KR20040006759A - Method for converting color space - Google Patents

Abstract

PURPOSE: A color spacer conversion method is provided to substitute an LUT(Look Up Table) storing 256 result values for converting YUV signals to RGB signals to an LUT storing 128 result values, thereby reducing the size of the entire LUT by half. CONSTITUTION: In a color spacer conversion method, an LUT(13) has 2¬(n-1) result values for multiplication included in a formula for calculating RGB signals of N bit from YUV signals of N bit. If input U/V signals exceed 2¬N, RGB signals are calculated by the result values stored in the LUT for the U/V signals. In the other case, complements of 2 for the U/V signals are obtained and RGB signals are calculated by using code values obtained by the inversion of the result values stored in the LUT for the complements of 2.

Description

Method for converting color space}

The present invention relates to a color space conversion method, and more particularly, to a color space conversion method for converting a YUV signal input from the outside into an RGB signal in a liquid crystal display (LCD).

Recently, LCDs have been widely used as flat panel display devices, and LCDs are being used in various devices due to their thin thickness and low power consumption.

The LCD includes an image scaler for scaling a TTL signal, a transition minimized differential signal (TMDS) signal, or image data transmitted in a YUV into a format suitable for output on an LCD screen, wherein the image scaler is inputted. When the video signal is a PC RGB signal or a TMDS RGB signal, the processing is performed to convert the image size of the input RGB signal into a form suitable for output since it is the same data format as the RGB format as the output data format.

When the input video signal is a YUV signal that is a video decorator output, the image scaler must convert the YUV signal to an RGB signal because the data format does not match, which is performed by the color space converter. All.

The color space converter converts a YUV signal input in a pixel unit into an RGB signal, and the calculation equation applied is as follows.

R = Y + 1.371 × (V-128) <Equation 1>

G = Y-0.689 × (U-128)-O.336 (V-128) <Equation 2>

B = Y + 1.732 x (U-128) <Equation 3>

In order to reflect this expression in the design, a method of designing and calculating the multiplier for each pixel of YUV and the result of pre-calculating the pixel values from 0 to 255 are described in the form of a Look Up Table (LUT). One way is to store it in memory and then use that LUT to find the RGB value.

However, since a multiplier requires four multipliers in order to calculate <Formula 1>, <Formula 2>, and <Formula 3>, a method using a LUT is commonly used.

According to the method using the LUT, an RGB value corresponding to an input YUV value is calculated when four LUTs are stored in a memory space or a combination logic area, and the size of the LUT is determined by the color space converter. It is closely related to size.

<Table 1> shows an example of the configuration of the LUT used in <Formula 1> in the conventional color space converter.

<Table 1> Configuration example of LUT

V Binary number V-128 × 1.371 0 0000_0000 -128 -175 One 0000_0001 -127 -174 2 0000_0010 -126 -173 3 0000_0011 -125 -171 ： ： ： ： 126 0111_1110 -2 -3 127 0111_1111 -One -One 128 1000_0000 0 0 129 1000_0001 One One 130 1000_0010 2 3 ： ： ： ： 253 1111_1101 125 171 254 1111_1110 126 173 255 1111_1111 127 174

The conventional color space converter includes an R value calculating section, a G value calculating section, and a B value calculating section, wherein the R value calculating section includes a LUT 1 and an adder 2, as shown in FIG. In the above configuration, when the Y signal and the V signal are input, the LUT 1 outputs the x1.371 value corresponding to the V signal, and the adder 2 sums the Y value and the output value of the LUT 10 to SUM. Output, the sum corresponds to an R value.

On the other hand, since the G value calculating section and the B value calculating section are also designed in the same concept as the R value calculating section, description of each component will be omitted.

Accordingly, the present invention has been made in view of the above circumstances, and provides a color space conversion method capable of reducing the size of the LUT to ½ and converting the YUV signal to the RGB signal using the reduced LUT. There is a purpose.

1 is a block diagram of a conventional color space converter.

2 to 4 are block diagrams of a color space converter according to an embodiment of the present invention.

A color space converter according to a preferred embodiment of the present invention for achieving the above object is applied to a color space converter for converting a YUV signal into an RGB signal using a look up table in an image scaler. To

A LUT having 2 ^N-1 result values for the multiplication operation included in the equation for calculating the N bit RGB signal using the N bit YUV signal is constructed.

When the input U / V signal exceeds 2 ^N , RGB is calculated using the result value stored in the LUT for the U / V signal,

If the input U / V signal does not exceed 2 ^N , the 2's complement for the U / V signal is taken and the result value stored in the LUT is called for the 2's complement code. It is characterized by calculating the RGB using.

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

2 to 4 are detailed configuration diagrams of an R value calculator of a color space converter to which a color space conversion method according to an exemplary embodiment of the present invention is applied.

In the embodiment of the present invention, only the detailed configuration diagram of the R value calculating section of the color space converter is presented, but since the G value calculating section and the B value calculating section are designed in the same concept as the R value calculating section, the G value calculating section and B The detailed configuration diagram of the value calculator is omitted.

In FIG. 2, the switching unit 10 determines whether the 8-bit V input signal i_v_ [7: 0] is 0000_0000, and when it is determined as 0000_0000, applies the predetermined selection signal to the multiplexer 17 and switches. When the selection signal is applied from (10), the multiplexer 17 outputs 11_0101_0000 inputted to the first terminal.

On the other hand, the 7-bit V signal i_v_ [6: 0] except the most significant bit from the V input signal i_v is input to the first and second complementary processing units 11 and 2 of the multiplexer 12. The complement processing unit 11 transmits a two's complement for the V signal i_v_ [6: 0] to the terminal 0 of the multiplexer 12. Subsequently, the multiplexer 12 uses the eighth bit i_v_ [7] of the V input signal i_v_ [0: 7] as a selection signal, and the eighth of the V input signal i_v_ [7: 0]. If the first bit i_v_ [7] is 1, the V signal i_v_ [6: 0] input to the first terminal is output, and the eighth bit i_v_ [of the V input signal i_v_ [7: 0] is output. 7]) outputs the output value of the two's complement processing unit 11 of 2.

The LUT 13 extracts the x1.371 value corresponding to the 7-bit V signal, converts the extracted x1.371 value to 8-bit binary number, and outputs it. The LUT 13 is configured as shown in Table 2 below.

TABLE 2

Binary number V-128 × 1.371 000_0000 0 0 000_0001 One One 000_0010 2 3 ： ： ： 111_1101 125 171 111_1110 126 173 111_1111 127 174

Subsequently, the 10-bit generator 14 generates 10 bits by adding 0 to the 9th and 10th bits for the 8-bit LUT 13 output value, and then generates the 10 bits, and then converts them to the inverter 15 and the multiplexer 16. Each inverter transmits, and the inverter 15 inverts it and transmits it to the 0 terminal of the multiplexer 16.

The multiplexer 16 uses the eighth bit i_v_ [7] of the V input signal i_v_ [0: 7] as a selection signal, and the eighth bit of the V input signal i_v_ [0: 7]. If (i_v_ [7]) is 1, the signal input to terminal 1 is outputted. If the 8th bit (i_v_ [7]) of the V input signal i_v_ [0: 7] is 0, it is inputted to terminal 0. Output the generated signal.

The output of the multiplexer 17 is sent to a 10-bit adder 22 (see FIG. 3) and added with the Y input signal.

Then, 8 bits (r_adder_out [7: 0]) excluding 2 bits of the output (r_adder_out [9: 0]) of the 10-bit adder 22 are applied to the multiplexer 30 (see FIG. 4). 30 denotes a 9th bit (r_adder_out [8]) of the output signal r_adder_out [9: 0] of the 10-bit adder 22 as a selection signal, and 9 of the output signal r_adder_out [9: 0]. If the 1st bit (r_adder_out [8]) is 1, the octal ff inputted to the 1st terminal is output.If the 9th bit (r_adder_out [8]) of the output signal r_adder_out [9: 0] is 0, the 0th terminal is output. The output signal (r_adder_out [7: 0]) of the 10-bit adder 22 inputted as is transmitted to terminal 0 of the multiplexer 32.

Subsequently, the multiplexer 32 uses the tenth bit r_adder_out [9] of the output signal r_adder_out [9: 0] as a selection signal, so that the tenth bit of the output signal r_adder_out [9: 0] is selected. If r_adder_out [9]) is 1, the octal number 00 inputted to terminal 1 is outputted. If the 10th bit (r_adder_out [9]) of the output signal r_adder_out [9: 0] is 0, it is inputted to terminal 0. The output signal of the multiplexer 30 is output.

The output of the multiplexer 32 is output by the flip-flop 34 as a result value o_r [7: 0] for the R value in synchronization with the clock signal i_vCLK.

Since the use of the multiplexers 30 and 32 requires that the R-values belong to 0≤R≤255, the value exceeding 255 is set to octal FF, that is, binary 1111_1111, and if the R-value is less than zero. This is to set the octal 00, that is, the binary 0000_0000, so that the R value output from the flip-flop 34 always belongs to 0≤R≤255.

According to the present invention as described above, in order to convert a YUV signal to an RGB signal, by replacing the LUT storing 256 result values with the LUT storing 128 result values, the size of the entire LUT can be reduced by half. There is.

Accordingly, as the size of the color space converter can be reduced, the total chip size of the image scaler in which the color space changer is configured can be reduced.

On the other hand, the present invention is not limited to the above-described embodiment, but can be modified and modified within the scope not departing from the gist of the present invention, such modifications and changes should be regarded as belonging to the following claims. will be.

Claims (1)

In a method applied to a color space converter that converts a YUV signal to an RGB signal using a look up table in an image scaler, A LUT having 2 ^N-1 result values for the multiplication operation included in the equation for calculating the N bit RGB signal using the N bit YUV signal is constructed. When the input U / V signal exceeds 2 ^N , RGB is calculated using the result value stored in the LUT for the U / V signal, If the input U / V signal does not exceed 2 ^N , the 2's complement for the U / V signal is taken and the result value stored in the LUT is called for the 2's complement code. Color space conversion method characterized in that to calculate the RGB using.