Video Residual Coefficient Decoding Using Hierarchical Significance Maps
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Solution Overview
Problem
The complexity of high efficiency video coding (HEVC) standards, particularly in encoding and decoding residual coefficients, is exacerbated by the need for numerous look-up tables, which consumes memory and increases complexity, especially when handling transform units of varying shapes and sizes.
Innovation Solution
The proposed solution involves a method for encoding and decoding residual coefficients using a two-layer hierarchy scan pattern, specifically a backward diagonal down-left scan, which reduces memory usage by dividing transform units into sub-blocks and using smaller scan patterns, such as 2x2 and 4x4, to encode significant coefficient groups, thereby minimizing the number of required look-up tables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transform units are subdivided into sub-blocks with multiple scan patterns, then coding efficiency is improved, but device complexity and memory consumption increase due to numerous look-up tables
Solution Approach 1:
The transform unit is segmented into multiple sub-blocks, and the significance map is divided into corresponding sub-regions. Each sub-block has its own simplified scan pattern and look-up table, reducing the complexity of managing large transform units while maintaining coding efficiency through localized processing.
Solution Approach 2:
The patent introduces a hierarchical dimension by organizing scan patterns and look-up tables at multiple levels (transform unit level and sub-block level). This dimensional organization allows efficient access to scan patterns based on transform unit size and shape without requiring all possible scan patterns to be stored simultaneously.
2Productivity
If transform units are subdivided into sub-blocks with multiple scan patterns, then coding efficiency is improved, but memory consumption increases due to numerous look-up tables
Solution Approach 1:
The large transform unit is segmented into smaller sub-blocks, each with its own simplified look-up table. This segmentation reduces the total memory required compared to storing comprehensive look-up tables for all possible transform unit configurations, while still providing the flexibility needed for efficient coding.
Solution Approach 2:
The patent implements a nested structure where sub-block look-up tables are contained within the broader transform unit processing framework. Smaller scan patterns for sub-blocks are nested within the larger transform unit scan patterns, allowing efficient memory utilization by storing only the necessary scan patterns at each hierarchical level.
3Adaptability or versatility
If the coding standard supports transform units of varying shapes and sizes, then adaptability is improved, but device complexity increases due to numerous look-up tables
Solution Approach 1:
The transform unit is segmented into sub-blocks that can independently handle different shapes and sizes. This segmentation allows the system to adapt to various transform unit configurations by applying appropriate scan patterns to sub-blocks without requiring complex overall processing logic for each possible transform unit size and shape combination.
Solution Approach 2:
The patent implements dynamic selection of scan patterns and processing methods based on the actual transform unit size and shape. The system can adaptively choose between different scan patterns (e.g., diagonal, horizontal, vertical) and processing approaches depending on the specific configuration, providing flexibility without requiring all possible configurations to be handled by complex fixed logic.
Data Source
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AI summary
Disclosed is a method of decoding residual coefficients of a transform unit from a bitstream of video data. The method receives the transform unit (1500) from the bitstream of video data in which the transform unit has upper (1503) and lower (1502) level square layers. The upper level layer represents a square arrangement of at most four significant coefficient group flags with each of the significant coefficient group flags representing a non-overlapping region of the lower level layer. The method determines determining the significant coefficient group flags of the square upper level layer for the received transform unit, and determines values of residual coefficients of the square lower layer according to the determined significant coefficient group flags to decode the transform unit of the bitstream of video data. Corresponding encoding methods are also disclosed.