KR960013563B1 - Circuit for separating the brightness signal or the chrominance signal - Google Patents

Abstract

a 1H delay means(1) delaying a composite image signal(Y+C) 1H; an auto gain control means(2) gain-controlling the image signal(Y+C) 1H-delayed from the delay means(1) automatically; a first adding means(3) outputting Y signal by adding the composite image signal(Y+C) and the 1H-delayed image signal; a first subtracter(4) outputting C signal by subtracting the composite image signal(Y+C) and the 1H-delayed image signal; a correlation detecting means(5) outputting a correlating pulse and a non-correlating pulse; a switching means(6); a broad band pass filter(7) passing C signal from the first subtracter(4) in the case of correlation and separating C signal from the composite signal(Y+C) in the case of non-correlation; a color carrier trap means(10); and a second adding means(12) improving the vertical resolution decrease and signal loss.

Description

Signal degradation compensation circuit of video signal separation circuit

1 is a block diagram illustrating a conventional video signal separation process.

2 is a waveform diagram for explaining the operation of the comb filter.

3 illustrates the operation of a correlation detector.

4 is a waveform diagram illustrating the operation of a switch and a bandpass filter.

(a) is an operation waveform diagram on the time axis,

(b) is a bandpass filter characteristic diagram on the frequency axis in uncorrelated state.

5 is a block diagram showing a luminance signal / color signal separation process of the present invention.

6 is a view showing a signal improvement process of the present invention.

* Explanation of symbols for main parts of the drawings

1: 1H delay unit 2: Automatic gain control unit

3: first adder 4: first subtractor

5: correlation detector 6: switch

7: bandpass filter 8: comb filter

10 color carrier trap 12 second adder

The present invention relates to a luminance (Y) / color (C) signal (hereinafter referred to as Y / C) separation circuit of the image signal, in particular to improve the degradation of the vertical resolution and signal loss of the Y signal generated during the Y / C separation A luminance signal / color signal separation circuit of a video signal.

The conventional Y / C separation circuit of the video signal includes a 1H delay unit 1 for delaying the composite video signal Y + C by 1H, as shown in FIG. 1, and a gain adjustment from the 1H delayed signal. An auto gain control unit 2, a first adder 3 for synthesizing the Y + C signal with a 1H delayed video signal and outputting a Y signal, and a video signal delayed by 1H from the Y + C signal. The first subtractor 4 subtracting the C signal and subtracting the 1H delayed signal with respect to the Y signal, and a high level if the similarity is higher than or equal to the reference level, and a low level if lower than or equal to the reference level, are compared. A correlation detector 5 for outputting, a switch 6 for switching the composite video signal Y + C at low level output from the correlation detector 5, and a composite video signal Y + C through the switch 6 It consists of bandpass filters (7) for separating the C signal at. The circuit including the bandpass filter 7 from the 1H delay unit 1 is commonly referred to as a comb filter.

However, in the prior art as described above, if the Y signal is somewhat lost during Y / C separation of the input signal, the vertical resolution is deteriorated to 1/2 by adding the n th H and the n + 1 th H.

Accordingly, the present invention is to solve the conventional problems as described above, and has an object of improving the degradation and signal loss of the vertical resolution generated when the Y / C separation of the video signal.

In order to achieve the above object, the present invention provides a 1H delay for delaying a complex video signal (Y + C) by 1H in a signal degradation compensation circuit of a video signal separation circuit from an input composite video signal (Y + C). Means (1); Automatic gain control means (2) for automatically gain control of the 1H delayed video signal (Y + C) from the delay means (1); A first addition signal (3) for adding the composite video signal (Y + C) and the 1H delayed video signal output from the automatic gain control means (2) to output a Y signal; First subtracting means (4) for subtracting the composite video signal (Y + C) and the 1H delayed video signal output from the automatic gain control means (2) to output a C signal; If the level difference between the delayed signal is detected by receiving only the 1H delayed signal output from the composite video signal (Y + C) and the automatic gain control means (2), a level difference of more than a predetermined level is uncorrelated. Correlation detecting means (5) for outputting a correlation pulse when a pulse or a level difference of a predetermined level or less occurs; When the C signal from the first subtracting means 4 and the composite video signal Y + C are received and the correlation pulse signal output from the correlation detecting means 5 is correlated, it is input from the first subtractor. Switch means (6) for selecting said C signal and selecting said composite video signal (Y + C) if there is no correlation; Passing the output signal C signal from the first subtractor 4 when there is correlation among the signals output from the switch means 6, and separating only the C signal of the composite video signal Y + C in case of uncorrelation A bandpass filter 7; Color carrier trap means (10) for receiving the vertical resolution degradation amount and the signal loss amount and the C signal from the first subtracting means (4) to remove only the C signal and output only the vertical resolution degradation amount and the signal loss amount; The vertical resolution deterioration and signal loss amount outputted from the color carrier trap 10 and the vertical resolution deterioration and signal Y lost signal are added to improve the vertical resolution deterioration and signal loss. A signal degradation compensating circuit of the video signal separating circuit composed of the second adding means 12 is characterized.

Hereinafter, described in detail with the accompanying drawings an embodiment of the present invention as follows.

2 is a waveform diagram for explaining the operation of the comb filter, the composite video signal Y + C, the 1H delayed signal Y + C, the Y signal output from the first adder 3, One subtractor 4 outputted C signal is shown.

3 is a waveform diagram showing the operation of the correlation detector 5, and the Y signal inside the correlation detector 5 and the signal output from the correlation detector 5 are shown.

In the Y signal inside the correlation detector 5, the A level of the nth H and the B level of the (n + 1) th H are shown, and in the Y signal delayed by 1H in the detector 5, (n-1) The A 'level of the first H and the A level of the nth H are shown. Therefore, the video signal Y + C and the 1H delayed signal are input to detect the level of the delayed signal centered only on the Y signal. Since the A level of the nth H of the Y signal and the A 'level of the (n-1) th H of the Y signal delayed by 1H cause a level difference (A = A') of a predetermined level or less, the correlation detector 5 generates a correlation pulse. Outputs a high level and detects the difference between the (n + 1) th H level of the Y signal and the A level of the nth Hth signal of the 1st delayed Y signal. Outputs

4 is a waveform diagram showing the operation of the bandpass filter (A) shows the output of the switch on the time axis, the output wave and the bandpass filter waveform of the correlation detector, (B) shows the input video signal of the bandpass filter The frequency distribution of (Y + C) and the output characteristics of the bandpass filter are shown.

5 is a block diagram showing a Y / C signal separation process according to the present invention, a 1H delay unit 1 for delaying a composite video signal Y + C by 1H, and an automatic gain control unit 2 for gain control from the 1H delayed signal. ), A first adder 3 for synthesizing the 1H delayed video signal output from the video signal Y + C and the automatic gain control unit 2 and outputting a Y signal, and the video signal Y + C A first subtractor 4 outputting the C signal by subtracting the video signal Y0 + C0 delayed from the AGC 2 and outputting the C signal, and a high level compared with the 1H delayed signal based on the Y signal; A correlation detector 5 for outputting a low level, a switch 6 for switching the video signal Y + C at the low level output from the correlation detector 5, and an image through the switch 6 Bandpass filter 7 separating the C signal from the signal Y + C, and the amount of vertical resolution degradation and the signal loss from the first subtractor 4 Color carrier trap (10) and the vertical resolution degradation from the first adder (3) to receive the C signal to remove the color carrier (color carrier) to output the vertical resolution degradation and signal loss amount to the second subtractor And a second adder 12 which receives the luminance signal from which the signal is lost and the vertical resolution degradation amount and the signal loss amount from the color carrier trap 10 and adds them.

FIG. 6 is a diagram illustrating a signal improvement process of FIG. 5 according to the present invention in more detail. The luminance signal output from the first adder 3 and the vertical resolution deterioration and the signal is lost, and from the first subtracter 40 are shown in FIG. A color signal including a vertical resolution degradation amount and a signal loss amount to be output, a color carrier trap 10 for removing only the color signal and transmitting only the vertical resolution degradation amount and a signal loss amount to the second adder 12, and a first adder And a second adder 12 that adds and outputs an input signal from (3) and an input signal from the color carrier trap 10, a switch 6, and a band pass filter 7.

First, as shown in FIG. 5, the composite video signal Y + C includes a first adder 3, a 1H delay unit 1, a first subtractor 4, a switch 6, and a correlation detector ( 5) is input at the same time. The composite video signal (Y + C) input to the 1H delay unit 1 is delayed by 1H and input to the automatic gain control unit 2 to automatically adjust the level. The first adder 3 and the first subtractor 4 are then adjusted. And output to the correlation detecting section 5. The output level at this time is the same as the level of the composite video signal Y + C.

In addition, the first adder 3, which receives the composite video signal Y + C and the video signal delayed by 1H from the 1H delay unit 1, adds the two video signals, and the correlation between the Y signal in the video signal and the C signal. The C signal is removed by the phase reversal characteristic of each H and only the Y signal is output.

Meanwhile, the first subtractor 4 receiving the composite video signal Y + C and the 1H delayed video signal subtracts the two video signals and outputs only the C signal from which the Y signal is removed by the characteristics of the video signal as described above. Let's do it. The operation of such a comb filter 8 is shown by a waveform as shown in FIG.

In addition, as shown in FIG. 3, the correlation detector 5 includes the n-th H level of the Y signal of the correlation detector 5 and the (n + 1) th A 'level of the Y signal among 1H delayed video signals. Since a level difference (A = A ') below this constant level is generated, a correlation pulse (high level) is output, but the Y signal of the n-th H level of the Y signal of the correlation detector 5 and the video signal delayed by 1H is output. Since the level difference occurs when the A level of the nth H exceeds a predetermined level, an uncorrelated pulse (low level) is output. That is, if the level difference between the delayed signal is input based on the Y signal only after receiving the composite video signal (Y + C) and the 1H delayed video signal, and the level difference occurs below a certain level, the correlation pulse (high level) and the level above the predetermined level are detected. If a difference occurs, an uncorrelated pulse (low pulse) is output.

The switch 6 receives the composite video signal Y + C and the signals of the first subtractor 4 and selects a signal under the control of the correlation pulse output from the correlation detector 5. If the pulse signal output from the correlation detector 5 is correlated, the switch 6 selects a signal input from the first subtractor 4, but if there is no correlation, the switch 16 is a composite video signal (Y + C). ) Is output to the bandpass filter (7).

The bandpass filter 7 separates the C signal by operating only the C signal as illustrated in FIG. 4, but in case of correlation, only the C signal of the composite video signal (Y + C) is frequency-related. Separate.

As shown in Fig. 6, the luminance signal output from the first adder 3 of the comb-shaped filter 8 is deteriorated in the vertical resolution and the signal is lost. In addition, the color signal output from the first subtractor 4 in the comb filter 8 includes a vertical resolution degradation amount and a signal loss amount.

The signal output from the first subtractor 4 is inputted to the color carrier trap 10 to remove the color signal, and only the vertical resolution degradation amount and the signal loss amount are input to the second adder 12. In the second adder, the signal deterioration (vertical resolution deterioration and signal loss) is improved by adding and outputting the input signal from the first adder 3 and the signal input from the color carrier trap 10. Therefore, the above operation is expressed by the following equation.

A is the Y signal component in the input composite video signal Y + C in the comb filter 8 B is the Y signal component in the 1H delayed composite video signal in the comb filter 8 K1 is the A, B order component of vertical resolution K2 is a signal deterioration component, and AB = K1 + K2.

Therefore, A = B + K1 + K2 is established and the equation in FIG. 6A is obtained by the first adder 3

A + B = 2B + K1 + K2 --------------------------- (1 set)

Becomes

In addition, the modification in FIG. 6B is performed by the first subtracter 4 and the color carrier trap 10.

A-B-K1 + K2 ----------------------------- (2ea)

Becomes

In Equation (2), K1 + K2 represents the amount of vertical resolution degradation and the signal loss.

The formula in FIG. 6C is converted by the second adder 12.

(C) = (A) + (B) = (Form 1) + (Form 2) = 2B + 2 (K1 + K2) = 2 (B + K1 + K2) = 2A (Form 3)

It can be seen that the Y signal in the original composite video signal Y + C is doubled and outputted at the output of the second adder 12, which is caused by the deterioration of the vertical resolution generated by the comb filter 8 and This means that signal loss is improved.

Claims (1)

A signal degradation compensation circuit of a video signal separation circuit from an input composite video signal (Y + C), comprising: 1H delay means (1) for delaying the composite video signal (Y + C) by 1H; Automatic gain control means (2) for automatically adjusting the 1H delayed video signal (Y + C) from the delay means (1); First adding means (3) for adding the composite video signal (Y + C) and the 1H delayed video signal output from the automatic gain control means (2) to output a Y signal; First subtracting means (4) for subtracting the composite video signal (Y + C) and the 1H delayed video signal output from the automatic gain control means (2) to output a C signal; When the level difference between the composite video signal Y + C and the 1H delayed signal output from the automatic gain control means 2 is detected and only the Y signal is detected and the level difference is higher than a predetermined level, uncorrelated. Correlation detecting means (5) for outputting a correlation pulse when a pulse or a level difference of a predetermined level or less occurs; When the C signal and the composite video signal (Y + C) are input from the first subtracting means (4), and the image and the pulse signal output from the correlation detecting means (5) are correlated, from the first subtraction formula Switch means (6) for selecting the input C signal and selecting the composite video signal (Y + C) if there is no correlation; If there is a correlation among the signals output from the switch means 6, the output signal C signal from the first subtractor 4 is passed, and if uncorrelated, only the C signal of the composite video signal Y + C is separated. A bandpass filter 7; Color carrier trap means (10) for receiving the vertical resolution degradation amount and the signal loss amount and the C signal from the first subtracting means (4) to remove only the C signal and output only the vertical resolution degradation amount and the signal loss amount; The vertical resolution deterioration and signal loss amount outputted from the color carrier trap 10 and the vertical resolution deterioration and the Y signal lost from the signal are added to improve the vertical resolution deterioration and signal loss. Signal degradation compensation circuit of the video signal separation circuit composed of the second addition means 12