Method for encoding and decoding a point cloud

A method for decoding a bitstream of compressed point cloud data to generate attributes of points in a reconstructed point cloud, wherein the point cloud’s geometry is represented by a voxel-based structure with a plurality of nodes having parent-child relationships by recursively splitting a volumetric space containing the point cloud into sub-volumes each associated with a node of the voxel-bases structure, the method comprising:

• decoding a residual of attributes of a present node of the point cloud from the bitstream;
• determining a difference between attributes of a present parent node and each parent node of a first set of parent nodes sharing a face or an edge with the present node, wherein the present parent node is the parent node of the present node;
• selecting a second set of parent nodes from the first set of parent nodes according to the difference, wherein the second set of parent nodes includes the present parent node;
• determining a predicted value for the attributes of the present node according to attributes of the second set of parent nodes;
• determining a predicted transform coefficient by applying Region-Adaptive Hierarchal Transform (RAHT) to the predicted value of the attributes of the present node;
• and
• determining from the residual and the predicted transform coefficient the attributes of the present node by applying an inverse RAHT.

An encoder for encoding attributes of points of a point cloud to generate a bitstream of compressed point cloud data, wherein the point cloud’s geometry is represented by a voxel-based structure with a plurality of nodes having parent-child relationships by recursively splitting a volumetric space containing the point cloud into sub-volumes each associated with a node of the voxel-based structure, the encoder comprising:

• a processor;
• and
• a memory storage device storing instructions executable by the processor,
• wherein the processor is configured to:
• determine a true transform coefficient by applying Region-Adaptive Hierarchal Transform (RAHT) to attributes of a present node;
• determine a difference between attributes of a present parent node and each parent node of a first set of parent nodes sharing a face or an edge with the present node, wherein the present parent node is the parent node of the present node;
• select a second set of parent nodes from the first set of parent nodes according to the difference, wherein the second set of parent nodes includes the present parent node;
• determine a predicted value for the attributes of the present node according to attributes of the second set of parent nodes;
• determine a predicted transform coefficient by applying the RAHT to the predicted value of the attributes of the present node;
• determine a residual from the true transform coefficient and the predicted transform coefficient;
• and
• encode the residual to produce encoded data of attributes of the point cloud for the bitstream.

A decoder for decoding a bitstream of compressed point cloud data to generate attributes of points of a reconstructed point cloud, wherein the point cloud’s geometry is represented by a voxel-based structure with a plurality of nodes having parent-child relationships by recursively splitting a volumetric space containing the point cloud into sub-volumes each associated with a node of the voxel-bases structure, the decoder comprising:

• a processor;
• and
• a memory storage device storing instructions executable by the processor,
• wherein the processor is configured to:
• decode a residual of attributes of a present node of the point cloud from the bitstream;
• determine a difference between attributes of a present parent node and each parent node of a first set of parent nodes sharing a face or an edge with the present node, wherein the present parent node is the parent node of the present node;
• select a second set of parent nodes from the first set of parent nodes according to the difference, wherein the second set of parent nodes includes the present parent node;
• determine a predicted value for the attributes of the present node according to attributes of the second set of parent nodes;
• determine a predicted transform coefficient by applying Region-Adaptive Hierarchal Transform (RAHT) to the predicted value of the attributes of the present node;
• and
• determine from the residual and the predicted transform coefficient the attributes of the present node by applying an inverse RAHT.