JPS63254886A - Color video signal processing circuit - Google Patents

Abstract

PURPOSE:To obtain a good resolution in a low cost delay circuit by delaying a carrier chrominance signal by one horizontal line period, adding and detecting an input and an output and controlling the quantity of the attenuation of a chrominance sub-carrier frequency component thereby. CONSTITUTION:A color video signal inputted to an input terminal 1 is separated in a Y/C saparating circuit 2, the carrier chrominance signal is demodulated in a chrominance signal processing circuit 3 and fed to a matrix circuit 4. A luminance signal is fed to the circuit 4 through a luminance signal processing circuit 5 and an adaptive type processing circuit 8, three primary color signals are formed herein and supplied to a CRT 6. The carrier chrominance signal is supplied to the control terminal 8c of the circuit 8 through a detecting circuit 7a. In the circuit 7a, the carrier chrominance signal is delayed by one horizontal line in a 1H delay circuit 9 and added to the signal of a next 1H in an adder 10. This output is detected in an amplitude detecting circuit 11 to obtain a correlation detection value, this is compared with a signal from a reference value generating circuit 14 in a comparator 13 and fed to the circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a color video signal processing circuit, and in particular, it separates a luminance signal and a carrier color signal from a frequency interleaving color video signal, and The present invention relates to a color video signal processing circuit that demodulates signals and generates color difference signals.

(Conventional example) In general, in conventional color video signal processing circuits, if Y/C separation is only performed by a Y/C separation circuit configured with a comb filter, cross color interference from the luminance signal to the carrier color signal occurs. However, there is a problem in that it is not possible to avoid dot interference from the carrier chrominance signal to the luminance signal. Among these, dot interference has a particularly remarkable effect on image quality, and is 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 consisting of a so-called comb filter using one horizontal delay circuit. Conventionally, for example, a 3.58 MI
- (Dot interference was reduced by inserting a trap circuit to attenuate the level of the color subcarrier frequency component of Z. However, in this case, the horizontal resolution especially around the frequency of 3.58 MH2 deteriorated. There is a problem with this.

On the other hand, the latter mode of occurrence is caused by the high cutoff frequency of the low-pass filter in the Y/C separation circuit, and can be improved by lowering the cutoff frequency sufficiently, but the resolution in diagonal directions on the screen will deteriorate.

Therefore, in order to solve the above problems, the applicant proposed two
The application is filed for a color video signal processing circuit that solves the above problems by selectively attenuating the level of color subcarrier frequency components in a luminance signal that adapts to line correlation based on level changes of different color difference signals. (Special application 1986-
No. 239822).

That is, the color subcarrier frequency component in the luminance signal separated by the Y/C separation circuit using one horizontal delay circuit is removed without deteriorating the image quality, especially the resolution, and the existing Y/C The objective is achieved in an auxiliary manner by adding a circuit or the like without changing the separation circuit or the like.

FIG. 4 shows a block system diagram of the above-mentioned conventional color video signal processing circuit. In the figure, a frequency interleaving color video signal, such as the NTSC system, which enters an input terminal 1 is separated into a carrier color signal and a luminance signal by a Y/C separation circuit 2, respectively. The output carrier color signal of this Y/C separation circuit 2 is supplied to a color signal processing circuit 3.

The color signal processing circuit 3 includes, for example, a bandpass filter for carrier color signal filtering, a color signal demodulation circuit and a necessary burst gate circuit, an automatic color saturation control circuit (ACC circuit), a killer circuit, and a subcarrier for color signal demodulation. It includes a reproduction circuit (generally composed of a phase-locked loop (PLL)) and the like. The color signal processing circuit 3 outputs color difference signals @ (for example, R-Y and B-Y) obtained by demodulating the input carrier signal □ to the matrix circuit 4.

On the other hand, the output luminance signal Y of the Y/C separation circuit 2 is supplied to the matrix circuit 4 via a luminance signal processing circuit 5 which includes, for example, a horizontal or vertical peaking correction circuit, a contrast control circuit, and the like. Matrix circuit 4
are the three primary color signals R, G based on the incoming color difference signal and the luminance signal Y.

B is generated and output to the CRT6.

Further, the color difference signal R- of two types from the color signal processing circuit 3 is
Y and BY are respectively supplied to the matrix circuit 4 and the detection circuit 7d. The detection circuit 7d is
As shown in FIG. 5, one horizontal line (H) delay circuit 16.
．． 17, a subtracter 18, a line correlation detection circuit 23 consisting of an absolute value circuit 20, 21, and an adder 22, a comparator 24, and a reference value generation circuit 25.

The color difference signal R-Y that enters the input terminal 7e is sent to the subtracter 18
The subtracter 18 is supplied directly to the subtracter 18 via the 1Hff delay circuit 16 and delayed by one horizontal line (1H). Subtraction is performed and a signal corresponding to the level difference between the two signals is output to the absolute value circuit 20.Here, if the hue does not change between the current line and the line 1H before, that is, there is no line between the two lines. If there is a correlation, the output subtraction signal level of the subtractor 18 is zero, but on the other hand, if there is no line correlation between the two lines, the level will be a positive or negative value corresponding to the change in hue. An output subtraction signal is obtained.

Absolute value circuit 20 generates an absolute value signal having a level corresponding to the absolute value level of the output subtraction signal of subtracter 18 and outputs it to adder 22 . This absolute value represents the strength of line correlation.

Same as above, one day delay circuit 17. The subtracter 19 and the absolute value circuit 21 input the input terminal 7 [the incoming color difference signal 8
An absolute value signal based on -Y is generated and output to the adder 22.

The adder 22 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 24.
Output to.

The comparator 24 compares the levels of the output luminance signal of the adder 22 and the output signal of the reference value generation circuit 25.

FIG. 3 shows a circuit diagram of an example of the adaptive processing circuit 8. As shown in FIG. In the figure, the detection signal input terminal 8C is grounded via resistors R1 and R2. The connection point of these resistors R1 and R2 is N
Connected to the base of PN transistor T. The emitter of the transistor T is grounded, while its collector is connected via a trap circuit 15 comprising a capacitor C and a coil to a connection point A between a luminance signal input terminal 8a and a luminance signal output terminal 8b. The trap circuit 15 has three
．． 543M)-12.

In the above configuration, during the period when the detection signal is at a high level, the transistor T is turned on, so that the connection point A is grounded through the trap circuit 15 and between the collector and emitter of the transistor T.

As a result, the adaptive processing circuit 8 operates as the trap circuit, and the 3.58 MHz color subcarrier frequency component in the output luminance signal of the luminance signal processing circuit 5 that enters the input terminal 8a is trapped. Luminance signals of other frequency components are sent to the matrix circuit 4 via the output terminal 8b.
Output to.

On the other hand, during the period when the detection signal is at a low level, the transistor T is turned off, so that the luminance signal entering the input terminal 8a is not trapped as described above, and is directly passed through the output terminal 8b to the matrix circuit 4. 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 trapping is performed on the luminance signal.

(Problems to be Solved by the Invention) As described above, the conventional color video signal processing circuit has 1H[
Two extension circuits are required, and the frequency band ranges from DC to
A wide range of characteristics such as about 1.5M l-IZ is required.

In addition, since the correlation is obtained by adding the two line correlation values in the two demodulation axis directions of the two color difference signals demodulated from the carrier color signal, for example, the R-Y signal and the B-Y signal If the line correlation detection sensitivity in the direction is 1, the correlation value for the intermediate phase between the two is ff-1,41.

FIG. 6 is a diagram showing the detection sensitivity with respect to hue, and the detection sensitivity IAI is expressed as 15 in θl + l cos θ1. However, although it is desirable that the line correlation detection sensitivity for all hues be constant, in reality it is not circular as shown in Figure 6 and is not constant, and it is not possible to perform optimal processing on the luminance signal for all hue changes. However, there was a problem in that the dot interference could not be removed optimally.

(Means for Solving the Problems) In order to solve the above problems, the present invention aims to reduce the number of carrier color signals to one
One horizontal line delay circuit that delays the horizontal line period, an adder that adds the input signal and output signal of this one horizontal line delay circuit, an amplitude detection circuit that detects the amplitude of the output signal of this adder, and The present invention provides a color video signal processing circuit characterized by comprising a processing circuit that controls attenuation of a color subcarrier frequency component included in a luminance signal based on an output signal of a detection circuit.

(Embodiment) FIG. 1 shows a block system 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. Attach and explain.

In the figure, the color video signal of the frequency interleaving system of the NTSC system, for example, which enters the input terminal 1 is Y/C.
A separation circuit 2 separates the signal into a carrier color signal and a luminance signal. The output carrier color signal of this Y/C separation circuit 2 is supplied to a color signal processing circuit 3.

The color signal processing circuit 3 demodulates the carrier color signal and sends the color difference signals (for example, R-Y, B-Y) to the matrix circuit 3.
is supplied to one input terminal of the

On the other hand, the output luminance signal Y of the Y/C separation circuit 2 is supplied to the other input terminal of the matrix learning circuit 4 via the luminance signal processing circuit 5 and the adaptive processing circuit 8, respectively.
This matrix circuit 4 generates three primary color signals R, G, and B from the supplied color difference signals and luminance signals, and outputs them to the CRT.
Supply to 6.

Further, the color signal carried by the Y/C separation circuit 2 is transmitted to the detection circuit 7a.
The signal is supplied to the control terminal 8C of the adaptive processing circuit 8 via the control terminal 8C. As shown in FIG. 2, the detection circuit 7a includes one horizontal line (H) delay circuit 9. Adder 10. l
The carrier color signal supplied from the i-width detection circuit 11 to the component circuit 7a is delayed by one horizontal line in the 1HilW delay circuit 9, and this signal and the next 1H carrier color signal are transferred to the accelerator 10.
is added by Since the output signal of the adder 10 has the opposite phase of the carrier color signals included in the adjacent 1H lines, the difference between the carrier color signals of the two adjacent 1H lines can be obtained. For example, when the respective color difference signals between adjacent one-day lines are equal, the output signal of the adder 10 is zero, and in this case, it can be said that there is a correlation.

On the other hand, if there is a change in hue between adjacent 1H lines and there is no correlation, the output signal of the adder 10 is the one corresponding to the change in hue.

The output signal of this adder 10 is subjected to amplitude detection in an amplitude detection circuit 11 using, for example, a diode.

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

Here, the comparator 13 generates a detection signal that becomes, for example, a high level when the added signal level is larger 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. Output to 7C. That is, the detection signal becomes high level when the line correlation is weak, and becomes low level when the line correlation is strong.

The output signal of the comparator 13 as described above is sent to the adaptive processing circuit 8.
As explained generally, during the period when the detection signal from the detection circuit 7a is at a high level, the transistor T is on, and therefore; Grounded. As a result, the adaptive processing circuit 8 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 5 entering the input terminal 8a is trapped. Luminance signals of other frequency components are output to the matrix circuit 4 via the output terminal 8b.

On the other hand, during the period when the detection signal is at a low level, the transistor T is turned off, so that the luminance signal entering the input terminal 8a is not trapped as described above, and is directly passed through the output terminal 8b to the matrix circuit 4. 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 trapping is performed on the luminance signal.

As described above, the present invention makes it possible to obtain a correlation detection signal that does not have a sensitivity difference due to a change in hue unlike the conventional technique by detecting a change in a carrier color signal that changes in response to a change in a color difference signal.

Note that the line correlation detection circuit 12 that constitutes the detection circuit 7a
It is also possible to supply the detection signal sent by the adaptive processing circuit 8 to the adaptive processing circuit 8 without going through the comparator 13 and process it.

However, in this case, the transistor T of the adaptive processing circuit 8 is
Rather than performing a switching operation, it may be configured to perform a linear operation corresponding to the level of the detection signal.

Further, although the above embodiment is a case in which the present invention is applied to an analog color video signal processing circuit, it goes without saying that the present invention can also be applied to a color video signal processing circuit using digital signal processing.

(Effects of the Invention) According to the present invention, since it is only necessary to detect the correlation of changes in the carrier color signal between adjacent 1H lines, it is sufficient that the frequency band of the 1H delay circuit can correspond to the band of the carrier color signal. An inexpensive glass delay circuit can be used instead of an expensive one such as COD, and only one delay circuit is required, which is advantageous in terms of cost.

Further, since the correlation of color signals is constant without changing depending on the hue, correct processing can be obtained in response to dot interference, so that good resolution can be obtained.

[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 diagram showing one embodiment of the main parts in the blocks in the figure, FIG. 4 is a block system diagram of a conventional color video signal processing circuit, and FIG. 5 shows the main parts in the blocks in FIG. 4. FIG. 6 is a block diagram for explaining FIG. 4. DESCRIPTION OF SYMBOLS 1... Color video signal input terminal, 2... Y/C separation circuit, 3... Color signal processing circuit, 4... Matrix circuit, 5... Luminance signal processing circuit, 6... CRT, 7
a...Detection circuit, 8...Adaptive processing circuit (processing circuit), 9...1 horizontal line (H) delay circuit, 10...
Adder, 11... Approximate width detection circuit, 12... Line correlation detection circuit, 13... Comparator, 14... Reference value generation circuit. ¥3 figure

Claims (1)

[Claims] In a color video signal processing circuit that separates a luminance signal and a carrier color signal from a frequency interleaving color video signal using a Y/C separation circuit configured with a comb filter, the carrier color signal is delayed by one horizontal line period. 1 horizontal line delay circuit, an adder that adds the input signal and output signal of this 1 horizontal line delay circuit, an amplitude detection circuit that amplitude detects the output signal of this adder, and an output signal of this amplitude detection circuit. A color video signal processing circuit comprising: a processing circuit that controls an attenuation amount of a color subcarrier frequency component included in the luminance signal based on the luminance signal.