Hierarchical LMCS, ALF, and SAO Control for Video Encoding Efficiency
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Solution Overview
Problem
Existing video coding standards face challenges in achieving optimal compression efficiency and quality trade-offs, particularly in advanced standards like VVC, where complex encoding processes can lead to inefficiencies and suboptimal use of resources.
Innovation Solution
Implementing control flags for luma mapping with chroma scaling (LMCS), adaptive loop filter (ALF), and sample adaptive offset (SAO) at sequence, picture, and slice levels, allowing for dynamic enablement and disablement based on specific control flags, to optimize encoding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If complex encoding processes are used to improve compression efficiency, then coding performance is improved, but device complexity and processing overhead increase
Solution Approach 1:
The patent implements dynamic control of loop filters (LMCS, ALF, SAO) through multiple enable/disable flags at different hierarchy levels. The encoder can adaptively activate or deactivate specific filter processes based on content characteristics and coding conditions, transforming static complex encoding into dynamic conditional processing that maintains high compression efficiency while reducing actual processing complexity when filters are disabled.
Solution Approach 2:
The patent divides the loop filtering process into separate, independently controllable modules: LMCS (luma mapping with chroma scaling), ALF (adaptive loop filter), and SAO (sample adaptive offset). Each module can be individually enabled or disabled through specific control flags, allowing selective application of filtering techniques rather than applying all filters uniformly, thus reducing overall device complexity while maintaining compression efficiency where needed.
2Adaptability or versatility
If multiple control flags are signaled at sequence, picture, and slice levels to enable dynamic filter control, then adaptability is improved, but loss of information and processing overhead increase
Solution Approach 1:
The patent applies different control granularities at different hierarchy levels: sequence-level flags provide global control for entire video sequences, picture-level flags offer frame-by-frame adaptability, and slice-level flags enable region-specific control within pictures. This multi-level approach allows the system to match the control granularity to the actual content variability, applying fine-grained control only where necessary and using coarser control elsewhere, thereby reducing overall bitstream overhead while maintaining adaptability.
Solution Approach 2:
The patent implements a hierarchical flag system where higher-level flags provide default control and lower-level flags offer optional overrides. Not all flag combinations are necessarily used in every scenario - the system enables only the necessary level of control based on content requirements. This partial action approach avoids the overhead of signaling all possible control parameters unconditionally, reducing bitstream loss while preserving adaptability when needed.
Data Source
AI summary
Methods and apparatuses for video encoding, comprising: receiving a video sequence; encoding the video sequence by using control flags for luma mapping with chroma scaling (LMCS) at a sequence level, a picture level, or a slice level, wherein the sequence level, the picture level, and the slice level are levels ranking from high to low; signaling a first control flag indicating whether the LMCS is enabled at a first level; and in response to the first control flag indicating the LMCS is enabled at the first level, signaling a second control flag indicating whether LMCS is enabled at a second level, wherein: the LMCS is enabled at the second level when a value of the second control flag equals to 1; the LMCS is disabled at the second level when the value of the second control flag equals to 0; and the second level is a lower level than the first level.