JPS6393290A - Color video signal processing circuit - Google Patents

Abstract

PURPOSE:To contrive to minimize the dot interference of a carrier chrominance signal with a luminance signal by providing duplicated detection means detecting the line correlation of two types of color difference signals, an addition means and a level attenuation means, and selectively attenuating a level based on an addition signal outputted from the addition means so that said level befits the line correlation. CONSTITUTION:Two types of color difference signals R-Y and B-Y are supplied not only to a matrix circuit 4a but also to a detection circuit 21. The adder 26 adds both absolute value signals based on the color difference signals R-Y and B-Y and outputs the added one to a comparator 28. It outputs such a signal that comes to a high level if the level of the addition signal is larger than a reference value: otherwise, comes to a low level, and outputs said signal to an output terminal 31. Thus the line correlation can be surely detected. The level of the frequency component of a chrominance subcarrier included in the luminance signal adapted to the detected line correlation is selectively attenuated so that dot interference to be applied to the luminance signal caused by carrier chrominance signal can be prevented at the output side of an Y/C separator.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color video signal processing circuit, and particularly to a color video signal processing circuit that separates a luminance signal and a carrier color signal from a frequency interleaving color video signal, and separates the carrier color signal from the color video signal. The present invention relates to a color video signal processing circuit that demodulates and generates color difference signals.

BACKGROUND OF THE INVENTION FIG. 4 shows a block diagram of an example of a conventional color video signal processing circuit. In the figure, a frequency interleaving color video signal of the NTSC system, for example, which enters an input terminal 1 is separated into a carrier color signal and a luminance signal by a Y/C division n1 circuit 2a. This Y/C separation circuit 2a
The output carrier color signal is supplied to the color signal processing circuit 3a.

The color signal processing circuit 3a includes, for example, a bandpass filter for the carrier color signal G-wave, a color signal demodulation circuit and a necessary burst gate circuit, an automatic color saturation control circuit (ΔCC circuit),
Killer circuit, subcarrier regeneration circuit for color signal demodulation (generally composed of phase-locked loop (PLL))? 7 is included. This color signal processing circuit 3
a demodulates the input carrier color signal and outputs 17 color difference signals (for example, R-Y and B-Y) to the matrix circuit 4a.

On the other hand, the output luminance signal Y of the Y/C separation circuit 2a is transmitted to a luminance signal processing circuit 5 which includes a horizontal or vertical peaking correction circuit, a contrast control circuit, etc.
The signal is supplied to the matrix circuit 4a via a. The matrix circuit 4a generates three primary color signals R, G, and B based on the incoming color difference signal and luminance signal Y, and outputs them to the CRT 6.

The above is the configuration of a color video signal processing circuit using conventional analog processing. On the other hand, a conventional color video signal processing circuit using digital processing has a configuration in which an A/D converter 7 and a D/A converter 8 are added, respectively, as shown in FIG.

Here, the Y/C separation circuit 2b, the color signal processing circuit 3b, the matrix circuit 4b, and the luminance signal processing circuit 5b are digitized versions of the circuits shown in FIG. 4.

In FIG. 5, a color video signal coming from an input terminal 1 is converted into an analog/digital signal by an A/D converter 7, and then supplied to a Y/C separation circuit 2b. After that, the same signal processing as shown in FIG. 4 is performed digitally, and then the digital three primary color signals R,
G and B are digital-to-analog converted by the D/A'fL converter 8 and supplied to the CRT 6.

By the way, as the Y/C separation circuit 2a or 2b, a line correlation type separation circuit (so-called comb filter) using one horizontal scanning period (11-()fl extension or 2-day delay line) is conventionally used. 6 shows a block diagram of an example of the Y/C separation circuits 2a and 2b.Here,
The color video signal that enters the input terminal 9 is delayed by 1H at the 11" delay line 10. The subtracter 11 subtracts the color video signal of the current line and the color video signal of the previous line outputted through the 1-to-1 delay line 10, and as is well known, fH/2 (however, fH is A signal with a frequency that is an odd multiple of the horizontal scanning frequency) is converted into a P wave, and is passed through a bandpass filter (B
A carrier color signal is output to the output terminal 13 via the PF) 12.

On the other hand, the adder 14 adds the color video signal of the current line and the color video signal of the previous line by 1 (G5),
As is well known, luminance signals with frequencies that are even multiples of fH/2 are extracted. Adder 15 adds the output luminance signal of adder 14 and the luminance signal passed through low-pass filter 16 and outputs the result to output terminal 17 .

Incidentally, there are generally two types of color difference signals demodulated by the color signal processing circuits 3a and 3b: RY and BY. To this, J: Matrix circuits 4a, 4b
Then, the color difference signal G-Y is generated, and these three types of color difference signals and the luminance signal Y are added to generate the three primary color signals QR.
, G, and B are obtained. The color difference signals R-Y and B-Y are obtained by setting demodulation axes for producing the color difference signals R-Y and B-Y, which are different from each other by 90 degrees, in the color signal processing circuits 3a and 3b. .In this case, the color difference signal is
Not limited to R-Y and B-Y, for example, I.

The Q-axis may be set to 1, and the Q signal may be set to 19.

Problems to be Solved by the Invention However, in the conventional color video signal processing circuit, Y/C separation is simply performed by the Y/C separation circuits 2a and 2b constituted by comb filters. There is a problem in that it is impossible to avoid cross color interference from the signal to the carrier color signal and dot interference from the carrier color signal to the luminance signal. Among these, disturbances 1 to 3 have a particularly remarkable effect on image quality, and are a major cause of image quality deterioration.

The modes in which the dot interference occurs are, firstly, when the hue of the carrier color signal suddenly changes in the vertical direction, and secondly, when the hue of the carrier color signal suddenly changes in the horizontal direction.

The former generation mode always occurs in a Y/C separation circuit using a horizontal delay line, and conventionally, a 1-wrap is used to attenuate the level of the color u1 carrier frequency component of, for example, 3.58 MH2 on the luminance signal output side. J to insert the circuit:
This reduced dot interference. However, in this case, there is a problem in that the horizontal resolution particularly around the frequency 3.58M1-IZ deteriorates.

On the other hand, v! The 1 person generation mode occurs because the cutoff frequency of the LPF 16 is high, and although it can be improved by lowering the cutoff frequency sufficiently, the resolution in diagonal directions on the screen deteriorates.

Therefore, the present invention provides color al+m in a luminance signal adapted to line correlation based on level changes of two types of color difference signals.
It is an object of the present invention to provide a color video signal processing circuit that solves the above problems by selectively attenuating the level of transmission frequency components.

Means for Solving the Problems The color video signal processing circuit according to the present invention includes two systems of detection means for respectively detecting the line correlation of two types of color difference signals, addition means, and level attenuation means. ing.

Two types of color difference signals separated and demodulated from a frequency interleaving type color video signal through a Y/C branching/shunting circuit constituted by a working comb filter are respectively input to the two detection means described above. Ru. The two systems of detection means are:
In order to detect line correlation, an absolute value signal indicating the absolute level difference between the color difference signals of the same scale of the current line and its twin lines is generated and output for each of the two types of color difference signals. . The adding means adds the absolute value signals corresponding to the two types of color difference signals, respectively, and outputs the summed signal to the level attenuation means.

Based on the output additive signal of this addition means, level attenuation adapted to line correlation is selectively applied to the color subcarrier frequency component included in the luminance signal separated from the color video signal by the Y/C separation circuit. It is done. That is, filters are selectively inserted.

Embodiment The present invention attempts to remove the color n1m transmission frequency component from a luminance signal separated by a Y/C separation circuit using a horizontal delay line without deteriorating the image quality, especially resolution. This objective is achieved in an auxiliary manner by adding a circuit or the like without changing the existing Y/C separation circuit or the like.

FIG. 1 shows a block diagram of an embodiment of a color video signal processing circuit according to the present invention. In the figure, the same components as in FIGS. 4 and 5 are denoted by the same reference numerals, and their explanations will be omitted. This embodiment is characterized in that a detection circuit 21 and an adaptive processing circuit 22 are provided in addition to the conventional color video signal processing circuit shown in FIG. 4.

Here, since the color difference signals R-Y and B-Y of the two scales are obtained in the color signal processing circuit 3a based on demodulation axes that have phases different from each other by approximately 90 degrees, detection of line correlation is performed on the color difference signals. A change in a vector will always be obtained approximately based on its magnitude (level).

The detection circuit 21 detects the line correlation of the color difference signal υ, that is,
A detection signal corresponding to the change in hue between each line is output to the adaptive processing circuit 22. The adaptive processing circuit 22 performs optimal measurement signal processing as described later in accordance with the input detection signal.

By the way, for example, if the hue changes greatly between the nth (where n is a natural number) line and the (n+1)th line, or the nth line has a certain hue and the (n+1)th line When the line is a so-called achromatic color in which no color subcarrier exists, signal dot interference multiplied by ti occurs.

As mentioned above, the above-mentioned dot interference is 3.58M to the embryonic degree Shintan.
This can be reduced by applying a trap that reduces the level of the color subcarrier frequency component of H2, so in this embodiment, the detection circuit 21 detects that there is no line correlation due to sudden changes in hue between lines, etc. Only when a detection signal is generated, the adaptive processing circuit 22 adds 3.58M to the luminance signal.
Make sure the H2 trap is turned on.

In this way, if the hue hardly changes between lines or if the change is gradual, 3.58
Since the MHZ trap is never turned on, it is possible to prevent the horizontal resolution of most parts of the screen from deteriorating.

Next, referring to FIG. 1, two types of color difference signals R-Y and B-Y from the color signal processing circuit 3a are respectively supplied to the matrix circuit 4a, and the detection circuit 2
1. The detection circuit 21, as shown in FIG.
1H delay line 23a.

23b, bell reducers 24a, 24b, absolute value circuit 25a.

Line correlation detection circuit 27 consisting of 25b and adder 26
, a comparator 28 and a reference value generation circuit 29.

The color difference signal RY entering the input terminal 30a is subtracted by Z2
4a and 11” delay n 23 a
is delayed by one day and supplied to the sieve reducer 24a.

The subtracter 24a subtracts the color difference signals of the current line and the line from one day ago, and outputs a signal corresponding to the level difference between the two signals to the absolute value circuit 25a. Here, if the hue does not change between the current line and the line 1H before, that is, if there is a line correlation between the two lines, the output subtraction signal level of the subtraction 324a is zero, but on the other hand, If there is no line correlation between the two lines, an output reduction signal having a positive or negative level corresponding to the change in hue is obtained.

The absolute value circuit 25a generates an absolute value signal having a level corresponding to the absolute value level of the output reduction signal of the attenuator 24a, and outputs it to the adder 26. This absolute value represents the weakness of the line correlation.

Same as above, 1H delay! ! 1123b, each reduction 211
b and the absolute value circuit 25b generate an absolute value signal based on the color difference signal B-Y input to the input terminal 30b, and output it to the adder 26.

The adder 26 adds both absolute value signals based on the color difference signals R-Y and B-Y, respectively, and sends the added signal to the comparator 28.
Output to.

The comparator 28 compares the levels of the output addition signal of the adder 26 and the output signal of the reference value generation circuit 29.

Here, the reference value is set at the design and manufacturing stage so that the deterioration of the resolution is practically minimized.

Here, the comparator 28 generates a detection signal that becomes, for example, a high level when the added signal level is higher than the reference value, and becomes a low level when the added signal level is smaller than the reference value, and outputs a detection signal to the output terminal 31. Output to. Zunawachi,
The detection signal becomes high level when the line correlation is weak, and becomes low level when the line correlation is strong.

By the way, in the detection circuit 21, when attempting to detect line correlation by detecting a level change in only one of the two color difference signals R-Y and B-Y, the following method is used. Defects occur. That is,
In the above case, since the level change of only one of the two types of color difference signals is detected, only the line correlation projected on the R-Y demodulation axis of the color difference signal can be extracted, and therefore, Changes in hue and saturation are color difference signals R-Y
If it hardly occurs in the color difference signal B-Y, but it occurs greatly in the color difference signal B-Y, it is determined that there is a line correlation even though there is no line correlation, and the circuit of the present invention does not operate normally. It becomes impossible to sufficiently extract changes in hue and saturation that occur in the color difference signals.

In contrast, according to this embodiment, two types of color difference signals R-
Since the line correlation is detected based on both the Y and BY levels, even if only one color difference signal level changes, the detection circuit 21 will detect the change. Therefore, according to this embodiment, line correlation can be detected reliably.

FIG. 3 shows a circuit diagram of one embodiment of the adaptive processing circuit 22. As shown in FIG. In the figure, the detection signal input terminal 32 is grounded via resistors R1 and R2. A connection point between the resistors R1 and R2 is connected to the bases of NPN1 to transistor T.

The emitter of the transistor T is grounded, while its collector is connected to a trap element 3 consisting of a capacitor C and a coil.
3 to a connection point A between a luminance signal input terminal 34 and a luminance signal output terminal 35. Wrap element 3 to above 1
3 has a resonant frequency of 3.58 MH2.

In the above configuration, during the period when the detection signal is at a high level, the transistor T is turned on, and therefore, the connection point Δ is grounded through the trap element 33 and between the collector and emitter of the transistor T.

Thereby, the adaptive processing circuit 22 operates as the trap circuit, and the 3.58 MH2 color subcarrier frequency component in the output luminance signal of the luminance signal processing circuit 5a that enters the input terminal 34 is trapped. Luminance signals of other frequency components are outputted to the matrix circuit 4a via the output terminal 35.

On the other hand, during the period when the detection signal is at a low level, the transistor T is off, so the luminance signal that enters the input terminal 34 is not trapped as described above, and is directly passed through the output terminal 35 to the matrix circuit 4a. Output to.

In this way, when the line correlation is weak, such as when the hue changes greatly between lines, trapping is performed on the luminance signal, whereas when the line correlation is strong, such as when the hue hardly changes, trapping is performed. , no trap is performed on the county signal.

The above explanation is about the case where the present invention is applied to an analog color video signal processing circuit as shown in FIG.
Of course, the present invention can also be applied to a digital circuit as shown in the figure. When the present invention is applied to a digital circuit, there are the following advantages.

(1) The one-day delay lines 23a and 23b in the detection circuit 21 can be easily obtained.

■ Subtractors 24a and 24b in the detection circuit 21.

Various arithmetic circuits such as absolute value circuits 25a and 25b can be easily obtained.

■ The processing filter in the adaptive processing circuit 22 (i.e.
The trap element 33) can be made freely, and the processing filter can be easily switched on and off at high speed according to the detection signal.

It should be noted that the output detection signal of the detection circuit 21 is not limited to one that changes in a binary manner as in this embodiment, but can be generated in many different ways depending on the type of processing mode of the adaptive processing circuit 22, for example. The configuration may be such that optimal luminance signal processing is performed by generating the luminance signal.

Further, the adaptive processing circuit 22 does not use a digital detection signal, but a detection signal whose level changes in an analog manner depending on the level difference of the color difference signal between the current line and the line 1H ago, for example. The color subcarrier frequency component in the luminance signal may be attenuated in level proportionally. In this case, for example, the detection circuit 21 detects the line correlation detection value (i.e., 1i of the output detection signal of the addition 2S26).
a) is directly output to the adaptive processing circuit 22 as a detection signal without passing through each comparison 28.

Although the detection circuit 21 detects the line correlation based on the color difference signal, it is also possible to detect the line correlation based on the luminance signal. However, the luminance signal is subjected to processing such as horizontal and vertical peaking correction and contrast control by the luminance signal processing circuit 5a, and is performed according to the user's intention, so the luminance signal is unstable. Therefore, it is not preferable to detect line correlation based on the luminance signal.

Note that the signal processed by the circuit of the present invention is not limited to a color video signal of the NTSC system, but may be a color video signal of the PAL system. In addition, the adaptive processing circuit 2
Of course, the configuration 2 is not limited to a configuration in which the trap circuit is turned on and off, but may be any configuration that attenuates the level of the color a1 carrier frequency component in the luminance signal according to the detection signal. Furthermore, a 2-day delay line may be used instead of the 11'' delay lines 23a, 23b.

In addition, the signals for line correlation detection are two types of color difference signals @R.
-Y and B-Y, for example, I,
Of course, the I signal and Q signal using the Q demodulation method may also be used.

Effects of the Invention As described above, according to the present invention, line correlation is detected based on level changes of two types of color difference signals, so even if only one color difference signal level changes, line correlation can be detected reliably. Correlation can be detected, and therefore, if either of the two types of color difference signal levels changes, it is determined that there is no line correlation, and the color subcarrier frequency in the luminance signal adapts to the line correlation. Since the level attenuation operation of the component can be performed accurately, and the level attenuation of the color z1 carrier frequency component in the luminance signal is selectively performed in accordance with the line correlation detected in this way, Y/C separation is possible. Even if the Y/C separation function of the circuit is insufficient, dot interference with the luminance signal due to the carrier color signal can be prevented on the output side of the Y/C separation circuit, so that the Y/C and M components can be prevented. For example, Y/C built in a large-scale integrated circuit (LSI)
Even if the separation circuit has to be improved to compensate for the insufficiency of its Y/C separation function, the present invention can be applied to improve the performance and thus overcome the deficiencies in the existing Y/C separation function. It has the advantage of being able to produce an image with good resolution and reduced dot interference by simply adding a simple configuration to a sufficient Y/C separation circuit.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram showing one embodiment of a color video signal processing circuit according to the present invention, and FIGS.
A block system diagram and a circuit system diagram showing an embodiment of the essential parts in the illustrated block system; FIGS. 4 and 5 are block system diagrams showing an example of a conventional color video signal processing circuit and another example, respectively; FIG. 6 is a block diagram showing an example of a conventional Y/C separation circuit. DESCRIPTION OF SYMBOLS 1... Color video signal input terminal, 2a... Y/C separation circuit, 3a... Color signal processing circuit, 4a... Matrix circuit, 5a... Luminance signal processing circuit, 6... CR
T, 21...detection circuit, 22...adaptive processing circuit,
23a. 23b-1Hfi wire extension, 24a, 24b--subtractor,
25a, 25b... Absolute value circuit, 26... Adder,
27... Line correlation detection circuit, 28... Comparator, 2
9... Reference value generation circuit, 30Q, 30b... Color difference signal input terminal, 31... Detection signal output terminal, 32...
Detection signal input terminal, 33... Trap element, 34...
・Brightness signal input terminal, 35...r++ degree signal output terminal, C...capacitor, L...coil, R+, R2
...Resistance, ■...1~Ran resistor. Figure 1/Figure 2 Figure 3 Figure 4 Figure 5 Figure 6rXJ

Claims (1)

[Claims] A Y/C separation circuit configured with a comb filter separates a luminance signal and a carrier color signal from a frequency interleaving color video signal, and demodulates the carrier color signal to generate two types of color difference signals. In the color video signal processing circuit, an absolute value signal indicating the absolute value of the level difference between the color difference signals of the same type on the current line and the previous line is generated and outputted in correspondence with the two types of color difference signals. system detection means; addition means for respectively adding the absolute value signals corresponding to the two types of color difference signals; and means for selectively inserting a filter having a frequency response adapted to line correlation.