JPS61170193A - Color demodulation circuit of video reproducing device - Google Patents

Abstract

PURPOSE:To change the hue in response to the preference of the user by provid ing a phase shift means shifting a chrominance carrier signal by an angle in response to a command at each other horizontal scanning period and demodulating a chrominance difference components included in the output of the phase shift means. CONSTITUTION:The output of the amplifier 5 of the phase shift circuit 15 is fed to a phase shifter 16 and inputted to a changeover switch 17. A control signal having a level in response to the operating state of a hue adjusting operation button at the operating section is fed to a control input terminal of the phase shifter 16 and the phase shifter 16 delays the phase of the input by an angle in response to the level of the control signal. Since the gain of the matrix circuit 14 is changed in response to the phase shift angle of the phase shifter 16, the combined vector length of two vectors corresponding respectively to B-Y and R-Y signals outputted from the matrix circuit 14 is made equal to a length D1. Thus, the combined vector of the two vectors is made identical to a vector formed by turning the combined vector D1 by an angle phi/2 and only the hue is changed without changing saturation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color demodulation circuit for a video reproducing device, and in particular to a color demodulation circuit for a video reproducing device.
L(Phase AltertLation Line
) method, and relates to a color demodulation circuit for a video reproducing device that reproduces video using a color video signal based on the method.

The PA, L system color video signal EMtL corresponding to n (n is a natural number) main scanning line is given by the following equation.

EMn-Y1EU sinωct +(-], )”Ev＼ωct ・・・ ・・・
...(1)ωc-2πf, □(m-%)
(2) Here, Y indicates a luminance signal, and EU and Ev indicate color difference signals B-Y and RY, respectively. Note that B and R indicate blue and red signals, respectively. Of course, fH is the horizontal scanning frequency, and m is a natural number.

The coefficient (-1,)'' in equation (1) means phase inversion for each horizontal scanning line, and the Ev acid component 1 of the conveyed color signal
Each horizontal scanning line has a phase difference of 180 from each other (-1)
It is transmitted by balanced modulation of a subcarrier signal with a range of ωct.Therefore, the color burst signal is required to have enough information to invert the phase of the subcarrier of the shame component line by line on the image receiving side. Therefore, the color burst signal is ±1 around the EU axis.
35 phases are switched every 1 in, and the phase-inverted one is sent out.

FIG. 1 shows a conventional color demodulation circuit in a device that reproduces video using such a PAL color video signal.

In FIG. 1, a PA,L color video signal is supplied to a bandpass filter 1. In FIG.

The bandpass filter 1 is configured so that its passband is approximately equal to the frequency band of a carrier color signal included in a FAT color video signal. A carrier color signal and a color burst signal are extracted by this bandpass filter 1 and supplied to a variable gain amplifier 2 and a burst gate amplifier f3. The burst signal generator f3 is supplied with the output of a pulse generator (not shown) configured to, for example, delay the horizontal synchronizing signal and output a burst signal pulse while the color burst signal is present. The burst signal amplifier 3 extracts the color burst signal and outputs it as is, and at the same time extracts the color burst signal and outputs it as is.
tomat'ic Chroma Corbtrol
) is configured to output a signal. The color burst signal and A, CC signals outputted from this burst gate amplifier 3 are respectively A, PC (A, autoP
The signal is supplied to a subcarrier generator 4 and a variable gain amplifier 02 according to the control method.

The variable gain amplifier 2 is configured so that when the input color burst signal becomes small, that is, when the signal level of the carrier color signal decreases, the gain becomes negative by the ACC signal. The saturation, or color density, is controlled to be constant. The output of the variable gain amplifier 2 is supplied to a 1H (one horizontal scanning period) delay circuit 6, an addition circuit 7, and a subtraction circuit 8 via an amplifier f5. ]The signal delay time in the H delay circuit 6 is
The time is set to be longer or shorter than 1H by (π/2)X(]/ωG). Therefore, in order to prevent vertical stripe interference, the phase of the subcarrier is shifted by π/2 between two consecutive scanning lines in the same field, so that the phase of the carrier color signal is accurately the same as the phase 1H before. π/
Although there is a shift of 2, the phase of the carrier color signal output from the IH delay circuit 1 approximately before IH almost matches the phase of the input signal. The output of this 1H delay circuit 6 is supplied to an addition circuit 7 and a subtraction circuit 8. In the adder circuit 7, when the output of the I* delay circuit 6 is added to the carrier color signal, the F2v component of the carrier color signal is canceled and only the EU acid component is outputted from the adder circuit 7. Further, in the subtracting circuit 8, for example, the output of the IH delay circuit 6 is subtracted from the carrying color signal, thereby canceling the EU acid component of the carrying color signal, and only the Ev acid component is outputted from the subtracting circuit 8. The outputs of these adder circuits 7 and subtracter circuits 8 are B-y, respectively.
The signal is supplied to the detection circuit 9 and the RY detection circuit 10.

The subcarrier generator 4 is configured to generate a color subcarrier signal having a predetermined phase difference from the color burst signal. The color subcarrier signal outputted from the subcarrier generator 4 is phase-shifted by 90 degrees by a phase shifter 11, and then used as a subcarrier for detection.
The signal is supplied to the Y detector 9. Further, this color subcarrier signal is supplied to a 180 phase shifter 12 which shifts the input by 180 degrees, and at the same time, the PAL switch 1301 is powered. The output of the 180 phase shifter 12 serves as another input to the PAL switch 13. The control input terminal of the PA/L switch 13 is supplied with the output of a phase discrimination circuit (not shown) that generates a phase discrimination signal consisting of a pulse that is inverted every IH depending on the phase state of the color/first signal. .

The PAL switch 13 is configured to alternately output the two-man power every 1H depending on the phase discrimination signal. The output of the PAL switch 13 is supplied to the RY detector 10 as a detection subcarrier. Then, the BY signal and the RY signal are detected in each of the BY detector 9 and the RY detector 10, and are supplied to the IJ sock path 14. In the matrix circuit 14, the G-Y signal is taken out from the BY signal and the RY signal and output together with the BY signal and the RY signal. Note that G indicates a green signal.

In the above configuration, the vector "NIAN+1" corresponding to the general color feed signal of the PAL color video signal corresponding to the n-th scanning line and the n+1-th scanning line is shown in FIG.
A,) and (B) of the same figure, the vector e corresponding to the outputs of the addition circuit 7 and the subtraction circuit 8, respectively.
lJ and ev are the sum and difference of the vector ANIAN+1, respectively, as shown in FIG. These vectors eU
, ev's composite vector D1 is as shown in FIG. 2(D). A hue corresponding to the angle θ formed by B −Y tlQl+ of this composite vector D1 and a saturation corresponding to the length of this composite vector D1 are obtained. Incidentally, the length dl of this composite vector D1 is expressed as in the following equation, assuming that the length of the vector AN is A.

= 2A, m stone in” 0 = 2 A ・Song・
・(3) However, in the conventional color demodulation circuit, the angle θ between the composite vector D1 and the BY axis changes only depending on the carrier color signal in the PAj color video signal, so it can be adjusted according to the user's preference. If it is desired to change the hue, for example, a complicated circuit for directly processing the color difference signal is required, which is not desirable.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color demodulation circuit for a video reproducing device that is capable of changing hue according to user's preference and has a simple configuration.

According to the present invention, a color demodulation circuit of a video reproducing device includes a phase shifting means for shifting the phase of a carrier color signal by an angle according to a command every horizontal scanning period, and the output of the phase shifting means includes It is configured to demodulate color difference signals.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 3 and 4.

In FIG. 3, a bandpass filter 1, a variable gain amplifier 2,
Burst gate amplifier f3, subcarrier generator 4, amplifier 05.1H delay circuit 6. Addition circuit 7, subtraction circuit 8, B
-Y detector 9, R-Y detector and matrix circuit 14
are connected in the same way as the circuit in FIG. However, in this example, the carrier color signal output from the amplifier 05 is supplied to the phase shift circuit 15. In the phase shift circuit 15, the output of the amplifier 05 is supplied to the phase shifter 16, and at the same time, it is operated by a changeover switch 17. Phase shifter 16
For example, a control signal having a level corresponding to the operation state of a hue adjustment operation button (not shown) in the operation section is supplied to the control input terminal of the phase shifter 16. The configuration is such that the phase of the input is delayed by a certain angle. The output of this phase shifter 16 is
There are 2 inputs. A phase discrimination signal is supplied to the control input terminal of the changeover switch 170. Changeover switch 1
Similarly to the PA and L switch I3, the switch 7 is configured to alternately output two manpowers every IH based on a phase discrimination signal. The output of this changeover switch 17 is the phase shift circuit 15
The output signal is supplied to an IH delay circuit 6, an addition circuit 7, and a subtraction circuit 8.

Further, the control signal supplied to the control input terminal of the phase shifter 16 is also supplied to the IJ node circuit 14.

The matrix circuit 14 extracts the G-Y signal from the B-Y signal and the R-, Y signals, and outputs these B-Y, R'
-Y, G-, and Y signals are amplified with a gain corresponding to the level of the control signal.

In the above configuration, the vectors AN and AN+1 corresponding to the carrier color signals of the PAL color video signals corresponding to the scanning lines of the n main exit and the n+1 main exit are shown in FIG.
Figure 4 (A,) and Figure 4 (B) are similar to Figure 4 (A) and Figure 4 (B).
B) shall be as shown by the solid line. At this time, the carrier color signal whose phase is shifted every IH by the phase shifter 16 is derived from the output terminal of the changeover switch 17, so the vector corresponding to the output of the changeover switch 17 is shown in FIG. 4(A). As shown by the broken line, the vector AN is alternately equal to the vector 8≦ and the vector AN+1, which are obtained by rotating the vector AN by an angle φ corresponding to the level of the control signal supplied to the phase shifter 16, for each IH. Therefore, the vectors e' and e' corresponding to the outputs of the adder circuit 7 and the subtracter circuit 8, respectively, are the sum and difference of the vector sum, AN+1, as shown in FIG. 4(C). Also,
At this time, the vectors corresponding to the EU acid component and the Ev acid component in the outputs of the addition circuit 7 and the subtraction circuit 8, that is, the outputs of the B'-y detector 9 and the R-Y detector 10, respectively, are vectors e.
This corresponds to the BY-axis direction component and the RY-axis direction component of J and eJ, respectively. These vectors eJ.

The length d2 of each B-y axis component and R-Y axis component of eC. d3 are as shown in the following equations.

d2-A (tassel θ ωS (θ-φ)) ・・・・・・・
(4) d 3 = A (sin θ sbi (θ−φ)
)...(5) It's a trench, these vectors e6. eC
The angle formed by the composite vector D2 of the BY-axis direction component and the RY-axis direction component element with the BY axis is θ-(φ/2) as shown in FIG. 4(D). -! In addition, the length d4 of this composite vector D2 is as shown in the following equation.

= V'E AlT; Electric ・・・・・・・・・(6)(
From equations (3) and (6), d4/d1 becomes as shown in the following equation.

d4A1-fiA, V' ] Jutei φ/2A As shown in equation (7), the length d4 of the composite vector D2 is not equal to the length dl of the composite vector D1, but the gain of the 7-trinox circuit 14 is equal to the control signal. Since the level of the phase shifter 16 changes depending on the phase shift angle, the length of the combined vector of the two vectors corresponding to the B-Y, RY signals output from the matrix circuit 14 is increased. Sa dl
This means that it can be made equal to . Therefore, the composite vector of the two vectors respectively corresponding to the B-Y and RY signals output from the 7-trinox circuit 14 can be made the same as the vector obtained by rotating the composite vector D1 by the angle φ/2. This means that only the hue can be changed without changing the intensity.

In the above embodiment, the gain of the matrix circuit 14 was variably controlled according to the change in hue, but if the variable range of hue is narrow, there may be a practical problem even if the gain of the matrix circuit 14 is not variably controlled. There isn't. For example, φ=40
When d and Jd are as shown in the following equation, the change in saturation is practically negligible.

0.94 (8) As detailed above, the color demodulation circuit of the video reproducing device according to the present invention phase-shifts the carrier color signal by an angle according to the command every one horizontal scanning period. With this configuration, with a simple configuration, the composite vector of two vectors corresponding to the color difference signals B-Y and RY, respectively, is rotated by an angle according to the command, and the hue can be changed according to the user's preference. This means that it is possible to do so.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a color demodulation circuit of a conventional video playback device, FIG. 2 is a vector diagram showing signal states of each part of the circuit in FIG. 1, and FIG. 3 is an embodiment of the present invention. FIG. 4, a block diagram illustrating an example, is a vector diagram showing the state of signals in each part of FIG. 3. Explanation of symbols of main parts 6... IH delay circuit 7... Addition circuit 8... Subtraction circuit 9... B-Y detector 10... R-Y
Detector 14... Matrix circuit 15... Phase shift circuit

Claims (1)

[Claims] A color demodulation circuit of a video reproducing device that reproduces video using a PAL color video signal in which one of the carrier color signals and a color burst signal are phase-inverted every one horizontal scanning period, 1. A color demodulation circuit for a video reproducing apparatus, characterized in that the circuit includes a phase shifter that shifts the phase by an angle according to a command every other time, and demodulates a color difference signal included in the output of the phase shifter.