IMAGE ENCODER, IMAGE DECODER, IMAGE ENCODING METHOD, AND IMAGE DECODING METHOD

摘要

PROBLEM TO BE SOLVED: To improve a subjective image quality of a macro block in which a complicated picture and a flat picture are mixed, without causing large increase in the amount of information of a quantization parameter to be transmitted to an image decoder.

SOLUTION: An image encoder determines a quantization parameter QP for each macro block. The image encoder specifies, according to an image feature amount of a macro block, a rectangular region within the macro block the quantization parameter QP of which is to be changed, calculates a shift value dQP of the quantization parameter, and calculates from the quantization parameter QP and the shift value dQP of the macro block, the quantization parameter QPt of the orthogonal transformation block included in the rectangular region.

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