INVERSE QUANTIZER AND IMAGE DECODER EMPLOYING SAME

摘要

PROBLEM TO BE SOLVED: To provide an inverse quantizer with a high efficiency by taking into account also the visual sense characteristic while keeping interchangeability with inverse quantizers of prior arts.

SOLUTION: The inverse quantizer includes: an inverse quantization scale computing unit 301; an inverse quantization scale multiplier 302 for multiplying an inverse quantization scale QS with a quantization orthogonal transform coefficient X; an offset adder 304 for summating an offset value changed depending on a value of a quantization parameter QP to an output value of the inverse quantization scale 302; and a shift computing unit 305 for applying shift arithmetic operation with a shift direction and a shift amount in response to the quantization parameter QP to an output of the inverse quantization scale multiplier 302 or an output value of the offset adder 304 selected depending on the value of the quantization parameter QP to obtain an inverse quantization orthogonal transform coefficient Y.

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