Chroma Array Signaling for Efficient Intra Prediction Decoding
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Solution Overview
Problem
The increasing demand for high-resolution, high-quality images and immersive media formats such as VR and AR necessitates more efficient image/video compression techniques to reduce transmission and storage costs, particularly in signaling information on chroma format and improving intra prediction efficiency.
Innovation Solution
A method and apparatus for signaling chroma format information, predicting current blocks based on chroma array type, and determining whether the tree type is single or dual, enhancing image decoding and encoding processes by deriving chroma components (Cb and Cr) efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution, high-quality image/video formats (4K, 8K, VR, AR) are used to meet increasing demand for immersive media, then image quality and resolution are improved, but transmission and storage costs increase due to larger data amounts
Solution Approach 1:
The patent segments the chroma information signaling into multiple levels: picture-level parameters (chroma_format_idc, separate_colour_plane_flag) and block-level parameters (chroma_array_type, intra_chroma_pred_mode). This segmentation allows different levels of detail to be transmitted at appropriate granularities, reducing redundant information while maintaining high image quality for 4K, 8K, and immersive media formats.
Solution Approach 2:
The patent applies local quality by allowing chroma prediction modes and array types to vary at the block level (4×4, 8×8, 8×16, 16×16 blocks) rather than uniformly across the entire picture. This enables high-frequency chroma details to be preserved in regions where they are important while using more compressed representations in other regions, thereby maintaining image quality while reducing overall data amount.
2Productivity
If detailed chroma format information is signaled for each block to improve compression efficiency, then compression efficiency is improved, but signaling complexity and bitstream overhead increase
Solution Approach 1:
The patent performs preliminary action by establishing picture-level chroma format parameters (chroma_format_idc, separate_colour_plane_flag) before block-level processing. This preliminary setup defines the chroma sampling structure (4:2:0, 4:2:2, 4:4:4) and array type (4:2:0, 4:2:2, 4:4:4, separated) for the entire picture, so that subsequent block-level operations can proceed with predetermined constraints, reducing the complexity of real-time decisions.
Solution Approach 2:
The patent introduces dynamics by allowing the chroma_array_type to change adaptively at the block level based on local image characteristics. The decoder can dynamically select between different chroma array types (4:2:0, 4:2:2, 4:4:4, separated) for different blocks within the same picture, enabling flexible adaptation to local requirements while maintaining manageable signaling complexity through context-based decoding.
3Measurement precision
If chroma prediction is performed using multiple array types (4:2:0, 4:2:2, 4:4:4, separated) to improve prediction accuracy, then prediction accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent applies parameter changes by systematically varying the chroma array type parameter across different blocks to optimize prediction accuracy. The chroma_array_type parameter can take values corresponding to 4:2:0, 4:2:2, 4:4:4, and separated configurations. By changing this parameter locally based on image content characteristics, the system achieves higher prediction accuracy without requiring a complete redesign of the processing architecture.
Solution Approach 2:
The patent uses the chroma_array_type as an intermediary that bridges the gap between different chroma sampling structures and prediction algorithms. This intermediary parameter allows the system to smoothly transition between different array types and select appropriate prediction modes (vertical, horizontal, DC, planar, CCLM) without requiring separate processing pipelines for each array type, thereby managing processing complexity while maintaining prediction accuracy.
4Measurement precision
If separate color plane coding is enabled to improve chroma quality, then chroma quality is improved, but bitstream overhead and processing load increase
Solution Approach 1:
The patent applies partial action by enabling separate color plane coding only when necessary, controlled by the separate_colour_plane_flag. Instead of always applying separate Cb and Cr plane coding, the system selectively enables this feature based on picture-level parameters and local requirements. This partial application of separate plane coding improves chroma quality in critical regions while avoiding the bitstream overhead and processing load in regions where it is not needed.
Data Source
AI summary
An image decoding method performed by a decoding device according to the present disclosure comprises the steps of: receiving a bitstream including prediction information for a current block; deriving a chroma array type for the current block on the basis of a separate color plane flag indicating whether three color components are separately coded and a chroma format index indicating a chroma format sampling structure for the current block, which are included in the prediction information for the current block; deriving prediction samples for the current block on the basis of the derived chroma array type; and deriving reconstructed samples for the current block on the basis of the prediction samples.