Partitioned Entropy Encoding for Time-Varying Syntax Statistics
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Solution Overview
Problem
Existing entropy coding schemes face challenges in achieving a balance between coding complexity and compression efficiency, particularly when dealing with time-varying source statistics and skewed probability distributions, as they often require substantial adaptation and resource-intensive algorithms.
Innovation Solution
The proposed solution involves decomposing syntax elements into a sequence of source symbols and encoding them using a combination of VLC coding and arithmetic coding, allowing for better adaptation to syntax element statistics and improved compression efficiency with moderate coding overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Huffman codes with VLC tables are used for entropy coding, then implementation is simple and efficient, but adaptation to time-varying source statistics is demanding in terms of algorithmic complexity and implementation costs
Solution Approach 1:
The patent implements dynamic adaptation of VLC tables based on time-varying source statistics. The system monitors symbol probabilities over time and dynamically adjusts the VLC table structure to match current statistical characteristics, enabling efficient coding while adapting to changing data patterns without requiring complex arithmetic coding algorithms
Solution Approach 2:
The patent changes the parameters of the VLC coding scheme by adjusting the alphabet size and code structure based on the observed probability distribution of the source data. When the source statistics change, the system modifies the VLC table parameters (such as code word lengths and symbol mappings) to optimize compression performance for the current statistical regime
2Productivity
If arithmetic coding is used to handle time-varying source statistics and skewed probability distributions, then compression efficiency is improved, but implementation complexity is substantially higher than VLC
Solution Approach 1:
The patent employs multiple pre-computed VLC tables that can be quickly switched between based on the current statistical characteristics of the source data. Instead of implementing complex arithmetic coding, the system uses a collection of simpler VLC tables designed for different probability distributions, selecting the appropriate table for the current data regime. This approach achieves good compression efficiency while maintaining the simplicity of VLC implementation
Solution Approach 2:
The patent pre-computes multiple VLC tables for different source statistics scenarios before actual coding begins. These pre-prepared tables cover various probability distributions and time-varying conditions. During encoding, the system simply selects from these pre-computed tables based on current statistics, avoiding the need for complex real-time arithmetic coding calculations
3Productivity
If multiple sets of VLC tables are used for higher-order probability modeling, then compression efficiency is improved, but implementation complexity and resource requirements increase
Solution Approach 1:
The patent segments the probability space into multiple distinct regions or contexts, each with its own dedicated VLC table. Instead of using a single complex table or arithmetic coding, the system divides the modeling task into multiple simpler sub-tasks, each handled by a specialized VLC table for a specific probability range or context. This segmentation allows efficient higher-order modeling while keeping each individual table simple
Data Source
Figure 1A
Figure 1B~1C
Figure 2A
AI summary
Decomposing a value range of the respective syntax elements into a sequence of n partitions with coding the components of z laying within the respective partitions separately with at least one by VCL coding and with at least one by arithmetic coding is used to greatly increase the compression efficiency at a moderate coding overhead since the coding scheme used may be better adapted to the syntax element statistics. Accordingly, in accordance with embodiments, syntax elements are decomposed into a respective number n of source symbols si with i=1...n, the respective number n of source symbols depending on as to which of a sequence of n partitions (1401-3) into which a value range of the respective syntax elements is sub-divided, a value z of the respective syntax elements falls into, so that a sum of values of the respective number of source symbols si yields z, and, if n>1, for all i=1...n-1, the value of si corresponds to a range of the ith partition.