KR20040085432A - Random dither pattern generator and method for dithering - Google Patents

Abstract

PURPOSE: An apparatus for generating a random dither pattern for dithering and a method thereof are provided to improve expression capability at a low level of a PDP by generating the random dither pattern for generating a dither pattern temporarily differently. CONSTITUTION: A synchronous signal count block(232) counts a vertical synchronous signal(Vsync) provided from a synchronous signal detector unit, and the vertical synchronous signal count value is transferred to a random selection signal generation block(234). The random selection signal generation block generates a pattern selection signal to select a random dither pattern at a constant period on the ground of the count value provided from the synchronous signal count block and then provides it to a random dither pattern storing block(236). The random dither pattern storing block selects one of a number of random dither patterns in response to a pattern selection signal and then transfers it to an exclusive OR block(XOR) through a line(L23).

Description

Random dither pattern generator and method thereof for dithering {RANDOM DITHER PATTERN GENERATOR AND METHOD FOR DITHERING}

The present invention relates to a dithering of a plasma display panel (PDP), and more particularly to a dithering suitable for generating a random dither pattern required to generate a dither pattern used to improve low levels of grayscale loss. The present invention relates to a random dither pattern generator and a method thereof.

In general, a PDP is formed of a transparent electrode arranged in a narrow gap between two thin glass substrates in a neon gap and arranged in a horizontal direction and a vertical direction on the inner surface of the glass. The image is displayed in such a way that a pixel at the point where a set of charged electrodes meets can emit light by gas ionization.

That is, PDP receives and reproduces video and audio data from various video output media such as broadcast signals, VCRs, DVDs, CDPs, and PCs. Especially, color images are mostly R (Red), G (Green), and B ( Blue signals are reproduced by receiving them from the image output media.In contrast to CRTs, the luminance characteristics of grayscale values are linear, so that inverse gamma with respect to the input data is required to match the image displayed on the plasma display with the image of the CRT. It must be corrected.

The inverse gamma correction performs inverse gamma so that a desired gamma is satisfied for each channel. In the process, the relationship between the output luminance with respect to the input gray level value for each of the R, G, and B channels is determined by adjusting the degree of the curve. .

However, in the case of such inverse gamma correction, image quality is degraded due to gradation loss (even at a low level) at low levels, and a dithering technique is used to prevent such degradation. The data below the decimal point discarded by the gamma correction is reflected in the final display data to realize smoother gradation representation.

Conventional typical dithering techniques for gray scale representation as described above include a method using an error diffusion algorithm (hereinafter referred to as conventional method 1) and a method using a comparator and an adder (hereinafter referred to as conventional method 2).

Conventional method 1 performs an operation for gray scale expression by feeding back an error and imputing it to surrounding pixels, and performing multiplication or division operations as well as addition and subtraction. In the conventional method 1, various operations are performed. Not only does it require complex computational circuitry for processing, but it also requires memory to store at least three lines of data, which not only complicates the entire system for inverse gamma correction, but also results in manufacturing costs for the entire product. This has the problem of increasing.

In addition, in the conventional method 2, when a binary number having information of an integer part and a decimal point part is provided as input data, the binary number having the information of the decimal part is compared with the binary value of the dither pattern through a comparator, and a decimal point. If the information value of the part is larger, '1' is added through the adder to the binary number containing the information of the integer part, otherwise the gray scale is expressed by not adding '1'.

However, this conventional scheme 2 has the advantage of not requiring complicated computational circuits and memory as compared to the conventional scheme 1, while the binary value of the dither pattern pattern has a constant pattern or is iterative and Due to the regularity, this not only causes a new problem that the pattern of the dither pattern is visually recognized on the display, but also has a fundamental problem that the expressive power of gradation is deteriorated.

On the other hand, as a solution for solving the problems of the conventional method 1 and the conventional method 2, it was proposed by the inventor and patented by the Korean Patent Office on May 7, 2002 under the name of "dithering device using a random dither pattern" Application No. 2002-025058 (hereinafter referred to as a prior patent) is filed.

In this prior patent, the dithering for gray scale expression is performed by generating a dither pattern for dithering by taking an exclusive logical sum (XOR) between a random number for each line generated using a random number generator and a prestored random dither pattern. By realizing the above, a new technique for solving the above-described problems in the conventional scheme 1 and the conventional scheme 2 is proposed.

In the case of this prior patent, when the general video, the viewer can not visually recognize the pattern of the dither pattern on the display can obtain a natural display image, but in the case of a still image due to the temporal regularity of the dither pattern pattern There is a problem that the pattern of the dither pattern is visually recognized on the display, which is another factor that eventually causes the service dissatisfaction of consumers.

Accordingly, the present invention is to solve the problems of the prior art described above, random dither for dithering that can improve the expressive ability at a low level of the PDP by generating a random dither pattern for the generation of the dither pattern in time differently. It is an object of the present invention to provide a pattern generator and a method thereof.

Another object of the present invention is random dither for dithering, which can improve the representation ability at a low level of the PDP by selectively generating random dither patterns different in time from a predetermined random dither pattern based on an image characteristic to be expressed. The present invention provides a pattern generator and a method thereof.

According to an aspect of the present invention, a random dither pattern required to perform a random number and an exclusive OR operation of every line period in order to generate a dither pattern used for dithering a gray scale representation of a PDP image is provided. An apparatus for generating an image, comprising: means for determining whether an input image is a moving image or a still image, generating a set pattern selection signal when the moving image is generated, and generating a random pattern selection signal when the moving image is still; Means for counting a vertical synchronizing signal of the input image and generating a count value when the random pattern selection signal is generated; Means for generating a pattern selection signal every predetermined period based on the generation count value; And a plurality of random dither patterns having different internal patterns, and when the pattern selection signal is generated, any one of the plurality of random dither patterns as a random dither pattern for an exclusive OR operation with a corresponding random number. A random dither pattern generator for dithering, comprising a means for selectively outputting and outputting a predetermined fixed random dither pattern as a random dither pattern for an exclusive OR operation with the corresponding random number when the set pattern selection signal occurs To provide.

According to another aspect of the present invention, a random dither pattern required to perform a random number and an exclusive OR operation of every line period in order to generate a dither pattern used for dithering for gray scale representation of a PDP image A method of generating a video, the method comprising: determining whether an input image is a video or a still image; Counting a vertical synchronization signal of the input image when the input image is a still image; Generating a pattern selection signal every predetermined period based on the count value; In response to the generated pattern selection signal, selecting and outputting any one of a plurality of random dither patterns having different internal patterns as a random dither pattern for an exclusive OR operation with a corresponding random number; And outputting a predetermined fixed random dither pattern as a random dither pattern for an exclusive OR operation with the corresponding random number when the input image is a video. .

1 is a schematic block diagram of a typical dithering system for generating a dither pattern for improving a low level of grayscale loss occurring during inverse gamma correction of a plasma display panel (PDP);

FIG. 2 is a detailed block diagram of the dither pattern generating device shown in FIG. 1;

FIG. 3 is a block diagram of a random dither pattern generating device according to a first embodiment of the present invention corresponding to the random dither pattern generating block shown in FIG. 2;

4 is a block diagram illustrating a random dither pattern generator according to a second exemplary embodiment of the present invention corresponding to the random dither pattern generator block shown in FIG. 2.

<Description of the symbols for the main parts of the drawings>

100: reverse gamma correction device 200: dither pattern generator

210: random number generation block 220: random number table

230: Random diet pattern generation block 231: Image judgment block

232: sync signal count block 234: random selection signal generation block

236: random dither pattern storage block 240: dither pattern generation block

300 dithering device

Hereinafter, with reference to the accompanying drawings will be described in detail the operation of the preferred embodiment according to the present invention.

A key technical aspect of the present invention is that, unlike the above-mentioned prior art in which a dither pattern required for dithering is formed by using a fixed random dither pattern that is previously set (stored), a number of different patterns having different patterns are different. Random dither patterns are stored and based on the count result of the vertical sync signal (Vsync), different random dither patterns are selectively generated at regular intervals, that is, random dither patterns are generated differently in time, and thus random dither generated differently in time. By generating a dither pattern necessary for dithering based on the pattern and the random number, it is easy to achieve the object of the present invention through such technical means. Here, a certain period of generating the random dither pattern differently (that is, generating a random dither pattern with different internal patterns) means a period that is not visually recognized by a person, for example, every period Frame period.

FIG. 1 is a schematic block diagram of a typical dithering system for generating a dither pattern for improving a low level of grayscale loss occurring during inverse gamma correction of a plasma display panel (PDP), and FIG. 2 is shown in FIG. Detailed block diagram of the dither pattern generating device.

Referring to FIG. 1, a typical dithering system includes an inverse gamma correction device 100, a dither pattern generation device 200, and a dithering device 300.

First, as the display characteristic of the PDP is linear, the inverse gamma adjusting device 100 performs inverse gamma correction on a binary number having information of an integer part and a decimal point part as input data DIN [7: 0], respectively. The integer part DIN_INT [7: 0] and the decimal part DIN_DEC [3: 0] are generated and provided to the dithering device 300.

In addition, the dither pattern generating apparatus 200 generates a dither pattern by using a random number generated every line and a random dither pattern generated according to the present invention. Referring to FIG. Reference will be made later in detail.

Next, the dithering device 300 is a binary number (DIN_DEC [3: 0]) having information of a decimal point part among binary numbers having information of each integer part and a decimal point part provided from the inverse gamma correction device 100. By comparing a binary value (threshold) of the dither pattern to be finally applied from the dither pattern generating device 200 through a comparator (not shown), the integer portion if the binary value (DIN_DEC [3: 0]) is larger Data that improves the expressive power of gradation by dithering by adding '1' through adder (not shown) to binary number (DIN_INT [7: 0]) containing information of '('), otherwise adding '1' Outputs (DOUT [7: 0]) to the display side, not shown.

FIG. 2 is a detailed block diagram of the dither pattern generating apparatus 200 of FIG. 1. The random number generation block 210, the random number table 220, the random dither pattern generation block 230, and the dither pattern generation are shown in FIG. 1. Block 240 is included.

Referring to FIG. 2, assuming that the random number generation block 210 uses a 4 * 4 dither pattern for a 42 inch wide VGA (853 * 480) PDP as an example, for example, 10-bit (bit) Random number (RN_OUT [3: 0] is refreshed by refreshing the random seed required for one line every line using a 1-bit random number generator by the Linear Feedback Shift Register (LFSR). ), And the generated random number is provided to the random number table 220.

In addition, the random number table 220 receives and stores a random number necessary for one line (that is, a 4 * 4 random number in a form corresponding to a 4 * 4 random diet pattern) from the random number generation block 210. The random number stored according to the timing is extracted and provided to the dither pattern generation block 240, that is, the exclusive OR block through the line L21.

Next, the random dither pattern generation block 230 stores a plurality of random dither patterns (for example, 16 4 * 4 random dither patterns having different internal patterns) according to the present invention. Any one of the patterns is selected according to the drawing timing in the random number table 220 and provided to the dither pattern generation block 240 through the line L23. The process of generating the random dither pattern is substantially direct to the present invention. As a related part, a detailed generation process of the random dither pattern will be described later in detail with reference to FIGS. 3 and 4.

Meanwhile, the dither pattern generation block 240 includes a random number (4 * 4 random number) provided from the random number table 220 through line L21 and a random dither provided from the random dither pattern generation block 230 through line L23. By performing an XOR operation between patterns (4 * 4 random dither patterns), a dither pattern to be finally applied to dithering is generated, and the dither pattern generated as described above is transferred to the dithering apparatus 300 of FIG. 1. do.

Next, the configuration of the random dither pattern generator for dithering according to the present invention and its operation will be described in detail.

[First Embodiment]

3 is a block diagram of a random dither pattern generator according to a first embodiment of the present invention corresponding to the random dither pattern generator block 230 shown in FIG. 2, and includes a synchronization signal count block 232 and a random selection signal. Generation block 234 and random dither pattern storage block 236.

Referring to FIG. 3, the sync signal count block 232 counts the vertical sync signal Vsync provided from the sync signal detecting means (not shown), where the vertical sync signal count value is a random selection signal generating block ( 234).

Next, the random selection signal generation block 234 generates a pattern selection signal for selecting a random dither pattern at regular intervals based on the count value provided from the synchronization signal count block 232 to generate a random dither pattern storage block 236. ) Here, the constant cycle means a cycle which is not visually recognized by a person. Examples of such cycles include every frame cycle.

Next, the random dither pattern storage block 236 stores a plurality of random dither patterns having different internal patterns, for example, 16 4 * 4 random dither patterns having different internal patterns. In response to the pattern selection signal provided from 234, one of the plurality of random dither patterns is selected and transferred to the dither pattern generation block 240, that is, the exclusive OR block of FIG. 2, through a line L23. .

Accordingly, in the dither pattern generation block 240 of FIG. 2, the random number (4 * 4 random number) provided from the random number table 220 through the line L21 and the random dither pattern storage block 236 through the line L23 are provided. By performing an XOR operation between the selected random dither patterns (4 * 4 random dither patterns), a dither pattern to be finally applied to dithering is generated, and the dither pattern generated as described above is the dithering device of FIG. 300).

As a result, in the dithering apparatus 300 of FIG. 1, a binary number having information of a decimal point part among binary numbers having information of each integer part and a decimal point part provided from the inverse gamma correction device 100 is provided (DIN_DEC [3: 0]) and the binary value of the finally applied dither pattern provided from the dither pattern generation block 240 of FIG. 2, and an integer if the binary value DIN_DEC [3: 0] is larger as a result of the comparison. A dithering process is performed to improve the expressive power of gray scales by adding '1' to a binary number (DIN_INT [7: 0]) having partial information, and otherwise adding '1'.

Therefore, according to the present exemplary embodiment, unlike the aforementioned prior art in which a dither pattern required for dithering is formed by using one fixed random dither pattern that is previously set (stored), a plurality of different patterns having different patterns are different. A random dither pattern is stored and a different random dither pattern is selectively used for a predetermined period (for example, every frame period that is not visually recognized by a human) based on the count result of the vertical sync signal Vsync, that is, the random dither pattern Is generated differently in time, and the dither pattern is generated randomly in time and space based on the random dither pattern and the dither pattern based on the random number. Visual image of the dither pattern pattern due to the regularity of the dither pattern in the image The can be effectively prevented.

Second Embodiment

FIG. 4 is a block diagram of a random dither pattern generator according to a second exemplary embodiment of the present invention, which corresponds to the random dither pattern generator block 230 shown in FIG. 2.

Referring to FIG. 4, the apparatus for generating a random dither pattern according to the present embodiment includes a synchronization signal count block 232, a random selection signal generation block 234, and a random dither pattern storage block that function substantially the same or similarly. 236, which is almost similar to the first embodiment described above, but determines whether the image input for display is a video or a still image, and based on the determination result, a plurality of random images having different internal patterns The difference is that one of the dither patterns is generated at a predetermined period (for example, every frame period) to generate selectively or to generate a predetermined fixed random dither pattern.

First, the image determination block 231 determines whether an image input for display is a moving picture or a still image. The determination method compares corresponding pixel values of adjacent frames or detects motion on a time axis. Etc. can be used.

That is, the image determination block 231 detects whether the input image is a moving image or a still image, and generates a setting pattern selection signal through the line L41 when it is determined that the input image is a moving image or a still image. To pass.

As a result, the random dither pattern storage block 236 selects a preset random dither pattern among a plurality of random dither patterns, and transfers it to the dither pattern generation block 240 of FIG. 2 through the line L23.

Therefore, when the input image is a video, the dither pattern generation block 240 of FIG. 2 is provided from the random dither pattern storage block 236 through the random number and line L23 provided from the random number table 220 of FIG. 2. The XOR operation between the preset random dither patterns will be performed.

Next, if it is determined that the input image is a still image, the image determination block 231 generates a setting pattern selection signal through the line L43, and as a result, random selection based on the count value from the synchronization signal count block 232. The signal generation block 234 generates a pattern selection signal on the line L45. In response, the random dither pattern storage block 236 selects and draws a corresponding one of a plurality of random dither patterns having different internal patterns. Transfer to the dither pattern generation block 240 of FIG. 2 through a line L23.

Therefore, when the input image is a still image, the dither pattern generation block 240 of FIG. 2 is provided from the random dither pattern storage block 236 through the random number and the line L23 provided from the random number table 220 of FIG. 2. An XOR operation between the randomly selected random dither patterns is performed.

That is, according to the present embodiment, unlike the above-described first embodiment in which a random dither pattern having different internal patterns is generated every certain period, such as every frame period, when the input image for display is a video, it is internal every certain period. Since a random dither pattern with different patterns and a preset random dither pattern are generated when the input image is a still image, not only the same effect as in the first embodiment described above can be obtained, but also adaptability according to necessity or use. It has further side effects that can further promote.

As described above, according to the present invention, unlike the above-described prior art in which a dither pattern required for dithering is formed by using a predetermined fixed random dither pattern, a plurality of different patterns having different patterns are different. Random dither pattern is stored and random dither patterns are selectively generated at regular intervals based on the count result of the vertical sync signal (Vsync), that is, random dither patterns are generated differently in time. Since dither patterns necessary for dithering can be generated based on patterns and random numbers, dither patterns can be generated randomly in time and space, and the dither pattern patterns due to the regularity of dither patterns can be generated not only in normal videos but also in still images. Display of PDP can be effectively prevented visual perception It can improve the image quality.

Claims (6)

An apparatus for generating a random dither pattern required to perform an exclusive OR operation with a random number of every line period in order to generate a dither pattern used for dithering a grayscale representation of a PDP image, Means for determining whether the input image is a moving image or a still image, generating a setting pattern selection signal when the moving image is generated, and generating a random pattern selection signal when the still image is moving; Means for counting a vertical synchronizing signal of the input image and generating a count value when the random pattern selection signal is generated; Means for generating a pattern selection signal every predetermined period based on the generation count value; And Stores a plurality of random dither patterns having different internal patterns, and selects any one of the plurality of random dither patterns as a random dither pattern for an exclusive OR operation with a corresponding random number when the pattern selection signal occurs And a means for outputting a predetermined fixed random dither pattern as a random dither pattern for an exclusive OR operation with the corresponding random number when the setting pattern selection signal is generated. The apparatus of claim 1, wherein the predetermined period is every frame period. The apparatus of claim 1 or 2, wherein the plurality of random dither patterns are 16 4 * 4 random dither patterns. A method of generating a random dither pattern required to perform an exclusive OR operation with a random number of every line period to generate a dither pattern used for dithering a grayscale representation of a PDP image, Determining whether the input image is a moving image or a still image; Counting a vertical synchronization signal of the input image when the input image is a still image; Generating a pattern selection signal every predetermined period based on the count value; In response to the generated pattern selection signal, selecting and outputting any one of a plurality of random dither patterns having different internal patterns as a random dither pattern for an exclusive OR operation with a corresponding random number; And And outputting a predetermined fixed random dither pattern as a random dither pattern for an exclusive OR operation with the corresponding random number when the input image is a moving image. The method of claim 4, wherein the predetermined period is every frame period. The method of claim 4 or 5, wherein the plurality of random dither patterns are 16 4 * 4 random dither patterns.