Predictor-Copy Point Cloud Coding for Occupancy Bitrate Reduction
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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 exploit predictive coding effectively, especially in geometric coding where the 3D residual vectors are costly to encode and decode.
Innovation Solution
The implementation of a predictor-copy coding mode that signals a predictor-copy coding mode flag in the bitstream, allowing for early termination of occupancy data encoding and copying predicted points within sub-volumes, reducing the need for further occupancy data encoding and decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If predictive coding is used in point cloud geometric coding, then compression efficiency is improved, but the 3D residual vectors become costly to encode and decode
Solution Approach 1:
The patent extracts only the necessary information for prediction (occupancy patterns and motion vectors) while discarding the costly 3D residual vectors. By using occupancy prediction to identify which sub-volumes contain points and copying points from reference frames based on motion compensation, the method achieves compression without transmitting full 3D residual data, thus reducing encoding/decoding complexity while maintaining efficiency
Solution Approach 2:
The patent employs copying by reconstructing point cloud data through motion compensation - copying points from reference frames using motion vectors rather than transmitting and reconstructing via costly 3D residual addition. This copying approach simplifies the encoding/decoding process while maintaining compression efficiency
2Measurement precision
If occupancy data encoding is performed for all sub-volumes, then prediction accuracy is improved, but bitrate increases
Solution Approach 1:
The patent applies local quality by encoding occupancy data selectively - only for sub-volumes where prediction uncertainty exists or where points are actually present. By using motion-compensated prediction to identify regions requiring detailed occupancy encoding versus regions that can be reconstructed through copying, the method maintains prediction accuracy where needed while reducing overall bitrate through selective encoding
Solution Approach 2:
The patent uses partial action by encoding occupancy information for only a subset of sub-volumes rather than all sub-volumes. Through motion compensation and occupancy prediction, the method identifies and encodes only the necessary portions of the point cloud data, achieving adequate prediction accuracy with reduced bitrate by leaving other regions to be reconstructed through copying
Data Source
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AI summary
Methods and devices for encoding a point cloud. A predictor-copy coding mode is described in which an encoder determines that it would be advantageous to copy 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.