Point Cloud Predictor-Copy Coding for Sparse Geometry Compression
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Solution Overview
Problem
Point cloud data compression is inefficient due to the sparsely populated nature of point clouds, making it challenging to effectively encode and decode the geometry of 3D vectors, particularly in predictive coding methods.
Innovation Solution
The implementation of a predictor-copy coding mode (PCCM) that signals the use of predicted points within a sub-volume, allowing for early termination of the coding tree and copying predicted points as reconstructed points, thereby reducing the need for occupancy data encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If predictive coding is used for point cloud compression, then compression efficiency is improved, but the error or residual is a 3D vector that is costly to encode and decode
Solution Approach 1:
The patent applies the copying principle by using predicted points from reference sub-volumes to replace actual point data in current sub-volumes. Instead of encoding full 3D vectors for residuals, the system copies coordinate information from predicted points and only encodes differential values, significantly reducing encoding complexity while maintaining compression efficiency.
Solution Approach 2:
The patent implements preliminary action by generating predicted points before the actual encoding process. The system performs prediction using reference sub-volumes and motion vectors in advance, so that when encoding occurs, only simple differential values need to be encoded rather than complete 3D vector residuals, reducing the computational burden during the main encoding phase.
2Reliability
If occupancy data is encoded for all sub-volumes, then coding completeness is ensured, but the sparsely-populated nature of point clouds makes encoding inefficient
Solution Approach 1:
The patent applies the extraction principle by separating the encoding of occupied and unoccupied sub-volumes. The system extracts and processes only the necessary occupancy information for sub-volumes that contain points, while using prediction for unoccupied or sparsely populated sub-volumes, thereby improving encoding efficiency without compromising coding completeness.
Solution Approach 2:
The patent implements partial action by encoding occupancy data selectively rather than for all sub-volumes. The system performs full occupancy encoding only where necessary (in occupied sub-volumes) and uses prediction-based copying for unoccupied sub-volumes, reducing the total amount of encoding operations while maintaining complete and accurate reconstruction of the point cloud.
Data Source
AI summary
Methods and devices for encoding a point cloud. A predictor-copy coding mode is described in which an encoder copies the predicted points for a sub-volume rather than encoding the occupancy data for the original points in the sub-volume. A predictor-copy coding mode flag is coded in the bitstream to signal to the decoder whether predictor-copy coding mode is active or inactive. The predictor-copy coding mode flag may only be coded for sub-volumes that are eligible to use the mode. Eligibility may be based on depth within the coding tree and/or size of the sub-volume. Predictor-copy coding mode has the result of early termination of a branch of the coding tree. Instead of decoding the occupancy for the remainder of the branch, a decoder copies the predicted points that are positioned within the sub-volume as the reconstructed points of the point cloud for that sub-volume.