Unified Coefficient Scan for 8x8 Transform Units in HEVC
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Solution Overview
Problem
The existing High Efficiency Video Coding (HEVC) system has complexity in coefficient scan methods for 8×8 transform units, particularly in partitioning and scanning patterns, which increases system complexity and cost due to the use of multiple scanning patterns for intra and inter-coded coefficients.
Innovation Solution
A unified coefficient scan method for 8×8 transform units is introduced, dividing the 8×8 TU into four 4×4 sub-blocks and applying double scanning patterns, where the first-layer scanning order and second-layer scanning pattern are determined based on the intra prediction mode, allowing for efficient scanning across and within the sub-blocks using diagonal, horizontal, or vertical scanning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple scanning patterns are used for intra and inter-coded coefficients, then coding efficiency is improved, but system complexity increases
Solution Approach 1:
The patent merges the previously separate scanning pattern selections for intra-coded and inter-coded 8x8 transform units into a unified approach. Both intra and inter-coded TUs now use the same set of scanning patterns (diagonal, horizontal, and vertical) selected based on prediction mode, eliminating the need for separate pattern definitions and reducing system complexity while maintaining coding efficiency.
Solution Approach 2:
The patent makes the scanning pattern selection mechanism universal by applying the same pattern selection logic to both intra-coded and inter-coded transform units. The scanning patterns are no longer exclusive to specific coding types but are universally applicable across different TU types, simplifying the overall system architecture.
2Manufacturing precision
If different scan patterns are selectively applied to intra-coded 4x4 and 8x8 TUs, then coding precision is improved, but device complexity increases
Solution Approach 1:
The patent combines the previously separate scanning pattern definitions for intra-coded 4x4 and 8x8 TUs into a unified set of patterns. Both TU sizes now utilize the same diagonal, horizontal, and vertical scanning patterns, selected based on their respective prediction modes, reducing the complexity of pattern management while preserving coding precision.
Solution Approach 2:
The patent maintains local quality by allowing different scanning patterns to be selected for different TU sizes and prediction modes within the unified framework. Each 4x4 or 8x8 intra-coded TU can still opt for the most appropriate scanning pattern (diagonal, horizontal, or vertical) based on its specific prediction mode, ensuring optimal coding precision for local characteristics.
3Loss of information
If mode-dependent coefficient scan is used for intra-coded TUs, then loss of information is reduced, but ease of operation decreases
Solution Approach 1:
The patent merges the mode-dependent coefficient scan implementation into a unified framework that handles both intra and inter-coded TUs. The same scanning pattern selection logic based on prediction mode is applied universally, reducing the operational complexity of managing separate scan mechanisms while preserving the information preservation benefits of mode-dependent scanning.
Data Source
AI summary
A method and apparatus for processing 2N×2N transform units (TUs) are disclosed. In one embodiment, the method comprises determining a first-layer scanning order among four N×N sub-blocks of the 2N×2N TU; determining a second-layer scanning pattern for said four N×N sub-blocks; and providing scanned 2N×2N transform coefficients of the intra-coded or the inter-coded 2N×2N TU using double scanning based on the first-layer scanning order and the second-layer scanning pattern. In another embodiment, said determining the first-layer scanning order is dependent on the second-layer scanning pattern. The second-layer scanning pattern can be diagonal, horizontal or vertical. In an embodiment, the first-layer scanning order can be from an upper-left sub-block, to an upper-right sub-block, to a lower-left sub-block and to a lower-right sub-block for the second-layer horizontal scanning pattern and from an upper-left sub-block, to a lower-left sub-block, to an upper-right sub-block and to a lower-right sub-block for other second-layer scanning patterns.