JP2502803B2 - Color signal processing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal processing device for processing a video color signal having a burst signal in a television, a video tape recorder or the like.

2. Description of the Related Art In a color television signal, in order to superimpose and transmit two color difference signals on a luminance signal at the same time, the luminance signal is amplitude-modulated by a dedicated carrier, and the color difference signal has a color subcarrier (burst) within the luminance signal band. One carrier called a signal) is provided, and a carrier color signal is modulated using a special modulation method called carrier suppression amplitude modulation (balanced modulation) and then superimposed on a luminance signal. When demodulating the carrier color signal in the color television signal into a color difference signal, an automatic phase control circuit (hereinafter referred to as APC) is used, but the APC is generally a feedback with a slow response speed in consideration of demodulation stability. It is often APC. However, in the case of a non-standard signal with jitter, such as the output of a video tape recorder, feedback APC does not sufficiently respond to the jitter, and residual jitter occurs, resulting in swaying of the demodulation axis. Since the fluctuation of the demodulation axis can be detected from the burst signals of the two color difference signals after demodulation, accurate color difference signals can be converted by rotating the demodulation axis so as to cancel the detected phase error. This is the feed-forward APC, which detects the phase of the burst signal and instantly cancels the error.

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

FIG. 4 is a block diagram of a conventional color signal processing device, and FIG. 5 is a vector diagram showing the operation of feedforward APC.

First, the RY signal input terminal 401 and the BY signal input terminal 4
An RY signal and a BY signal, which are color difference signals, are input to 02. And burst gate pulse input terminal 403
The RY signal is averaged by the burst averaging circuit 404 and the BY signal is averaged by the burst averaging circuit 405 only during the period of the burst gate input to the. As shown in FIG. 5 this time, the color difference signal in the demodulation axis before correction phase angle ψ amplitude E, the burst signal and has a phase angle θ the amplitude E _X, R-Y signal E _R
= E sin ψ, the BY signal can be expressed as E _B = E cos ψ, the signal averaged by the burst averaging circuit 404 can be expressed as E _X sin θ, and the signal averaged by the burst averaging circuit 405 can be expressed as −E _X cos θ. θ is the phase error. This burst averaging circuit 404 and 4
The output of 05 is input to the amplitude calculation circuit 406, and the amplitude of the burst is calculated. The output of the amplitude calculation circuit 406 is E _X. The outputs of the amplitude calculation circuit 406 of the burst averaging circuit 404 inputs the amplitude normalization circuit 407 performs a calculation of E _X sinθ / E _X, and outputs the result sin [theta. Similarly, the output of the burst averaging circuit 405 and the output of the amplitude calculating circuit 406 are input to the amplitude normalizing circuit 408, and -E _X cos θ / E _X is calculated, and as a result, -cos θ is output. In this way, the phase error signal si
nθ and cosθ are obtained. Here, as shown in FIG. 5, if the demodulation axis is rotated by the phase error θ to correct the phase of the input color difference signal, RY is obtained on the corrected demodulation axis.
The signal can be expressed as ER _′ = E sin (ψ + θ) = E (cos ψ · sin θ + sin ψ · cos θ) = E (E _B / E · sin θ + E _R / E · cos θ) = E _B · sin θ + E _R · cos θ (1) Similarly, the BY signal is EB _′ = Ecos (ψ + θ) = E (sinψ ・ sinθ + cosψ ・ cosθ) = E (−E _R / E ・ sin θ + E _B / E ・ cos θ) = − E _R・ sin θ + E _B・ cos θ It can be expressed as (2).

Eventually, the phase correction circuit 409 sends the RY signal E _R to the delay circuit 41.
Signal delayed by 3, delays the input B-Y signal E _B circuit 414
Signal delayed by, the output of the amplitude normalization circuit 407 sin
By inputting θ and −cos θ, which is the output of the amplitude normalization circuit 408, and calculating equation (1), the corrected RY signal ER _′ is obtained as the output. Similarly, the phase correction circuit 410 is a signal obtained by delaying the RY signal E _R by the delay circuit 413, a signal obtained by delaying the input BY signal E _B by the delay circuit 414, and an output of the amplitude normalization circuit 407. By inputting sin θ and −cos θ, which is the output of the amplitude normalization circuit 408, and calculating equation (2), the corrected RY signal EB _′ is obtained as the output.

Problems to be Solved by the Invention In such a conventional color signal processing device, the following 2
There are two challenges.

One is to consider the case where the input color difference signal is a non-standard signal such as a signal recorded on a video tape recorder in which the edge portion is blunted due to band limitation, and the burst gate pulse is originally a burst signal. It must be set wider than the existing period. However, if noise is superimposed before and after the burst signal of the input color difference signal in order to set it wide, it is not possible to accurately calculate the phase error. In particular, when noise is biasedly superposed on one of the two color difference signals, or when pulse-shaped noise is superposed, the calculated phase error is largely deviated from the original phase error. The problem is that it ends up.

The other is that, when actually implementing this feedforward APC, at least the burst gate time is required to calculate the phase error, so the input color difference signal is delayed by that time before the phase correction circuit. This is a problem that needs to be corrected. Of course, there is a method in which only the burst signal is corrected by the phase error of one horizontal period before, or the phase error itself is delayed by one horizontal period and corrected.
If the input color difference signals are uncorrelated before and after one horizontal period, incorrect correction will be performed.

In view of the above problems, the present invention provides a color signal processing device which can accurately calculate a phase error even when noise is superimposed on a portion other than a burst signal of an input color difference signal, and a second problem. An object of the present invention is to provide a color signal processing device capable of performing phase correction with almost no delay of an input color difference signal.

Means for Solving the Problems In order to achieve the above object, a color signal processing device of the present invention calculates an amplitude from a first input color difference signal and a second input color difference signal, and the amplitude is smaller than a predetermined value. A minute signal detection circuit for generating a pulse, a first switch means for switching between a first input color difference signal and a zero level by the pulse, and a second switch for switching between a second input color difference signal and a zero level by the pulse. Means, a first burst averaging circuit for averaging the output of the first switch means for the duration of the burst gate pulse, and a second burst averaging means for averaging the output of the second switch means for the duration of the burst gate pulse. A circuit, an amplitude calculation circuit for calculating the amplitude of the burst signal from the output of the first burst averaging circuit and the output of the second burst averaging circuit, A first amplitude normalization circuit that divides the output of the first burst averaging circuit by the output of the amplitude calculation circuit, and a second amplitude normalization circuit that divides the output of the second burst averaging circuit by the output of the amplitude calculation circuit
And an amplitude normalization circuit for correcting the phase of the first input color difference signal with the second input color difference signal, the output of the first amplitude normalization circuit, and the output of the second amplitude normalization circuit. A first phase correction circuit, and a first phase correction circuit for correcting the phase of the second input color difference signal by the first input color difference signal, the output of the first amplitude normalization circuit, and the output of the second amplitude normalization circuit. No. 1 phase correction circuit.

The present invention also provides a first burst averaging circuit for averaging the first input color difference signal for the period of the first burst gate pulse, and a second burst averaging circuit for averaging the second input color difference signal for the period of the first burst gate pulse. 2 burst averaging circuits, an amplitude calculating circuit that calculates the amplitude of a burst signal from the outputs of the first burst averaging circuit and the second burst averaging circuit, and the output of the first burst averaging circuit. A first amplitude normalization circuit that divides by the output of the amplitude calculation circuit;
A second amplitude normalization circuit for dividing the output of the second burst averaging circuit by the output of the amplitude calculation circuit; and a phase of the first input color difference signal for the second input color difference signal and the first input color difference signal. A first phase correction circuit that corrects by the output of the amplitude normalization circuit and the output of the second amplitude normalization circuit, and the phase of the second input color difference signal with the first input color difference signal and the first input color difference signal. Of the amplitude normalization circuit and the output of the second amplitude normalization circuit, and the output of the first phase correction circuit is at zero level for the period of the second burst gate pulse. The first burst replacement circuit for replacing the output of the first phase replacement circuit with the output of the amplitude calculation circuit for the period of the second burst gate pulse.
It is provided with a second burst replacement circuit that replaces the value by a factor of 1.

According to the present invention having the above-described configuration, the amplitude of the input color difference signal is calculated by the minute signal detection circuit for the first problem, and when the amplitude is smaller than the predetermined level, the color difference is input to the burst averaging circuit by the switch means. By fixing the signal to the zero level, the noise superimposed on the part other than the burst signal is not calculated, so that the phase error can be calculated accurately.

For the second problem, R of the burst signal after being corrected by the phase correction circuit as long as the phase error is accurately calculated
Since it has been determined that the −Y-axis component is a zero level and the B-Y-axis component is a value obtained by multiplying the value calculated by the amplitude calculation circuit by −1, the burst signal is set to that value for the second burst gate pulse. It is not necessary to delay and correct the input color difference signal by replacing only the period. It is multiplied by -1 because the burst signal calculated by the amplitude calculation circuit is always positive, and the corrected B-Y axis component of the burst signal is always negative.

Embodiment An embodiment of the color signal processing device according to the present invention will be described below with reference to the drawings.

However, the same components as those of the conventional color signal processing device shown in FIG. 4 are designated by the same reference numerals, and the description of the operation thereof is omitted.

FIG. 1 is a block diagram of a color signal processing device according to the first embodiment of the present invention.

The minute signal detection circuit 101 calculates the amplitudes of the RY and BY signals, which are color difference signals input to the RY signal input terminal 401 and the BY signal input terminal 402, respectively. If the RY signal is E _R = Esin ψ and the BY signal is E _B = Ecos ψ, the amplitude E
Is The root mean square is calculated as follows. For example, assuming that the input color difference signal has a dynamic range of 1V, E is 5
It is assumed that the minute signal detection circuit 101 outputs a pulse that makes a high level when%, that is, 50 mV or less, and makes a low level otherwise. The switch means 102 receives R- of the input color difference signal.
The Y signal and the zero level input to the zero level input terminal 104 are input, and similarly, the BY signal and the zero level are input to the switch means 103. When the output pulse of the minute signal detection circuit 101 is at low level, the switching means 102 and 103
Switches to the input color difference signal and switches to the zero level when the level is high. Thus, E is 50 mV
In the following, the burst averaging circuits 404 and 405 operate so as not to calculate the burst average.

FIG. 2 is a block diagram of a color signal processing device according to the second embodiment of the present invention.

The RY signal corrected by the phase correction circuit 409 is input to the burst replacement circuit 201, and the RY signal is replaced to the zero level input to the zero level input terminal 203 only during the burst gate input to the burst gate pulse input terminal 204. Similarly, the BY signal after being corrected by the phase correcting circuit 410 is input to the burst substituting circuit 202, and the burst amplitude calculated by the amplitude calculating circuit 406 during the period of the burst gate input to the burst gate pulse input terminal 204 is- Change the level to 1x.

FIG. 3 is a block diagram of a color signal processing device according to a third embodiment of the present invention. In this embodiment, the minute signal detection circuit 101, the switch means 102 and 103, the zero level input terminal 104 of the first embodiment, the burst replacement circuits 201 and 202, the zero level input terminal 203, and the burst gate of the second embodiment are used. The pulse input terminal 204 is also configured.
Therefore, the color signal processing device has the effects of both the first and second embodiments.

As described above, according to the present invention, by providing the minute signal detection circuit 101, the switch means 102 and 103, and the zero level input terminal 104, the amplitude of the input color difference signal is calculated by the minute signal detection circuit 101. When the amplitude is smaller than the predetermined level, the color difference signals input to the burst averaging circuits 404 and 405 are fixed to zero level by the switching means 102 and 103, so that the noise superimposed on the part other than the burst signal is not calculated, so that it is accurate. It is possible to calculate the phase error.

Further, by providing the burst substituting circuits 201 and 202, the zero level input terminal 203, and the burst gate pulse input terminal 204, the burst signals after being corrected by the phase correcting circuits 409 and 410 are zero level for the RY signal, respectively. Further, since the BY signal is replaced by a value obtained by multiplying the value calculated by the amplitude calculation circuit 406 by -1 during the burst gate pulse period, the input color difference signal is delayed and the phase correction circuit 40 is delayed.
No need to compensate at 9 and 410. If it is assumed that the input color difference signal is a signal whose gain is controlled by the automatic gain control circuit to the standard value of the standard color television signal, the burst replacement circuit 202 simply shifts the BY signal to the standard value. However, if the amplitude of the burst signal of the input color difference signal does not exactly match the standard value, the saturation of the color signal after phase correction will change. However, in the present invention, since the replacement is performed using the value calculated by the amplitude calculation circuit, the amplitude of the burst signal after the replacement exactly matches the amplitude of the input color difference signal, and the saturation does not change.

As described above, it is extremely useful when color signal processing is performed using feedforward APC, and has great industrial value.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a color signal processing device according to a first embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a color signal processing device according to a second embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of a color signal processing device according to a third embodiment of the present invention, FIG. 4 is a block diagram showing the configuration of a conventional color signal processing device, and FIG. 5 is a diagram showing the operation of a feedforward APC. It is a vector illustration. 101 ... Minute signal detection circuit, 102, 103 ... Switch means, 104,
203 ... Zero level input terminal, 201, 202 ... Burst replacement circuit, 401 ... RY signal input terminal, 402 ... BY signal input terminal, 403, 204 ... Burst gate pulse input terminal, 404, 4
05 ... Burst averaging circuit, 406 ... Amplitude calculation circuit, 407, 408 ...
Amplitude normalization circuit, 409, 410 ... Phase correction circuit, 411 ... RY
Signal output terminal, 412 ... BY signal output terminal.

Claims (4)

(57) [Claims] 1. A minute signal detection circuit for calculating an amplitude from a first input color difference signal and a second input color difference signal, and generating a pulse when the amplitude is smaller than a predetermined value, and the first input by the pulse. First switch means for switching between the color difference signal and the zero level, second switch means for switching between the second input color difference signal and the zero level by the pulse, and output of the first switch means only during the burst gate pulse period. A first burst averaging circuit for averaging; a second burst averaging circuit for averaging the output of the second switch means for a period of a burst gate pulse; an output of the first burst averaging circuit and the second burst An amplitude calculation circuit for calculating the amplitude of the burst signal from the output of the averaging circuit, and the output of the first burst averaging circuit is divided by the output of the amplitude calculation circuit. A first amplitude normalization circuit; a second amplitude normalization circuit for dividing the output of the second burst averaging circuit by the output of the amplitude calculation circuit; and a phase of the first input color difference signal for the first amplitude normalization circuit. A second input color difference signal, the output of the first amplitude normalization circuit and the output of the second amplitude normalization circuit, and a phase of the second input color difference signal A color signal processing device comprising: a first input color difference signal; a first phase correction circuit that performs correction using the output of the first amplitude normalization circuit and the output of the second amplitude normalization circuit. 2. A first burst averaging circuit for averaging a first input color difference signal for a period of a first burst gate pulse, and a second burst averaging circuit for averaging a second input color difference signal for a period of a first burst gate pulse. A second burst averaging circuit; an amplitude calculation circuit that calculates the amplitude of a burst signal from the outputs of the first burst averaging circuit and the second burst averaging circuit; and the output of the first burst averaging circuit. A first amplitude normalization circuit that divides by the output of the amplitude calculation circuit; a second amplitude normalization circuit that divides the output of the second burst averaging circuit by the output of the amplitude calculation circuit; A first phase correction circuit that corrects the phase of the input color difference signal by the second input color difference signal, the output of the first amplitude normalization circuit, and the output of the second amplitude normalization circuit; Input color difference signal level of A first phase correction circuit that corrects the first input color difference signal, the output of the first amplitude normalization circuit, and the output of the second amplitude normalization circuit, and the output of the first phase correction circuit. To a zero level for the duration of the second burst gate pulse, and the output of the second phase correction circuit for the output of the amplitude calculation circuit for the duration of the second burst gate pulse. A color signal processing device comprising: a second burst replacement circuit that replaces the value by a factor of 1. 3. A minute signal detection circuit for calculating an amplitude from a first input color difference signal and a second input color difference signal and generating a pulse when the amplitude is smaller than a predetermined value, and the first input by the pulse. First switch means for switching between a color difference signal and a zero level, second switch means for switching between a second input color difference signal and a zero level by the pulse, and output of the first switch means as a first burst gate pulse. , A second burst averaging circuit for averaging the output of the second switch means for the period of the first burst gate pulse, and an output of the first burst averaging circuit And an amplitude calculation circuit for calculating the amplitude of the burst signal from the output of the second burst averaging circuit, and an output of the first burst averaging circuit for the amplitude calculation circuit. A first amplitude normalization circuit that divides by a force, a second amplitude normalization circuit that divides the output of the second burst averaging circuit by the output of the amplitude calculation circuit, and the first input color difference signal A first phase correction circuit that corrects the phase of the second input color difference signal, the output of the first amplitude normalization circuit, and the output of the second amplitude normalization circuit; and the second input color difference signal. A first phase correction circuit that corrects the phase of the signal with the first input color difference signal, the output of the first amplitude normalization circuit, and the output of the second amplitude normalization circuit; and the first phase correction circuit. A first burst substituting circuit for substituting its output to zero level for a second burst gate pulse period, and an output of the second phase correction circuit for the second burst gate pulse period of the amplitude computing circuit The second to replace the value with -1 Color signal processing device having a burst replacement circuit of. 4. The color signal processing device according to claim 1, 2 or 3, wherein the first input color difference signal is an RY signal and the second input color difference signal is a BY signal.