Variable length encoding method and apparatus for differential motion vector values using an improved differential motion code table

摘要

A variable-length coding apparatus for encoding motion vector values using improved differential motion code table variable-length-codes, wherein the differential motion vector value is the difference between the motion vector values of a single frame. A delay in the encoder delays an input motion vector value until a next motion vector value is input thereto, and outputs the delayed motion vector value. A subtracter calculates a difference value between the delayed motion vector value and the next motion vector value. A variable-length code uses an altered differential motion code table so that a longer variable-length code is assigned thereto as the magnitude of the absolute value of the differential motion vector value is larger, while a shorter variable-length code is assigned thereto as the magnitude of the absolute value of the differential motion vector value is smaller, even for the differential motion vector values outside the range of the motion vector values generated in a single frame, from a differential motion code table generated based on a method proposed by "ISO/IEC 11172-2", and variable-length-codes of an input differential motion vector value. Thus, the motion vector values can be more efficiently encoded than that of using the existing table without modifying the existing hardware structure.