Chroma Bitstream Signaling for Adaptive LMCS and CC-ALF Decoding
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Solution Overview
Problem
Existing video coding technologies face inefficiencies in handling chroma components, leading to suboptimal compression and increased bandwidth requirements due to the variable likelihood of intra prediction directions and motion vector redundancy.
Innovation Solution
Implementing chroma-related coding tools such as Luma Mapping with Chroma Scaling (LMCS) and Cross-Component Adaptive Loop Filter (CC-ALF) with syntax elements to manage chroma component coding independently, based on a first syntax element indicating dependency on a second component, and disabling these tools when not needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chroma-related coding tools (LMCS, CC-ALF) are always enabled and coded, then chroma component quality is improved, but bitstream overhead and decoding complexity increase
Solution Approach 1:
The patent implements dynamic enabling/disabling of chroma-related coding tools based on actual chroma component presence. A syntax element (chroma_present_flag) is introduced to dynamically control whether LMCS and CC-ALF tools are applied, allowing the decoder to adaptively process only necessary chroma data rather than always executing complex chroma processing pipelines.
Solution Approach 2:
The patent extracts the chroma component presence information as a separate syntax element (chroma_present_flag) that can independently control the processing of chroma-related tools. This allows the decoder to selectively ignore complex chroma processing when chroma is not present, removing unnecessary computational steps from the decoding pipeline.
2Productivity
If chroma-related coding tools are always applied, then compression ratio is improved, but bandwidth requirements increase due to additional syntax elements
Solution Approach 1:
The patent dynamically adjusts bitstream content based on chroma presence. When chroma is not present (chroma_present_flag=0), the bitstream omits LMCS and CC-ALF related syntax elements entirely, reducing bandwidth requirements. This dynamic adaptation allows the encoder to achieve high compression ratios only when chroma-related tools provide actual benefit.
Solution Approach 2:
The patent applies chroma-related coding tools partially - only when chroma component is actually present in the video stream. This avoids the excessive action of always applying these tools, thereby eliminating unnecessary bitstream overhead while maintaining compression efficiency where it matters.
3Adaptability or versatility
If chroma component is always processed independently with separate syntax elements, then chroma coding flexibility is improved, but device complexity and processing overhead increase
Solution Approach 1:
The patent implements dynamic control of chroma processing through the chroma_present_flag syntax element. This single flag enables the system to adapt between different processing modes: when set to 1, full independent chroma processing with LMCS and CC-ALF is enabled; when set to 0, chroma processing is completely bypassed. This dynamic approach provides flexibility without permanently increasing processing overhead.
Data Source
AI summary
Aspects of the disclosure provide a method and an apparatus including processing circuitry for video decoding. The processing circuitry decodes, from a coded video bitstream, a first syntax element indicating whether a first component in the coded video bitstream is coded based on a second component in the coded video bitstream. The processing circuitry determines whether to decode one or more second syntax elements for a chroma related coding tool based on the first syntax element. The chroma related coding tool is a luma mapping with chroma scaling coding tool or a cross-component adaptive loop filter. The one or more second syntax elements are decoded when the first syntax element indicates that the first component is coded based on the second component. The one or more second syntax elements are not decoded when the first syntax element indicates that the first component is not coded based on the second component.