JP2021182715A - Video processing device, and method for improving image quality - Google Patents

Abstract

To provide a video processing device capable of improving the sensory contrast.SOLUTION: A video processing device comprises: an image quality improvement part 101 that has a selector 103 which respectively receives a plurality of primary color signals S1 and a luminance signal S2 obtained from these primary color signals and selectively outputs any one of the received signals, and a two-dimensional low-pass filter 104 that respectively extracts low-frequency components in vertical and horizontal directions from an output signal S3 of the selector 103, and that performs processing for improving an image quality of a video signal by using an edge signal obtained by subtracting a low-frequency extraction signal S4 extracted by the two-dimensional low-pass filter 104 from the output signal S3 of the selector 103; and an input switching part 102 that switches the selector 103 depending on a luminance level of a plurality of primary color images.SELECTED DRAWING: Figure 1

Description

The present invention relates to a video processing apparatus and a method for improving image quality.

In an image display device such as a projector, flare may occur and the image quality may deteriorate. Here, flare refers to a phenomenon in which an edge portion (for example, the boundary between a white region and a black region) having a large luminance difference in a displayed image is blurred.
Patent Documents 1 and 2 describe an image quality improving device capable of suppressing the flare and improving the image quality. This image quality improving device has a two-dimensional low-pass filter that takes a luminance signal obtained from a video signal as an input and extracts low-frequency components in the vertical and horizontal directions of the luminance signal. An edge signal is acquired by subtracting a low-frequency extraction signal extracted by a two-dimensional low-pass filter from the luminance signal, and the edge signal is added to the original luminance signal to improve the contrast feeling.

Japanese Unexamined Patent Publication No. 2002-290772 Japanese Unexamined Patent Publication No. 2003-46810

However, in the above-mentioned image quality improving device, since the signal that is the source of the edge signal is only the luminance signal, there are the following problems.
According to the recommendation "ITU-RBT.601" that defines a video signal for SDTV (standard definition television), the luminance signal Y is given by the following equation 1.

According to the above equation 1, for example, when displaying a single green color, a single red color, and a single blue color, the maximum signal levels of the luminance signal Y are 0.587 times, 0.299 times, and 0.114 times, respectively. In this case, since the amplitude of the edge portion of the edge signal at the time of monochromatic display becomes small, the effect of improving the contrast feeling is reduced.

An object of the present invention is to provide a video processing apparatus capable of solving the above problems and improving a sense of contrast and a method for improving image quality.

In order to achieve the above object, according to one aspect of the present invention, it is a video processing device that processes a video signal for displaying a color image composed of a plurality of primary color images, and corresponds to each of the plurality of primary color images. A selector that takes a plurality of primary color signals and a brightness signal obtained from these primary color signals as inputs and selectively outputs one of the inputs, and a selector that selectively outputs one of the inputs, and a selector output signal of the selector in the vertical and horizontal directions of the color image. The image is provided with a two-dimensional low-pass filter for extracting each low-frequency component, and an edge signal obtained by subtracting the low-frequency extraction signal extracted by the two-dimensional low-pass filter from the output signal of the selector. Provided is an image processing apparatus including an image quality improving unit that performs processing for improving the image quality of a signal, and an input switching unit that switches the input of the selector according to the brightness level of the plurality of primary color images.

According to another aspect of the present invention, there is an image quality improving method for improving the image quality of a video signal for displaying a color image composed of a plurality of primary color images, and the plurality of primary color signals corresponding to each of the plurality of primary color images. And the brightness signal obtained from these primary color signals are input to the selector, one of the inputs is selectively output from the selector, and the color image is output from the output signal of the selector using a two-dimensional low-pass filter. The video signal is used by extracting the low-frequency components in the vertical and horizontal directions of the above and subtracting the low-frequency extraction signal extracted by the two-dimensional low-pass filter from the output signal of the selector. A method for improving the image quality is provided, which comprises performing a process for improving the image quality of the image and switching the input of the selector according to the brightness level of the plurality of primary color images.

According to the present invention, it is possible to improve the contrast feeling even when displaying a single color.

It is a block diagram which shows the structure of the image processing apparatus according to 1st Embodiment of this invention. It is a block diagram which shows the structure of the part which concerns the image processing of the projector by the 2nd Embodiment of this invention. It is a figure for demonstrating the condition of the comparison result of the value of a 2-bit switching signal and the number of pixels. It is a block diagram which shows the structure of the image quality improvement circuit part of the projector shown in FIG. It is a block diagram which shows the structure of the image quality improvement circuit part which is a comparative example. It is a waveform diagram which shows an example of a luminance signal YOU.

Next, an embodiment of the present invention will be described with reference to the drawings.
(First Embodiment)
FIG. 1 is a block diagram showing a configuration of a video processing apparatus according to the first embodiment of the present invention.
Referring to FIG. 1, the video processing device is a video processing device that processes a video signal for displaying a color image composed of a plurality of primary color images, and includes an image quality improving unit 101 and an input switching unit 102. The image quality improving unit 101 has at least a selector 103 and a two-dimensional low-pass filter 104.

The selector 103 takes a plurality of primary color signals S1 corresponding to each of the plurality of primary color images and a luminance signal S2 obtained from these primary color signals S1 as inputs, and selectively outputs one of the inputs. The two-dimensional low-pass filter 104 extracts low-frequency components in the vertical and horizontal directions of the color image from the output signal S3 of the selector 103, respectively. The image quality improving unit 101 performs processing for improving the image quality of the video signal using the edge signal obtained by subtracting the low frequency extraction signal S4 extracted by the two-dimensional low-pass filter 104 from the output signal S3 of the selector 103. conduct.
The input switching unit 102 switches the input of the selector 103 according to the luminance levels of the plurality of primary color signals S1.

According to the image processing apparatus of the present embodiment, the signal that is the source of the edge signal can be selectively switched from the plurality of primary color signals S1 and the luminance signal S2, so that the contrast feeling can be improved even at the time of monochromatic display. Can be done.
For example, when displaying a single red color, an edge signal is acquired using the primary color signal corresponding to red among the plurality of primary color signals S1. Since the amplitude of the edge portion of this edge signal is larger than that of the edge signal acquired based on the luminance signal, the sense of contrast can be improved.

In the video processing apparatus of this embodiment, the configuration shown in FIG. 1 is an example and can be appropriately changed.
For example, the plurality of primary color signals S1 may be RGB signals indicating an RGB image. In this case, the input switching unit 102 may switch the input of the selector 103 according to the luminance distribution of the RGB image based on the RGB signal.

Further, the input switching unit 102 may compare the number of pixels at the lowest luminance level with the total number of effective pixels for each of the RGB images. In this case, the input switching unit 102 has the first condition that the number of pixels at the lowest luminance level is equal to the total number of effective pixels for all of the RGB inputs, or the number of pixels at the lowest luminance level is not equal to the total number of effective pixels. When the second condition is satisfied, the luminance signal may be selected by the selector 103. Further, the input switching unit 102 may select the G signal of the RGB signal by the selector 103 when the inputs of R and B satisfy the first condition. Further, the input switching unit 102 may select the R signal of the RGB signal by the selector 103 when the inputs of G and B satisfy the first condition. Further, the input switching unit 102 may select the B signal of the RGB signal by the selector 103 when the inputs of R and G satisfy the first condition.
Further, the RGB signal may be a signal whose luminance level is indicated by 8-bit gradation. In this case, the pixels in which all the bits are 0 or the upper 6 bits are 0 may be the pixels having the lowest luminance level.

(Second embodiment)
FIG. 2 is a block diagram showing a configuration of a portion related to image processing of a projector according to a second embodiment of the present invention.
Referring to FIG. 2, the projector has a video input unit 10, a resolution conversion unit 20, a signal processing unit 30, an LCD (Liquid Crystal Display) drive unit 40, and a CPU (Central Processing unit) 50. The CPU 50 is connected to each of the video input unit 10, the resolution conversion unit 20, the signal processing unit 30, and the LCD drive unit 40 via the system bus 60.

The video input unit 10 receives the video signal S11 from a video device (not shown). The video signal S11 is a video signal for displaying a color image composed of a plurality of primary color images, and is, for example, an RGB signal. The video input unit 10 supplies the video signal S11 received from the video device to the resolution conversion unit 20.
The video input unit 10 includes a signal discrimination unit 110. The signal discrimination unit 110 discriminates signals in each cycle based on the vertical synchronization signal of the video signal S11. For example, the signal discrimination unit 110 can discriminate the aspect ratio and the resolution of the video signal S11 and output the discrimination result to the CPU 50 or the like.

The resolution conversion unit 20 converts the resolution of the video signal S11 received from the video input unit 10 into the resolution of the output image output by the LCD drive unit 40. The resolution conversion unit 20 supplies the video signal S12 whose resolution has been converted to the signal processing unit 30. The vertical synchronization signal of the video signal S12 is synchronized with the vertical synchronization signal of the video signal S11.
The signal processing unit 30 processes the video signal S12 to improve the image quality. The video signal S13 that has undergone image quality improvement processing is supplied to the LCD drive unit 40. The LCD drive unit 40 includes, for example, a light source, an LCD panel, and an optical system. In the LCD drive unit 40, the LCD panel modulates the light from the light source to form a color image based on the video signal S13 received from the signal processing unit 30. The optical system projects a color image formed on the LCD panel onto a screen or the like. A single LCD panel may form a color image, or a plurality of LCD panels may form a color image.

Hereinafter, the configuration of the signal processing unit 30 will be specifically described.
The signal processing unit 30 includes an image quality improvement circuit unit 310, an image quality improvement setting holding unit 320, and a color information discrimination unit 330. The video signal S12 received from the resolution conversion unit 20 is supplied to both the image quality improvement circuit unit 310 and the color information discrimination unit 330.
The image quality improvement circuit unit 310 performs processing for improving the image quality on the video signal S12. Here, the image quality improving process is a process for improving the contrast feeling of the image, and includes a correction operation using an edge signal. The image quality improvement circuit unit 310 includes a two-dimensional low-pass filter for acquiring an edge signal, and is configured to switch the input of the two-dimensional low-pass filter according to the switching signal S14. The image quality improvement circuit unit 310 corresponds to the image quality improvement unit 101 shown in FIG.

The image quality improvement setting holding unit 320 holds the settings necessary for the image quality improvement processing in the image quality improving circuit unit 310. The image quality improvement setting holding unit 320 is set by the CPU 50.
The color information discrimination unit 330 supplies the image quality improvement circuit unit 310 with a switching signal S14 for switching the input of the two-dimensional low-pass filter according to the color distribution information of the video signal S12 received from the resolution conversion unit 20. The color distribution information of the video signal S12 includes, for example, the luminance distribution of each primary color image based on the video signal S12. The color information discrimination unit 330 corresponds to the input switching unit 102 shown in FIG.

For example, when the video signal S11 is an RGB signal, the color information discriminating unit 330 determines that each RGB input has the lowest luminance level in the vertical valid period and the horizontal valid period of the image signal in one vertical period of the video signal S12. The determined number of pixels is obtained for each. For example, when the video signal S11 is an RGB signal expressing the brightness level of a pixel with 8-bit gradation, a pixel in which all bits are 0 may be determined as a pixel having the lowest brightness level, and the upper 6 bits may be determined. A pixel in which is 0 may be determined as a pixel having the lowest luminance level.
The color information discriminating unit 330 compares the number of pixels at the obtained minimum luminance level with the total number of effective pixels within one vertical period at each RGB input. Then, the color information discrimination unit 330 generates the switching signal S14 based on the comparison result of the number of pixels. For example, when the video signal S11 is a signal corresponding to FHD (Full High Definition), the total number of effective pixels is 2,073,600 (= 1920 × 1080).

FIG. 3 shows the conditions of the comparison result between the value of the 2-bit switching signal S14 and the number of pixels. In the example shown in FIG. 3, when the number of pixels at the lowest brightness level of each RGB input is equal to the total number of effective pixels, or when the number of pixels at the lowest brightness level of each RGB input is not equal to the total number of effective pixels. , The value of the switching signal S14 is set to "00". When the number of pixels at the lowest luminance level of the inputs of R and B is equal to the total number of effective pixels, the value of the switching signal S14 is set to "01". When the number of pixels at the lowest luminance level of the inputs of G and B is equal to the total number of effective pixels, the value of the switching signal S14 is set to "10". When the number of pixels at the lowest luminance level of the input of R and G is equal to the total number of effective pixels, the value of the switching signal S14 is set to "11".

FIG. 4 is a block diagram showing the configuration of the image quality improvement circuit unit 310. FIG. 4 shows, as an example, the configuration of the image quality improving circuit unit 310 when the video signal S11 is an RGB signal.
Referring to FIG. 4, the image quality improvement circuit unit 310 includes an RGB / color difference conversion unit 1, a selector 2, a delay circuit 3, 4, a two-dimensional low-pass filter 5, a subtractor 6, a gain adjustment circuit 7, an adder 8, and a color difference /. It has an RGB conversion unit 9.

The RGB / color difference conversion unit 1 performs color difference signal conversion when the input of the video signal S12 is “RGB”. Specifically, the RGB / color difference conversion unit 1 calculates the luminance signal Y and the color difference signals Cb and Cr from the RGB signal. The luminance signal Y is calculated according to the above-mentioned equation 1. The color difference signals Cb and Cr are calculated according to the following equations 2 and 3, respectively.

Here, when calculating the luminance signal Y and the color difference signals Cb and Cr with 8-bit gradation, α = 128. When the luminance signal Y and the color difference signals Cb and Cr are calculated with 10-bit gradation, α = 512.
Further, the RGB / color difference conversion unit 1 outputs an R'G'B' signal whose RGB signal is delayed adjusted so as to be output at the same timing as the luminance signal Y and the color difference signal Cb / Cr. The R'G'B' signal output by the RGB / color difference conversion unit 1 is branched into two, one branch signal is supplied to the delay circuit 3, and the other branch signal is supplied to the selector 2. The luminance signal Y output by the RGB / color difference conversion unit 1 is branched into two, one branch signal is supplied to the selector 2, and the other branch signal is supplied to one input terminal of the adder 8. The color difference signal Cb / Cr output by the RGB / color difference conversion unit 1 is supplied to the delay circuit 4.

The selector 2 takes the brightness signals Y and R'G'B'signals output by the RGB / color difference conversion unit 1 as inputs, and selectively inputs either of them according to the switching signal S14 supplied from the color information discrimination unit 330. Output to.
Specifically, when the switching signal S14 is "00", the selector 2 outputs a Y signal (= luminance signal Y). When the switching signal S14 is "01", the selector 2 outputs a G'signal. When the switching signal S14 is "10", the selector 2 outputs an R'signal. When the switching signal S14 is "11", the selector 2 outputs a B'signal. The YR'G'B' signal output by the selector 2 is supplied to the "+" terminal of the two-dimensional low-pass filter 5 and the subtractor 6.

The two-dimensional low-pass filter 5 extracts the vertical low-frequency component of the brightness signal Y or R'G'B'signal output by the selector 2, and further extracts the low-frequency component in the horizontal direction from the extracted low-frequency component in the horizontal direction. Extract regional components. The two-dimensional low-pass filter 5 outputs the signal LPF_YGRB which is the extraction result of the low frequency component in the vertical direction and the low frequency component in the horizontal direction. The output signal LPF_YGRB of the two-dimensional low-pass filter 5 is supplied to the “−” terminal of the subtractor 6.
The subtractor 6 subtracts the output signal LPF_YGRB of the two-dimensional low-pass filter 5 input to the “-” terminal from the output signal YR'G'B' of the selector 2 input to the “+” terminal to obtain the edge signal 15. obtain. The subtractor 6 supplies the edge signal 15 to the gain adjustment circuit 7.

The gain adjustment circuit 7 multiplies the edge signal 15 supplied from the subtractor 6 by a predetermined gain so that the gamma characteristic becomes a linear characteristic. The gain adjustment circuit 7 supplies the edge signal 15 obtained by multiplying the gain to the other input terminal of the adder 8.
The gain adjustment circuit 7 adjusts the gain in order to prevent the sensitivity of the flare correction filter from being lowered in the dark part of the image where the signal level is low when the non-linear signal multiplied by the gamma value is used as the input signal. The output of the gain adjustment circuit 7, that is, the edge signal S15 corrected so that the gamma characteristic becomes linear is input to one input terminal of the adder 8.

The adder 8 adds the output signal (gain-adjusted edge signal S15) of the gain adjustment circuit 7 to the brightness signal Y supplied from the RGB / color difference conversion unit 1. Then, the adder 8 outputs the added result as a luminance signal YOUD to the color difference / RGB conversion unit 9.
The delay circuit 3 performs delay processing on the R'G'B' signal supplied from the RGB / color difference conversion unit 1. The delay circuit 3 outputs the R''G''B'' signal, which is a signal obtained by delaying the R'G'B' signal, to the color difference / RGB conversion unit 9. The delay circuit 4 performs delay processing on the color difference signal Cb / Cr supplied from the RGB / color difference conversion unit 1. The delay circuit 4 outputs the color difference signal CbOUT / CrOUT, which is a signal obtained by delaying the color difference signal Cb / Cr, to the color difference / RGB conversion unit 9. The delay processing by these delay circuits 3 and 4 is for matching the supply timing of each signal in the three signal supply systems between the RGB / color difference conversion unit 1 and the color difference / RGB conversion unit 9. By this delay processing, the delay-adjusted R''G''B'' signal and the color difference signal CrOUT / CrOUT are supplied to the color difference / RGB conversion unit 9 at the same timing as the luminance signal YOUT.

The color difference / RGB conversion unit 9 calculates the following for the R `` G''B'' signal, the color difference signal CrOUT / CrOUT, and the luminance signal YOUT according to the switching signal S14 supplied from the color information discrimination unit 330. And outputs the ROUT / GOUT / BOUT signal.
When the switching signal S14 is "00", the color difference / RGB conversion unit 9 outputs the ROUT / GOUT / BOUT signal by performing the calculations of the following equations (4) to (6).

When the switching signal S14 is "01", the color difference / RGB conversion unit 9 outputs the ROUT / GOUT / BOUT signal by performing the calculations of the following equations (7) to (9).

When the switching signal S14 is "10", the color difference / RGB conversion unit 9 outputs the ROUT / GOUT / BOUT signal by performing the calculations of the following equations (10) to (12).

When the switching signal S14 is "11", the color difference / RGB conversion unit 9 outputs the ROUT / GOUT / BOUT signal by performing the calculations of the following equations (13) to (15).

According to the projector of the present embodiment, the color information discrimination unit 330 controls the selector 2 to switch the input of the two-dimensional low-pass filter 5.
Specifically, when the switching signal S14 is "00", the Y signal is input to the two-dimensional low-pass filter 5. When the switching signal S14 is "01", the G'signal is input to the two-dimensional low-pass filter 5. When the switching signal S14 is "10", the R'signal is input to the two-dimensional low-pass filter 5. When the switching signal S14 is "11", the B'signal is input to the two-dimensional low-pass filter 5. Here, "01", "10", and "11" correspond to green single color display, red single color display, and blue single color display, respectively. That is, the edge signal S15 is generated based on the G'signal when displaying a single green color, the edge signal S15 is generated based on the R'signal when displaying a single red color, and the edge is generated based on the B'signal when displaying a single blue color. The signal S15 is generated. The edge signal S15 is generated based on the Y signal (= luminance signal Y) except for the display of monochromatic green, monochromatic red, and monochromatic blue. By switching the input of the two-dimensional low-pass filter 5 in this way, it is possible to improve the contrast feeling even when displaying a single color.

Hereinafter, as a comparative example, the image quality improvement circuit unit in which the signal that is the source of the edge signal is only the luminance signal will be mentioned, and the difference from the projector of the present embodiment will be specifically described.
FIG. 5 is a block diagram showing a configuration of an image quality improvement circuit unit as a comparative example. The image quality improvement circuit unit includes an RGB / color difference conversion unit 11, a delay circuit 14, a two-dimensional low-pass filter 15, a subtractor 16, a gain adjustment circuit 17, an adder 18, and a color difference / RGB conversion unit 19.

The RGB / color difference conversion unit 11 calculates the luminance signal Y and the color difference signals Cb and Cr from the RGB signals in the same manner as the RGB / color difference conversion unit 1 shown in FIG. However, unlike the RGB / color difference conversion unit 1, the RGB / color difference conversion unit 11 outputs the luminance signal Y and the color difference signals Cb and Cr, but does not output the R'G'B' signal.
The color difference signal Cb / Cr output by the RGB / color difference conversion unit 11 is supplied to the color difference / RGB conversion unit 19 via the delay circuit 14. The delay circuit 14 is the same as the delay circuit 4 shown in FIG.

The brightness signal Y output by the RGB / color difference conversion unit 11 is branched into two, one branched signal is supplied to the “−” terminal of the subtractor 16 via the two-dimensional low-pass filter 15, and the other branched signal is subtracted. It is supplied to one of the "+" terminal of the device 16 and the one input terminal of the adder 18. The output of the subtractor 16 is supplied to the other input terminal of the adder 18 via the gain adjustment circuit 17. These two-dimensional low-pass filters 15, subtractor 16, gain adjustment circuit 17, and adder 18 also differ only in the connection relationship, and basically, the two-dimensional low-pass filter 5, subtractor 6, and gain adjustment shown in FIG. 4 are different. It is the same as the circuit 7 and the adder 8.
The adder 18 adds the edge signal acquired by the two-dimensional low-pass filter 15 and the subtractor 16 to the brightness signal Y output by the RGB / color difference conversion unit 11. The output signal (luminance signal YOUT) of the adder 18 is supplied to the color difference / RGB conversion unit 19. Similar to the operation of the color difference / RGB conversion unit 9 when the switching signal S14 is “00”, the color difference / RGB conversion unit 19 has a color difference / RGB conversion unit 19.
The ROUT / GOUT / BOUT signal is output by performing the calculation of the above-mentioned equations (4) to (6).

FIG. 6 is a waveform diagram showing an example of the luminance signal YOUT output by the adder 18. The vertical axis shows the brightness level, and the horizontal axis shows the time t. The waveform shown by the solid line is the luminance signal YOUT. The part shown by the broken line represents the apparent brightness. As shown in FIG. 6, the waveform of the luminance signal YOUT to which the edge signal is added is formed so as to emphasize the edge portion. In this case, the viewer can see the output image having the luminance change as shown by the broken line. This makes it possible to improve the sense of contrast.
However, in the image quality improvement circuit unit of the comparative example, since the signal that is the source of the edge signal is only the luminance signal Y, the amplitude of the edge portion of the edge signal at the time of monochromatic display is small. Therefore, the effect of improving the contrast feeling is reduced.
On the other hand, in the projector of the present embodiment, the contrast feeling can be improved even at the time of monochromatic display by switching the input of the two-dimensional low-pass filter 5.

101 Image quality improvement unit 102 Input switching unit 103 Selector 104 Two-dimensional low-pass filter

Claims (5)

A video processing device that processes a video signal for displaying a color image consisting of a plurality of primary color images.
A selector that takes a plurality of primary color signals corresponding to each of the plurality of primary color images and a brightness signal obtained from these primary color signals as inputs and selectively outputs one of the inputs, and the output signal of the selector. It is provided with a two-dimensional low-pass filter that extracts low-pass components in the vertical and horizontal directions of a color image, respectively, and is obtained by subtracting the low-pass extraction signal extracted by the two-dimensional low-pass filter from the output signal of the selector. An image quality improving unit that performs processing for improving the image quality of the video signal using the obtained edge signal, and
An image processing device including an input switching unit that switches the input of the selector according to the luminance level of the plurality of primary color images. The plurality of primary color signals are RGB signals indicating an RGB image, and are
The video processing device according to claim 1, wherein the input switching unit switches the input of the selector according to the luminance distribution of the RGB image based on the RGB signal. The input switching unit compares the number of pixels at the lowest luminance level with the total number of effective pixels for each of the RGB images.
All of the RGB inputs have a first condition in which the number of pixels at the lowest luminance level is equal to the total number of effective pixels, or a second condition in which the number of pixels at the lowest luminance level is not equal to the total number of effective pixels. When the condition is satisfied, the luminance signal is selected by the selector.
When the inputs of R and B satisfy the first condition, the selector is used to select the G signal of the RGB signal.
When the inputs of G and B satisfy the first condition, the selector is used to select the R signal of the RGB signal.
The video processing apparatus according to claim 2, wherein when the inputs of R and G satisfy the first condition, the B signal of the RGB signal is selected by the selector. The video processing according to claim 3, wherein the RGB signal is a signal whose luminance level is indicated by 8-bit gradation, and pixels having 0 for all bits or 0 for the upper 6 bits are pixels having the lowest luminance level. Device. It is an image quality improvement method for improving the image quality of a video signal for displaying a color image consisting of a plurality of primary color images.
A plurality of primary color signals corresponding to each of the plurality of primary color images and a luminance signal obtained from these primary color signals are input to the selector, and any of the inputs is selectively output from the selector.
Using a two-dimensional low-pass filter, the vertical and horizontal low-frequency components of the color image are extracted from the output signal of the selector, respectively.
Using the edge signal obtained by subtracting the low-frequency extraction signal extracted by the two-dimensional low-pass filter from the output signal of the selector, processing for improving the image quality of the video signal is performed.
A method for improving image quality, which comprises switching the input of the selector according to the luminance level of the plurality of primary color images.

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