JPS61256885A - Color demodulating circuit video - Google Patents

Abstract

PURPOSE:To rotate a phase of a carrier chrominance signal and change a hue by providing a variable delay means for delaying an output of delay means for delaying the carrier chrominance signal and a color burst signal by a prescribed time by a time according to a command. CONSTITUTION:A carrier chrominance signal included in a color video signal together with a color burst signal is supplied to a 1H (horizontal scanning period) delay circuit 1, an adding circuit 2 and a subtraction circuit 3. The output of the 1H delay circuit 1 is supplied to the adding circuit 2 and the subtraction circuit 3 through a variable delay circuit 11. The outputs of the adding circuit 2 and the subtraction circuit 3 are respectively supplied to a B-Y demodulator 5, and a R-Y demodulator 6. In the variable delay circuit 11, by a command from an operating section of a video reproducing device, a signal delay time is changed and an output is inputted to a burst gate 4. Detecting subcarriers supplied respectively through a 90 deg. phas converter 8, a 180 deg. phase converter 9 and a PAL switch 10 from a subcarrier generator 7 are those rotating the detecting subcarrier when the signal delay time of the variable delay circuit 11 is zero.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field 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.
A L (Phase Alternation L
The present invention relates to a color demodulation circuit for a video playback device that plays back video using a color video signal based on the ine) method.

BACKGROUND TECHNIQUE n (n is a natural number) The PAL color video signal EM corresponding to the grain scanning line is given by the following equation: −・
(1) ω, ==2πfH (m-1/4)
......(2) Here, Y is the luminance signal, EU and E
v indicates the color difference signals B-Y and RY-ii, respectively. Note that B and R [indicate blue and red signals, respectively. Also, fHn horizontal scanning frequency, 77LI
I-j is a natural number.

The coefficient (-1) n in equation (1) means a phase inversion for each horizontal scanning line, and the Ev component of the carrier color signal has a phase difference of 180° from each other for every 1 horizontal scanning line ( -1)
It is transmitted by balanced modulating the subcarrier signal ncmωct. Therefore, the color burst signal is required to have information for inverting the phase of the Ev acid component subcarriers line by line on the image receiving side. For this reason, the color burst signal is switched line by line to a phase of ±135° around the EU axis, and the phase-inverted signal is sent out.

FIG. 3 shows a conventional color demodulation circuit in a device that reproduces video using such a PAL color video signal.

In FIG. 3, a carrier color signal included in a PAL color video signal is accompanied by a color burst signal.
(One horizontal scanning period) Supplied to delay circuit 1, addition circuit 2, subtraction circuit 3, and burst gate 4. IH delay circuit 1
The output is added and combined with the carrier color signal in the adder circuit 2, and at the same time, a signal corresponding to the difference between the carrier color signal and the output of the IH delay circuit 1 is generated in the subtracter circuit 3. The outputs of the addition circuit 2 and subtraction circuit 3 are supplied to a BY demodulator 5 and an RY demodulator 6, respectively.

The burst gate 4 is also supplied with the output of a pulse generator (not shown) configured to delay the horizontal synchronization signal and output a gate pulse while the color burst signal is present. It consists of an analog switch circuit that turns on and off according to the output of the pulse generator.The burst gate 4 separates and extracts the color burst signal from the carrier color signal, and then outputs the APC (Au
t.

Phase Control) is supplied to the subcarrier generator 7 according to Equation 75. The subcarrier generator 7 is configured to generate a companion color subcarrier signal whose phase matches the average phase of the color burst signal.

The color subcarrier signal output from the subcarrier generator 7 is phase-shifted by 90' by a 90° phase shifter 8 and is supplied to the BY demodulator 5 as a subcarrier for detection. In addition, this color subcarrier signal is
18o0 phase shifter 9 and PAL switch 10 with 0° phase shift
is also supplied. The PAL switch 10 is configured to alternately output the color subcarrier signal and the output ilH of the 1800 phase shifter 9. The output of this PAL switch 10 is supplied to the RY demodulator 6 as a subcarrier for detection.

In the above configuration, vectors A and B corresponding to the carrier color signal and the color burst signal, respectively, when there is no color change during consecutive 4H are shown in FIG. 4 (A, ) to CD in the same figure. . Figure 4 (A) to Figure 4 CD)
As shown in Figure 2, in order to prevent vertical stripe interference, a 1/4 line offset is adopted in which the subcarrier phase is shifted by 90' between two consecutive scanning lines in the same field. It rotates by 90 degrees every dIH, and the RY axis rotates by 90' every IH and is simultaneously reversed. The color burst signal is B −
Since the phase is switched to ±135° around the Y axis every IH and the phase is inverted, the phase is inverted every 2H.

However, since the R-Y component of the carrier color signal is transmitted by balanced modulation of the subcarrier signal having a phase difference of 180' for each IH, the carrier color signal is transmitted every 2H as well as the color burst signal. It will be reversed.

Here, the signal delay time of IH delay circuit l is longer than IH (
It is assumed that the time is set to be longer or shorter by π/2)X(1/ω0). At this time, I
Vectors A' and B' respectively corresponding to the carrier color signal and color burst signal output from the H delay circuit 1 are shown in FIGS. 5(A) to 5(CD). Figure 5 (A
) to CD), there is no 90° phase difference due to the 1/4 line offset between the input and output of the IH delay circuit.

Therefore, as shown in FIG. 6, the vector AN+1 ? corresponds to the carrier color signal and color burst signal of the color video signal corresponding to the scan line of the grain +1 grain, respectively. BN+1
If the polar coordinates of is (r, φ)t(L17), then l H
A vector AN corresponding to the carrier color signal and the color burst signal of the color video signal corresponding to the grain scan line outputted from the delay circuit 1 and supplied to the addition circuit 2 and the subtraction circuit 3, respectively.

The polar coordinates of BN are (γ, φ)+('+4).

As a result, a vector C corresponding to a signal obtained by adding and combining the carrier color signal and the output of the IH delay circuit 1, and a vector Di corresponding to a signal obtained by subtracting the output of the IH delay circuit 1 from the carrier color signal. As shown in Fig. 6, the Ev acid component of the carrier color signal is canceled in the addition circuit 2, and only the E■ acid component is output, and the Ev acid component of the carrier color signal is canceled in the subtraction circuit 3, and the Ev acid component is output. Only the components are output. The outputs of the adder circuit 2 and the subtracter circuit 3 are supplied to a BY demodulator 5 and an R, -Y demodulator 6 to demodulate color difference signals BY, RY.

In a video playback device that performs color demodulation using the conventional color demodulation circuit as described above, if the hue is changed according to the user's preference, a separate circuit with a complicated configuration for processing color difference signals, for example, is required. I didn't like it.

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

The color demodulation circuit of the video reproducing apparatus according to the present invention includes the output of the first signal synthesizing means for adding and synthesizing the input and output of the signal delaying means for delaying the carrier color signal and the color burst signal by a predetermined time, and the input and output of the signal delaying means. The circuit is configured to demodulate two color difference signals included in the output of a second signal synthesis means for synthesizing a signal according to the difference between the outputs, and the circuit demodulates the output of the signal delay means for a time corresponding to a command. The configuration includes variable delay means for delaying.

EXAMPLES Hereinafter, examples of the present invention will be described in detail with reference to FIGS. 1 and 2.

In FIG. 1, IH delay circuit 1, addition circuit 2, subtraction circuit 3, burst gate 4, B-Y demodulator 5, R-Y demodulator 6, subcarrier generator 7, 90° phase shifter 8, 180°
The phase shifter 9 and the PAL switch 10 are connected in the same way as the circuit shown in FIG. However, in this example, the output of the IH delay circuit 1 is passed through the variable delay circuit AE to the adder circuit 2.
and is supplied to the subtraction circuit 3. The variable delay circuit 11 is configured to change the signal delay time in accordance with a command issued in response to a user's operation of a hue adjustment operation button (not shown) in the operation section of a video playback device, for example. The output of the circuit 11 is also input to the burst gate 4.

In the above configuration, similarly to FIG. 6, vectors AN+0.
The polar coordinates of BN+ are 3π (r, φ) + (l+4) as shown in FIG. Vectors AN, BN corresponding to the signal carrying color signal and color burst signal, respectively
polar coordinates e(f, -φ).

Let it be 5π (Z!7). Well, if the signal delay time of the variable delay circuit 11 corresponds to the phase θ of the color subcarrier, then the signal delay time of the variable delay circuit 11 corresponds to the carrier color signal output from the variable delay circuit 11 and supplied to the addition circuit 2 and subtraction circuit 3. The vector A'N u is obtained by rotating the vector AN by θ.

Therefore, the polar coordinates of vector A/, are (r, -φ10)
becomes. Similarly, the polar coordinates of the vector s/, which corresponds to the color burst signal output from the variable delay circuit 11 and supplied to the addition circuit 2 and the subtraction circuit 3, are c t , 5
! ! −+θ).

On the other hand, since the subcarrier generator 7 is configured to generate a subcarrier whose phase matches the average phase of the color burst signal whose phase is inverted every zH, the B-Y demodulator 5 and the R-Y demodulator The detection subcarriers supplied to each of the detectors 6 are obtained by rotating the detection subcarriers by a total of θ/2 when the signal delay time of the variable delay circuit 11 is zero.

Therefore, the demodulation axes at this time are the B-Y axis and the R-Y axis.
The (B-Y)' and (RY)' axes are rotated by /2. Vector AN+0 by these (B-Y)' axes and (R-Y'n' axes. The polar position θ of A'N
The θ marks are (-r, φ-H)t(r, -(φ-d)ton, respectively. Therefore, the phase of the carrier color signal is rotated by -θ/2 and the same color as the original is reproduced. As a result, the hue of the resulting color changes according to the command.

In the above embodiment, the variable delay circuit 11 is connected as a circuit after the IH delay circuit 1, but the variable delay circuit 11 may be connected as a circuit before the IH delay circuit 1. IH delay circuit] and variable delay circuit 11
The signal delay time is 1 if the phase relationship shown in Figure 6 is obtained.
It may be any time before or after 8.

Effects of the Invention As detailed above, the color demodulation circuit of the video reproducing apparatus according to the present invention includes a variable delay element 9 that delays the output of the signal delay means for delaying the carrier color signal and the color burst signal by a predetermined time in accordance with a command. Since it has a double stage configuration, it is possible to rotate the phase of the carrier color signal according to a command with a simple configuration and change the hue according to the user's preference.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a vector diagram showing signals of each part in the circuit of FIG. 1, and FIG. 3 is a block diagram showing a conventional color demodulation circuit. Fourth
5 is a vector diagram showing a human-powered PAL carrier color signal and a color burst signal, FIG. 5 is a vector diagram showing a carrier color signal and a color burst signal delayed by the lH delay circuit 1, and FIG. FIG. 3 is a vector diagram showing signals of each part of the circuit shown in the figure. Explanation of symbols of main parts

Claims (1)

[Claims] 1 of the orthogonal modulation components of the carrier color signal and color burst signal
In a video reproducing apparatus that reproduces video using a PAL color video signal whose phase is inverted every horizontal scanning period, a signal delaying means for delaying the carrier color signal and the color burst signal by a predetermined time; a first signal synthesizing means for adding and synthesizing outputs, and a second signal synthesizing means for synthesizing a signal according to a difference between an input and an output of the signal delaying means, the outputs of the first and second signal synthesizing means A color demodulation circuit configured to demodulate two color difference signals included in each of the video images, characterized in that the circuit includes variable delay means for delaying the output of the signal delay means by a time according to a command. Color demodulation circuit for playback equipment.