Image Decoding Context Selection for Lower HEVC Memory Use
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Solution Overview
Problem
In image coding and decoding methods, particularly in High-Efficiency Video Coding (HEVC), the memory usage is high due to the need to hold conditional values from neighboring blocks, which increases computational resources and memory requirements.
Innovation Solution
The proposed method determines contexts for image blocks based on signal types, using decoded control parameters from neighboring blocks only when necessary, thereby reducing memory usage by not relying on the upper block for certain types of control parameters like 'cbf_luma', 'cbf_cb', and 'cbf_cr', and selecting appropriate contexts for hierarchical tree structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If decoded control parameters of neighboring blocks are used for context determination, then coding accuracy is improved, but memory usage increases
Solution Approach 1:
The patent segments the context determination process by dividing control parameters into different types (first type and second type) and applying different context determination methods to each type. For first type parameters, both left and upper neighboring blocks are used, while for second type parameters, only the left neighboring block is used, avoiding memory access to upper blocks.
Solution Approach 2:
The patent applies different context determination strategies to different types of control parameters based on their local characteristics. This local differentiation allows the system to optimize memory usage for specific parameter types (second type) while maintaining coding accuracy for other types (first type), rather than applying a uniform approach to all parameters.
2Measurement precision
If contexts are determined using neighboring blocks, then reconstruction accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent simplifies processing complexity by segmenting the context determination logic into type-specific rules. The signaling unit determines parameter types and applies corresponding context determination methods, avoiding the need for complex dynamic decisions about which neighboring blocks to access for each parameter.
3Productivity
If arithmetic coding is used for high probability events, then data compression is improved, but computational requirements increase
Solution Approach 1:
The patent changes the parameter of context determination (which neighboring blocks are used) based on the type of control parameter being coded. This parameter change optimizes the balance between compression efficiency and computational requirements by using simpler context models for parameter types where high compression is less critical.
Data Source
AI summary
The image decoding method includes: determining a context for use in a current block to be processed, from among a plurality of contexts; and performing arithmetic decoding on a bit sequence corresponding to the current block, using the determined context, wherein in the determining: the context is determined under a condition that control parameters of neighboring blocks of the current block are used, when the signal type is a first type, the neighboring blocks being a left block and an upper block of the current block; and the context is determined under a condition that the control parameter of the upper block is not used, when the signal type is a second type, and the second type is one of “cbf_luma”, “cbf_cb”, and “cbf_cr”.