JPH0393384A - Yc separator circuit - Google Patents

Abstract

PURPOSE:To improve the picture quality to a black white video signal and a special video signal by using a color killer detection output signal of a video/ chroma IC so as to control a switch provided to a color signal addition line for luminance signal separation in a YC separation circuit. CONSTITUTION:When a video signal without a burst reference signal is inputted to a video/chroma IC 8, a color killer circuit in the IC is operated and non- execution of color signal band amplification ia ensured. Since a switch 7 provided to an addition line of a color signal for luminance signal separation of YC separation is controlled by a color killer detection output signal, mis-addition of a luminance signal component in a chrominance sub-carrier band to an input video signal without a burst reference signal is avoided. Thus, the picture quality to a black-and-white video signal and a special video signal is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to video signal processing for television receivers, etc.)
，Especially the brightness signal! The present invention also relates to a yc separation circuit suitable for separating color signals C.

[Conventional technology]

As for the conventional technology, "Television Technology" October 1988 special edition TV TV Prosecution Technical Book (Jf & Child Technology Issue 7)
1 (a)) The configuration shown in the wideband comb filter circuit of the Victor GIGA series AV-11290 and AV-H320 on page 69 of J was common. An example of use is shown in FIG.

In Figure 4, 1 is a delay circuit, 2 is a bread-pass filter (BPF), 4 is a subtracter, 5 is a 1/2 times circuit, 6 is an adder, and 10 is a 1H delay line. Signal S. When inputting ft-jIA next, pandobus filter 2
If the signal S2 that has passed through has a perfect correlation with the signal S5, which was 82 1H before (1H indicates one horizontal scanning period), the color signal will have a phase inversion every 1H. Therefore, the color signal amplitude is twice as large as the output 110 F3 of the subtracter 4.
a, multiply it by 172, adder 6, and add S
1, only the luminance signal component can be extracted in s4 and only the color signal component can be extracted in S5.

However, if a black and white video signal without a burst reference signal is input to So, S2 and 85 (I II previous 8
2), if there is a perfect correlation, no output signal will appear in S4. Ss is zero) 84 has S1
(Delayed version of So) is output 7/1, but
If S2 and SS are not correlated, s4
When an output signal appears on , and when S, multiplied by 1/2 is added to S1, the brightness signal S6, which should not be affected by it, is damaged by S5. CGD111 shown
The basic operation is exactly the same with a nine YC separation circuit using a delay line, but in this case, especially when a black and white video signal without a burst reference signal is input, the color subcarrier flo obtained from the video/chroma YC8 is Since the rerun state becomes unstable, the delay amount of the CCDIH delay line 3 is also unstable. A much larger signal is output to S4, so in the conventional method, Ss is multiplied by 172. S6 obtained by adding to 81 has a large influence as a result of the fluctuation of the color subcarrier tsc being superimposed on the luminance signal.

[Problem to be solved by the invention]

Although the above-mentioned conventional technology takes into consideration the case where a monochrome video signal without a burst reference signal is input, there is a problem in that the brightness signal is affected on the operation of the circuit. The object of the present invention is to realize a YC separation circuit that performs the same YC separation operation as conventional for input signals having a burst reference signal and does not affect the luminance signal for input signals without a burst reference signal.

[Means to solve the problem]

In order to achieve the above object, the present invention uses a video/chroma YC color killer detection output signal to control a switch provided on a color signal addition line for luminance signal separation in a YC separation circuit. This is what I did.

[Effect]

Video signal without burst reference signal is video/chroma YC
If the input signal is input to
In order to control the switch installed on the chrominance signal addition line for luminance signal separation in c-separation to produce a color killer detection output signal, the luminance signal component within the chrominance subcarrier band is will not be added incorrectly.

〔Example〕

Embodiments of the present invention will be explained below with reference to FIGS. 1, 2, and 3. FIG. 1 is a block diagram showing the basic configuration of an embodiment of the present invention, and FIG. A waveform diagram showing the signal status in Figure 1,
Figure 3 is a circuit diagram showing a specific example of the main parts shown in Figure 1;
It is.

In Figure @1, when the normal color video signal SQ is input, no signal is output to the color killer detection output GK in the video/chroma YC8, so the switch SW in the switch circuit 7 is in the ON state. Te>,! ) SS
and S5/ operate as a conventional YC separation circuit in a short-circuited state, and when So is a black and white video signal, there is no burst reference signal, so the color killer circuit in V/C/J/YCB operates and is cut off. - A signal is output to the killer detection output CK, and the switch SW is in the 01'F state (F) Ss and S
5/ is in the open state and operates to prevent the luminance signal near the color subcarrier from being regarded as a color signal and being erroneously added to the luminance signal. Figure 2 shows the case where a monochrome video signal is input to Figure 1. In the signal waveform of each part when the luminance signal component near the color subcarrier output to Ss is
', and in S4, So is delayed I1iI1
, and the delayed luminance signal S1 is output as is. Also, if a normal color video signal is input to 80 after that, the burst reference signal and color signal are input to video/chroma YC8, Stop the operation of the color killer circuit, turn on the switch SW, and! 3s − s5/
Short the line and normal! Figure 3 shows a specific example of the switch circuit 7 shown in Figure 1. (&) uses an analog switch for the switch SW, (b). (C) uses a transistor switch.●The contact opens and closes depending on the presence or absence of the color killer detection output CK.

According to this embodiment, when a monochrome video signal without a burst reference signal is input, it is effective to prevent deterioration of the luminance signal due to the luminance signal component in the color subcarrier, which was affected by the conventional YC separation circuit. .

〔Effect of the invention〕

According to the present invention, compared to the conventional XC component lIm circuit, in the case of a monochrome video signal without a burst reference signal in the input video signal, the luminance of the uncorrelated part in the color subcarrier band, which has an influence on the circuit operation. Since it is possible to avoid adding a certain part of the signal, it is effective in improving the image quality of black and white video signals and special video signals.Also, a simple switch circuit can be added without impairing the performance of the conventional YC separation circuit. It can be easily achieved by just

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
5 is a specific circuit diagram of the switch circuit shown in FIG. 1, FIG. 4 is a block diagram of a conventional YC separation circuit, and FIG. YC
The block diagram of the separation circuit is ◎ 1... slow [11. 2...Band pass filter,
3...CCDIH delay line, 4...subtractor, 5...
1/2 amplifier, 6...adder, 7...switch circuit, 8...video/chroma! C19...5 multiplier,
10...Glass 1H delay line●

Claims (1)

[Claims] 1. Consists of a video signal 1H delay circuit (where 1H represents one horizontal scanning period) and an adder/subtractor, which converts the input video signal to the color signal C.
A YC separation circuit comprising: a C separation circuit that separates a C separation circuit; and an addition circuit that adds a color signal C separated in the C separation circuit to the input video signal to obtain a luminance signal Y; A switch is provided on an addition line that supplies the color signal C separated in the C separation circuit for addition, and a detection means detects whether or not the burst reference signal is included in the input video signal. The YC separation circuit is characterized in that when it is detected that the color signal C separated by the C separation circuit is not added to the input video signal by turning off the switch.