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

摘要

PROBLEM TO BE SOLVED: To improve efficiency of compression by variable-length encoding in accordance with characteristics in the image data of a processing object.

SOLUTION: The device for encoding quantized data in a variable length and compressing it includes a statistic-information storage memory (212) for storing the statistic information (MB Typ, CBPL) of the encoded image data, a variable-length encoding table-preparing unit (213) for preparing the variable-length encoding table on the basis of the statistic information stored in the statistic-information storage memory, and a variable-length encoder (205) for performing a variable-length encoding operation on the basis of the variable-length encoding table prepared by the variable-length encoding table-preparing unit. The variable-length encoding table-preparing unit adds the occurrence probability of the statistic information processed within the predetermined region of the encoded image data, to an initial occurrence probability selected on the basis of an encoding parameter at a step (S3005) and allocates a shorter code in the order of the statistic information with the higher occurrence probability thus obtained at the step (S3006), to prepare the variable-length encoding table.

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