Cross-Component Prediction and Adaptive Color Transform in Video Coding
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Solution Overview
Problem
Existing block-based video coding systems, such as HEVC, face inefficiencies in architectural and operational implementations, leading to suboptimal coding performance, particularly in handling different color spaces and bit depths of luma and chroma components.
Innovation Solution
The implementation of cross-component prediction (CCP) and adaptive color transform (ACT) coding, where ACT is enabled or disabled at the transform unit level, allowing for multiple color spaces to be used for coding residuals, and dynamic adjustment of weighting parameters, bit depths, and quantization parameters to optimize coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If block-based video coding systems are used with standard architectures, then implementation is simplified, but coding performance becomes suboptimal
Solution Approach 1:
The video coding system is segmented into multiple independent processing paths (first parallel processing path and second parallel processing path), each handling different color spaces independently. This segmentation allows complex color space transformations to be broken down into manageable, parallelizable units that maintain coding performance while simplifying implementation through modular architecture.
Solution Approach 2:
The system dynamically selects between different color spaces (original color space and transformed color space) for different transform units based on content characteristics. This dynamic adaptation allows the system to optimize coding performance for each region while maintaining a standardized overall architecture, resolving the contradiction between implementation simplicity and coding performance.
2Productivity
If ACT is enabled at the TU level with multiple color spaces, then coding efficiency is improved, but processing complexity increases
Solution Approach 1:
The processing complexity is segmented by creating independent parallel processing paths for different color spaces. Each path handles a specific color space independently, allowing the complex color space transformations to be distributed across multiple simple, identical processing units rather than requiring one complex sequential processor.
Solution Approach 2:
The system merges the processing of multiple color spaces by executing multiple parallel processing paths simultaneously. The first parallel processing path processes the original color space while the second parallel processing path processes the transformed color space, and their results are combined to achieve improved coding efficiency without significantly increasing the complexity of individual processing units.
3Speed
If parallel processing paths are used for de-quantization and inverse transform, then decoding speed is improved, but synchronization complexity increases
Solution Approach 1:
The decoding process is segmented into independent parallel processing paths that operate on different color spaces independently. Each path performs de-quantization and inverse transform operations separately, allowing them to proceed at the same speed without requiring complex inter-path synchronization, as the segmentation creates natural independence between processing streams.
Data Source
AI summary
Cross-component prediction (CCP) and adaptive color transform (ACT) may be performed concurrently in a video coding system. CCP and ACT may be enabled/disabled at the same level (e.g. at the transform unit level) via an indicator signaled in the bitstream such as the ACT enable indicator for the CU. Inverse CCP and ACT may be operated at the same level (e.g. at the transform unit level). Prediction residuals may be converted to original color space without waiting for reconstruction of luma and chroma residuals of an entire prediction unit or coding unit. CCP and ACT transforms may be combined into one process to reduce encoding/decoding latency. Differences in dynamic ranges of color components may be compensated by variable dynamic range adjustments. Differences in bit depths between luma and chroma components may be compensated by selectively disabling the ACT coding tool, scaling a component output of the CCP, adjusting a quantization parameters (QPs) and/or shifting a component output of an inverse transform of the video coding system.