JPS63269886A - Color video signal processor - Google Patents

Abstract

PURPOSE:To properly decide the correlation of a C signal by adding a color burst signal included in a color video signal input to the Y signal output of a comb line filter and applying an automatic gain control so as to have a constant level. CONSTITUTION:When a burst gate pulse is supplied to an input terminal 12, after the color burst signal included in the color video signal inputted to the input terminal 1 is added to the Y signal of the comb line filter 3, it is supplied to a level detecting circuit 14 through a gain control circuit 13. The level detecting circuit 14 detects the color burst signal to supply a control signal according to a detected value to the gain control circuit 13, thereby, the level of the color burst signal included in the output signal of the gain control circuit 13 is controlled so as to be constant. When the decision reference of a level detecting circuit 7 is set to an optimum, if the level ratio of the Y signal and the C signal is a standard value, a C signal component is also set and maintained to an optimum state.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a color video signal processing device useful for separating a luminance signal and a color signal from a color video signal used in magnetic recording and reproducing devices, etc. .

Conventional technology When separating a luminance signal and a color signal from a color video signal, a comb filter using line correlation, field correlation, or frame correlation is used, but during periods of weak correlation,
Alternatively, in a period where there is no correlation, separation of the luminance signal and color signal is not performed well, so methods are used to change the characteristics of the comb filter or to limit the band according to the degree of correlation.

FIG. 2 shows a block diagram of an example of a conventional color video signal processing device.

In FIG. 2, a color video signal inputted from an input terminal 1 is passed through a comb-shaped filter 3 having a 1H delay element 2 (H is a horizontal period) as a component to generate a luminance signal (hereinafter abbreviated as Y signal) and a color signal (hereinafter referred to as Y signal). C signal).

The Y signal is output to the first output terminal 6 via the band limiting circuit 4 composed of a C signal component trap, and
Level detection circuit 7 via C signal component peaking circuit 6
supplied to

One input a of the signal switching circuit 8 is connected to the comb filter 3 , the other input a is connected to the input terminal 1 , and its output is connected to the bandpass filter 9 . Therefore, the C signal is output from the second output terminal 1o.

Here, the comb filter 3 uses the strong vertical correlation of color video signals to separate the Y signal and C signal by taking the sum and difference with the signals before 1H.
In periods of weak or no vertical correlation,
Since Y and C are not separated well, the C signal component leaks into the Y signal. Therefore, the level detection circuit 7 can determine the strength of the vertical correlation of the C signal, and during periods when the correlation is strong, the trap of the band limiting circuit 4 is turned off and the signal switching circuit 8 is controlled so that the C signal is output. ,
(Select input a) Y and C signals with little crosstalk were obtained. On the other hand, during a period when the correlation is weak, Y The C signal component leaking into the signal is removed by a trap, so that a C signal can be obtained by the BPF 9, which theoretically does not suffer from the discoloration that occurs when a C signal passes through a cross-shaped filter.

Problems to be Solved by the Invention However, in the color video signal input to the input terminal 1, the level ratio of the Y signal and the C signal is not necessarily constant, and especially when receiving television broadcasting, the tuning deviation of the receiver may occur. etc., the level of the C signal often decreases with respect to the standard level ratio, and it is extremely difficult to set the determination criterion of the level detection circuit 7 to an optimal value, and the vertical correlation cannot be determined properly. The problem was that there was no.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide an excellent color video signal processing device that can appropriately determine the degree of correlation of C signals even when the level of C signals decreases.

Means for Solving the Problems In order to solve the above problems, the color video signal processing device of the present invention includes a comb filter that separates a luminance signal and a color signal from a color video signal, and a luminance signal comb filter. mixing means connected to the output and mixing a reference signal according to the level of the color burst signal included in the color video signal; and automatic gain control means connected to the output of the mixing means and keeping the level of the reference signal constant. , a level detection means connected to the output of the automatic gain control means, a limiting means for limiting the band of the luminance signal according to the output of the level detection means, and a comb-shaped color signal according to the output of the level detection means. The configuration includes means for preventing the filter from passing through the filter.

Effect: With the above-described configuration, the present invention eliminates C leaked into the Y signal supplied to the level detection circuit, regardless of the magnitude of the level ratio between the Y signal and the C signal included in the input color video signal. Since it operates so that the level of the signal component is constant, even if the level of the C signal decreases, it is possible to appropriately determine the degree of correlation of the C signal.

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

FIG. 1 shows a block diagram of the same embodiment, and the second
The same parts as those in the figure are given the same reference numerals.

In FIG. 1, a color video signal inputted from an input terminal 1 is separated into a Y signal and a C signal by a comb filter 3 having a 1H delay element 2 as a component. The Y signal is output to the first output terminal 6 via the band limiting circuit 4 configured with a C signal component trap, and is also supplied to one input d of the second signal switching circuit 11. The other input e of the second signal switching circuit 11 is connected to the input terminal 1, the control terminal is connected to the second input terminal 12, and the output has a gain fl
jj” are connected to both circuits 13. The output of the gain control circuit 13 is supplied to the level detection circuit 7 via the C signal component peaking circuit 6 and also to the second level detection circuit 14.
supplied to The second level detection circuit 14 detects the level in synchronization with the control signal input to the second input terminal 12 and supplies the gain control circuit 13 with a control signal according to the detected value.

The C signal is supplied to one input of the signal switching circuit 8, the other input is connected to the input terminal 1, and its output is outputted to the second output terminal 1o via the bandpass filter 9.

Here, the level detection circuit 7 detects the level of the C signal component leaked into the Y signal output of the comb filter 3, and when the detected value is a dog, that is, the vertical correlation of the C signal is weak, the band limiter circuit 4 By turning on the trap and controlling the signal input from the signal switching circuit 8 to the input terminal 1 so that it is output as is (selecting the input), the C component leaking into the Y signal is removed by the trap. Moreover, to prevent color fading from occurring in the C signal.

On the other hand, during a period in which the detected value is small, that is, the vertical correlation of the C signal is strong, the trap of the band limiting circuit 4 is turned off and the input a is controlled so that the C signal output of the comb filter 3 is output from the signal switching circuit 8. ), and supplies the Y signal and C signal separated by the comb filter 3 to the first output terminal 6 and the second output terminal 1°, respectively.

In the color video signal processing device configured as described above, consider a case where a burst gate pulse synchronized with a color burst signal included in a color video signal input to the input terminal 1 is supplied to the second input terminal 12. here,
The second signal switching circuit 11 outputs the signal input to the input terminal 1 by selecting the input e during the burst gate pulse period, and selects the input d during the other periods and outputs the signal input to the input terminal 1. A Y signal output is output.

Since the color burst signal has a strong vertical correlation, it is not output at all to the Y signal output of the comb filter 3, but the color burst signal included in the color video signal input to the input terminal 1 is changed by the second signal switching circuit 11. is added to the second level detection circuit 1 via the gain control circuit 13.
4.

The second level detection circuit 14 detects the signal level during the burst gate pulse period, that is, the level of the color burst signal added to the Y signal, and supplies the gain control circuit 13 with a control signal according to the detected value. The level of the color burst signal included in the output signal of the gain control circuit 13 is controlled to be constant.

Therefore, the determination criteria for the level detection circuit 7 are the Y signal and the C signal.
If the signal level ratio is set to be in the optimal state when it is at the standard value, even if the level ratio changes, the C signal component supplied to the level detection circuit will be at almost the same signal level and will still be in the optimal state. Settings are retained.

In the above embodiment, it goes without saying that the circuit for detecting the C signal component leaking into the Y signal output of the comb filter 3 may have a configuration other than that shown here.

Furthermore, various configurations can be applied to the configuration of the comb filter 3 or the band limiting circuit 4.

Further, in the above embodiment, the detection value of the level detection circuit 7 is a dog during the color burst period, but the level detection circuit 7
This may be inhibited by using a color burst gate pulse input to the second input terminal 12 on the input side or output side of the input terminal 12.

Effects of the Invention As is clear from the above explanation, according to the present invention, the color burst signal included in the color video signal input is added to the Y signal output of the comb filter, and the automatic gain is adjusted so that the level of the color burst signal is constant. By performing the control, it is possible to realize an excellent color video signal processing device that can appropriately determine the correlation degree of the C signal regardless of the magnitude of the level ratio of the Y signal and C signal of the color video signal input.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a color video signal processing device according to the present invention, and FIG. 2 is a block diagram showing an example of a conventional color video signal processing device. 1.12...Input terminal, 2...1H delay element, 3...Comb filter, 4...Band limit circuit, 6°10... ...Output terminal, 6...
... Peaking circuit, 7... Level detection circuit,
8, 11... Signal switching circuit, 9... Band pass filter, 13... Gain m control circuit,
14...Synchronization level detection circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 3-m-ζshi! Filter Otsu 7

Claims (1)

[Claims] a comb filter for separating a luminance signal and a color signal from a color video signal; and a mixing means connected to an output of the luminance signal comb filter for mixing a reference signal corresponding to the level of a color burst signal included in the color video signal. , automatic gain control means connected to the output of the mixing means to keep the level of the reference signal constant; level detection means connected to the output of the automatic gain control means; 1. A color video signal processing device, comprising: limiting means for limiting a signal band; and means for preventing a color signal from passing through a comb filter in accordance with the output of the level detecting means.