supplied to the clock input terminal of the D-type flip-flop 47, the phase-shifted signal fSC2 is stored and held in the D-type flip-flop 47 by the rising edge of the reference signal r1, and the D-type flip-flop 47 stores and holds the phase shift signal fSC2. The Q output of 47 is a phase-shifted signal f as shown in FIG. 2(B).
The signal is obtained by advancing the phase of se2 by 45@. The O output of this D-type flip-flop 47 is connected to the fixed contact A of the changeover switch SW1 as a phase shift signal f sc+.
1.

Here, when an NTSC color video signal a as shown in FIG. 3(A) is supplied to the input terminal IN, the switching control signal generating circuit 9 changes the movable contact E1 of the changeover switch SW1 to the fixed contacts AI + CI, DI +B. , as shown in FIGS. 3(B) to 3(E). That is, during the period T1 where the color burst exists, the movable contact E1 contacts the fixed contacts A1 and C1 alternately every IH, and during the period T2 where the video information signal exists, the movable contact E1 contacts the fixed contact B1 every IH. and D1 alternately. Then, in the period T1, the phase-shifted signals fsc1 and rsc3 are alternately led out to the movable contact E1 every IH, and in the period T2, the phase-shifted signals fs
c2 and ground level signal are alternately connected to movable contact E every IH.
1. The signal derived from this movable contact E1 is supplied to the multiplier 42, and the 3.58 MHz reference signal "2" is supplied to the multiplier 42.
Therefore, in the multiplier 42, a signal with a frequency equal to the frequency difference between the phase-shifted signals fsc+ to fsc3 and the reference signal r2, that is, a signal of 854 kHz, is generated alternately at every IH during the period T1. Phase is +4
A conversion signal C as shown in FIG. 3(F) is formed in which the amplitude changes by 5 degrees and -45 degrees, and the amplitude becomes zero at every IH during period T2.

The conversion signal C of 854kHz is passed through the bandpass filter 4.
1 to the multiplier 4. Then, in the multiplier 4, a 4.43 MHz signal whose frequency differs by 854 kHz from the color signal component according to the NTSC system, the phase of the color burst signal alternately changes by +45° and -45° every IH, and the image The amplitude of the information part is IH
The color signal component d, as shown in FIG. 3 (G), becomes zero every other time.
is formed. This color signal component d is supplied to the gain control circuit 50 via the bandpass filter 6, and the level of the color burst is lowered by a predetermined value.

The color signal e as shown in FIG. 3(H) outputted from the gain control circuit 50 is supplied to the adder 10, and is added and synthesized with the luminance signal component delayed by TD by the delay circuit 51. A color video signal b as shown in (I) is formed.

The color video signal b is supplied to an amplitude suppression circuit 52 and a vertical synchronization separation circuit 53. Then, Figure 4 (A)
Vertical blanking period TE of color video signal b as shown in
A vertical synchronization signal V as shown in FIG. When this vertical synchronization signal V is supplied to the MMV 54, the rising edge of the vertical synchronization signal V causes the MMV to
54 is triggered, and the pulse p existing over the period To is outputted from the MMV 54 as shown in FIG. 4(C).

When this pulse p is supplied to the amplitude suppression circuit 52, the instantaneous level of the color video signal b becomes a level vA slightly higher than the pedestal level over the period in which this pulse p exists.
Since the amplitude is limited so that
), the code signal inserted in a predetermined line within the vertical blanking period TE of the color video signal almost disappears.

The color video signal b outputted from the amplitude limiting circuit 51 is supplied to the output terminal OUT and sent to a PAL video reproducing device (not shown), so that the color video signal b outputted from the amplitude limiting circuit 51 is transmitted to the PAL video reproducing device (not shown), so that the color video signal b output from the amplitude limiting circuit 51 is not obtrusive due to the change in brightness caused by the code signal. No image is generated.

Furthermore, since the frequency of the horizontal synchronization signal of the color video signal b derived to the output terminal OLIT is equal to the horizontal synchronization frequency of the NTSC system, this color video signal b is
When the signal is supplied to a video playback device (not shown) based on the IH
The delay time of the delay line 24 is IH of the PAL color video signal.
In other words, since it is set to 64 μs, color misregistration will occur. That is, during the period when the amplitude of the color signal component of the color video signal b is zero, the IH delay line 24
Only the pre-IH color signal component supplied to the adder 26.27 via Only the detected color signal components are supplied to the synchronous detection circuits 28 and 29 to reproduce a color image.
The colors on e3 are PAL color video signal IH and NT
It has a deviation W corresponding to 500 nS, which is the difference between IH of the SC color video signal. However, as shown in FIG. 6(A), the color video signal b is
) and a luminance signal component as shown in FIG. scanning line L n '= L
The contour formed by the luminance signal component on rhJ is
As shown by the dashed dotted line y in Figure m5, the color shift is located in the middle of the shift width between the colors, and the color shift is not noticeable.

Furthermore, since the amplitude of the color signal component of the color video signal b becomes zero over the period T2 every IH, when this color video signal b is supplied to a PAL video playback device (not shown), The amplitude of one of the two outputs of the adders 26 and 27 in the demodulation circuit shown in FIG. 15 in the video reproducing apparatus, that is, the color signal component and the signal obtained by IH delaying this color signal component, is , becomes zero. Therefore, the level of the color signal component output from the adders 26 and 27 is lower than if a regular PAL color video signal in which the amplitude of the color signal component does not become zero is supplied during the period T2.

The color signal components of a regular PAL color video signal can be represented by a vector diagram as shown in FIG. 7(A). FIG. 7A shows a color signal component f1 in continuous 2H and a color burst signal g1 accompanying this color signal component f1. The R-Y component of the color signal component f1 has a phase inversion with respect to the B-Y axis for each IH, and the color burst signal g1 has a B-Y component corresponding to the phase inversion of the R-Y component.
It is output at ±135° from the Y axis. In the case of a regular PAL color video signal, the signal shown in FIG. 7(B) is obtained by adding the color signal component f1 and a signal obtained by inverting only the RY component of the color signal component f1 before IH. A color signal component f2 as shown in is synchronously detected.

On the other hand, the color signal component of color video signal b is
It can be represented by a vector diagram as shown in Figure (A).

In Fig. 8 (A), continuous 2H as in Fig. 7 is also shown.
The color signal component f1 and the color burst signal g1' associated with the color signal components f and l are shown. The color burst signal g1' is output in the same way as the color burst signal g1 of the regular PAL color video signal, but the color signal component (, I has an amplitude of zero at every IH. Therefore, in the case of color video signal b, As shown in FIG. 8(B), the color signal components f and l become the color signal component f2' that is synchronously detected as they are, and the level of the color signal component supplied to the synchronous detection circuit 28 and 29 is equal to that of the regular PAL. This is lower than that for color video signals.

However, the level of the color burst signal g1' of the color video signal b is reduced by the amplitude suppression circuit 52 as shown in FIG. 9(A).

Therefore, the ACC circuit 22 in the video reproducing apparatus controls the color burst signal g1' until the level of the color burst signal g1' reaches a predetermined level as shown in FIG. 9(B).
' and the gain of the amplifier that amplifies the color signal component f1' increases, and the level of the synchronously detected color signal component f2' increases as shown in FIG. becomes.

FIG. 10 is a block diagram showing another embodiment of the present invention, in which IH delay circuit 1. Subtractor 2, adder 3, multiplier 4,
Bandpass filter 6, delay circuit 51. Amplitude suppression circuit 5
2. The vertical synchronization separation circuit 53 and MMV 54 are connected in the same way as in the device shown in FIG. However, in this example, the output of the bandpass filter 6 is directly supplied to the adder 10, and the multiplier 4 is supplied with the changeover switch SW2.
The derived signal is supplied to the movable contact C2. The output of the switching control signal generation circuit 61 is supplied to the control input terminal of the switching switch SW2.

The changeover switch SW2 has a movable contact C2 as a fixed contact A2,
B. The switch is configured to contact one of the switches according to the switching control input. The switching control signal generation circuit 61 generates a period T1 in which a color burst exists during each horizontal scanning period by using, for example, a horizontal synchronizing signal in an NTSC color video signal.
and the period T2 in which the video information signal exists, and the period T2 is detected.
, the movable contact C2 contacts the fixed contact B2, and during the period T2, the movable contact C2 contacts the fixed contact A every IH.
2 and B2, and generates a control signal to alternately contact the terminals B2 and B2.

The output of the bandpass filter 62 is supplied to the fixed contact A2 of the changeover switch SW2. The center frequency of the passband of this bandpass filter 62 is 8.01 MHz. In addition, the fixed contact B2 of the changeover switch SW2
is supplied with the output of the bandpass filter 41.

The output of the multiplier 42 is supplied to these bandpass filters 62 and 41. Multiplier 42 is supplied with the output of digital phase shifter 40 and the output of oscillator 43, similar to the device shown in FIG.

The digital phase shifter 40 is configured similarly to the device shown in FIG. 1, but in this example, the switching control signal generation circuit 9 in the digital phase shifter 40 is
The movable contact E1 of the changeover switch SW1 alternately contacts the fixed contacts A1 and C1 every H, and a switching control signal is generated so that the movable contact E1 contacts the fixed contact B1 during the period T2.

In the above configuration, the NTS as shown in FIG. 11(A)
When the C color video signal a is supplied to the input terminal IN,
The switching control signal generating circuit 9 causes the movable contact E1 of the changeover switch SW1 to contact each of the fixed contacts AI+CI and Bl as shown in FIGS. That is, during the period T1 in which the color burst exists, IH
The movable contact E1 alternately contacts the fixed contacts A1 and C1 at every interval, and during the period T2 in which the video information signal exists, the movable contact E1 contacts the fixed contact B1. Then, in the period T1, the phase-shifted signals fsc+ and fs- are alternately led out to the movable contact E1 every IH, and in the period T2, the phase-shifted signal f sex is led out to the movable contact E1. The signal derived from this movable contact E1 is supplied to the multiplier 42 and multiplied by the 3.58 MHz reference signal "2," so that the multiplier 42 outputs the phase-shifted signals fsc1 to fsc3.
and the reference signal '2, and the two signals each have a frequency equal to the sum of both frequencies, that is, 854kHz.
and 8. Two OIMHz signals are formed whose phases alternately change by +45° and -45° every IH during period T1, and do not change during period T2. Of these two signals, the 854 kHz signal is supplied to the fixed contact B2 of the changeover switch SW2 via the bandpass filter 41, and the 8.01MHz signal is supplied to the changeover switch S via the bandpass filter 62.
It is supplied to the fixed contact A2 of W2.

The movable contact C2 of the changeover switch SW2 is connected to each of the fixed contacts B2 and A2 by the changeover control signal generation circuit 61.
Contact is made as shown in Figure (D) and Figure (E). That is, in the period T1, the movable contact C2 contacts the fixed contact B2, and in the period T2, the movable contact C2 contacts the fixed contacts A2 and B2 alternately at every IH. Then, in period T1, the 854kHz signal is transmitted to the movable contact C.
2, and in period T2, 854kHz and 8
．． Two signals of 0.01 MHz are alternately led out to the movable contact C2 every IH, and a conversion signal C' as shown in FIG. 11(G) is formed.

The conversion signal C' is supplied to a multiplier 4. Then, in the multiplier 4, the color signal component based on the NTSC system and the conversion signal C' are multiplied together.

Here, one input of the multiplier 4 is set to ωSα, and the multiplier 4
Let the other input of be the enclosure β. Then, the output of the multiplier 4 is expressed by the following equation.

Surrounding αφ Surrounding β - (1/2) + Surrounding (α + β) + CDs (α - β))...
(1) Now, one input of the multiplier 4 is the conversion signal C', so the range α is the range (ωP - ωN) in the period T1, and the range α is the range IH in the period T2. Zheng (ωP1ω) alternately
N) and o)s(ωρ+ωN). Also, multiplier 4
Since the other input of is a color signal component based on the NTSC system, Aβ becomes (ωN+φ). Furthermore, ωP is P
The angular frequency of the subcarrier in the AL system, ωN, is NTSC
is the angular frequency of the subcarrier of the system.

Therefore, the output of the multiplier 4 becomes a signal expressed by the following equation during the period T1.

OgoS (ωP −ωN) Conflict 0goS (ωN +
φ) − (1/2) tcos (ωP + φ) + enclosure (ωp − 2ωN − φ)} ・・・・・・(2) Also,
The output of the multiplier 4 becomes a signal expressed by equation (2) and a signal expressed by the following equation alternately every IH during period T2.

■S(ωP+ωN)4COS(ωN+φ)− (1/2
)<Size (ωp+2ωN+φ)+V3(ωP+φ)}
......(3) The output of this multiplier 4 is
Since it passes through the band pass filter 6 of 4.43 MHz (ωp), a 4.43 MHz color signal component d' as shown in FIG. It will be. This color signal component d' is supplied to the adder 10, and is added and synthesized with the luminance signal component delayed by the delay circuit 51 by TC).
) is formed as a color video signal b'.

The color signal component of this color video signal b' has an amplitude of IH.
Color video signal b
Even if ' is supplied to a PAL video playback device, the saturation will not decrease.

FIG. 12 is a block diagram showing a video disc player equipped with a signal format conversion circuit according to the present invention. In the figure, a disk 71 is connected to a spindle motor 72.
Rotationally driven by.

As the disk 71 rotates, a signal recorded on the disk 71 is read by a pickup 73. A so-called RF (high frequency) signal, which is a read signal output from the pickup 73, is supplied to a demodulation circuit 74 consisting of an FM demodulator or the like, and a color video signal is demodulated. The color video signal is CCD (Charge Cou
pled Dev1cc) 7 5. C
A clock pulse output from a VCO (voltage controlled oscillator) 76 is supplied to the OD75. COD75
In this case, the color video signal is delayed by a time corresponding to the frequency of this clock pulse. This COD7
5 is supplied to a variable phase shifter 77, a burst gate circuit 78, and a sync separation circuit 79.

In the synchronization separation circuit 79, the horizontal synchronization signal is separated from the color video signal and supplied to the phase comparison circuit 80 as a reproduced horizontal synchronization signal. In the phase comparison circuit 80, the reference horizontal synchronization signal outputted from the reference signal generation circuit 81 and the reproduced horizontal synchronization signal are compared in phase, and a time axis error signal is generated according to the phase difference between the two signals. This time axis error signal is supplied to the equalizer 82. In the equalizer 82, the time axis error signal is amplified and phase compensated to generate a control voltage for the VCO 76 and a drive signal for the spindle motor 72. The drive signal formed by the equalizer 82 is supplied to the spindle motor 72 via a drive circuit 83, and the rotational speed of the disk 71 is controlled so that the phase difference between the reference and reproduction horizontal synchronization signals becomes a predetermined value. . Further, the control voltage formed by the equalizer 82 is VC076
The signal delay time in the CCD 75 is controlled so that the phase difference between the reference and reproduced horizontal synchronizing signals becomes a predetermined value, thereby compensating for time axis errors.

On the other hand, the burst gate circuit 78 separates the color burst signal or pilot burst signal from the color video signal and supplies it to the phase comparator circuit 85 . In the phase comparison circuit 85, a phase comparison is made between this burst signal and the reference subcarrier signal outputted from the reference signal generation circuit 81, and a phase error signal is generated according to the phase difference between the two signals. This phase error signal is supplied to a variable phase shifter 77, and the color video signal is phase-shifted so that the phase of the color burst signal matches the phase of the reference subcarrier signal. The color video signal output from variable phase shifter 77 is supplied to character insertion circuit 86 . The character insertion circuit 86 generates a video signal according to the character indicated by the data output from the system controller (not shown) etc. using the reference signal "3" output from the reference signal generation circuit 81, and converts it into a color video signal. It is configured to be inserted into.

In the reference signal generation circuit 81, the reference horizontal synchronization signal is
It is output from the movable contact C3 of the changeover switch SW3. The output of the frequency divider S81b is supplied to the fixed contact A3 of the changeover switch SW3. The frequency divider 81b has a changeover switch S
The signal derived to the movable contact CB of Ws is 1/9 1 0
The configuration is such that the frequency is divided into The outputs of the oscillators 81a and 81g are supplied to each of the fixed contacts A8+88 of the changeover switch SW9. The oscillator 81a is NTSC
It is configured to generate a signal with a frequency of 4 f sc (N), which is four times the frequency of the color subcarrier in the system. Furthermore, the oscillator 81g has a frequency of 4 fsc (
N) · f H (N) / f H (P) signals are generated. In addition, fH (N) represents the horizontal synchronization frequency in the NTSC system, and fH
(P) represents the horizontal synchronization frequency in the PAL system.

When the changeover control input is at a high level, the changeover switch SW8 causes the movable contact C8 to contact the fixed contact 88 to turn off the oscillator 81a.
When the switching control input is at a low level, the movable contact CB contacts the fixed contact B8, and the oscillator 81
The configuration is such that the output of g is selectively output. The changeover control input terminal of this changeover switch SW8 is connected to one end of the lock type switch SWs. This switch S
A power supply voltage is applied to one end of W6 via a resistor R. Further, the other end of the switch SWs is grounded.

When this switch SWε is turned on, a low level signal derived from one end is output as a signal format conversion command signal.

The fixed contact B3 of the changeover switch SW3 is supplied with the output of a frequency divider 81e that divides the output of the oscillator 81d by 1/240. The oscillator 81d is configured to generate a frequency of 3.75 MHz, which is the frequency of a pilot burst signal inserted into a predetermined section of the PAL color video signal when recording the PAL color video signal on a disc.

In the changeover switch SW3, when the changeover control input is at a high level, the movable contact C3 contacts the fixed contact A3 and the frequency divider 81b is switched on.
When the switching control input is at a low level, the movable contact C3 contacts the fixed contact B3, and the frequency divider 81
e, that is, a signal having a frequency equal to the horizontal synchronization frequency in the PAL system is selectively output. The output of the signal format discrimination circuit 87 is supplied to the switching control input terminal of the changeover switch SW3.

For example, the signal format determination circuit 87
Detects whether or not a pilot signal is inserted into the color video signal read from the system, and generates a signal format discrimination signal indicating whether the signal is a PAL or NTSC color video signal based on the detection result. The structure is as follows. The signal format discrimination circuit 87 is described in detail in Japanese Patent Application No. 12240/1983.

Further, the reference subcarrier signal is output from the movable contact C4 of the changeover switch SWa. The fixed contact A4 of the changeover switch SWa is supplied with the output of a frequency divider 81c which divides the output of the changeover switch SW8 into 1/4 and outputs a reference signal r2.

In addition, an oscillator 8 is connected to the fixed contact B4 of the changeover switch SW4.
1d output is supplied. The changeover switch SW▲ is
When the switching control human power is at a high level, the movable contact C4 contacts the fixed contact A4 to selectively output the output of the frequency divider 81C,
When the switching control input is at a low level, the movable contact C4 contacts the fixed contact B4 and selectively outputs a signal having a frequency equal to the output of the oscillator 81d, that is, the frequency of the pilot burst. The output of the signal format discrimination circuit 87 is supplied to the switching control input terminal of the changeover switch SWa.

Further, the reference signal "3" is output from the movable contact C5 of the changeover switch SW5. The fixed contact A of the changeover switch SW5
5 is supplied with the output of the changeover switch SW9. Further, an oscillator 81 is connected to the fixed contact B5 of the changeover switch SW5.
The output of f is being distributed. The oscillator 81f is configured to generate a reference signal r1 having a frequency four times the frequency of the color subcarrier in the PAL system. When the changeover control input is at a high level, the changeover switch SW5 causes the movable contact C5 to contact the fixed contact A5 and switch SW5.
9 is selectively output, and when the switching control input is at a low level, the movable contact C5 contacts the fixed contact BS and the oscillator 8
1f, that is, a reference signal r1 having a frequency four times as high as the frequency of the color subcarrier in the PAL system. The output of the signal format discrimination circuit 87 is supplied to the switching control input terminal of the switching switch SW5.

The color video signal output from the character insertion circuit 86 is
The signal is supplied to the fixed contact A7 of the changeover switch SW7 and also to the signal format conversion circuit 97. The output of the signal format conversion circuit 91 is supplied to the fixed contact B7 of the changeover switch SWy. In the signal format conversion circuit 97, each part is constructed in the same manner as the circuit shown in FIG. 1, except that the oscillators 43 and 44 are removed. The multiplier 42 in the signal format conversion circuit 97 is supplied with the reference signal r2 output from the frequency divider 84c. In addition, the signal format conversion circuit 97
The reference signal "1" output from the oscillator 81f is supplied to the frequency divider 45, the D-type flip-flop 47, and the inverter 48.

In the changeover switch SW7, when the changeover control input is at a high level, the movable contact C7 contacts the fixed contact A7 and outputs the color video signal output from the character insertion circuit 86, and when the changeover control input is at a low level, it is movable. Contact C7 is fixed contact B7
The color video signal whose format has been converted by the signal format conversion circuit 97 is outputted by contacting the signal format conversion circuit 97. Movable contact C7 of changeover switch SW7
The color video signal derived from the output terminal OUT is supplied to the output terminal OUT.

In the above configuration, if switch SW6 is off,
The low-level signal format conversion command signal is not output, and the output of the oscillator 81a, that is, the signal of 4 f sc (N) is selectively output from the changeover switch SW9 in the reference signal generation circuit 81, and the signal format conversion command signal of the signal format determination circuit 87 is selectively output. The output controls switching of the changeover switches SW3 to SW5, and it is possible to read any of the two types of discs recorded with NTSC and PAL color video signals. Further, at this time, the color video signal output from the character insertion circuit 86 is outputted as is from the changeover switch SW7 and supplied to the output terminal, and the color video signal read from the disc is outputted as is.

Next, when the switch SW5 is turned on by manual operation, a low-level signal format conversion command signal is output. Then, the output of the oscillator 81g, that is, 4 fs, is output from the changeover switch SW8 in the reference signal generation circuit 81.
The signals c(N)·f H (N) / f H(P) are selectively output. As a result, a reference horizontal synchronization signal having the same frequency as the horizontal synchronization frequency in the PAL system is output. Also, the burst phase comparison is performed using this oscillator 8.
The conversion of the color signal is done based on the signal obtained by dividing the output of 1g into 1/4, and the conversion of the color signal is also done by dividing the output of this oscillator 81g into 1/4.
This is done using a signal obtained by dividing the frequency by /4. Also,
At the same time, the output of the signal format conversion circuit 91 is derived from the changeover switch SW7.

Therefore, by loading a disc on which an NTSC color video signal is recorded, the signal format conversion circuit 91
A pseudo PAL color video signal is obtained. The horizontal synchronization frequency of this pseudo PAL color video signal is equal to the horizontal synchronization frequency of the regular PAL color video signal. Therefore, when this pseudo PAL color video signal is supplied to a PAL demodulation circuit as shown in FIG. This will not occur. Therefore, the signal format conversion circuit 91
In this case, the delay amount of the delay circuit 51 that delays the luminance signal component may be the same as that of the bandpass filter 6.

Effects of the Invention As detailed above, in the signal format conversion circuit for video signals according to the present invention, a color video signal based on the NTSC system is separated into a color signal component and a luminance signal component, and the frequency of the color signal component is converted into a color signal component based on the PAL system. The signal format is converted by converting the frequency of the component corresponding to the video signal, while reducing the amplitude of the color signal component to a predetermined value or less for a predetermined period every other horizontal scanning period, and then combining it with the luminance signal component. The present invention is characterized in that it includes a delay means for delaying the luminance signal by a predetermined period of time.

Therefore, in the signal format conversion circuit for video signals according to the present invention, the IH
Even if there is a shift in the horizontal position of colors on scanning lines that are close to each other due to the delay time of the delay line, the color shift can be avoided by positioning the outline formed on the scanning line by the luminance signal component in the middle of the color shift width. can be made inconspicuous, and visually color shift can be prevented.

In addition, a disc player equipped with a signal format conversion circuit according to the present invention includes a pickup that reads an NTSC color video signal recorded on the disc, and a horizontal synchronization signal that is separated from the color video signal output from the pickup. A phase comparison is made with a reference horizontal synchronization signal to generate an error signal according to the phase difference between the two signals, and the relative speed between the information reading point of the disk and the pickup is controlled according to this error signal. , converts the frequency of the color signal component of the color video signal output from the pickup into the frequency of the component corresponding to the PAL color video signal, while changing the amplitude of the color signal component to a predetermined value over a predetermined period every other horizontal scanning period. In order to convert the signal format by converting the frequency below the value, a signal with a frequency of 4 f sc (N), which is four times the color subcarrier of the NTSC system, is converted into a signal with a frequency of 4 f sc (N)
c(N) ・[H(N) / f By switching to the H(P) signal and obtaining the reference horizontal sync signal and reference subcarrier signal, the frequency of the reference horizontal sync signal is changed to PAL.
It is characterized by having the same frequency as the horizontal synchronizing signal in the color video signal according to the system.

Therefore, in the disc player equipped with the signal format conversion circuit according to the present invention, the frequency of the horizontal synchronizing signal of the color video signal output from the pickup is PA
It is equal to the frequency of the horizontal synchronization signal of the L color video signal. Therefore, the frequency of the horizontal synchronization signal of the pseudo PAL color video signal obtained by converting the signal format of the color video signal output from this pickup is also equal to the frequency of the horizontal synchronization signal of the regular PAL color video signal. Therefore, when this pseudo PAL color video signal is supplied to the F'AL demodulation circuit, the color signal component will be delayed by exactly IH by the IH delay line in the PAL demodulation circuit, and the color signal will be delayed by exactly IH. There is no discrepancy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 to 4 are waveform diagrams showing the operation of each part of the device shown in FIG. 1, and FIG. 5 shows a part of the reproduced image. 6 is a waveform diagram showing the action of the delay circuit 51, FIGS. 7 to 9 are vector diagrams showing color signal components, and FIG. 10 is a block diagram showing another embodiment of the present invention. 11 is a waveform diagram showing the action of each part of the IQ diagram, FIG. 12 is a block diagram showing still another embodiment of the present invention, and FIG. 13 is a block diagram showing a conventional format conversion circuit. 14 is a waveform diagram showing the action of each part of the circuit in FIG. 13, and FIG.
FIG. 2 is a block diagram showing a demodulation circuit in the method. Explanation of symbols of main parts 40... Digital phase shifter 42... Multiplier 43, 44... Oscillator 50... Gain control circuit 51... ...Delay circuit 52...Amplitude suppression circuit Applicant: Pioneer Corporation

Claims (2)

[Claims] (1) separation means for separating a color video signal according to the NTSC system into a color signal component and a luminance signal component; Comprised of a color signal component processing means for reducing the amplitude of a signal component to a predetermined value or less for a predetermined period every other horizontal scanning period, and a synthesizing means for synthesizing the output of the color signal component processing means and the luminance signal component. A signal format conversion circuit for a video signal,
A signal format conversion circuit for a video signal, comprising a delay means for delaying the luminance signal by a predetermined time. (2) A pickup for reading a color video signal according to the NTSC system recorded on a disc, a separation means for separating a horizontal synchronization signal from the color video signal output from the pickup, and a horizontal synchronization signal output from the separation means. and a reference horizontal synchronizing signal to generate an error signal corresponding to the phase difference between the two signals; a speed control means for controlling the speed; and a speed control means for converting the frequency of the color signal component of the color video signal output from the pickup into a frequency of a component corresponding to a color video signal according to the PAL system, while changing the amplitude of the color signal component by one horizontal line. A disc player comprising a signal format conversion circuit that converts the signal format by converting the signal format to a predetermined value or less for a predetermined period every scanning period, wherein the frequency of the reference horizontal synchronization signal is a color video signal based on the PAL system. A disc player equipped with a signal format conversion circuit characterized in that the frequency is the same as that of a horizontal synchronizing signal in the disc player.