JPS60224390A - Pal system color signal processor - Google Patents

Abstract

PURPOSE:To make a circuit size smaller and to reduce points to be adjusted by applying the PAL phase correction and time base correction with the aid of a single PLL circuit so formed as to produce signals having the same frequency as that of a color burst. CONSTITUTION:A color burst extracted by a burst gate 5 is supplied to a PLL circuit, and its phase variation components are detected. A phase comparator 6 executes the sampling hold of a phase comparison output for every 1H, impresses the hold output as an error signal to a phase demodulator 2, and applies the time base correction of a color video signal outputted from an FM demodulator 1. A Y/C separator 10 separates Y components and C components, and the latter is supplied to a PAL phase inverter 12, where the C components are multiplied by an output of a multiplying equipment 16 in a multiplier 13. From an output of a BPF the C components subjected to the PAL phase inversion can be obtained. From a selection output of a switch 18 a color video signal subjected to the PAL phase correction can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus that performs processing such as time axis correction of a PAL color video signal.

Background Art The PAL color video signal Eρ is El) ='y
'+ (B-Y) stnωst±(RY) cO
5ωst−·−(1). Here, Y
is a luminance signal, B and R are blue and red signals, and ωS is the angular frequency of a color subcarrier, which is about 4°43 MHz. The symbol in equation (1) means a phase inversion for each horizontal scanning line, and the R-Y component of the carrier color signal is a sub-substrate of a + sst that has a phase difference of 180' from each other for each horizontal scanning line. The carrier signal is AM-modulated and sent out. Therefore, the color burst signal must also serve as information for inverting the phase of the demodulating subcarrier of the RY component line by line on the receiver side. Therefore, the color burst signal is sent out as a phase-inverted signal whose phase is switched line by line at ±135 degrees around the B-Y axis.

As described above, 1] Jump operation during special playback modes such as still image playback and double speed playback when playing back AL color video signals from a recording medium such as a video disk using a playback device such as a video disk player. In other words, the regularity of the phase reversal of the R-Y component and color burst in the reproduced color video signal is disturbed by the interlacing movement of the information detection point over a predetermined number of tracks. It becomes necessary to process PAL color video signals. Further, at the same time, the signal reproduced from the recording medium is usually accompanied by time axis fluctuations, and therefore it is necessary to detect this time axis fluctuation component and correct the time axis of the reproduced color video signal.

The following method can be considered as a method for performing PAL phase correction, that is, correction for making constant the regularity of the phase reversal of the RY component and color burst.

That is, a subcarrier part ωst having the same frequency as the color burst signal is generated using a PLL (phase-locked loop) circuit, this subcarrier part ωst is doubled, and then multiplied by the carrier color signal including the color burst signal to generate the color signal. This is a method of obtaining a carrier color signal in which the burst and RY components are inverted, and using the carrier color signal obtained by this multiplication. In addition, a method for time axis correction is to extract the 3.75 MHz pilot burst signal inserted into the PAL color video signal during recording from the playback signal, and then generate a signal with the same frequency as this pilot burst signal. PL formed as
A possible method is to use the phase detection output obtained by supplying it to the L circuit as a time axis error signal.

However, if a PAL color signal processing device that performs PAL phase correction and time axis correction is formed by the method described above, two PLl-circuits with different frequencies, ie, 3.75 MHz and 4.43' MHz, are required. This results in a disadvantage that the configuration becomes complicated and the number of parts or adjustment points increases.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a PAm color signal processing device that can perform PAL phase correction and time axis correction with a simple configuration.

The PAL color signal processing device according to the present invention includes PAL
The configuration is such that PAL phase correction and time axis correction are performed by a single PLL circuit formed to generate a signal having the same frequency as the color burst component of a color video signal.

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

In FIG. 1, an RF signal obtained from a recording disk (not shown) on which a PAL color video signal is recorded.
A (high frequency) signal is supplied to an FM demodulator 1 . FM
A PAL color video signal is demodulated by a demodulator 1 and supplied to a phase modulator 2 . At the same time, this color video signal becomes the single power of switch 3 and 9
After being phase-shifted by 90'' by the 0° phase shifter 4, it becomes the other input of the switch 3.The selected output of the switch 3 is supplied to the burst I gate 5, and a color burst is extracted.The extracted color The burst is supplied to a PLL circuit 9 consisting of a phase comparator 6, a loop filter 7, and a VCO (voltage controlled oscillator) 8, and a phase fluctuation component is detected.The phase comparator 6 samples the phase comparison output every day. The hold output of this sample and hold circuit is applied as an error signal to the control input terminal of the phase modulator 2.
Time axis correction of the color video signal output from the M demodulator 1 is performed.

The color video signal subjected to time axis correction by the phase modulator 2 is input to a Y-C (luminance-color signal) separator 10 and is separated into a Y component and a C (carrier color signal) component including a color burst. . The C component serves as a power source for the switch 11 and is also supplied to the PAL phase inverter 12 . This P
The AL phase inverter 12 includes a multiplier 13 and this multiplier 13
BPF (burned pass filter) whose input is the output of
14, and subcarrier rals by shifting the phase of the output of VCO8.
It consists of a phase shifter 15 that outputs ωst and a multiplier 16 that doubles this subcarrier signal frequency, and a multiplier 13 multiplies the C component and the output range 2ωst of the multiplier 16. C with PAL phase inversion performed from the output of BPF14
The components are obtained and serve as other inputs to the switch 11.

The selected output from the switch 11 is added to the Y component in the adder 17 and becomes the single input of the switch 18. switch 1
A time-axis corrected color video signal is applied to the other input of 8, and the selected output by this switch 18 becomes a phase-corrected color video signal.

Controller 1 for control of switches 1.1 and 18
9 is provided. This controller 19 uses a jump signal a whose state changes every time a jump operation is commanded.
and a reproduction mode signal whose state changes depending on the reproduction mode, and is configured to output the signal and supply it to the switches 11 and 18, respectively. The jump signal a output from this controller 19 is also supplied to a line selection signal generator 20. In the line selection signal generator 20, the jump signal a is applied to one input terminal of the exclusive OR gate G1. The output C of a frequency divider 22 that divides the frequency of the reference horizontal synchronization signal outputted from the reference horizontal synchronization signal generator 21 is applied to the other input terminal of the exclusive OR gate G萱. The output of exclusive OR gate G1 is applied to one m input terminal of exclusive OR gate G2. The output d of the PAL phase detector 23 is applied to the other input terminal of the exclusive logic gate G2. The output of this exclusive OR gate G2 is the control power e of the switch 3.

The error signal f output from the phase comparator 6 is supplied to the PAL phase detector 23. In this PA phase detector 23, the error signal f is supplied to a comparator 24 and compared with a reference voltage Vr1. Comparator 2
The output of 4 is applied to the input terminal of a retriggerable mono multivibrator (hereinafter abbreviated as RMMV) 25.

The d output of the RMMV 25 is supplied to a comparator 27 via a time constant circuit 26 and compared with a reference voltage Vr2.

The output of the comparator 27 is applied to one input terminal of a NAND (negation logic @Maki) gate G3. The output C of the frequency divider 622 is applied to the other input terminal of the NAND gate G3. The output of this NAND gate G3 is applied to the trigger input terminal of the T-type flip-flop 28. This one
The output of the flip-flop 28 is connected to the PAL phase detector 23.
This is the output.

In the above configuration, it is assumed that the time axis error of the RF signal supplied to the FM demodulator 1 is compressed to about several tens of n5ecp-p by a tangential mirror servo or the like in the reproducing device. Also, here the frequency of the color subcarrier of the PAL color video signal is 4.43MHz, that is, (
284-(1/4)) r+-1-25 (Hz) (fH is the horizontal synchronization frequency), and since the period corresponds to one image, the playback order of the recorded images was changed due to jump operations, etc. At this time, a phase transition will occur in the color subcarrier. However, here, an offset is added to the tangential servo etc. in the playback device so as to correct the phase transition every time the playback order changes, and a jump operation is applied to the color subcarrier of the color video signal output from the FM demodulator 1. It is assumed that no phase transition occurs due to

Then, the P and A L phases of the PAL color video signal output from the FM demodulator 1, that is, the color burst phase, are inverted with respect to the BY axis every 1 to 1, as shown in Fig. 2 (A). Therefore, the color burst phase of the color video signal phase-shifted by the 90° phase shifter 4 becomes a signal that is inverted with respect to the RY axis as shown in FIG. Since the output C is inverted every 1H, if the states of the jump signal a output from the controller 19 and the output d of the PAL phase detector 23 do not change, the switch 30 control is output from the exclusive OR gate G2. The human power e becomes a signal that is inverted every <IH as shown in FIG. The signal is alternately supplied to the burst gate 5 every day.Then, the phase state of the color burst output from the burst gate 5 is shown in the same figure (D
As shown in >, all the phases are unified to +135". By changing the phase direction in the 90" phase shifter 4, the phase state of the color burst output from the burst gate 5 is changed to -135°. It is also possible to unify the phase to .

Next, when a jump operation is commanded at time t1, the color burst phases of the color video signals output from the FM demodulator 1 around this time t1 become in phase as shown in FIG. 3(A). Therefore, the color burst phase shift of the color video signal phase-shifted by the 90° phase shifter 4 also becomes the same phase around time 11. On the other hand, the output C of the frequency divider 22 is inverted every other time (<1) as shown in FIG. Further, the jump signal a output from the controller 17 is inverted at time tl as shown in FIG. Therefore, if the state of the output d of the PAL phase detector 23 does not change, the state of the control input e of the switch y-3 does not change at time t1 as shown in FIG. As a result, even immediately after time t1, the phase of the color burst output from the burst gate 5 is 135°, as shown in (F) in the same figure, so that it is always switched regardless of the jump operation. All H are in phase.

In addition, in the scan operation mode, that is, the operation mode for searching for a desired frame, the number of tracks over which the information detection point moves is not constant, so there are rules for the phase state of the color burst in the color video signal output from the FM demodulator 1. As shown in Fig. 4 (A>), the color burst phase becomes in phase around time 12.
'The color burst phase of the color video signal phase-shifted by the phase shifter 4 also becomes the same phase around time 12, as shown in FIG. 4(B). However, in this case as well, the frequency divider 2
The output C of 2 is reversed every other day as shown in the same figure (1)),
Since the states of the jump signal a and the output d of the PAL phase detector 23 do not change, the human power e to control the switch 3 is as shown in the figure (F
) is also reversed at time t2 as shown in 1. Therefore, the phase of the color burst output from the burst gate 5 is 1135 every day after time t22, as shown in FIG.
The angle will alternately change from 0 to 45 degrees. Then, the phase comparator 1 to which this color burst is supplied
1 outputs a pulse that occurs at a 2H period. The pulse output from the phase comparator 11 is detected by the PLL phase detector 23, and the state of the output d of the PLL phase detector 23 changes as shown in FIG.
). Then, the control force e of the switch 3 is at time t3.
Thereafter, the signal becomes a signal having an opposite phase to the output C of the frequency divider 22. As a result, the phases of the color bursts being selectively output from the switch 3 are unified to +135°, and after time t3, the phases of the color bursts output from the burst gate 5 are in the same phase ~ Here, the PAL phase detector 23 We will discuss the effects of If the phase of the color burst output from the burst gate 5 changes alternately between -135° and +45° every 1H, the PLL circuit 9 will not be in a locked state, so there will be no beat in the error signal f output from the phase comparator 6. Ingredients are generated. Also, since signals whose phases differ by 18° are supplied to the phase comparator 6 every day, the error signal t output from the phase comparator 6 is <2H as shown in FIG. This is a signal that is formed by pulses that occur periodically.In addition, the envelope shown by the broken line in the figure shows the waveform of the beat component.

Therefore, as shown in FIG. 6 (A), if the phase of the color burst output from the burst gate 5 changes alternately from -135° to -45° every 1H after time t4, the phase comparator 6 outputs a pulse-like error signal ``.When the peak level of this error signal f becomes equal to or higher than the reference voltage Vr1, the comparator 24 outputs the error signal f as shown in the same figure (B).
A positive pulse Q is output as shown in FIG. RMMV25 is triggered at a moment of this pulse a, and the output is as shown in the figure (
The level becomes low as shown in C). When this zero output becomes a low level, the output voltage i of the time constant circuit 26 changes as shown in the figure (D).
As shown in , it increases with a time constant τ. When this output voltage becomes equal to or higher than the reference voltage Vr2, the output j of the comparator 27 becomes a high level as shown in FIG.
>. The output of this comparator 27 is the NAND gate G3
is applied to one input terminal of the NAND gate G
The other input terminal of 3 is connected to 1H as shown in the same figure (F, ).
Since the output C of the frequency divider 22, which is inverted every other time, is applied,
A negative pulse k is outputted from this NAND gate G3 as shown in FIG. 3(G) (time Is). This negative pulse k
Since the T-type flip-flop 28 is inverted by 1)
The output of the T-type flip-flop 28, which becomes the output d of the A1 phase detector 23, is inverted at time t5 as shown in ()-1) of the figure.

Then, the control force e of the switch 3 is reversed, and the phase of the color burst output from the burst gate 5 is +1.
The angle is unified to 35°.

As a result, after time [6], the PLL circuit 9 is in a locked state, the level fluctuation of the error signal f output from the phase comparator 6 becomes small, and the pulse g is no longer output from the comparator 24.

Then, the 0 output of the RMMV25 returns to a high level after a time T (T'-38) equal to the inversion time of the RMMV25 from the generation of the last pulse 0. Then, the output voltage l of the time constant circuit 26 decreases with a time constant τ. When the output voltage i of the time constant circuit 26 becomes lower than the reference voltage Vr2 (time [7), the comparator 2
7's output t will be at a low level. As a result, after time [7], the NAND gate G3 no longer outputs a pulse.

Note that even if the peak level of the error signal outputted from the phase comparator 6 instantaneously exceeds the reference voltage Vr1 due to noise or the like and the RMMV 25 is erroneously triggered, the output voltage of the time constant circuit 26 will not match the reference voltage. By setting the time constant τ so that it does not exceed Vr2, it is possible to prevent the output d of the PAL phase detector 23 from being erroneously inverted.

Next, the operation of the PAL phase inverter 12 will be explained.

C component including color burst is Sinωst +φ)
and the output of the phase shifter 15 is assumed to be ωSωst. however,
ωS[-2πfs (rs=4.43MH2). Then, the output M of the multiplier 13 is expressed as follows: .

Here, since the B-Y component of the carrier color signal is φ-0, the output of the BPFI 4 becomes 5illωS and does not undergo phase inversion. Since the same <RY component is φ=π/2, the output of BP'F24 is 5111 (ωst-π/
2), and undergoes phase inversion with respect to the input sm (ωst +π/2). Also, the color burst signal is φ−±1
35°, the output of BPFI4 is sin (ωStT 135°) for the input sin (ωst±135°).
) and similarly undergoes phase inversion. Therefore,
This makes PAL phase inversion possible.

Here, the switch 18 bypasses the PAL phase inverter 12 etc. and directly derives the time-base corrected color video signal in the normal playback mode by the playback mode signal supplied from the controller 19, and in the special playback mode. In some cases, a color video signal that has passed through a PAL phase inverter 12 or the like is derived. Also, at the same time,
If f11 is assumed to alternately derive the C component by the jump signal a output from the controller 19 and the C component subjected to PΔL phase inversion by the PAL phase inverter 12, the rule for inverting the PAL phase even after the jump operation. The gender will be maintained constant.

Note that the C component output from the Y/C separator 10 and the output of the phase shifter 15 include a time axis error component. If this time axis error is +Δθ, the C component output from the Y/G divider 10 and the output of the phase shifter 15 are each sin (
ωst+φ+Δθ), a+S(ωst+80). Therefore, in this case, the output JM of the multiplier 13 is as shown in the following equation.

M=cos (2ωst+2Δθ) ・sin (ωs
tiφ+Δθ)= (1/2> (sln <3ωst
+φ+380)~-s:n (ωst+φ−tΔθ)
) ...... (3) Therefore, in this case as well, 510 (ωst + φ + Δθ) components are obtained as in the case where the time axis error is not considered, and the time axis error of Δθ, that is, the so-called residual jitter, is obtained. However, it is possible to invert the PAL phase.

Effects As detailed above, the PAL color signal processing device according to the present invention performs PAL phase correction and time axis correction using a single PLL circuit formed to generate color burst and frequency signals. Because of this configuration, it is possible to reduce the circuit scale, reduce the number of parts and adjustment points, and reduce the frequency between oscillators that would be expected when using multiple PLL circuits that generate signals of different frequencies. This means that malfunctions due to interference can be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing one embodiment of the present invention, and FIGS. 2 to 6 are waveform diagrams showing the operation of each part of the device shown in FIG. 1. Explanation of symbols of main parts 3.11.18... Switch 9... P L 1 circuit 12... PAL phase inverter 20... Line selection signal Generator 23...
・PAL phase detector Applicant Pioneer Co., Ltd. Agent Patent attorney Motohiko Fujimura 2 Figure 3 Figure #A Figure f, z '1. s etc. 75 diagrams, 6 diagrams-1, 7-51'! ty procedure? ...Authentic book (method) % formula % 1, Indication of the case 1980 Patent Application No. 080977 2, Name of the invention PAL color signal processing device 3, Relationship with the person making the amendment case Patent applicant address Tokyo 1-4-1 Meguro, Meguro-ku Name <5
01) Pioneer Corporation 4, Agent 104

Claims (1)

[Claims] Color burst component of PAL video signal is 1
a phase-shifting means for shifting the phase by a predetermined angle every horizontal scanning period; and a phase-locked loop circuit formed to generate a signal having the same frequency as the color burst component outputted from the phase-shifting means; A signal corresponding to the phase difference between the signal generated by the locked loop circuit and the color burst component outputted from the phase shifting means is used as a time axis error signal, and the signal generated by the phase locked loop circuit is used to generate the PAL color video signal. PAL, characterized in that the phase of one of the carrier color signals and the color burst is inverted.
method color signal processing device.