Localized Luma Prediction Mode Inheritance for Chroma Coding
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Solution Overview
Problem
The existing HEVC standard's chroma prediction mode inheritance is not suitable when luma and chroma coding structures are separated, leading to inefficient compression performance due to the use of a single prediction mode for large chroma prediction units.
Innovation Solution
Localized Luma Prediction Mode Inheritance (LLMI) method, where a chroma prediction block is divided into sub-blocks, each inheriting a prediction mode from a corresponding luma block, allowing for adaptive prediction modes that match local characteristics, and using a combined predictor for improved encoding and decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single prediction mode is used for large chroma prediction units, then device complexity is reduced, but compression performance deteriorates due to inability to adapt to local characteristics
Solution Approach 1:
The chroma prediction unit is divided into multiple sub-blocks, with each sub-block independently inheriting prediction modes from corresponding luma blocks. This segmentation allows different prediction modes to be applied to different regions, improving compression performance while maintaining manageable complexity through systematic processing.
Solution Approach 2:
Each chroma sub-block inherits prediction modes from its corresponding luma block, enabling local adaptation to different characteristics within the chroma prediction unit. This local quality approach allows the system to optimize prediction accuracy for each region without requiring complex global optimization.
2Productivity
If chroma prediction mode is inherited from luma block, then encoding efficiency is improved, but accuracy deteriorates when luma and chroma coding structures are separated
Solution Approach 1:
By segmenting the chroma prediction unit into sub-blocks that correspond to luma blocks, the system maintains the efficient inheritance mechanism while improving accuracy through localized matching. Each sub-block's prediction mode is inherited from its corresponding luma block, ensuring structural alignment even when coding structures differ.
Solution Approach 2:
The inheritance is performed at the sub-block level rather than the entire chroma prediction unit level, allowing local adaptation to matching characteristics between luma and chroma blocks. This resolves the accuracy issue when coding structures are separated by ensuring correspondence at the appropriate granular level.
3Measurement precision
If chroma prediction unit is divided into sub-blocks with individual prediction modes, then prediction accuracy is improved, but device complexity increases
Solution Approach 1:
The chroma prediction unit is divided into sub-blocks that correspond to luma blocks, enabling independent prediction mode inheritance for each sub-block. This segmentation improves prediction accuracy by allowing local optimization while maintaining systematic processing that manages complexity through structured inheritance rules.
Solution Approach 2:
The same prediction mode inheritance mechanism is applied universally across all chroma sub-blocks, each inheriting from corresponding luma blocks. This multi-functional application of the inheritance principle improves accuracy across different regions without requiring separate complex processing logic for each sub-block.
Data Source
AI summary
A method and apparatus of Inter/Intra prediction for a chroma component performed by a video encoder or video decoder are disclosed. According to this method, a current chroma prediction block (e.g. a prediction unit, PU) is divided into multiple chroma prediction sub-blocks (e.g. sub-PUs). A corresponding luma prediction block is identified for each chroma prediction sub-block. A chroma prediction mode for each chroma prediction sub-block is determined from a luma prediction mode associated with the corresponding luma prediction block. A local chroma predictor for the current chroma prediction block is generated by applying a prediction process to the multiple chroma prediction sub-blocks using respective chroma prediction modes. In other words, the prediction process is applied at the chroma prediction sub-block level. After the local chroma predictor is derived, a coding block associated with the current chroma prediction block is encoded or decoded using information comprising the local chroma predictor.