CODER

摘要

PURPOSE:To ensure the accuracy of orthogonal transformation and to realize a coding section with less circuit scale by increasing an output word length of orthogonal transformation. CONSTITUTION:An orthogonal transformation device 12 implements orthogonal transformation in the unit of blocks and outputs the result in m-bits. The transformed orthogonal components are rearranged and a component (maxAC) except its DC component is detected. Amax detector 13 detects a maximum value of an absolute value of the amplitude in the orthogonal component and the result is classified into four classes 0,1.2.3 depending on the magnitude. The maximum 3-class is quantized so as to be kept in (m-1) bits of dynamic range. The lower class is quantized to be within an m-bit word length. Moreover, the rearrangement method is implemented in the order of the arrow in figure as one method. Since the dynamic range of the input data to a variable length coder 19 is in a range of -MAX(m-1)-+MAX(m-1), the capacity of the table of the coder is enough to be that corresponding to the dynamic range of the (m-1) bit input.