KR950022993A - Method and apparatus for determining quantization level according to image characteristics of image data - Google Patents

Abstract

The present invention relates to a method and apparatus for determining quantization level according to image characteristics of image data. The present invention obtains the DC absolute match, the low frequency absolute match, the edge absolute match, and the high frequency absolute match in the frequency conversion region or the DCT region of the blocks constituting the macroblock (simple, edge, complex, ordinary). To judge. By using each block region information, macroblocks are also divided into one of four regions, thereby providing an effect of visually improving image quality by applying an appropriate quantization level to each macroblock.

Description

Method and apparatus for determining quantization level according to image characteristics of image data

Since this is an open matter, no full text was included.

1 is a block diagram showing an image data encoding apparatus to which the present invention is applied;

2 is a conceptual diagram showing a processing unit of image data.

Claims (11)

A coding apparatus including a DCT unit, a quantization unit, and a buffer for maintaining a constant bit ratio of a transmission signal, the transform coefficient values of predetermined block data applied from the DCT unit according to energy distribution characteristics of DC, low frequency, and edge. A first region judging unit taking an absolute value for each high frequency to obtain a sum thereof, and determining an image region of the block according to the absolute value sum; A second region determination unit for determining a corresponding region among a plurality of regions in which image information of a macroblock including a plurality of blocks is reflected on the area information of a block unit applied from the first region determination unit; And a quantization level determination unit configured to receive region information in macroblock units from the second region determination unit, and to receive an quantization level in slice units supplied from the buffer to determine an optimal quantization level. Quantization level determination device according to. The apparatus of claim 1, wherein the image regions comprise a simple region, an edge region, a complex region, and ordinary regions. A method for converting image data divided into blocks of a predetermined size into DCT-converted data into frequency domain data and determining quantization levels in macroblock units using energy distribution characteristics in the DCT domain, wherein the encoded image data is encoded. Outputting a variable quantization level such that the input image data and the amount of image data output for transmission are kept constant; Determining an image region of a block according to preset conditions according to conversion coefficient values of regions classified according to energy distribution characteristics in the DCT region; Determining region of a corresponding macroblock among a plurality of regions in which image characteristics are reflected according to a predetermined conditional expression by receiving region information of the block in macroblock units; And outputting an optimal quantization level by adjusting the quantization level by using the image characteristic. 4. The method of claim 3, wherein the block unit image area comprises: obtaining absolute values of transform coefficient values for each of DC, low frequency, edge, and high frequency classified according to energy distribution characteristics of the DCT area; Obtaining a sum of the absolute values of the DC, the low frequency, the edge, and the high frequency; And determining a corresponding block region among a plurality of regions in which image characteristics are reflected according to a sum of absolute values obtained for each of DC, low frequency, edge, and high frequency. 5. The method of claim 4, wherein the block region determination step satisfies any one of the following conditions. Condition 1: "a simple area" when a <DC <b → E + H <c and L> d Condition 2: a <DC <b → L + E <k x H "Edge area" Condition 3: a <DC <b → L + E <k x H "Complex area" Condition 4: If the conditions 1, 2, and 3 are not satisfied, the "normal area" Here, a, b, c, d, and k are preset constants, E is an edge region absolute match in block units, H is a high frequency region absolute match in block units, and L is a low frequency region absolute match in block units. The method of claim 5, wherein the determining of the area of the macroblock unit comprises receiving the area information of the blocks constituting the macroblock, and determining that the area of the macroblock is a simple area if more than half of the areas of the blocks are simple areas. If at least one DCT block is an edge region, it is determined as an edge region; if all DCT blocks are complex regions, it is determined as a complex region; otherwise, it is determined as an ordinary region. The quantization level determination method according to claim 6, wherein the optimal quantization level output step decreases the quantization level in the simple region and the edge region of the macroblock, and increases the quantization level in the complex region. The quantization level output step of claim 6, wherein the quantization level of the slice unit is changed to the quantization level of the macroblock unit in order to maintain a constant bitrate of input / output data when the macroblock region is a normal region. A quantization level determination method characterized in that the output. 8. The method of claim 7, wherein the optimal quantization level in the simple region satisfies the following formula. MQUANT = SQUANT-SQUANT / 2 Here, MQUANT is an optimal quantization level in macroblock units, and SQUANT is a quantization level in slice units that is varied to maintain a constant bitrate of input and output data. 8. The method of claim 7, wherein the optimal quantization level in the edge region satisfies the following formula. MQUANT = SQUANT-SQUANT / 4 Here, MQUANT is an optimal quantization level in macroblock units, and SQUANT is a quantization level in slice units that is varied to keep the bit rate of input and output data constant. 8. The method of claim 7, wherein an optimal quantization level in the complex region satisfies the following formula. MQUANT = SQUANT-SQUANT / 4 Here, MQUANT is an optimal quantization level in macroblock units, and SQUANT is a quantization level in slice units that is varied to keep the bit rate of input and output data constant. ※ Note: The disclosure is based on the initial application.