| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image decoding apparatus and method for reducing the bit size required in the computation of video coding transformations. <P>SOLUTION: A quantization parameter QP and a quantization value L are decoded from encoded data and dequantized by a dequantization means to determine a transformation coefficient K. When obtaining a decoded image by performing inverse integer transformation on image data using the dequantized transformation coefficient K, the number of bits required for intermediate results of dequantization computation is reduced. In an image decoding apparatus, the dequantization means uses a mantissa part Bm(QP) and an exponent part Be(QP) that are functions of the quantization parameter QP to determine the transformation coefficient K according to K=L×Bm(QP)<<Be(QP). Furthermore, structures for the functions of the mantissa part and the exponent part are represented, using constants P and B, as Bm(QP)=Bm(QP_mod_P) and Be(QP)=B+QP/P. <P>COPYRIGHT: (C)2010,JPO&INPIT |
