KR20110036422A - A method for processing an image signal and an apparatus thereof - Google Patents

Abstract

PURPOSE: An image signal processing method and image signal processing apparatus are provided to compensate luminance through local dimming and to maintain the brightness of an original image. CONSTITUTION: A first dimming value is calculated about the inputted frame of an image(S604). Histogram data of a local dimming block is extracted and analyzed for a frame. A second dimming value is calculated based on the analyzed histogram data. Each local dimming block is controlled based on the calculated second dimming value.

Description

Image signal processing method and image signal processing apparatus {A METHOD FOR PROCESSING AN IMAGE SIGNAL AND AN APPARATUS THEREOF}

The present invention relates to a method and an apparatus for processing an image signal, and more particularly, to an image signal for compensating for luminance when it is difficult to compensate luminance lost through local dimming even through pixel compensation. It relates to a processing method and apparatus.

Recently, a video signal processing apparatus including a local dimming module has been mainly used.

In the related art, in order to determine the degree of local dimming, the degree of local dimming is determined in a block-by-block manner or by calculating average brightness for each section according to the peak value of the gray level of each partition. Decided.

The former method is to determine the amount of dimming according to the largest level of the image data in one block.In general, if only one point having a dark image or a peak level exists in the image, the amount of local dimming is greatly reduced and local. There is a problem that the effect of dimming is significantly reduced.

In addition, the latter method implements an average brightness of an image in a block by using a calculation formula such as RGB average, in which local dimming takes a lot, while bright areas of image are also darkened so that the pixel compensation is as strong as dark. To compensate.

However, the peak level at which the pixel compensation is not performed much cannot be compensated anymore, so the luminance level is darkened. For example, assuming that there is a light white text in a dark image, local dimming occurs due to the dark image, but the peak level of the text is no longer compensated for brightness, which causes the text to be very dark.

In order to solve the above problems, it is an object of the present invention to provide an image signal processing method and apparatus that compensates for luminance when it is difficult to compensate for luminance dropped through local dimming through pixel compensation.

Another object of the present invention is to provide an image signal processing method and apparatus which readjusts a dimming amount in consideration of histogram distribution characteristics when it is difficult to compensate through the pixel compensation.

It is still another object of the present invention to provide a method and apparatus for maintaining the same brightness as an original image by compensating brightness through dimming compensation even in a region where pixel compensation is impossible, such as a texture image such as light colored letters on a dark background. .

The present invention relates to an image signal processing method and an image signal processing apparatus.

According to an aspect of the present disclosure, an example of an image signal processing method includes: calculating a first dimming value with respect to a frame of an input image; Extracting and analyzing histogram data in each local dimming block for the frame; Calculating a second dimming value based on the calculated first dimming value and the analyzed histogram data; And controlling each local dimming block based on the calculated second dimming value.

In this case, the first dimming value may be calculated using APL values for the frame, APL values for each local dimming block, and a peak value.

The second dimming value may use a dimming coefficient determined according to the analyzed histogram data.

The second dimming value may be calculated by adding the first dimming value and a value obtained by multiplying the difference between the first dimming value and the determined dimming coefficient by a dimming value applied to the entire local dimming block.

The dimming coefficient may have a value of 0 to 1, and when the dimming coefficient is 0, the calculated first dimming value may not be adjusted.

Each local dimming block may be controlled by determining a dimming amount for the corresponding block according to the calculated second dimming value.

Each local dimming block may generate and distribute a pulse width modulation (PWM) for each display block according to the determined dimming amount.

In another aspect of the present invention, an image signal processing apparatus includes: a first dimming calculator configured to calculate a first dimming value for a frame of an input image; A histogram extracting / analyzing unit for extracting and analyzing histogram data in each local dimming block for the frame; A second dimming calculator configured to calculate a second dimming value based on the first dimming value and the analyzed histogram data; And a controller configured to compensate for each pixel constituting the frame based on the calculated second dimming value and to individually control each local dimming block.

In this case, the first dimming calculator may calculate the first dimming value by using APL values for the frame, APL values and peak values for each local dimming block.

The histogram extractor / analyzer may output a dimming coefficient to be differentially applied to each local dimming block.

The second dimming calculator may further include a value obtained by subtracting the calculated first dimming value from the calculated dimming value applied to the entire local dimming block and multiplied by the output dimming coefficient. The second dimming value may be calculated by adding up.

The histogram extractor / analyzer may output a dimming coefficient such that the second dimming value is the same as the first dimming value when the histogram data is not reflected based on the analyzed histogram data.

The controller may determine an individual dimming amount for each local dimming block according to the calculated second dimming value.

The controller may generate and distribute a pulse width modulation (PWM) for each local dimming block according to the determined dimming amount.

According to the invention,

First, in the case where it is difficult to compensate luminance lost through local dimming through pixel compensation, the luminance can be compensated.

Second, when the compensation is difficult even through the pixel compensation, the dimming amount may be readjusted in consideration of the histogram distribution characteristic.

Third, the brightness compensation by adjusting the dimming amount even for a texture image such as light colored letters on a dark background has the effect of maintaining the same brightness as the original image.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, preferred embodiments of the present invention in which the above object can be specifically realized are described with reference to the accompanying drawings.

Hereinafter, a video signal processing method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings. Particularly, in the present invention, an image signal processing method and apparatus capable of compensating luminance when it is difficult to compensate luminance lost through local dimming even through pixel compensation in processing an image signal. To provide. In this case, for the convenience of description, the local dimming amount initially determined as described above is adjusted, and for this adjustment, the characteristics of the histogram will be described as an example.

Video signal processing device

1 is a block diagram illustrating an example of an image signal processing apparatus constructed in accordance with the present invention.

Referring to FIG. 1, an image signal processing apparatus according to an exemplary embodiment may include a first calculator 110, a second calculator 120, a first dimming calculator 130, and a histogram extractor / analyzer. 140, a second dimming calculator 150, a controller 160, a pulse width modulation (PWM) generator / distributor 170, a pixel compensator 180, and a module information unit 190.

The first calculation unit 110 is image information necessary for pixel compensation on an input image, and includes an average picture level (APL) in the entire frame of the image. Calculate the values.

The second calculator 120 calculates an APL and / or a peak value for each LED (Light Emitting Diode) block as image information for determining a local dimming amount.

The first dimming calculator 130 uses the APL values in the entire image frame calculated by the first calculator 110 and the APL and / or peak values for each LED block calculated by the second calculator 120. The first dimming value is calculated.

The histogram extractor / analyzer 140 extracts histogram data for each block of an input image frame to obtain a histogram distribution. Here, the histogram distribution information may be all according to the number of blocks.

FIG. 2 illustrates an example diagram for explaining a histogram distribution in an input image frame.

The histogram may consist of x bins for each of the red-green-blue sums or RGB.

In the diagram shown in FIG. 2, for example, 16 bins are set, and the distribution of the histogram for a specific image is shown.

Referring to FIG. 2, 16 bins are shown in the bin 0 to Bin 15 region on the horizontal axis, and a sum of RGB or a value for each of the RGB is shown in the range of 0 to 40, for example.

The sum of the RGB at the first bin (Bin 0) or the value of RGB each is 15, 32.5 at the second bin (Bin 1), 1 at the seventh bin (Bin 6) and eighth bin (Bin 7). After the ninth bin (Bin 8), it has a value of 0.5.

When analyzing the histogram distribution diagram shown in FIG. 2, the closer to Bin 0, the darker the image, and the closer to Bin 15, the brighter image.

Therefore, in the case of FIG. 2, the histogram is intensively distributed between bins 0 to 3, and thus it may be determined that the corresponding image is a dark image.

In the present invention, as described above, first, the first local dimming amount is calculated using the entire APL according to a specific image and the APL and / or peak value of each block, and the dimming amount according to the histogram analysis according to the present invention. In order to adjust the second local dimming amount, the luminance may be appropriately compensated by dimming compensation through the second local dimming even when the luminance is degraded through the first local dimming and the pixel compensation is impossible.

3 illustrates an example of an image including letters in a dark image to explain an algorithm according to the present invention, and FIG. 4 illustrates a histogram distribution of the image of FIG. 3.

3 illustrates a texture image with white letters on a black background to explain the technical idea of the present invention.

Referring to FIG. 3, there are six blocks 311 to 316 in total, and white letters are disposed in each block.

In this case, when local dimming is performed according to the local dimming value initially calculated on the texture image, the luminance is generally reduced due to the black background. In such a case, to compensate for the dropped luminance, the pixel compensation may be quadratic to compensate for the dropped luminance.

However, in connection with the present invention, as shown in FIG. 3, in the case of a texture image, it is generally based on a dark image such as white letters on a black background and displaying a bright colored letter thereon to construct a texture image. It is common. Therefore, in this case, the RGB level of the white letters is at most 255 (8 bits), so pixel compensation is no longer difficult.

If the initial dimming value is applied as it is, the luminance of the texture image itself 330 may be reduced due to local dimming according to a black background, and thus an image may be blurred.

Accordingly, in the present invention, if pixel compensation is impossible after the first local dimming, the local dimming is performed secondarily. Here, in the case of the second local dimming, it may mean that the local dimming is performed again, or it may mean that the first local dimming amount is readjusted.

As an example of such a method, the following description will describe a method of adjusting the amount of local dimming initially determined using the histogram data in each of the blocks 311 to 316 of FIG. 3.

That is, referring to the histogram distribution 320 of the second block 312 in FIG. 3, it can be seen that the distribution is shown in FIG. 4.

Referring to FIG. 4, the histogram data represents a dark image as the bin 0 is closer, and a bright image as the bin 15 is closer. Referring to the distribution of the histogram data of FIG. 4 in the case of the second block 312 of FIG. 3, it can be seen that histogram data is mainly distributed at both ends, that is, bin 0 and bin 1, and bin 14 and bin 15. This means that it means white letters on a dark background.

Therefore, as described above, when local dimming is performed by considering only the first dimming value without considering the histogram distribution characteristic of the texture image, the luminance is lowered due to the black background, but the RGB level of the white letters is maximum. Since it is 255 (8 bits), luminance compensation due to pixel compensation is difficult. As a result, the white letters can only be expressed with low luminance.

According to the present invention, after the first dimming value is calculated, the second dimming value is calculated to adjust the local dimming value initially determined. If pixel compensation is not possible, the dimming amount can be adjusted to increase efficiency and compensate for luminance.

Therefore, in this case, it may be determined whether to adjust the local dimming amount initially determined according to the present invention, and for this purpose, it may be determined by using the sum of the highest two to three bin information among histogram bin distributions. For example, when the 16 bins are used as described above, the sum of bins 14 and 15 may be calculated to adjust the local dimming amount initially determined. In this case, the sum of the upper bins may determine the final dimming amount by calculating the second dimming amount using an equation or a look-up table (LUT) as shown in the following figure.

Hereinafter, a method of adjusting the local dimming amount initially determined according to the present invention will be described in more detail. Equation 1 below shows an example of equations required to adjust the local dimming amount according to the present invention.

Dimming_2 = Dimming_1 + (Dimming_Global-Dimming_1) * a

In Equation 1, Dimming_1 refers to the first dimming value determined using the entire APL and the block APL, Dimming_Global refers to the global dimming value as a dimming value applied to the entire block, and a is a histogram It means the dimming coefficient to be differentially applied according to the distribution. Dimming_2 refers to the final dimming value considering the histogram distribution characteristic using the above values.

In the case of Figure 5 is an example of a diagram shown for explaining the above-described dimming coefficient (a).

Referring to FIG. 5, the dimming coefficient a is determined according to the Histogram_weighting_sum value of the horizontal axis, and the dimming coefficient may have a value between the minimum value 0 and the maximum value 1.

In the case of the threshold (x) in FIG. 5, for example, as described above, the threshold x is used as a reference for determining whether to adjust the dimming amount initially determined in the receiver. That is, before the threshold x, the first determined local dimming amount is applied as it is. In this case, the dimming coefficient a has a minimum value of 0. If adjustment is necessary, dimming for adjusting the local dimming value initially determined with an appropriate value within the maximum value of 1, such as the first (1st) to the third (3rd) value, for example, the first (1st) to the third (3rd). Used as a factor.

In addition, in FIG. 5, the n inflection points (for example, 1st to 3rd) may be used to design non-linearly. As described above, if the dimming coefficient is 0, the current dimming_1 is maintained. If the a coefficient is large according to the histogram distribution, (dimming_global-dimming_1) is applied. That is, the brightness is further added by compensating for the dimming amount.

According to Equation 1 described above, even when the luminance is degraded through local dimming and the pixel compensation is impossible, as in the texture image, the luminance may be compensated by adjusting the local dimming amount appropriately to compensate for the brightness again.

Video signal processing method

6 is an example of a flowchart shown to explain a video signal processing method according to the present invention.

The video signal processing method according to the present invention will be described with reference to the above description and the configuration of the video signal processing device of FIG. 1.

First, an input image signal is received (S601), and total APL values of the image are calculated therefrom (S602).

Thereafter, APL values and / or peak values for each dimming block for performing local dimming are calculated (S603).

The first local dimming amount is determined using the calculated total APL values of the image, APL values for each dimming block, and / or a peak value (S604).

Subsequently, as described above, when it is determined that luminance compensation is impossible by the pixel compensation method, for example, when the luminance needs to be improved, histogram data is extracted and analyzed for each dimming block (S605).

The dimming coefficient is determined based on the analysis result, and the second dimming amount is calculated by using Equation 1 described above using the determined dimming coefficient (S606).

The dimming amount is determined for each dimming block based on the calculated second dimming amount (S607), and the image is output by controlling the dimming block based on the determined dimming amount for each dimming block (S608).

In this process, the final local dimming is performed by generating and distributing PWM for each block based on the determined dimming amount for each dimming block. In addition, when pixel compensation is possible, pixel compensation is also performed.

According to the present invention, if the luminance decrease due to local dimming is expected according to the present invention, when there is no compensation for the luminance dropped by another method, the local luminance can be adjusted appropriately by adjusting the amount of local dimming. have.

According to the image signal processing method and apparatus according to the present invention described above, by considering the histogram distribution characteristics of the input image together, it is possible to appropriately determine the degree of local dimming to compensate for the luminance.

It will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential features of the present invention.

Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative.

The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

1 is a block diagram showing an example of an image signal processing apparatus constructed according to the present invention;

2 is a diagram illustrating an example of a diagram illustrated to explain a histogram distribution in an input image frame;

3 illustrates an example of an image including letters in a dark image to explain an algorithm according to the present invention;

4 illustrates a histogram distribution of the image of FIG. 3;

In the case of Figure 5 is an example of a diagram shown to explain the above-described dimming coefficient (a), and

6 is an example of a flowchart shown to explain a video signal processing method according to the present invention.

Claims (14)

Calculating a first dimming value with respect to a frame of an input image; Extracting and analyzing histogram data in each local dimming block for the frame; Calculating a second dimming value based on the calculated first dimming value and the analyzed histogram data; And And controlling each of the local dimming blocks based on the calculated second dimming value. The method of claim 1, The first dimming value is, The image signal processing method is calculated by using the APL values for the frame and the APL values and peak values for each local dimming block. The method of claim 1, The second dimming value is, And a dimming coefficient determined according to the analyzed histogram data. The method of claim 3, The second dimming value is, And calculating the sum of the first dimming value and a value obtained by multiplying the difference between the first dimming value and the determined dimming coefficient by a dimming value applied to the entire local dimming block. The method of claim 3, The dimming coefficient is, Have a value of 0 to 1, And if the dimming coefficient is 0, do not adjust the calculated first dimming value. The method of claim 1, Each local dimming block, And controlling the dimming amount of the corresponding block according to the calculated second dimming value. The method of claim 6, Each local dimming block, And generating and distributing pulse width modulation (PWM) for each display block according to the determined dimming amount. A first dimming calculator configured to calculate a first dimming value for a frame of an input image; A histogram extracting / analyzing unit for extracting and analyzing histogram data in each local dimming block for the frame; A second dimming calculator configured to calculate a second dimming value based on the first dimming value and the analyzed histogram data; And And a controller configured to compensate for each pixel constituting the frame based on the calculated second dimming value and to individually control each local dimming block. The method of claim 8, The first dimming calculator, And calculating the first dimming value using the APL values for the frame, the APL values for each local dimming block, and the peak value. The method of claim 8, The histogram extraction / analysis unit, And a dimming coefficient to be differentially applied to each local dimming block. The method of claim 10, The second dimming calculator, The second dimming value is calculated by adding the calculated first dimming value and a value obtained by subtracting the calculated first dimming value from the dimming value applied to the entire local dimming block and multiplied by the output dimming coefficient. Video signal processing device. The method of claim 10, The histogram extraction / analysis unit, And outputting a dimming coefficient such that the second dimming value is equal to the first dimming value when the histogram data is not reflected based on the analyzed histogram data. The method of claim 8, The control unit, And a dimming amount for each local dimming block is determined according to the calculated second dimming value. The method of claim 13, The control unit, And generating and distributing pulse width modulation (PWM) for each local dimming block according to the determined dimming amount.

Images