JPH0229190A - Color demodulator - Google Patents

Abstract

PURPOSE:To demodulate a color information signal using an arbitrary demodulation axis with simple circuit composition without selecting a clock for sampling by detecting the difference in a sampling phase for the phase of the demodulation axis and demodulating the color information signal based on the phase difference. CONSTITUTION:A burst synchronizing clock generating circuit 6 generates the first clock to phase-synchronize with a color burst signal and have a frequency integer-times as frequent as the frequency of the color burst signal, and a horizontal synchronizing clock generating circuit 8 generates the second clock to phase-synchronize with a horizontal synchronizing signal and have the frequency integer-times as frequent as the frequency of the horizontal synchronizing signal and approximately the same as the frequency of the first clock. Further, the phase difference between the sampling phase of a chromaticity signal and the demodulation axis of the color information signal is detected from two types of clocks, namely, the clock to phase-synchronize with a color sub carrier and the clock for sampling the chromaticity signal, and the color information signal is calculated from the detected phase difference and the sampled value. Thus, the chromaticity signal can be sampled using the optimum clock, and the color information signal can be demodulated with the simple circuit composition.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color demodulation device that samples a chromaticity signal of a color television eye signal and then demodulates it into a color information signal.

Conventional technology Conventionally, such a color demodulation device samples a chromaticity signal using a clock whose phase is synchronized with a color subcarrier, and there is a certain relationship between the phase of the color subcarrier and the sampling phase. The chromaticity signal can be phase synchronized with the horizontal synchronization signal, sampled with a clock that is an integral multiple of the horizontal synchronization period, and reproduced from a color subcarrier regeneration circuit that operates at the period of that clock. In many cases, the color information signal is demodulated by multiplying the sample value of the chromaticity signal by the repé μ value of the color subcarrier having the phase corresponding to the demodulation axis of the chromaticity signal.

An example of a conventional color demodulation device will be described below with reference to the drawings.

Here, a color demodulation device that demodulates a chromaticity signal based on an NTSC color television signal will be described.

FIG. 4 shows a block diagram of a first example of a conventional color demodulation device. In Fig. 4, 2 is a chromaticity signal input terminal;
4 is a (RY) color information signal output terminal, and 4 is a (B-Y) color information signal output terminal. The burst gate circuit 5 selectively extracts the color burst signal contained in the chromaticity signal and supplies it to the burst synchronization clock generation circuit 6. The burst synchronization clock generation circuit 6 generates a clock that is phase synchronized with the color burst signal and has a frequency that is an integral multiple. Now, the phase of the clock is (R-Y) and (B-) of the chromaticity signal shown in FIG.
corresponds to the phase of the demodulation axis of each color information signal of Y),
It is assumed that the frequency is four times the brown subcarrier frequency. The clock is supplied to a sampler 9 and a sample value selection circuit 31, and the sampler 9 samples the chromaticity signal using the phase and period of the clock. Based on the conditions of the phase and frequency of the clock, the sampling phase coincides with the (RY) and (B-Y) demodulation axes, and when the chromaticity signal of the vector C in Fig. 2 is sampled, its Sample value is OR+CB
+ -CR+ -CB + Turtles lined up on the neck of CR... As is clear from this, the sample value selection circuit 31
By selecting sample values like CR* (-CR), you can obtain the color information signal (RY), and
By selecting sample values such as ca, ('s), a color information signal of (B-Y) can be obtained.

FIG. 5 shows a block diagram of a second example of a conventional color demodulation device. In FIG. 6, 1 is a luminance signal input terminal, 2
is the chromaticity signal input terminal, 3 is the (RY) color information signal output terminal, 4 is CB-Y) f! 3 information signal output terminal.

First, the synchronization signal separation circuit 7 selectively extracts a horizontal synchronization signal from the synchronization signal included in the luminance signal and supplies it to the horizontal synchronization clock generation circuit 8 . The horizontal synchronization clock generation circuit 8 generates a clock that is phase synchronized with the horizontal synchronization signal and has a frequency that is an integral multiple of the period of the horizontal synchronization signal. The clock is first supplied to a sampler 9, which samples the chromaticity signal. Next, the burst gate circuit 41 selectively extracts the color burst signal included in the sampled chromaticity signal and supplies it to the color subcarrier reproduction circuit 42 . The clock is also supplied to the color subcarrier reproducing circuit 42, which detects the phase information and frequency information of the color subcarrier from the sampled color burst signal, and detects (RY) and (B) in FIG. -Y) Two types of color subcarriers whose phases coincide with the demodulation axis of the color information signal are reproduced in the state of sample values of the clock period. The first color subcarrier is in phase with the demodulation axis of the (RY) color information signal, and is multiplied by the chromaticity signal in the first multiplier 43 to obtain the (RY) color. An information signal is obtained. The second color subcarrier is in phase with the demodulation axis of the (B-Y) color information signal, and is multiplied by the chromaticity signal in the second multiplier 44 to obtain the (R-Y) color. An information signal is obtained.

In addition, the low-pass filter 31.3 in FIGS. 4 and 6
2 removes unnecessary high frequency signal components generated when demodulating color information signals.

Problems to be Solved by the Invention In the first and second conventional examples described above, the process of sampling the chromaticity signal and demodulating the color information signal was mainly explained. In television digital signal processing equipment, it is common to sample and process luminance signals using the same clock that samples chromaticity signals, so horizontal synchronization, such as that seen in the playback signals of simple home VTRs, is required. Various problems arise when processing so-called non-standard signals in which a fixed frequency relationship defined between the signal and the color subcarrier is not maintained. In other words, in the first conventional example, the frequency of the sampling clock is an integral multiple of the frequency of the color subcarrier, so the configuration of the circuit that demodulates the color information signal is simple, but the phase of the sampling clock is As the horizontal synchronization processing circuit 174 becomes more complex, vertical correlation, inter-field correlation, and inter-frame correlation are required for the non-standard signal. The problem is that it is extremely difficult to carry out signal processing using such methods. Furthermore, in the second conventional example, since the frequency of the sampling clock is an integral multiple of the period of the horizontal synchronization signal, the circuit configuration for horizontal synchronization processing is simplified, and the above-mentioned This makes it easier to perform signal processing using various correlations, but since a constant relationship between the sampling clock phase and the color subcarrier phase cannot be maintained, the configuration of the color subcarrier recovery circuit becomes complicated and It has the problem of being large scale.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color demodulation device that eliminates the drawbacks of the prior art described above, has a simple circuit configuration, and can be easily applied to signal processing using the various correlations described above for the non-standard signals. be.

Means for Solving the Problems In order to solve the above problems, the color demodulation device of the present invention samples two types of clocks having almost the same frequency, that is, a clock whose phase is synchronized with the color subcarrier and a chromaticity signal. A device with a configuration that detects the phase difference between the sampling phase of the chromaticity signal and the demodulation axis of the color information signal from a clock used for the purpose of color processing, and calculates and obtains the color information signal from the phase difference and the sample value. It is.

Effect: With the above-described configuration, the present invention samples chromaticity signals using the most suitable clock for performing horizontal synchronization processing and signal processing using various correlations on both standard signals and non-standard signals. At the same time, the color information signal can be demodulated with a simple circuit configuration without requiring a complicated color subcarrier regeneration circuit.

Furthermore, it becomes easy to arbitrarily set the demodulation axis of the color information signal, for example, to the IQ demodulation axis.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of a color demodulation device according to a first embodiment of the present invention. 1 is a luminance signal input terminal, 2 is a chromaticity signal input terminal, 3 is a (RY) color information signal output terminal, and 4 is a (B-Y) color information signal output terminal. The burst gate circuit 6 selectively extracts the color burst signal included in the chromaticity signal and generates a burst synchronization clock generation circuit 6.
supply to. The burst synchronization clock generation circuit 6 generates a first clock that is phase synchronized with the color burst signal and has a frequency that is an integral multiple. The synchronization signal separation circuit 7 selectively extracts a horizontal synchronization signal from the synchronization signal included in the luminance signal and supplies it to the horizontal synchronization clock generation circuit 8 . The horizontal synchronization clock generation circuit 8 generates a second clock that is phase-locked to the horizontal synchronization signal and has a frequency that is an integral multiple of the period of the horizontal synchronization signal and substantially the same frequency as the first clock. Now, the phase of the first clock is (R) in the vector diagram of the chromaticity signal shown in FIG.
-Y) and (B-Y), and has a frequency four times the brown subcarrier frequency, and the second clock has a period of the horizontal synchronization signal. It is assumed that the frequency is 910 times higher. In this case, the frequencies of the first clock and the second clock match with respect to the input of the NTSG standard signal. The second clock is supplied to a sampler 9, which samples the chrominance signal. Further, the first clock and the second clock are supplied to a phase difference detection circuit 1o, which detects the phase difference between the clocks and calculates the inclination angle θ of the sampling phase with respect to the phase of the demodulation axis. Figure 3 shows the timing diagram of each clock.
The figure shows a vector diagram of the chromaticity signal. In Figure 2, 8
1 to S4 are the sampling phase axes, (RY) and (
Inclination angle θ of the sampling phase with respect to the phase of the demodulation axis of B-Y)
is obtained as follows. That is, in FIG. 3, the phase difference between the second clock and the first clock is d.
, if the period of the first clock is detected as t, then the phase inclination angle θ is θ=-1...
・Mountain・・・・・・・・・・Mountain It is given by (1).

In Fig. 2, the sampling phase is S1+S2, S
5 + S4 and sample the chromaticity signal of the vector C in Figure 2, the sample value is C1 + 02
The order is +-c, , -02. Once the inclination angle θ of the sampling phase with respect to the phase of the demodulation axis is determined, each color information signal (RY) and (BY) is determined as follows.

(RY)=C1CO52θ+C25InHθ(C
1cts-θ-02sm 2θ) (B-Y)--C15in 'θ+C2゜-θ...
・・・・・・(2) π (clsm-θ-C2 positive-θ) ・・・・・・・・・
(3) From equations (2) and (3), it can be seen that the color information signal can be obtained from at least two sample values. That is, (
RY)=C+cos-θ+C25in-θ・
・・・・・・・・・(4)(B-Y)=(+5fnNθ
+a2crsHθ .--Machi-(5), which can be found from the sampled values of the sampling phases of S and S2. The sampling phase of S5 and 84 is 18Q with respect to the sampling phase of Sl and 82.
The sample value is obtained by inverting the sign of the sample value of the sampling phase of Sl and S2. Therefore, if the sign of the sampled value in the sampling phase of 83 and S4 is inverted, equations (4) and (5) can be applied, and the sign inversion circuit 11 converts the sampled value in the sampling phase of S3 and S4. Selectively flip the sign.

- The force cylinder 1 calculator 12 inputs the tilt angle θ and calculates the CQSi
The i@2 calculator 13 inputs the tilt angle θ and calculates 5in-θ. Equation (4) and (
The calculation of equation 5) is performed as follows to demodulate the color information signal. Assuming that the phase of the second clock, that is, the sampling clock, is Sl in FIG. The signal is supplied to the 2 multiplier 15, multiplied by the trick θ in the first multiplier, and temporarily held in the second register 7. Further, the second multiplier 1
5 by 5irI-θ and temporarily held in the second register 7.

Next, if the phase of the sampling clock is 82, the sample value is C
2, the signal passes through the sign inversion circuit 11 with the same sign, is supplied to the first multiplier 14 and the second multiplier 15, is multiplied by sUQ'Hθ by the second multiplier, and is input to the adder 18. At this time, the value of ClXcm-〇 held in the second register 7 is input to the adder 18 (4
) is performed to obtain a color information signal of (RY).

Furthermore, the first multiplier 14 multiplies the GI by -θ and supplies it to the subtracter 19, where the GI held in the two registers is
The value of Xsiniθ is subtracted to obtain the color information signal (B-Y).
Color information signals of (RY) and (BY) are obtained through the same processing as above except that the sign is inverted in step 1. The demodulated (R-Y) and (B-Y) signals are outputted after unnecessary high frequency signal components are removed by a first low-frequency F wave filter 20 and a second low-frequency wave filter 21, respectively.

Note that in the above explanation, when the sampling phases are orthogonal in the chromaticity signal vector )/i diagram shown in FIG. 2, that is, the frequencies of the first clock and the second clock match. Although the case is shown above, the frequencies do not need to match. That is, it is clear that the tilt angle θ in equations (4) and (6) can be replaced with the values at each sampling phase.

Further, in FIG. 1, a case has been described in which the clock frequency corresponds to four times the frequency of the color subcarrier, but a clock having a frequency corresponding to another integer multiple may be used. In this case, the color information signal is determined by a modified mathematical formula different from the mathematical formulas shown in equations (2) and (3), and the circuit configuration can also be changed to a different form depending on the mathematical equation.

Further, in the above description, a color demodulating device for chromaticity signals has been described in accordance with the NTSC system, but the present invention can also be applied to a PAL system and an equal color television system.

Effects of the Invention As is clear from the above explanation, in conventional color demodulation devices that sample chromaticity signals and then obtain color information signals, the method of sampling using a clock that is phase-synchronized with the color subcarrier has a simple circuit configuration. However, it is not suitable for so-called non-standard signals such as those seen in the reproduced signals of simple home VTRs, and a method of sampling using a clock that is phase-synchronized with the horizontal synchronization signal has often been used. However, in this case, the circuit configuration is complicated and a large-scale color subcarrier regeneration circuit is required, which poses technical and economic difficulties in realizing the device.

In contrast, the present invention detects the difference in the sampling phase with respect to the phase of the demodulation axis and demodulates the color information signal based on the phase difference, so the sampling clock can be selected and the circuit configuration is simple. A color demodulation device that can demodulate color information signals using any demodulation axis can be easily realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a color demodulation device in an embodiment of the present invention, FIG. 2 is a vector diagram of a chromaticity signal, FIG. 3 is a timing diagram of tarokku in an embodiment of the present invention, and FIG. The figure is a block diagram of a first example of a conventional color demodulating device, and FIG. 6 is a block diagram of a second example of a conventional color demodulating device. 1... Luminance signal input terminal, 2... Chromaticity signal input terminal, 3... (R-Y) color information signal output terminal, 4... ( B-Y) Color information signal input terminal,
5... Burst gate circuit, 6... Burst synchronization clock generation circuit, 7... Synchronization signal separation circuit, 8... Horizontal synchronization clock generation circuit,
9... Sampler, 10... Phase difference detection circuit, 11... Sign inversion circuit, 12...
・First computing unit, 13...Second computing unit, 14...
....First multiplier, 16...Second multiplier, 1
6...2nd register, 17...2nd register, 18...adder, 19...subtractor, 2o...2nd register 1 low frequency F wave device, 21...
...Second low-pass filter. Name of agent: Patent attorney Shigetaka Awano and 1 other person 2nd
Figure 3

Claims (1)

[Claims] In demodulating at least two color information signals from the chromaticity signal by processing a color television signal transmitted with a chromaticity signal having a constant color subcarrier frequency and a luminance signal including a synchronization signal, the color means for generating a first clock that maintains a constant phase relationship with respect to the phase of a chrominance subcarrier included in the luminance signal and has a frequency that is an integral multiple of the chrominance subcarrier; means for generating a second clock that is an integral multiple of the horizontal synchronization period and has substantially the same frequency as the first clock; and means for sampling the chromaticity signal with the phase and period of the second clock. means for detecting a phase difference between the first clock and the second clock; and means for detecting a phase difference between the first clock and the second clock;
means for calculating an inclination angle of the sampling phase with respect to the phase of the demodulation axis of the color information signal from the clock cycle;
A color demodulation device comprising means for calculating the color information signal from at least two of the calculation results of the inclination angle and at least two of the sampling values.