Unified Coded Block Flag Coding for Video Residual Quad Trees
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Solution Overview
Problem
Current video coding techniques face complexity in signaling significant coefficient blocks, particularly with different methods for luma and chroma components, leading to increased complexity in video encoders and decoders.
Innovation Solution
The proposed solution involves generating and parsing a residual quad tree (RQT) for coding units larger than a maximum-allowable transform unit size, where a root node associated with a coded block flag indicates the presence of significant chroma coefficient blocks, simplifying the signaling of chroma CBFs and unifying the coding of luma and chroma components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate methods are used for signaling luma and chroma coded block flags, then coding precision is maintained, but device complexity increases
Solution Approach 1:
The patent merges the signaling of luma and chroma coded block flags into a unified process. The encoder and decoder use the same RQT-based structure and flag signaling mechanism for both luma and chroma components, eliminating the need for separate signaling methods while maintaining coding precision through the hierarchical RQT structure that adapts to the actual distribution of significant coefficients in both components.
2Measurement precision
If multiple coded block flags are signaled for chroma components, then measurement precision is improved, but loss of information increases due to redundant signaling
Solution Approach 1:
The patent extracts only the necessary coded block flag information from the chroma coefficient blocks and signals it efficiently using the RQT structure. By traversing the RQT and signaling flags only where needed (when significant coefficient blocks are present), the method avoids redundant signaling while maintaining precise tracking of significant chroma blocks, thereby reducing bitstream overhead without losing important information.
3Measurement precision
If a detailed RQT structure is used for large CUs, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments large coding units into smaller transform units using a residual quad tree structure, where each node represents a transform unit and leaves correspond to actual TU partitions. This segmentation allows precise tracking of significant coefficient blocks at the TU level while providing a systematic hierarchical framework that simplifies the encoding and decoding processes through recursive partitioning, rather than requiring complex ad-hoc handling of large CUs.
Data Source
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AI summary
A video encoder generates a bitstream that includes a residual quad tree (RQT) for a coding unit (CU). The CU is larger than a maximum-allowable transform unit (TU) size and the RQT includes a hierarchy of nodes. A root node of the RQT corresponds to the CU as a whole and leaf nodes of the RQT correspond to TUs of the CU. The root node is associated with a coded block flag (CBF) for a chroma component. The CBF for the chroma component indicates whether any of the TUs of the CU are associated with a significant coefficient block that is based on samples of the particular chroma component. A video decoder receives the bitstream and determines, based on the CBF, whether coefficient blocks associated with TUs that correspond to the leaf nodes include non-zero coefficients.