Dynamic Huffman Code-Length Control Under Upper Limits
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Solution Overview
Problem
Dynamic Huffman coding faces challenges in setting code word lengths within an upper limit due to constraints in data compression standards and hardware implementation, leading to potential violations and degradation in compression performance.
Innovation Solution
A compression device with a coding information generation unit that adjusts code lengths by changing those exceeding the upper limit and selecting shorter code lengths in descending order to ensure all code lengths conform to the limit, generating a coding table that maintains the integrity of variable-length codes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dynamic Huffman coding is used to generate variable-length codes based on symbol frequency, then compression efficiency is improved, but code word length may exceed the upper limit imposed by hardware constraints
Solution Approach 1:
The patent changes the code length parameter from its optimally calculated value to a constrained value that does not exceed the upper limit. When a symbol's assigned code length exceeds the hardware-imposed upper limit, the code length is adjusted to the maximum allowable value, thereby resolving the contradiction between achieving optimal compression efficiency and adhering to hardware constraints on code word length.
2Ease of manufacture
If code word length is constrained to an upper limit to meet hardware requirements, then hardware implementation feasibility is improved, but compression performance degrades
Solution Approach 1:
The patent applies parameter changes by adjusting the code length to the upper limit when the originally assigned code length exceeds the constraint. This modification ensures hardware implementation feasibility while minimizing the impact on compression performance by only changing code lengths when necessary and by setting them to the maximum allowable value rather than a fixed arbitrary value.
Data Source
AI summary
According to one embodiment, a compression device includes a coding information generation unit. The unit determines code lengths that are respectively associated with a plurality of symbols, based on a frequency of occurrence of each of the plurality of symbols. When the plurality of symbols include one or more first symbols that are respectively associated with one or more first code lengths exceeding an upper limit, the unit changes the first code lengths to the upper limit, selects, from one or more second symbols of the plurality of symbols that are respectively associated with one or more second code lengths shorter than the upper limit, at least one symbol in descending associated code length order, changes at least one code length associated with the symbol to the upper limit.