Adaptive Subband Coding for Point Cloud Color Compression
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Solution Overview
Problem
The existing lifting transform method for point cloud color compression in three-dimensional graphics is not optimally implemented, particularly in the PCC test model TMC13, as it does not effectively suppress chroma and allocate quality and bandwidth efficiently between luminance and chrominance coefficients.
Innovation Solution
The method involves dividing lifting coefficients into subbands based on their weights, deriving adaptive dead-zones for each color component, and adjusting dead-zone sizes based on the weight of points used for prediction and their distances to predicted points, allowing for improved quality allocation between luminance and chrominance coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the original lifting scheme is used without subband division, then the implementation is simple, but chroma is not suppressed and quality allocation is inefficient
Solution Approach 1:
The patent divides lifting coefficients into multiple subbands based on their weights, separating luminance and chrominance coefficients into distinct subbands. This segmentation enables independent processing and selective quantization of different color components, improving compression efficiency by suppressing chroma while preserving luminance quality.
Solution Approach 2:
The patent applies different dead-zone sizes for different color components (luminance vs. chrominance) based on their local importance. Luminance coefficients receive smaller dead-zones (higher precision) while chrominance coefficients receive larger dead-zones (lower precision), achieving local quality optimization that matches human visual perception characteristics.
2Manufacturing precision
If uniform dead-zone sizes are used for all color components, then the processing is simple, but quality allocation between luminance and chrominance is not optimized
Solution Approach 1:
The patent derives different dead-zone sizes for different color components based on their weights and importance. Luminance coefficients receive smaller dead-zones to preserve detail, while chrominance coefficients receive larger dead-zones to reduce artifacts, achieving optimized local quality for each color component.
Solution Approach 2:
The patent dynamically adjusts dead-zone parameters based on the weight of each lifting coefficient and the importance of each color component. By changing the dead-zone parameter according to component characteristics, the system optimizes compression quality without requiring complex manual configuration.
3Measurement precision
If more quality and bandwidth are provided for luminance coefficients, then luminance quality improves, but chroma suppression is enhanced
Solution Approach 1:
The patent applies different quantization precision locally to different color components. Luminance coefficients receive higher precision (smaller dead-zones) to maintain image quality, while chrominance coefficients receive lower precision (larger dead-zones) to suppress color distortion and artifacts, matching the human visual system's greater sensitivity to luminance variations.
Data Source
AI summary
Lifting is a transform designed for color compression of point clouds which is adopted in one of the MPEG test models. The performance of lifting is improved herein. All the lifting coefficients are first divided into several subbands based on their assigned weights, which indicate the level of importance of each coefficient. Then, for each subband, a set of three dead-zones are derived for the three color components. The dead-zones of Cb and Cr channels are typically larger than that of Luma channel. In the original lifting scheme, Chroma is not suppressed at all. In contrast, as described herein, the size of the dead-zone is increased for different color components, which means that more quality (and bandwidth) is able to be adaptively provided for luminance coefficients than chrominance coefficients.