KR100570968B1 - Method and apparatus for processing video data of plasma display panel - Google Patents

Abstract

The present invention relates to a video data processing method and apparatus for a plasma display panel capable of expanding gray scale expression power while reducing error diffusion patterns.

A video data processing method according to the present invention comprises the steps of: random error diffusion of video data of a pixel using error conversion coefficients and random error diffusion coefficients calculated from each of pixels adjacent to the pixel; Dithering the random error spread video data using a plurality of dither mask patterns divided by gray and frame.

Random Error Diffusion, Dithering

Description

Method and apparatus for processing video data of plasma display panel {Method And Apparatus of Processing Video Data For Plasma Display Panel}             

1 is a perspective view illustrating a discharge cell structure of a general plasma display panel.

2 is a diagram illustrating a configuration of subfields included in one frame.

3 is a view for explaining a conventional error diffusion method.

4 is a block diagram illustrating a video data processing apparatus of a plasma display panel according to an exemplary embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration of a random error spreading and dithering unit illustrated in FIG. 4.

FIG. 6 is a diagram for describing a random error diffusion method of the random error diffusion unit illustrated in FIG. 5.

FIG. 7 is a diagram illustrating a specific configuration of the dithering unit shown in FIG. 5. FIG.

FIG. 8 is a diagram illustrating a dither mask pattern in units of cells stored in the dither mask table shown in FIG. 7. FIG.

FIG. 9 is a diagram for explaining an increase in gray scale expression power by the random error spreading and dithering unit illustrated in FIG. 4. FIG.

<Brief description of symbols for the main parts of the drawings>

10: upper substrate 18: lower substrate

12A: Scanning electrode 12B: Sustaining electrode

14 upper dielectric layer 16 protective film

20: data electrode 22: lower dielectric layer

24: partition 26: phosphor

30: gamma correction unit 32: error diffusion and dithering unit

34: subfield mapping unit 36: data driver

38: PDP 40: random error diffusion unit

50 dithering unit 52 mask control unit

54: dither mask table 56: the adder

The present invention relates to a method and apparatus for processing digital video data, and more particularly, to a method and apparatus for processing video data of a plasma display panel capable of minimizing error diffusion and dithering noise.

Recently, a plasma display panel (PDP), which is easy to manufacture a large panel, has attracted attention as a flat panel display device. The PDP displays an image by adjusting the gas discharge period of each of the pixels according to the digital video data. As such a PDP, a PDP having three electrodes as shown in FIG. 1 and driven by an AC voltage is representative.

The discharge cell of the AC PDP shown in FIG. 1 includes sustain electrode pairs 12A and 12B formed on the upper substrate 10 and data electrodes 20 formed on the lower substrate 18.

Each of the sustain electrode pairs 12A and 12B has a double layer structure of a transparent electrode and a metal electrode. The sustain electrode pairs 12A and 12B mainly provide a scan electrode 12A mainly supplying a scan signal for address discharge and a sustain signal for sustain discharge, and a sustain signal alternately supplied to the scan electrode 12A. It is separated by the sustain electrode 12B. The data electrode 20 is formed to intersect with the sustain electrode pairs 12A and 12B to supply a data signal for address discharge.

An upper dielectric layer 14 and a passivation layer 16 are stacked on the upper substrate 10 on which the sustain electrode pairs 12A and 12B are formed, and a lower dielectric layer 22 is formed on the lower substrate 18 on which the data electrode 20 is formed. do. The upper dielectric layer 14 and the lower dielectric layer 22 accumulate charges generated by the discharge. The protective film 16 prevents damage to the upper dielectric layer 14 due to sputtering of plasma particles during discharge and increases the emission efficiency of secondary electrons. The dielectric layers 14 and 22 and the protective layer 16 may lower the driving voltage applied from the outside.

A partition wall 24 is formed on the lower substrate 18 on which the lower dielectric layer 22 is formed, and a phosphor layer 26 is formed on the lower dielectric layer 22 and the surfaces of the partition wall 24. The partition wall 24 separates the discharge space to prevent the ultraviolet rays generated by the gas discharge from leaking into the adjacent discharge space. The phosphor layer 26 emits red (hereinafter, R), green (hereinafter, G), or blue (hereinafter, B) visible light by emitting light by ultraviolet rays generated by gas discharge. The discharge space is filled with an inert gas for gas discharge.

This discharge cell is selected by address discharge by the data electrode 20 and the scan electrode 12A, and the selected discharge cell maintains the discharge by sustain discharge by the sustain electrode pairs 12A and 12B. The discharge cell emits the phosphor 26 by ultraviolet rays generated during the sustain discharge to emit R, G, or B visible light. In this case, the discharge cell adjusts the sustain discharge period, that is, the number of sustain discharges according to the video data, thereby implementing gray scale for displaying an image. A color of one pixel is realized by a combination of three discharge cells coated with R, G, and B phosphors 26, respectively.

As a method of driving such a PDP, an ADS (Address and Display Separation) driving method that is driven by being divided into an address period and a display period, that is, a sustain period is typical. As shown in FIG. 2, the ADS driving method divides one frame 1F into a plurality of subfields SF1 to SF8 corresponding to each bit of video data. Each of the subfields SF1 to SF8 again has a reset period RPD for initializing a radiation cell, an address period APD for selecting a discharge cell, and a sustain period SPD for maintaining the discharge of the selected discharge cell. Is divided into Here, the PDP implements the corresponding gradation by assigning different weights to the subfields SF1 to SF8 in the sustain period SPD and combining the sustain period SPD according to the video data.

In addition, the PDP uses an error diffusion method or the like to increase the gray scale expressive power.

The error diffusion method calculates quantization error data of digital video data using a Floyd-Steinberg error diffusion filter and spreads the calculated error data to adjacent pixels with different weights. For example, when the error diffusion operation is performed on the current P5 pixel as shown in FIG. 3, the error diffusion method has a weight of 1/16 on P1 adjacent to the P5 pixel, a weight of 5/16 on P2, and a value of 3 on P3. The weight of / 16 is weighted to P4 and 7/16 to calculate the error diffusion coefficient for each of the P1 to P4 pixels. Subsequently, the calculated error diffusion coefficients are added to generate a carry signal to be added to the current P5 pixel data. However, such an error diffusion method has a problem in that an error diffusion pattern is generated by constantly setting error diffusion coefficients (ie, weights) for neighboring pixels and repeating each line and frame.

Accordingly, it is an object of the present invention to provide a method and apparatus for processing video data of a PDP that can extend gray scale expression power while reducing error diffusion patterns.

In order to achieve the above object, the video data processing method of the PDP according to the present invention randomly spreads the video data of the pixel using error diffusion coefficients and random error diffusion coefficients calculated from each of the pixels adjacent to the pixel. Steps; And dithering the random error spread video data using a plurality of dither mask patterns divided by gray and frame.

The input video data is inverse gamma corrected video data.

In the random error diffusion step, a carry signal is generated by adding the lower bits of a part of the input video data, error diffusion coefficients calculated by giving different weights to the data of the adjacent pixel, and the random error diffusion coefficient. Making a step; And adding the carry signal to the remaining upper bits of the input video data and outputting the carry signal.

The random error spreading step comprises random substituting with one of the lower bit bits of the input video data, the error spreading coefficients calculated by giving different weights to the data of the adjacent pixel, and one of the error spreading coefficients. Adding a spreading coefficient to generate a carry signal; And adding the carry signal to the remaining upper bits of the input video data and outputting the carry signal.

The dithering may include selecting a dither mask pattern of a corresponding gray level among the plurality of dither mask patterns by using lower bits of some of the random error spread video data; Selecting a dither value at a position corresponding to the random error spread video data among the selected dither mask patterns; And adding the selected dither value to upper bits of the remaining part of the random error spread video data.

The selecting of the dither value includes counting a vertical sync signal, a horizontal sync signal, and a pixel clock signal input from an external source, and selecting a position corresponding to the random error spread video data using the counted signal. Characterized in that it comprises a.

The selecting of the dither value may include selecting the dither mask pattern by toggling dither mask patterns of different gradations for each frame according to the signal counting the vertical synchronization signal.

The dither mask pattern corresponding to the same gray scale and the same frame among the dither mask patterns may be different for each of red, green, and blue pixels.

The bit used in the random error spreading step of the video data may be a lower bit of the bit used in the dithering step.

A video data processing apparatus of a PDP according to the present invention includes a random error diffusion unit for random error diffusion of video data of a pixel using error diffusion coefficients and random error diffusion coefficients calculated from each of pixels adjacent to the pixel; And a dithering unit dithering the random error spreading video data by using a plurality of dither mask patterns divided by gray and frame.

The input video data may further include an inverse gamma correction unit for outputting by inverse gamma correction.

The random error spreader generates a carry signal by adding the lower bits of a part of the input video data, error diffusion coefficients calculated by giving different weights to the data of the adjacent pixel, and the random error diffusion coefficient. And add the generated carry signal with the remaining upper bits of the input video data to output the carry signal.

The random error diffusion unit random spreading is substituted with any one of the error diffusion coefficients calculated by applying different weights to the lower bits of a portion of the input video data, the data of the adjacent pixel, A carry signal is generated by adding a coefficient, and the generated carry signal is added to the remaining upper bits of the input video data and output.

A dither mask table configured to store the plurality of dither mask patterns and to select and output a dither value corresponding to the random error spread video data among the stored dither mask patterns; A mask controller for indicating a position where the dither mask table corresponds to the random error spread video data; And an adder for adding the dither value to the random error spread video data and outputting the dither value.

The mask controller may count vertical sync signals, horizontal sync signals, and pixel clock signals input from an external device, and select positions corresponding to the random error-diffused video data using the counted signals.

The mask controller is characterized in that to select while toggling the dither mask pattern of the corresponding gradation for each frame by the signal counting the vertical synchronization signal.

The dither mask table may further include different dither mask patterns for red, green, and blue pixels corresponding to the same gray level and the same frame.

The bit used in the random error spreader of the video data may be a lower bit of the bit used in the dithering unit.

Other objects and advantages of the present invention in addition to the above object will become apparent from the description of the preferred embodiment of the present invention with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 3 to 11.

3 is a block diagram schematically illustrating a video data processing apparatus of a PDP according to an embodiment of the present invention. The video data processing apparatus of the PDP shown in FIG. 3 includes a gamma correction unit 30, an error diffusion and dithering unit 32, a subfield mapping unit 34, connected between an input line of the video data and the PDP 38, The data driver 36 is provided.

The gamma correction unit 30 receives digital video data gamma-corrected to suit the luminance characteristic of the cathode ray tube CRT from the outside, that is, pixel data to be supplied to each of the cells (sub pixels) constituting the PDP 38. . The gamma correction unit 30 performs inverse gamma correction on each of the input pixel data to make the luminance characteristic according to the pixel data linear. For example, the gamma correction unit 30 outputs inverse gamma correction pixel data corresponding to the input pixel data by using a look-up table LUT that is set so that luminance characteristics according to the pixel data follow a 2.2 gamma curve. In this case, each of the pixel data output from the gamma correction unit 30 includes an integer part and a fractional part. For example, when 8-bit pixel data is input, the gamma correction unit 30 outputs pixel data corrected to 16 bits having an 8-bit integer part and an 8-bit decimal part.

The error diffusion and dithering unit 32 corrects each of the pixel data from the gamma correction unit 30 by an error diffusion method and a dithering method using a dither mask pattern, thereby outputting pixel data of which the number of bits is reduced while increasing the gray scale expression power. do. In this case, the error diffusion and dithering unit 32 adds a random error diffusion (hereinafter referred to as R-ED) coefficient to the error diffusion operation to prevent an error diffusion pattern caused by a constant error diffusion coefficient. In addition, the error diffusion and dithering unit 32 performs random error diffusion using the lower bits of the bits used in the dithering operation to subdivide the step between the dithering patterns to allow more gray scale expression. Detailed description of the error diffusion and dithering unit 32 will be described later.

The subfield mapping unit 34 maps each pixel data from the error diffusion and dithering unit 32 to a preset subfield pattern and outputs the mapping.

The data driver 36 latches the input data which is separated bit by bit according to the subfield pattern in the subfield mapping unit 34, and then, when the horizontal line drives the latched data line by line, Supply to address electrode lines.

The PDP 38 includes an address electrode line and a pair of sustain electrode lines intersecting the address electrode line with the discharge space therebetween. Each cell having a discharge space corresponding to the subpixel is formed at each intersection of the address electrode line and the sustain electrode line pair. The PDP 38 is a cell to be turned on by an address discharge according to data supplied from the data driver 36 to the address electrode line whenever the scan electrode line of the pair of sustain electrode lines is driven in the address period of each subfield. Select them. The PDP 38 causes the selected cells to maintain a discharge in the sustain period of each subfield by driving a pair of sustain electrode lines. In this case, as the number of bits of the video data is reduced by the error diffusion and dithering unit 32, the number of subfields constituting one frame is reduced, thereby sufficiently securing the address period. This drive is possible.

FIG. 5 illustrates a specific configuration of the error diffusion and dithering unit 32 shown in FIG. 4, and the error diffusion and dithering unit 32 may include a random error diffusion unit 40 and a dithering unit 50. Equipped.

The random error diffusion unit 40 calculates the error diffusion coefficients of adjacent pixels calculated by the video data and the error diffusion filter from the gamma correction unit 30 and error diffusions to reduce and output the number of bits of the pixel data. In this case, the random error diffusion unit 40 adds an R-ED coefficient to the error diffusion operation to prevent an error diffusion pattern caused by a constant error diffusion coefficient. To this end, the random error diffusion unit 40 includes an error diffusion filter and an R-ED coefficient generator connected to the error diffusion filter.

For example, when the error diffusion filter performs an error diffusion operation on the current P5 pixel as shown in FIG. 6, a weight of 1/16 is assigned to a fractional part (lower 5 bits of the 8-bit decimal part) of the P1 pixel adjacent to the P5 pixel. And a weight of 5/16 to a part of the fractional part of the P2 pixel, a weight of 3/16 to a part of the fractional part of the P3 pixel, and a weight of 7/16 to a part of the fractional part of the P4 pixel to give an error for each of the P1 to P4 pixels. Calculate the diffusion coefficient. Then, the R-ED coefficient R generated from the R-ED coefficient generator is added to the calculated error diffusion coefficients, or one of the calculated error diffusion coefficients is added to the R-ED coefficient generator. The first carry signal " 0 " or " 1 " is generated by substituting the ED coefficient R and adding it with a part of the decimal part (lower five bits of the decimal part) of the current pixel P6 data. Then, the error diffusion filter outputs 11-bit pixel data by adding the first carry signal to the remaining bits of the current pixel data (integer part 8 bits + fractional part 3 bits).

The dithering unit 50 dithers the pixel data from the random error diffusion unit 40 through the dither mask pattern and outputs the pixel data having the reduced number of bits to the subfield mapping unit 34.

To this end, the dithering unit 50 includes a dither mask table 54, a dither mask table 54, and the random line connected to the output lines of the dither mask controller 52 and the random error diffusion unit 40 as shown in FIG. 7. And an adder 56 connected to the output line of the error diffusion section 40.

The dither mask table 54 stores different dither mask patterns for each gray level and for each frame. For example, as shown in FIG. 8, dither mask patterns having a cell size (subpixel) of 4 × 4 are separated by eight gray levels, such as 0 to 7/8, corresponding to the lower 3 bits of the pixel data. As each of the dither mask patterns is separated into four frames (1F to 4F), the dither mask table 54 stores a total of 32 dither mask patterns. Referring to FIG. 8, dither value " 1 in each of the dither mask patterns of 0, 1/8, 2/8, 3/8, 4/8, 5/8, 6/8, 7/8, 7/8 gradation It can be seen that the number of cells set to "" increases in the order of zero, two, four, six, eight, ten, twelve, and fourteen. The positions of the cells set to the dither value "1" for each of the four frames 1F to 4F are different from each other. The position of "1" in each of these dither mask patterns may vary in accordance with the designer's needs. According to the dither mask pattern, the position of the on cell corresponding to the dither value "1" can be controlled spatially and temporally. In addition, as the position of the dither value "1" in the dither mask patterns is different for each gray level and for each frame, dither noise such as lattice noise due to repetition of a constant dither mask pattern may be reduced. Further, the dither mask table 54 may include different dither mask patterns for each of red, green, and blue pixels in order to further reduce noise due to the dither mask pattern.

The dither mask table 54 storing such dither mask patterns includes the lower bits of a part of the pixel data input from the random error diffusion unit 40, for example, 11 bits (8 integers plus 3 bits integer). Input 3 bits of decimal part. The dither mask table 54 selects a dither mask pattern having a gray level corresponding to the input lower 3 bits from among the dither mask patterns shown in FIG. 8. Subsequently, the dither mask table 54 selects the dither value D2 corresponding to the frame and cell position indicated by the mask controller 52 among the dither mask patterns of the selected gray level and outputs the dither value D2 to the adder 56.

To this end, the dither mask controller 52 counts the vertical synchronizing signal V input from an external controller (not shown) and indicates a corresponding frame among the four frames 1F to 4F, and the horizontal synchronizing signal H Each pixel clock signal P is counted to indicate a horizontal line and a vertical line, that is, a cell position in the corresponding frame. In this case, the dither mask controller 52 uses the signal of counting the vertical synchronizing signal V, and the dither mask table 54 toggles the first to fourth frames 1F to F4 while the dither mask pattern of the corresponding gray level is used. Allows you to select

The adder 56 adds the dither value D supplied from the dither mask table 54 as a carry signal to data of the upper 8 bits except the lower 3 bits of the pixel data supplied from the random error diffusion unit 40. The bit pixel data is supplied to the subfield mapping unit 34.

As described above, the method and apparatus for processing video data of the PDP according to the present invention are limited by the limited error diffusion unit 40 and the dithering unit 50 to expand the pixel data extended from the initial 8 bits to 16 bits by inverse gamma correction. By dithering correction, 8-bit pixel data is reduced and output. By using the output 8-bit pixel data, the basic 256 gray levels can be expressed. In addition, the video data processing method and apparatus of the PDP according to the present invention increases the number of grays that can be expressed by subdividing the grays between the respective basic grays by dithering using dither mask patterns as shown in FIG. 8 of the dithering unit 50. Let's go. This is made possible by a combination of spatially and temporally distributed data " 1 &quot; such as the dither mask patterns shown in FIG. In addition, the video data processing method and apparatus of the PDP according to the present invention further increase the number of gradations that can be expressed by further subdividing the gray levels divided by dithering due to the error diffusion of the random error spreading unit 40 as shown in FIG. 9. do. For example, in the present invention, the basic 256 gray scales are implemented by 8-bit pixel data finally output by the error diffusion and dithering operation, and 8 gray scales by dithering and 32 gray scales by random error spreading as shown in FIG. 2 ¹⁶ Gradation can be expressed. As a result, the video data processing method and apparatus of the PDP according to the present invention can increase the gradation power while minimizing error diffusion and dithering noise.

As described above, the video data processing method and apparatus of the PDP according to the present invention can increase the gray scale expression power while minimizing the error diffusion and the dithering noise by using the random error diffusion method and the dithering method.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (18)

A video data processing method of a plasma display panel for reducing the number of bits of inverse gamma corrected input video data by an error diffusion method and a dithering method, Random error diffusion of video data of the pixel using error diffusion coefficients and random error diffusion coefficients calculated from each of the pixels adjacent to the pixel; Dithering the random error spread video data using a plurality of dither mask patterns divided by gray and frame. delete The method of claim 1, The random error spreading step Generating a carry signal by adding the lower bits of a part of the input video data, the error diffusion coefficients calculated by giving different weights to the data of the adjacent pixel, and the random error diffusion coefficient; And adding the carry signal with the remaining upper bits of the input video data to output the carry signal. The method of claim 1, The random error spreading step Carry by adding the lower bits of a part of the input video data, the error diffusion coefficients calculated by giving different weights to the data of the adjacent pixel, and the random diffusion coefficient substituted with any one of the error diffusion coefficients. Generating a signal; And adding the carry signal with the remaining upper bits of the input video data to output the carry signal. The method of claim 1, The dithering step Selecting a dither mask pattern of a corresponding gray level among the plurality of dither mask patterns using lower bits of a part of the random error spread video data; Selecting a dither value at a position corresponding to the random error spread video data among the selected dither mask patterns; And adding the selected dither value to upper bits of the remaining part of the random error-diffused video data. The method of claim 5, wherein Selecting the dither value And counting the vertical synchronizing signal, the horizontal synchronizing signal, and the pixel clock signal respectively inputted from the outside, and selecting a position corresponding to the random error-diffused video data by using the counted signal. Method of processing video data on display panel. The method of claim 6, Selecting the dither value And toggling dither mask patterns of different gradations for each frame based on the counted signal of the vertical synchronization signal. The method of claim 1, The dither mask pattern corresponding to the same gradation and the same frame among the plurality of dither mask patterns is again different for each of red, green, and blue pixels. The method of claim 1, The bit used in the random error diffusion step of the video data is a lower bit of the bit used in the dithering step. A video data processing apparatus of a plasma display panel for reducing the number of bits of video data by an error diffusion method and a dithering method, A random error diffusion unit for random error diffusion of video data of the pixel using error diffusion coefficients and random error diffusion coefficients calculated from each of the pixels adjacent to the pixel; And a dithering unit dithering the random error-diffused video data using a plurality of dither mask patterns divided by gray and frame. The method of claim 10, And an inverse gamma correction unit configured to output the inverse gamma correction by outputting the input video data. The method of claim 10, The random error diffusion unit A carry signal is generated by adding the lower bits of the input video data, error diffusion coefficients calculated by giving different weights to the data of the adjacent pixel, and the random error diffusion coefficient, and generating the carry signal. And outputting a signal by adding the signal with the remaining upper bits of the input video data. The method of claim 10, The random error diffusion unit Carry by adding the lower bits of a part of the input video data, the error diffusion coefficients calculated by giving different weights to the data of the adjacent pixel, and the random diffusion coefficient substituted with any one of the error diffusion coefficients. And generating a signal and adding the generated carry signal with the remaining upper bits of the input video data to output the signal. The method of claim 10, The dithering unit A dither mask table for storing the plurality of dither mask patterns and selecting and outputting a dither value corresponding to the random error spread video data among the stored dither mask patterns; A mask controller for indicating a position where the dither mask table corresponds to the random error spread video data; And an adder for adding the dither value to the random error spread video data and outputting the dither value. The method of claim 14, The mask control unit And counting the vertical synchronizing signal, the horizontal synchronizing signal, and the pixel clock signal inputted from the outside, and selecting the positions corresponding to the random error-diffused video data using the counted signals. Data processing unit. The method of claim 15, The mask control unit And dither mask patterns of different gradations corresponding to the frames are selected while the vertical synchronization signal is counted. The method of claim 14, The dither mask table And a dither mask pattern different for each of red, green, and blue pixels corresponding to the same gray level and the same frame. The method of claim 10, And a bit used in the random error diffusion unit among the video data is a lower bit of the bit used in the dithering unit.

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