KR20020024672A - Look Up Table Based Error Diffusion Algorithm for Dynamic False Contour Depreciation of Plasma Display Panel - Google Patents

Abstract

PURPOSE: An error spreading method using a look-up table for a pseudo outline reduction in a plasma display panel is provided to reduce a pseudo outline generated when displaying a moving picture on the plasma display panel. CONSTITUTION: An (n-1)-th frame gray value and an n-th frame gray value of an input digital image signal are stored in first and second memory areas of a frame memory(10). A gray value conversion LUT(50) is searched based on an ordered pair of the (n-1)-th frame gray value and the n-th frame gray value of an input digital image signal and new gray values are searched. A gray value of a current frame is changed. An error spreading section(30) defines a difference between a gray value of a current frame of an original image signal and the changed gray value as an error. The error spreading section(30) provides and sends a weight value to be multiplied to a location and an error of a pixel to a neighboring pixel.

Description

Look Up Table Based Error Diffusion Algorithm for Dynamic False Contour Depreciation of Plasma Display Panel}

The present invention relates to an error diffusion method using a look-up table (LUT) for reducing pseudo contours in a plasma display (PDP). An error diffusion method for reducing contours is provided.

The gray scale representation in the CRT (Cathode Ray Tube) is conventionally made by controlling the intensity of the electron beam emitted from the electron gun. On the other hand, unlike conventional CRTs, plasma displays express various gray scales using a pulse number control method.

In other words, the plasma display can be turned on or off, and the gray scale is expressed by adjusting the length of the on time. Due to this driving method and the human visual characteristics following the motion of a moving picture, pseudo contours occur in a moving image having a smooth gradation change.

Unlike CRT, the plasma display uses a driving method by controlling the number of pulses. One field is divided into a plurality of subframes, and the brightness is adjusted by turning on or off, that is, coding the subframe.

1 shows an example of a subfield. In Fig. 1, the entire horizontal axis represents one TV field. The TV field represents 16.7 msec, which is 1/60 when 60 Hz. In addition, the white portion represents the addressing portion and the black portion represents the light emitting portion.

Addressing means selecting the grid to be displayed on the screen. The number shown above in FIG. 1 means the number of sustain pulses for light emission. That is, a combination of {1, 2, 4, 8, 16, 32, 64, 128} represents 256 gray levels between 0 and 255. Each element of {1, 2, 4, 8, 16, 32, 64, 128} is called a subframe. Referring to FIG. 1, the addressing has a certain time. For example, in order to express the gradation of 9, it is realized by emitting a sustain pulse of 1 and a sustain pulse of 8.

Due to the gray scale expression method by adjusting the number of pulses and the visual characteristics of the human body that moves the moving screen along with the pupil when the image moves on the screen, an unsightly pseudo contour is generated in the moving image where the gray level value is smooth.

2 shows an example in which pseudo contours occur. FIG. 2 shows a case in which the (n-1) th frame is shown at gradation 127 when the light emission pattern shown in FIG. At this time, pseudo contours occur because positions of the sub-frames that emit light are different. In particular, since sf8 (128) and sf7 (64) use a relatively large sub-frame is different whether or not the pseudo contour is large.

FIG. 3 illustrates an example of generating another pseudo contour. FIG. 3 illustrates a subfield having a luminance weight of {1, 2, 4, 8, 16, 32, 48, 48, 48, 48}, unlike FIG. It has a case. FIG. 3 is a diagram illustrating a cause of pseudo contours when grayscale values of an input image are 63 and 64 and 1 P / F (pixel / frame) moves from left to right. As shown in FIG. 3, since the position of the vision is continuous with respect to the moving direction of the image, the position of the vision is represented as a dotted line, and the gray scale value recognized according to the movement of the vision becomes 55 instead of 64 to generate a pseudo contour.

As a method for solving such a pseudo contour of the video, an equalization pulse method (Japanese Patent Laid-Open No. 10-39828), optimization of a subfield pattern (Korean Patent Application No. 99-36926), and an error diffusion method (Korean Patent Publication No. 98) -32237), halftone display method and display device (Korean Patent Publication No. 2000-1193), copper pixel distortion reduction method (Domestic Patent Publication No. 1999-78432) for display device using pulse number equalization and image display Apparatus and image evaluation apparatus (Domestic Patent Publication No. 1999-14172) etc. are mentioned.

In the present invention, to solve the problem of the pseudo contour in the plasma display, a new pixel value to be converted the pixel value of the current frame for each of the ordered pair of the pixel value of the previous frame and the pixel value of the current frame. Using the gradation conversion LUT (Look Up Table) stored, find the corresponding pair of gradation conversion LUT, read out the pixel value of the current frame to be converted, convert the current pixel value, and between the current pixel value and the converted pixel value Pseudo-contour in plasma display (PDP) that propagates the error, which is the difference of, to surrounding pixels to be processed in advance, so that it is not necessary to check whether the motion area is detected in advance or whether to generate a moving image pseudo contour. To provide an error diffusion method using a lookup table (LUT) for reduction Enemy

1 is a diagram illustrating an example of a subfield in a plasma display;

2 and 3 illustrate examples of pseudo contour generation in a plasma display;

4 is a block diagram of a display device for reducing pseudo contours in a plasma display (PDP) according to the present invention;

5 is a flowchart for determining a conversion gray value of the present invention;

6 illustrates a position of a pixel to propagate to surrounding pixels of the present invention.

♣ Explanation of symbols for the main parts of the drawing ♣

10: frame memory unit 20: gradation value converting unit

30: error diffusion unit 40: plasma display (PDP)

50: Gray Value Conversion LUT

In order to achieve the above object, according to the present invention, a (n-1) th frame gray value of an input digital video signal and an n th frame gray value, which is a current frame, are respectively stored in the first and second memory areas of the memory unit. step; A second step of searching for a gray scale value conversion LUT based on an ordered pair of the (n-1) and nth frame gray scale values stored in the frame memory unit to find a new gray scale value, and then converting the gray scale value of the current frame to determine the gray scale value; In the error diffusion unit, a difference between the gray level value of the current frame and the converted gray level value of the original video signal is defined as an error, and the third step of weighting the pixel position and the predetermined weight to be multiplied by the error to propagate to the surrounding pixels is performed. Is characteristic.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The gradation value to be displayed represents 256 different gradations from 0 to 255. Thus, the previous frame and current frame pixel value ordered pairs are all 256x256 at a given pixel position.

Unlike the conventional method, the present invention uses a gradation conversion look-up table (LUT) that stores a new pixel value to be converted to a pixel value of the current frame for each pair of pixel values of the previous frame and pixel values of the current frame. will be.

Therefore, given the previous and current pixel values, find the corresponding pair of the grayscale conversion LUT, read out the pixel value of the current frame to be converted, convert the current pixel value, and error that is the difference between the current pixel value and the converted pixel value. Will propagate to surrounding pixels to be processed.

Therefore, the feature of the present invention is that it is not necessary to confirm whether to detect a motion region in advance or generate a video pseudo contour through a separate process.

In the block diagram showing the configuration of the display device of FIG. 4, the frame memory 10 includes a frame memory 10, a gray value converting unit 20, an error diffusion unit 30, a plasma display 40, and a gray value converting LUT 50. The frame memory 10 includes a first memory area for storing information corresponding to a screen of a previous frame from a digital input video signal, and a second memory area for storing information corresponding to a screen of a current frame.

In the error diffusion method for pseudo contour reduction in the plasma display of the present invention, first, the (n-1) th frame gradation value and the n th frame gradation value of the digital image signal input in the first step are converted into the frame memory unit 10. Are stored in the first and second memory areas of < RTI ID = 0.0 >), < / RTI > and the gray value conversion LUT 50 is retrieved based on the ordered pairs of (n-1) and n-th frame grayscale values stored in the frame memory unit 10 in the second step. After finding a new gray scale value, the gray scale value of the current frame is converted and determined.In step 3, the error diffusion unit 30 defines the difference between the gray scale value of the current frame and the converted gray scale value of the original video signal as an error. It propagates to surrounding pixels by weighting it with a predetermined weight to be multiplied by the position and error of the pixel.

The gray value converter 20 searches the gray value conversion LUT 50 based on the ordered pairs of the stored gray value of the previous frame memory and the gray value of the current frame to find a new gray value, and then converts the gray value of the current frame. .

The gray scale value conversion LUT 50 is calculated in advance through a separate offline process, and referring to an example of gray scale values to be converted in Table 1, the gray scale value conversion LUT 50 indicates a determination process of the gray scale value conversion LUT 50.

Input image gradation value Pseudo contour (p, y) Contents of gradation LUT to be converted Mapping (x, y) (n-1) th frame x nth frame y ： 63 54 2 53 63 55 2 55 63 56 3 59 63 57 2 59 63 58 2 59 63 59 One 59 63 60 2 61 63 61 One 61 63 62 One 63 63 63 0 63 63 64 ★ 8 63 63 65 8 63 63 66 7 63 63 67 8 63 63 68 7 63 63 69 6 63 63 70 6 76 63 71 5 76 63 72 7 79 ：

In Table 1, x, an element of the first column, represents a gray value of the ( n-1) th frame, and y , a second column, represents a gray value of the nth frame, which is the current frame. The third column pseudo contour ( x , y ) represents the amount of pseudo contour calculated by the simulation when the gray level values of the given ( n-1) and n th frames are x and y , respectively. In addition, the last fruit Ping (x, y) is (n- 1) n and the gray level value of the n-th frame to be converted to a gray level value of the second frame to minimize the false contour in the case of each of x, y, i.e. the tone value conversion The contents of the LUT 50 are shown.

The method of determining the gray scale value to be changed in the second step will now be described in detail. First, assume that the current y value is α. In this case, the value y of the pseudo contour is minimized by searching the range α ± pseudo contour ( x , y ) of the y value and selected as the changed gradation value. For example, if x = 63 and y = 64 (★ in Table 1), pseudo contours (63, 64) = 8. Therefore, y gradation with minimum pseudo contour is searched by searching for pseudo contour ( x , y ) values (bold in the table 1) corresponding to the range of x = 63 and y value is 64-8 ≤ y ≤ 64 + 8. The value 63 is selected, ie stored in the mappings 63 and 64. If there are multiple minimum y values, choose the one with the smallest difference.

5 is a flowchart illustrating a process of determining the contents of the gray value conversion LUT described above. In the second step of setting the converted grayscale value, in step S10, x , which is the gray value of the ( n- 1) th frame, is set to 0, and in step S11, y, which is the gray value of the nth frame, is set to 0. In step S12, the mapping gray level values (x, y) are set to y. In step S13, a k value representing a range of y values to be searched is set to zero.

In step (S14) the false contour (x, y) in this case, the doctor is greater in the contour (x, y + k) step (S15) to determine if it is greater than, the mapped gray level value is changed (x, y) = y + k If the pseudo contour ( x , y ) is greater than the pseudo contour ( x , y - k ) in step S16, and the value of the gray scale value mapping ( x , y ) to be changed is large in step S17 = set to y - k

In step S18, after setting k to k + 1, it is determined whether the set k value is greater than the pseudo contour ( x , y ) in step S19, and if it is not large, the process returns to step S14. in (S20) sets a y in the case where k is larger than the set false contour (x, y) to y +1. Thus, the final map (x, y) value to be set for the y value is in the "y - false contour (x, y) ≤ y ≤ y + false contour (x, y)" false contour corresponding to the range (x , y ) is searched to determine the y value that is the minimum amount of pseudo contour.

In addition, if it is determined in step S21 that y is greater than 255 and not large, the flow returns to step S12. If y is greater than 255 in step S22, x is set to x + 1, and step ( In step S23, it is determined whether x is greater than 255, and when it is not large, the process returns to step S11, and when large, the process ends. That is, the conversion gray value mapping (x, y) for the 256 × 256 case is all determined, and thus the content is set to the content of the gray value conversion LUT 50.

The error diffusion unit 30 defines the difference between the grayscale value of the original video signal (the grayscale value of the current frame) and the converted grayscale value as an error and propagates to surrounding pixels. The weight to be multiplied by the position and error of the pixel to be propagated may have various positions and values. Examples of various positions and values are shown in FIG. 6. In FIG. 6, A is the pixel position currently being processed, B is the pixel position on the right side where the error is propagated, and the weight is 7/16, C is the pixel position on the lower left side where the error is propagating, and the weight is 3/16. , D is the pixel position at the bottom of which the error is propagated, and the weight is 5/16, and E is the pixel location at the bottom right of which the error is propagated, and the weight is 1/16.

As described above, an error diffusion method using a look-up table (LUT) for pseudo contour reduction in a plasma display (PDP) according to the present invention has n-th frame gray level value of the input digital image signal and n which is the current frame. The first frame gray value is stored in the first and second memory areas of the memory unit, respectively, and the new gray value is found by searching the gray value conversion LUT based on the ordered pairs of the (n-1) and nth frame gray values. After converting and determining the gray scale value, the error diffusion unit defines the difference between the gray scale value of the current frame and the converted gray scale value of the original video signal as an error, and weights it with a predetermined weight to be multiplied by the pixel position and the error to propagate to the surrounding pixels. This is to display without needing to check the processing so that pseudo contour does not occur. Reduced by four contour has the effect of outputting the image of the more clear image quality.

Claims (3)

A first step of storing the (n-1) th frame gradation value and the current nth frame gradation value, which are the previous frame of the input digital video signal, in the first and second memory regions, respectively; A second step of searching for a gray scale value conversion LUT based on an ordered pair of the (n-1) and nth frame gray scale values stored in the frame memory unit to find a new gray scale value, and then converting the gray scale value of the current frame to determine the gray scale value; In the error diffusion unit, a difference between the gray level value of the current frame and the converted gray level value of the original video signal is defined as an error, and the third step of weighting the pixel position and the predetermined weight to be multiplied by the error to propagate to the surrounding pixels is performed. Error diffusion method using a look-up table (LUT) for reducing the pseudo contour in the plasma display (PDP). The method of claim 1, wherein the second step of determining the converted gray scale value When the tone value of y value of the n-th frame is the current frame, α d, and search for the range of y values α ± false contour amount (x, y) to the false contour amount selected it is changed the value of y is the minimum gradation value, the y value y - a false contour (x, y) ≤ y ≤ y + false contour (x, y) the false contour that corresponds to the range of the (x, y) to retrieve the value to pseudo-gray-scale value of y that minimizes contour amount Select and store in mapping (x, y), and in the case of several minimum y- values, a value having the smallest difference is selected and a look-up table for pseudo contour reduction in a plasma display (PDP) Error diffusion method using LUT). The method of claim 1, wherein the weight to be multiplied by the position and the error of the pixel to propagate to the surrounding pixels in the third step, (1) the weight to the right is 7/16, (2) The weight on the bottom left is 3/16, (3) At the bottom, the weight is 5/16, (4) an error diffusion method using a look-up table (LUT) for reducing pseudo contours in a plasma display (PDP), wherein an error diffusion coefficient having a weight of 1/16 may be applied to a lower right side.