Chroma Intra-Block Copy with Luma-Derived Block Vectors
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Solution Overview
Problem
Existing video encoding and decoding technologies face challenges in efficiently utilizing intra-block copy techniques, particularly for chroma components, and in minimizing coding information for residual blocks of both luma and chroma components.
Innovation Solution
The method involves encoding and decoding processes that utilize intra-block copy to derive block vectors for chroma blocks from luma blocks, allowing for various resolutions, including integer and fractional pixel resolutions, and incorporating syntax elements to indicate block vector resolution and prediction modes, while generating residual blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If intra-block copy is used for chroma blocks, then coding efficiency is improved, but device complexity increases due to deriving block vectors from luma blocks with multiple resolution options
Solution Approach 1:
The patent applies parameter changes by introducing multiple block vector resolutions (integer and fractional pixel resolutions) for intra-block copy in chroma blocks. The encoder can select from different resolution options (e.g., 1/2, 1/4, 1/8 pixel precision) to optimize the balance between coding efficiency and complexity. This allows the system to adaptively change the precision parameter based on content characteristics and rate-distortion optimization.
Solution Approach 2:
The patent implements dynamics by making the block vector resolution configurable and adaptive rather than fixed. The encoder can dynamically select different resolution levels for different chroma blocks based on their complexity and correlation with luma blocks. This dynamic approach allows the system to use higher precision where needed and lower precision where sufficient, optimizing the complexity-efficiency tradeoff.
2Measurement precision
If multiple block vector resolutions are supported, then prediction accuracy is improved, but loss of information increases due to additional syntax elements required for signaling resolution
Solution Approach 1:
The patent uses parameter changes by introducing a resolution indicator parameter that signals which block vector resolution is being used. Instead of encoding multiple separate syntax elements for each resolution level, the system changes the interpretation of the block vector syntax based on this indicator parameter, reducing the overall information overhead while maintaining multiple resolution options.
Solution Approach 2:
The patent applies universality by designing a unified syntax structure that can represent multiple resolution levels. The same block vector syntax elements serve multiple functions depending on the resolution indicator value, eliminating the need for separate encoding paths for each resolution level and reducing redundant information signaling.
3Loss of substance
If intra-block copy is applied to both luma and chroma components, then data redundancy is reduced, but device complexity increases due to separate processing requirements
Solution Approach 1:
The patent applies merging by combining the intra-block copy processing for luma and chroma components into a unified framework. The block vector derivation for chroma blocks is merged with the luma block processing, allowing shared computation and data structures. This reduces device complexity by eliminating separate processing pipelines while still achieving redundancy reduction for both components.
Solution Approach 2:
The patent implements self-service by allowing chroma blocks to derive their block vectors from corresponding luma blocks within the same picture. This self-service mechanism eliminates the need for external reference pictures or additional inter-block copy operations, reducing complexity while effectively removing redundancy between luma and chroma components.
Data Source
AI summary
A method and an apparatus for video encoding/decoding based on an intra-block copy are disclosed. A method for decoding video data comprises decoding coding information for a chroma block from a bitstream, determining that the chroma block is decoded using intra-block copy based on the coding information, identifying a previously decoded luma block using the intra-block copy in a luma area corresponding to the chroma block, deriving a block vector for the chroma block based on a block vector of the previously decoded luma block, and deriving a prediction block for the chroma block based on the block vector of the chroma block.