IMPROVED IMAGE CODING SYSTEM USING ADAPTIVE QUANTIZATION TECHNIQUE AND ADAPTIVE QUANTIZATION CONTROL METHOD THEREOF

摘要

In the hybrid image encoding system, the present invention refers to time activity using energy distribution of each DCT block included in each macro block of an input current frame and time activity using a motion compensation error value between a current input frame and a prediction error signal. Improved image with adaptive quantization control function to calculate local characteristic information of each macroblock to be quantized and to adaptively adjust the quantization scale in the quantization step based on the calculated local characteristic information of the image The present invention relates to an encoding system and a quantization control method. To this end, the present invention divides a frame input for encoding into a plurality of blocks of size N × N, and outputs an image signal of a spatial domain for each divided N × N block. DCT transform coefficients in frequency domain of each N × N block using cosine function And conversion; Grouping specific coefficients of the DCT into a plurality of preset groups using the DCT energy distribution for each of the transformed N × N transform coefficient blocks; Classify each of the grouped N × N transform coefficient blocks into a flat region, a texture region, or an edge region; Assigning a specific class value among a plurality of class values preset as a sequential level value by using the coefficient distribution of the classified area for each macro block including a plurality of area-classified N × N transform coefficient blocks; Calculating an average value of integer values of a class value of a plurality of neighboring macroblocks adjacent to the corresponding macroblock to be currently encoded; Adjusting the class value of the corresponding macroblock to be currently encoded using the calculated average class value up or down; Determining whether a peripheral region of the corresponding macroblock to be currently encoded is a texture region by using average class values of the plurality of neighboring macroblocks; A motion compensation error value is calculated between each macroblock in the current frame before encoding and each macroblock in the prediction error signal corresponding thereto, and when the calculated motion compensation error value is larger than a preset threshold, a corresponding weight signal is generated. and ; Local characteristic information in the quantization process of the macroblock to re-adjust the adjusted class value downward based on the weight signal generated when the surrounding area of the macro block is the texture region. As provided; By determining the quantization parameter in the quantization process based on the local characteristic information of the corresponding macroblock to be encoded and the data fullness state information of the output transmission buffer, it is possible to perform adaptive quantization that is very suitable for human visual characteristics, thereby subjective to the playback image. The picture quality can be improved.