KR20090044215A - Image format transformation apparatus and method - Google Patents

Abstract

The present invention relates to image conversion, and in particular, by applying a three-tab filter when converting image data such as RGB, YCbCr, and YUV formats into luminance chrominance data such as YUV or YCbCr to suit an efficient use of memory or an application system. The present invention relates to an image format conversion device and method for minimizing image degradation and improving distortion. The apparatus of the present invention receives the RGB format data from a memory and a memory for storing and providing RGB format data and storing and providing the designated luminance color difference format data obtained by converting the RGB format data to convert the luminance color difference format data into the luminance color difference format data. And a video format converter which converts the format data into designated luminance color difference data so as to have a designated bandwidth by using a three-tap filter, and stores the format data in the memory.

Controller, Direct Memory Access (DMA) I / O, Format Converter, Converter

Description

Image format transformation apparatus and method

The present invention relates to image conversion, and in particular, by applying a three-tab filter when converting image data such as RGB, YCbCr, and YUV formats into luminance chrominance data such as YUV or YCbCr to be useful for an efficient use of memory or an application system. The present invention relates to an image format conversion device and method for minimizing image degradation and improving distortion.

In general, the reason for converting an image of YCbCr format into YCbCr 4: 2: 2, YCbCr 4: 1: 1 or YCbCr 4: 2: 0 format is used to reduce image data. The area where the human eye responds most sensitively is luminance Y, and the data corresponding to Y are considered to be very important information, while the Cb and Cr chrominance information containing color information is luminance. Reactions are relatively slower, which reduces the amount of image data by reducing color difference information rather than luminance.

1 is a diagram illustrating a video format conversion using a conventional CPU.

In the conventional video format conversion, the video format is converted using a high-speed general purpose CPU or a hardware converter.

Referring to FIG. 1, the CPU 20 reads image data stored in the YCbCr 4: 4: 4 format in the memory 10 and converts the output format into YCbCr 4: 2: 2 or YCbCr 4: 2: 0. In this case, image conversion is performed by deleting pixels of the hatched portions of the CPU 20 to generate image data suitable for the format and storing the image data in the memory 10 again. That is, the data corresponding to Cb and Cr were deleted and converted to YCbCr 4: 2: 2 or YCbCr 4: 2: 0.

The method using general purpose CPU or hardware converter (H / W converter) that converts the conventional video format is dependent on the performance of the CPU. Therefore, the CPU generates a load and the other general CPU needs to handle it. Problems affect the work.

In addition, as the original image reading operation of the general-purpose CPU proceeds and the storing operation of the converted image is repeated, a load is generated on the main bus. In addition, as the image processing apparatus finally performs a read operation for outputting the converted image, additional power loss may occur due to performance degradation and frequent memory access.

In addition, since the pixels are deleted to convert to a format suitable for the format, the image quality is degraded and the degradation is caused.

2 is a screen example illustrating a process of converting a conventional RGB image into YCbCr 4: 2: 2.

FIG. 2 is a diagram disclosed in the prior art Patent Application No. 10-2004-0064194 (Image Format Conversion Method with Low Image Distortion), which is a method for improving image quality distortion caused by a method of deleting pixels during format conversion.

Prior application patent is the first step in converting RGB color information into YCbCr 4: 2: 2 in the process of converting RGB color information into YCbCr 4: 4: 4 information, and in the converted YCbCr information, Y And a second step of obtaining the average value of the components of Cb and Cr of two adjacent pixels as they are, and converting the information into YcbCr 4: 2: 2 information. to be.

When converting RGB color information into YCbCr 4: 2: 2, the distortion of the image quality is improved by obtaining and converting the information value of each color.

However, the conventional method using the H / W converter as shown in FIG. 2 improves the image quality deterioration phenomenon by applying an average value, but does not sufficiently overcome the image quality deterioration phenomenon as shown in FIG. There is a problem.

In the conventional image format conversion method described above, deterioration of image quality is visually displayed in an artificial image, that is, an image such as an OSD (On Screen Display) or a Graphical User Interface (GUI). In addition, since the user's required image quality is very high, the conventional format conversion method is unreasonable, and a countermeasure for this is required.

The present invention has been proposed to solve the above-mentioned problems, and an object of the present invention is applicable to various image processing apparatuses such as a case of displaying on a LCD or compressing and transmitting an image taken from a camera. Since the format converter handles the compression conversion of the image, it does not need to refer to the separate CPU load or the virtual address of the CPU, and it is easy to improve performance and implementation, and to obtain a conventional sampling method or average value. An object of the present invention is to provide an image format conversion device and method for greatly improving image quality distortion and degradation.

According to an aspect of the present invention, there is provided an apparatus for converting an image format from a memory and a memory configured to store and provide RGB format data and to store and provide designated luminance color difference data obtained by converting the RGB format data. And an image format converter for converting the RGB color data into luminance color difference format data, converting the luminance color difference format data into designated luminance color difference data so as to have a specified bandwidth using a 3-tap filter, and storing the same in the memory. have.

The image format converter may be configured to read and provide the RGB format data stored in the memory, and to receive the RGB format data from the DMA input / output unit and the DMA input / output unit to write the converted luminance color difference data back to the memory and to convert the RGB luminance data into the designated luminance color difference data. After the conversion process, a format converter for providing the DMA input / output unit and the DMA input / output unit and the control necessary for the operation of the format converter are transferred. The DMA input / output unit transmits the address of the memory in which the data before and after the conversion is stored and the format converter It may include a controller for providing format information of the data.

In addition, the format converter includes an RGB converter for converting data in RGB format into a luminance chrominance format, and a converter for reconverting the luminance chrominance format data output from the RGB converter into designated luminance chrominance data suitable for an applied system. In the format data, color difference data representing Cb, Cr, U, or V may be configured as a 3-tap filter to which the following equation is applied. The luminance color difference format data includes YCbCr and YUV formats, and includes designated luminance. The color difference data may include data converted to various bandwidths such as 4: 4: 4, 4: 2: 2, 4: 2: 0, and 4: 1: 1 so as to be suitable for an application system.

In addition, the image format conversion method according to an embodiment of the present invention is a first step of converting the RGB format data into luminance chrominance format data when a DMA input / output unit provides the RGB format data and the converted luminance chrominance And filtering the format data to suit the application system, reconverting the designated luminance chrominance data into the designated luminance chrominance data, and providing the designated luminance chrominance data to the DMA input / output.

The filtering and reconversion of the converted luminance chrominance format data may include converting the luminance chrominance format data into the designated luminance chrominance data having a desired bandwidth in a system by applying a three-tap filter. Converting the RGB format data into the luminance chrominance format data may include converting and outputting the RGB format data into YCbCr format or YUV format data by the RGB converter of the format converter.

The present invention does not need to refer to the CPU load or the virtual address of the CPU because the CPU reads the original video and processes the original video in a separate video format converting apparatus.

In addition, the present invention is a conventional sampling method or average value by applying a three-tab filter in the case of compressing and converting RGB, YCbCr or YUV data into YCbCr 4: 2: 2 or YCbCr 4: 2: 0 format. Compared with the average method, the image distortion is greatly improved. In addition, the present invention can be equally applied to converting other luminance chrominance formats such as YUV.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted. For convenience, the same reference numerals are assigned to components that perform the same functions and roles even in other embodiments (drawings).

3 is a schematic configuration diagram of an image format conversion apparatus according to the present invention.

The video format converter 80 of the present invention includes a direct memory access (DMA) input / output unit 60, a format converter 70, and a controller 50 block.

The DMA input / output unit 60 processes reading / writing of image data to the memory 30, and the format converter 70 converts RGB format image data into YCbCR data or YUV data, which is a luminance chrominance format. The controller 50 block controls the overall conversion processing operation.

In the present invention, the conversion of the image format is performed in units of horizontal lines of the RGB image. The RGB format data stored in the memory 30 is transferred to the format converter 70 block by using the DMA input / output device 60, and the format converter 70 converts the luminance color difference format. The YCbCr data or YUV data is processed in the order of storing the YCbCr data or YUV data again in the memory 30 using the DMA input / output unit 60.

Control signals for performing such an operation are in charge of processing in the controller 50 block.

In addition, the controller 50 blocks a function of transferring information necessary for the operation of the DMA input / output unit 60 and the format converter 70.

The controller 50 blocks an address of the memory 30 in which the RGB format image data is stored and an address of the memory 30 in which the YCbCr data or YUV image data, which is the converted luminance color difference format, are stored. To pass.

In addition, the controller 50 block transmits format information of YCbCr data or YUV data, which is a luminance chrominance format to be converted, to a format converter 70 block.

As described above, the DMA input / output unit 60 transfers data of the address where the image data of the RGB format is stored to the format converter 70 block, and then returns YCbCr data or YUV data, which is the converted luminance color difference format. Saves to the memory address to be saved.

The format converter 70 converts the image data of the RGB format received from the DMA input / output unit 60 into YCbCr 4: 4: 4 data, and then finally sets YCbCr 4: 2: 2 or 4: 2: The image data is converted into the 0 format and then converted into the DMA input / output unit 60 block.

In the above-described video format converting apparatus, when the DMA input / output unit 60 receives the image data in RGB format, the format converter 70 first converts the data into YCbCr 4: 4: 4 data, which is a luminance chrominance format. Later, the YCbCr 4: 4: 4 data is filtered and converted into the YCbCr 4: 2: 2 format, or converted into the YCbCr 4: 2: 0 format, which is then provided to the DMA I / O 60 block to display the converted image data on the screen. To be possible.

In addition, the image format conversion apparatus of the present invention can convert not only the image data of the RGB format into the YCbCr form, which is the luminance chrominance format, but also into the YUV form.

4 is a detailed view of the format converter shown in FIG. 3 of the present invention.

The format converter 70 of the present invention includes an RGB converter 100 for converting image data in RGB format into YCbCr or YUV 4: 4: 4 image, and a three-tap filter for minimizing image quality deterioration. It consists of a converter (110) consisting of three tab filters (120, 130).

As mentioned above, the RGB converter 100 receives image data in RGB format and converts the image data into YCbCr 4: 4: 4 format or YUV 4: 4: 4 format and converts the following Equation 1 into hardware. Implement and process There is no deletion of video data at the time of conversion in the RGB converter 100 of the present invention.

The two three-tap filters 120 and 130 forming the converter 110 exclude Y from the YCbCr 4: 4: 4 format or YUV 4: 4: 4 format image data converted by the RGB converter 100. Filter Cb, Cr data or U, V to 4: 2: 2 format to convert or refilter to 4: 2: 0 format to convert image data to 4: 1: 1 format. I can convert it.

The 4: 2: 2 format consists of Cb and Cr configured to have half of the horizontal resolution of Y in the 4: 4: 4 format, and is often used in a considerable high quality image. The 4: 4: 4 format is a common format for converting to other color spaces.

The 4: 2: 0 format allows Cb and Cr to be configured to have half of the vertical resolution of Y. This format is also used in H.261 / 263.

As described above, the three-tab filters 120 and 130 applied to the present invention reduce the number of Cb, Cr, U, and V image data, which are color difference data, to convert 4: 4: 4 data to 4: 2: 2, Or 4: 2: 0, but other conversion types such as 4: 1: 1 are possible.

In the present invention, Y information of the input Y, Cb, Cr image information is used as it is, and Cb, Cr information is applied to three tab filters 120 and 130 as shown in FIG. The detailed configuration is implemented by processing hardware by applying the following Equation 2.

The values of the filter coefficients a, b, and c used in Equation 2 below are weights transmitted in the controller 60 block.

Y = 0.257 R + 0.504 G + 0.098 B + 16

Cb = -0. 148 R -0.291 G + 0.493 B + 128

Cr = 0.439 R-0.368 G -0.071 B + 128

'C 0 = (C 0 * (a + b) + C 1 * c) / (a + b + c)

'C 1 = (C 1 * a + C 2 * b + C 3 * c) / (a + b + c)

'C 2 = (C 3 * a + C 4 * b + C 5 * c) / (a + b + c)

In Equation 2, C0, C1, C2, C3, C4, and C5 represent input image data, and 'C0,' C1, and 'C2 are image data converted and output from a 3-tap filter, and filter coefficients a, b, and c Is a weight provided by the controller 60 block. Here, since C0 is a color difference signal Cr or Cb of the leftmost pixel on the line, 'C0 is obtained as in Equation 2 when C0 is obtained.

Equation 1 is a formula for converting an RGB image into an image of YCbCr or YUV 4: 4: 4 format in the RGB converter 100, and the detailed configuration is implemented by hardware to which Equation 1 is applied. Equation 2 is applied to a 3-tab filter.

5 is a diagram illustrating a three-tap filter of the present invention.

The three-tap filter 120, 130 of the present invention is processed to reduce the Cb, Cr or U, V shape in half, and is implemented to process the above equation (2).

Referring to the drawings, when the data C0 to C5 inputted by the 3-tap filter are outputted by Equation 2 and outputted as' C0, 'C1, and' C2 data, the amount of data is reduced by half. Can be.

As described above, the present invention converts an image converted into YCbCr or YUV 4: 4: 4 format into a 4: 2: 2 format when passed through a 3-tap filter, and then converts it into a 4: 2: 0 format when filtered again. do. It can also be converted to a format representing various bandwidths such as 4: 1: 1 format.

So far, the configuration and operation of the embodiment of the present invention have been described. The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the claims but also by the equivalents of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram for explaining image format conversion using a conventional CPU.

2 is a diagram illustrating a process of converting a conventional RGB image into YCbCr 4: 2: 2.

3 is a schematic structural diagram of a video format conversion apparatus according to the present invention;

4 is a detailed view of a format converter of the present invention.

5 illustrates a three-tab filter.

<Description of Major Symbols in Drawing>

30: memory 50: controller

60: DMA (Direct Memory Access) I / O 70: Format Converter

100: RGB converter 110: converter

120, 130: 3-tab filter)

Claims (7)

A memory for storing and providing RGB format data and storing and providing specified luminance color difference data obtained by converting the RGB format data; And Receiving the RGB format data from the memory and converting it into luminance chrominance format data, converting the luminance chrominance format data into designated luminance chrominance data so as to have a specified bandwidth by using a 3-tap filter, and converting the image format into the memory format. An image format converter comprising a portion. The method of claim 1, The image format converter A DMA input / output unit for reading and providing RGB format data stored in the memory and writing the converted luminance data of the converted chromaticity data back to the memory; A format converter which receives the RGB format data from the DMA input / output unit, converts it into the designated luminance color difference data, and then provides the converted format to the DMA input / output unit; Control for the operation of the DMA input / output unit and the format converter, wherein the DMA input / output unit includes a controller which transmits an address of a memory in which data before and after the conversion is stored, and the format converter provides format information of data to be converted. Video format converter. The method of claim 2, The format converter An RGB converter for converting data of an RGB format into a luminance chrominance format; And a converter for reconverting the luminance chrominance format data output from the RGB converter into designated luminance chrominance data for an application system. The method according to any one of claims 1 to 3, And the luminance chrominance format data includes any one of YCbCr and YUV formats. A first step of converting the data of the RGB format into luminance chrominance format data by a format converter when the DMA input / output unit provides the data of the RGB format; And And converting the converted luminance chrominance format data into a specified luminance chrominance data by filtering the converted luminance chrominance format data according to an applied system, and providing the designated luminance chrominance data to the DMA input / output unit. The method of claim 5, Re-filtering and converting the converted luminance color difference format data, And converting the luminance chrominance format data into the designated luminance chrominance data having a desired bandwidth in a system by applying a 3-tap filter. The method of claim 5, Converting the RGB format data into luminance chrominance format data by the format converter, And converting the data of the RGB format from the RGB converter of the format converter into data of the YCbCr format or the YUV format.

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