Adaptive Color Transform for Size-Constrained Video Block Coding
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Solution Overview
Problem
Existing video coding technologies face challenges in efficiently handling large video blocks and adapting color transforms to optimize bandwidth usage and compression efficiency, particularly in emerging standards like Versatile Video Coding (VVC).
Innovation Solution
The implementation of adaptive color transform (ACT) mode in video encoding and decoding, which includes determining maximum and minimum block sizes, enabling ACT at sub-block levels, and applying format rules for palette modes and flags to optimize color transform usage, along with other coding tools like block-based delta pulse code modulation (BDPCM) and reference picture resampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If adaptive color transform (ACT) mode is applied to large video blocks, then compression efficiency is improved, but block size constraints limit the applicability and flexibility
Solution Approach 1:
The patent divides a large video block into multiple sub-blocks, allowing ACT mode to be applied selectively to each sub-block. This segmentation enables the coding process to handle blocks of various sizes by recursively partitioning larger blocks until reaching a suitable size for ACT application, thereby resolving the contradiction between compression efficiency on large blocks and adaptability to different block sizes.
Solution Approach 2:
The patent introduces dynamic block size determination through recursive partitioning, where the block size is not fixed but adaptively adjusted based on content characteristics and coding conditions. The encoder can dynamically select whether to apply ACT to the entire block or partition it into sub-blocks, providing flexibility across different block sizes while maintaining compression efficiency where applicable.
2Device complexity
If video block size increases, then fewer blocks are needed covering the same area, but ACT mode cannot be applied when block size exceeds maximum allowed size
Solution Approach 1:
When a video block exceeds the maximum allowed size for ACT mode, the patent automatically partitions it into smaller sub-blocks that meet the size requirements. This segmentation strategy allows the system to work with larger blocks when beneficial for complexity reduction, while ensuring ACT mode can still be applied to the resulting sub-blocks, thus resolving the contradiction between reducing block count and maintaining ACT applicability.
Solution Approach 2:
The patent performs preliminary partitioning of oversized blocks before applying ACT mode. By pre-dividing blocks that would otherwise be too large for ACT into appropriate sub-blocks, the system ensures that ACT can be successfully applied without losing the benefits of working with larger block structures, thereby resolving the contradiction between block size management and ACT mode requirements.
3Productivity
If ACT mode is applied to all blocks, then compression efficiency is maximized, but computational complexity and processing overhead increase
Solution Approach 1:
The patent applies ACT mode selectively rather than uniformly across all blocks. By determining whether to apply ACT based on local block characteristics, size, and content type, the system achieves compression efficiency improvements where ACT is beneficial while avoiding unnecessary processing overhead in blocks where ACT would not provide significant gains, thus resolving the contradiction between compression efficiency and processing complexity.
Solution Approach 2:
The patent implements partial application of ACT mode, applying it only to blocks or sub-blocks that meet specific size and content criteria rather than to all blocks. This partial action approach achieves sufficient compression efficiency improvement without the excessive processing overhead that would result from universal ACT application, resolving the contradiction between compression gain and computational cost.
Data Source
AI summary
A method for implementing an adaptive color transform (ACT) during image/video encoding and decoding, includes determining, for a conversion between a video including a block and a bitstream of the video, that a size of the block is greater than a maximum allowed size for an ACT mode, and performing, based on the determining, the conversion, wherein, in response to the size of the block being greater than the maximum allowed size for the ACT mode, the block is partitioned into multiple sub-blocks, and wherein each of the multiple sub-blocks share a same prediction mode, and the ACT mode is enabled at a sub-block level.