JP2823283B2 - Color signal processing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal processing apparatus in a video tape recorder capable of recording and reproducing an NTSC color video signal and reproducing a PAL recording tape.

2. Description of the Related Art In recent years, there has been a remarkable development of rental video shops, and the usage of home video tape recorders is not limited to simply recording and reproducing television signals, but the frequency of reproducing video soft tapes is also increasing. . There is a similar tendency in other countries. In the countries adopting the PAL broadcasting system, a PAL system video tape recorder having a function of reproducing a video soft tape of an NTSC system recording tape in the United States where a video soft tape has been developed has become a hot topic. Conversely, NTSC video tape recorders capable of reproducing PAL recording tapes are also being studied in countries adopting the NTSC broadcasting system.

Hereinafter, an example of video signal processing of an NTSC video tape recorder will be described with reference to the drawings. FIG. 8 is a block diagram of a reproduction system of video signal processing centering on color signal processing of a conventional VHS video tape recorder. In FIG. 8, a reproduced signal input from an input terminal 1 is amplified by a first-stage amplifier (hereinafter, referred to as PRE AMP) 2,
The high-pass filter (hereinafter, referred to as HPF) 3 removes the reduced conversion chrominance signal, and extracts a frequency-modulated (hereinafter, referred to as FM) luminance signal. Next, an FM demodulator (hereinafter FM DEM)
The signal is demodulated in 4), an unnecessary component is removed in a ropes filter (hereinafter referred to as LPF) 5 and sent to an adder 6.
On the other hand, the LPF 7 removes the FM luminance signal and extracts the low-frequency conversion color signal. Frequency converter (hereinafter referred to as Freq.Conv.)
At 8, the signal is returned to the carrier chrominance signal, and an unnecessary component is removed by a bandpass filter (hereinafter referred to as BPF) 9. next,
One horizontal period (hereinafter referred to as 1H) comb filter (hereinafter COMB)
The adjacent crosstalk component is removed at 10, mixed with the luminance signal at the adder 6, and output from the output terminal 35. The output signal of the 1H COMB 10 is sent to a phase comparator (APC PC) 14. In the phase comparator 14,
Signal from reference subcarrier oscillator (hereinafter referred to as XO) 13 and 1H
Color burst signal of COMB 10 is a phase comparator, the error signal passes through the LPF 15, a voltage controlled oscillator (hereinafter VCO approximately the center frequency of 320 times the horizontal scanning frequency (hereinafter referred to as f _H)
16) is controlled. The output signal frequency of the VCO 16 is divided into 1/8 by the 1/8 frequency divider 17, and four signals whose phases differ by 90 degrees are output. The selection circuit 18 sequentially selects the signal from the 1/8 frequency divider 17 according to the VHS standard and sends the signal to a sub-frequency converter (hereinafter referred to as SUB Conv.) 19. SUB Con
In v.19, the signal from the selection circuit 18 and the signal from the XO 13 are balanced-modulated, and the output signal passes through the BPF 20 to remove unnecessary components, and becomes a carrier of Freq.Conv.8.

With the above configuration, the low-frequency conversion color signal can be returned not only to the carrier color signal but also to absorb a jitter component generated due to uneven rotation of the cylinder during reproduction.

Problems to be Solved by the Invention However, in the above-described configuration, the NTSC recording tape can be reproduced, but the PAL recording tape has a problem that the chrominance signal cannot be reproduced even if the luminance signal can be reproduced.

The present invention solves the above problems, and in an NTSC video tape recorder, a color signal can be reproduced even when a PAL recording tape is reproduced, and a color signal can be reproduced even when connected to an NTSC television. It is an object of the present invention to provide a color signal processing device for a video tape recorder.

Means for Solving the Problems In order to solve the above problems, a chrominance signal processing apparatus according to the present invention comprises a multiplier for generating a double subcarrier frequency from an output signal of a reference subcarrier frequency oscillator phase-locked to a reproduced carrier chrominance signal. A balancer for balance-modulating the output signal of the multiplier and the reproduced carrier chrominance signal; a first filter for extracting a carrier chrominance signal band from the output signal of the balanced modulator; A first phase shifter that advances the phase of the reproduced carrier color signal by approximately 45 degrees.
A second phase shifter that delays the phase by one of the following four signals: the reproduced carrier color signal, the output signal of the first filter, the output signal of the first phase shifter, and the output signal of the second phase shifter. A switch circuit for selecting one of the signals; a phase comparator for comparing the phase of a signal obtained by inverting the output signal of the reference subcarrier frequency oscillator every one horizontal scanning period with the reproduced carrier color signal color burst signal; A second filter for smoothing an output signal of the phase comparator, a comparator for comparing an output voltage of the second filter with a reference voltage,
A control signal generator for generating a signal for controlling the switch circuit based on an output signal of the comparator;
It is configured to convert a carrier color signal of the system into a carrier color signal of the NTSC system.

Further, the control signal generator in the color signal processing apparatus of the present invention includes a horizontal synchronizing signal separating circuit for extracting a horizontal synchronizing signal from the decoding synchronizing signal, a voltage controlled oscillator having a horizontal scanning frequency substantially as a center frequency, and the horizontal synchronizing signal. A second phase comparator for comparing a phase of a signal and an output signal of the voltage controlled oscillator, a third filter for smoothing an output signal of the second phase comparator and controlling the voltage controlled oscillator, A frequency divider for dividing the output signal of the control oscillator by 、, a signal generator for generating a pulse indicating a color burst signal period with reference to the output signal of the voltage controlled oscillator, the frequency divider and signal generation And a logic circuit for performing a logical operation on the output signal of the container.

According to the above-described configuration, the reproduced carrier chrominance signal is input to the balanced modulator, and an output signal having twice the number of subcarriers output from the multiplier is input to the balanced modulator as a carrier.
Since the carrier chrominance signal is extracted from the output signal of the balanced modulator by the first filter, the carrier chrominance signal extracted by the first filter is RY with respect to the reproduced carrier signal input to the balanced modulator. The output signal of the first phase shifter which advances the phase of the reproduced carrier chrominance signal by approximately 45 degrees and the approximately 45 degree phase of the reproduced carrier chrominance signal can be obtained by a switch circuit. Output signal of the second phase shifter, the reproduced carrier color signal, and the first
By selecting the output signal of the filter described above, the carrier color signal of the PAL system can be converted into the carrier color signal of the NTSC system. For this reason, while reproducing the color signals of the PAL recording tape, the reproduced PAL carrier color signals are converted to NTSC.
The color signal can be converted into a color signal and reproduced on an NTSC television.

Hereinafter, a color signal processing apparatus according to an embodiment of the present invention will be described.
This will be described with reference to the drawings.

FIG. 1 is a block diagram of a reproduction system mainly showing a color signal processing device of a VHS video tape recorder according to an embodiment of the present invention. In FIG. 1, input terminal 1, PRE
AMP 2, HPF 3, FM DEM 4, LPF 5, Adder 6, Output terminal 3
5, LPF 7, Freq.Conv.8, BPF 9, 1H COMB 10, phase comparator 14, LPF 15, VCO 16, 1/8 frequency divider 17, selection circuit 18, SUB
Conv. 19, XO 13, and BPF 20 operate in the same manner as the conventional example shown in FIG. Input terminal
A control signal indicating whether the playback is NTSC playback or PAL playback is input to 21 and sent to the selection circuit 18 and the switch circuit 12. This is because the VHS standard differs between PAL and NTSC. The selection circuit 18 selects four input signals according to the standard, and the switch circuit 12 selects the input signal when reproducing the NTSC recording tape.
1H COMB 10 to which the output signal of BPF 9 is input is selected and P
2H COMB 11 to which the output signal of BPF 9 is input at the time of AL system recording tape reproduction is selected. This allows the switch circuit
The 12 output signals are such that an NTSC transport color signal is output during NTSC recording tape playback, and a PAL transport color signal is output during PAL recording tape playback. When the output signal of the switch circuit 12 is an NTSC carrier color signal,
The switch circuit 25 selects only the path C and sends it to the adder 6.

Next, how the output signal of the switch circuit 12 is converted to an NTSC carrier color signal when the output signal is a PAL carrier color signal will be described. First, the PAL carrier color signal will be described with reference to a vector diagram represented by U-axis and V-axis shown in FIG. Now, assuming that the color burst signal on the n-th scanning line is a, the RY axis becomes the direction shown by c at this time. On the (n + 1) th line, b is a color burst signal,
d is the direction of the RY axis. In order to make this a carrier color signal of the NTSC system, as shown in FIG. 5, a, b, c, and c of FIG.
d must be a ', b', c ', d', respectively. First, the conversion of the color burst signal from a to a 'is +
What is necessary is just to rotate a phase by 45 degrees. Second, the conversion of the color burst signal from b to b 'may be performed by rotating the phase by -45 degrees. Third, the conversion of c → c ′ may be left as it is. Fourth, d
The conversion of d 'requires scanning to invert the RY axis. With the above conversion, the PAL carrier color signal shown in FIG. 6A is converted to the NTSC carrier color signal shown in FIG. 6B. Such a → a ′, b → b ′, c → c ′, d
The conversion of d 'is performed by the switching circuit 25 of FIG.
The processing is performed on two input paths A, B, C, and D. That is, in the −45 degree shifter 22, the color burst signal is shifted by −45 degrees,
The color burst signal is shifted +45 degrees by the 45 degree shifter 23,
Balance converter (hereinafter referred to as BM) 24 and first filter 24 '
, A carrier color signal whose RY axis is inverted is extracted. BM24
To the sub-carrier frequency from XO13 (hereinafter, referred to as f _sc) output signal passes through the phase shifter 26, 2f, which is doubled in the multiplier 27
The output signal of _sc is input as a carrier.
Although a result, the output signal of the BM24 is converted into the carrier chrominance signal centered at the carrier chrominance signal and 3f _sc around the f _sc, the carrier chrominance signal centered at these f _sc is the first filter 24 '
Taken out at The output carrier color signal of the first filter 24 'is obtained by setting the phase of the phase shifter 26 to a predetermined phase.
The RY axis can be inverted with respect to the input carrier color signal of the BM24. In the switch circuit 25, A, B, C, D
By sequentially selecting the paths, the carrier color signal of the PAL system can be converted into the carrier color signal of the NTSC system.
However, when the B path is selected for the color burst signal a and the A path is selected for the color burst signal b shown in FIG. 4, the conversion from the PAL system to the NTSC system cannot be performed. Therefore, when the color burst signal is a,
A control circuit for controlling the switch circuit 25 so as to select the path B when the color burst signal of the path b is required is required.

Next, a control circuit of the switch circuit 25 shown in FIGS. 28 to 34 in FIG. 1 will be described. F _sc signal from XO13 the phaser 2
Through 8, the signal is supplied to the switch circuit 29. Switch circuit 2
In step 9, the output signal of the phase shifter 28 and the signal obtained by inverting the phase of the output signal of the phase shifter 28 are selected every 1H, and the first phase comparator (P
C) Supplied to 30. The carrier color signal from the switch circuit 12 is input to the first phase comparator 30, and the color burst signal and the _fsc signal from the switch circuit 29 are compared in phase. Now, the relationship between the phase of the output signal of the phase shifter 28 and the phase of the output carrier color signal of the switch circuit 12 is shown in FIG.
The phase of the phase shifter 28 is set so that the phase of the output signal of the phase shifter 28 is on the V axis of the signal. Since the switch circuit 29 inverts the phase every 1H, the output signal of the first phase comparator 30 is
In the case where the switch circuit 29 selects the output signal of the phase shifter 28 on the side a of FIG. 4 and selects the inverted signal of the phase shifter 28 on the side b, during the color burst signal period,
Outputs Hi-side pulse signal. Conversely, when the switch circuit 29 selects the inverted signal of the phase 28 on the side a, and selects the output signal of the phase shifter 28 on the side b, the output signal of the first phase comparator 30 is and it outputs a pulse signal of a constant L ₀ side.
The output signal of the first phase comparator 30 is smoothed by a second filter 31, and the output signal of the second filter 31 is
Is compared with the reference voltage 32, and if the level of the output signal of the second filter 31 is lower than the reference voltage 32, an error signal is output to the control signal generator 34. Control signal generator
At 34, when an error signal is input from the comparator 33, the polarity of the control signal Y for inverting the switch circuit 29 every 1H is in an inverted state, and the switch circuit 25 is controlled by the control signal X for controlling the switch circuit 25. Assuming that the selection is in a malfunction state, the control signals X and Y are corrected.

Hereinafter, the configuration of the control signal generator 34 will be described. FIG. 2 is a block diagram of the control signal generator 34. Input terminal
The synchronization signal separated from the luminance signal is input to 36, the horizontal synchronization signal is extracted by a horizontal synchronization signal separation circuit (hereinafter referred to as HHK) 37, and supplied to a second phase comparator (PC) 38. In the second phase comparator 38, a signal from HHK37, approximately (hereinafter referred to as f _H VCO) center frequency f _H is a voltage controlled oscillator performs phase comparison of the signals from 40, the error signal of the third through the filter 39, to control the f _H VCO 40. 38,39,40
Constitutes an automatic frequency control circuit (hereinafter referred to as AFC)
Even if the sync signal to the input terminal 36 by such as drop-out is not input, f _H VCO 40 frequency signal stably f _H outputs.

The output signal of the f _H VCO 40 is halved frequency with 1/2 frequency divider 41, whereas the pulse signal indicating the color burst signal period from the output signal of the signal generator 42, f _H VCO 40 is generated. The logic circuit 43 receives the output signals of the 1/2 frequency divider 41 and the signal generator 42, and outputs the control signals X and Y shown in FIG.
Output from 45.

FIG. 3 shows a circuit example of the 1/2 frequency divider 41 and the logic circuit 43 shown in FIG. In FIG. 3, F1 and F2 are D-type flip-flops, G1, G2, G3, G4, G7, G8, G9, G10, G13, G14, and G16 are AND elements, G5, G6, and G15 are OR elements, G11 and G12 are inverter elements, and the input terminal 21 is the same as the input terminal 21 in FIG.
For PAL system recording tape player L _0, and the case of the NTSC system recorded tape reproducing becomes Hi, the input terminal 40a is an input terminal of the output signal of the f _H VCO 40 of FIG. 2, F1 1/2 The frequency divider 41 is shown. 33a is an input terminal of the output error signal of the comparator 33 in FIG. 42a is the signal generator 42 shown in FIG.
Is an input terminal of the output signal. Output terminals A, B, C, D are first
When the control signal X is Hi, as shown in the figure, the switch 25 selects the A path, the B path, the C path, and the D path.

Hereinafter, the specific operation of FIGS. 1, 2 and 3 will be described with reference to the timing chart shown in FIG. 7 is an output signal of the switch circuit 12 in FIG. 1 and 25 is an output signal of the switch circuit 25. In the I period shown at the bottom of FIG. 7, the selection of the switch circuit 25 is in a normal state, and the output signal of the switch circuit 25 is a carrier color signal of the NTSC system converted from the carrier color signal of the PAL system. In the period II, the polarity of the color arrangement of the carrier color signal of the PAL system, which is the output signal of the switch circuit 12, is inverted from that in the period I. At this time, the selection of the switch circuit 25 is in a malfunction state, and the output signal of the switch circuit 25 is It does not become the NTSC color signal. The period III is a period in which the malfunction state in the period II shifts to the normal state. In FIG. 7, reference numerals 12 and 25 indicate a color burst signal and a chroma signal in this order.
In the direction of the vector diagram shown in FIG.
-The direction of the Y axis. 37 of FIG. 7 is HHK37 of FIG. 2 in the output signal, 40 of Figure 7 is the output signal of the f _H VCO 40 of FIG. 2. Reference numeral 42 in FIG. 7 is an output signal of the signal generator 42 in FIG. 2, and F1 in FIG. 7 is an output signal of F1 in FIG. FIG. 7 (12) is a color burst signal of the output carrier color signal of the switch circuit 12 inputted to the first phase comparator 30 of FIG. 1, and the direction of the arrow indicates the phase of the color burst signal. I have. Reference numeral 29 in FIG. 7 denotes an output signal of the switch circuit 29 in FIG. 1, and an arrow indicates a phase with respect to (12). Reference numeral 30 in FIG. 7 is an output signal of the first phase comparator in FIG. 1, and outputs a Hi-side pulse during a normal state in the I period.
In malfunction state of II period and outputs a pulse of L ₀ side. Reference numeral 31 in FIG. 7 denotes an output signal of the second filter 31 in FIG. 1. The output signal gradually decreases in the period II according to the direction of the pulse 30 in FIG. Will also go down. Reference numeral 33 in FIG. 7 indicates an output signal of the comparator 33 in FIG. 1. When 31 in FIG. 7 falls below the reference voltage 32, an error pulse is output. F2 in FIG. 7 is F2 in FIG.
When the comparator 33 outputs an error pulse, the output polarity of F2 is inverted. G5, G6, A in FIG.
B, C, and D indicate the output signals of the respective parts in FIG. 3, and change as shown in FIG. 7 when the polarity of F2 in FIG. 3 is inverted. For this reason,
The selection polarity of the switch circuit 29 is inverted, and 30 in FIG. 7 becomes a pulse on the Hi side, and the level of 31 in FIG. 7 also gradually rises above the reference voltage 32, and the switch circuit 25 in FIG.
Becomes normal. Thus, the switch circuit 25 of FIG. 1 is controlled.

As described above, according to the present embodiment, the multiplier 27 for generating a subcarrier frequency twice as high as the output signal of the XO 13 phase-locked to the reproduced carrier chrominance signal output from the switch circuit 12,
BM24 that balance-modulates the output signal of 27 and the reproduced carrier color signal
And the first to extract the carrier color signal band from the output signal of BM24
Filter 24 ', a first phase shifter 23 for advancing the phase of the reproduced carrier color signal by approximately 45 degrees, a second phase shifter 22 for delaying the phase of the reproduced carrier color signal by approximately 45 degrees, The output signal D of the first filter 24 'and the output signal A of the first phase shifter 23
A switch circuit 25 for selecting one of the four signals of the output signal B of the second phase shifter 22, and a signal from the XO 13
A phase comparator 30 for comparing the phase of the signal whose phase has been inverted every 1H and the color burst signal of the reproduced carrier color signal, a second filter 31 for smoothing an output signal of the phase comparator 30,
A comparator 33 for comparing the output voltage of the second filter 31 with the reference voltage 32, and a control signal generator for generating a signal for controlling the switch circuit 25 based on the output signal of the comparator 33
By providing the carrier signal 34, it is possible to convert the carrier color signal of the PAL system into the carrier color signal of the NTSC system.

Effect of the Invention As described above, according to the present invention, it is possible to convert a PAL playback carrier color signal into an NTSC carrier color signal, so that a PAL recording tape can be played back on an NTSC video tape recorder. Thus, it is possible to obtain an excellent effect that an image can be projected even when an NTSC system television is used.

[Brief description of the drawings]

FIG. 1 is a block diagram of a color signal processing device according to one embodiment of the present invention, FIG. 2 is a block diagram of a control signal generator in the same color signal processing device, and FIG. 4 and 5 are vector diagrams of carrier chrominance signals and vector diagrams after conversion, and FIG. 6 is a PAL system and N diagram.
FIG. 7 is a waveform diagram of the carrier color signal of the TSC system, and FIGS.
FIG. 8 is a block diagram of a conventional color signal processing device. 1 ... input terminal, 3 ... high-pass filter, 4 ... FM demodulator, 5 ... low-pass filter, 6 ... adder, 7 ...
Low pass filter, 8 frequency converter, 9 band pass filter, 10 horizontal period comb filter, 11
... 2 horizontal period comb filters, 12 ... switch circuits, 13
… Reference sub-carrier oscillator, 14… Phase comparator, 15 …… Low-pass filter, 16 …… Voltage controlled oscillator, 17… 1/8 frequency divider, 18 …… Selection circuit, 19 …… Sub-frequency 1 conversion Vessels, 20…
... Band pass filter, 21 ... NTSC PAL control signal input terminal, 22 ...- 45 degree phase shifter, 23 ... + 45 degree phase shifter, 24 ...
Balance modulator, 24 'first filter, 25 switch circuit, 26 phase shifter, 27 multiplier, 28 phase shifter, 29
... Switch circuit, 30 first phase comparator, 31 second filter, 32 reference voltage, 33 comparator
34 ... Control signal generator, 35 ... Output terminal.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 9/79-9/898 H04N 11/00-11/24

Claims (2)

(57) [Claims] 1. A chrominance signal processing apparatus for a video tape recorder for converting a carrier chrominance signal to a reduced frequency for recording, and converting the carrier chrominance signal back to a carrier chrominance signal at the time of reproduction, comprising: A multiplier for generating a double sub-carrier frequency from the output signal of the frequency oscillator, a balanced modulator for performing balanced modulation of the output signal of the multiplier and the reproduced carrier color signal, and a carrier color based on the output signal of the balanced modulator. A first filter for extracting a signal band, a first phase shifter for advancing the phase of the reproduced carrier color signal by approximately 45 degrees, and a second phaser for delaying the phase of the reproduced carrier color signal by approximately 45 degrees.
And one of four signals of the reproduced carrier color signal, the output signal of the first filter, the output signal of the first phaser, and the output signal of the second phaser. A switch circuit that performs phase comparison of a signal obtained by inverting the output signal of the reference subcarrier frequency oscillator every one horizontal scanning period and the reproduced carrier chrominance color burst signal, and a phase comparator. Second to smooth the output signal
, A comparator for comparing an output voltage of the second filter with a reference voltage, and a control signal generator for generating a signal for controlling the switch circuit based on an output signal of the comparator, and a PAL type carrier. NTS color signal
A color signal processing device for converting into a C type carrier color signal. 2. A control signal generator comprising: a horizontal synchronizing signal separating circuit for extracting a horizontal synchronizing signal from a decoding synchronizing signal; a voltage control oscillator having a horizontal scanning frequency substantially as a center frequency; A second phase comparator for comparing the phase of the output signal of the oscillator, a third filter for smoothing the output signal of the second phase comparator and controlling the voltage controlled oscillator, and an output signal of the voltage controlled oscillator A frequency divider that divides the output signal of the voltage controlled oscillator, a signal generator that generates a pulse indicating a color burst signal period based on the output signal of the voltage-controlled oscillator, and an output signal of the frequency divider and the signal generator. The color signal processing device according to claim 1, further comprising a logic circuit that performs a logical operation.