Methods and devices for entropy coding point clouds

An encoder for encoding a point cloud to generate a bitstream of compressed point cloud data, the point cloud being defined in a tree structure having a plurality of nodes having parent-child relationships and that represent the geometry of a volumetric space recursively split into sub-volumes and containing the points of the point cloud, the encoder comprising:

• a processor;
• memory;
• and
• an encoding application containing instructions executable by the processor that, when executed, are to cause the processor to:
• for a current node associated with a sub-volume split into further sub-volumes, each further sub-volume corresponding to a child node of the current node,
• determine an occupancy pattern for the current node based on occupancy status of the child nodes;
• select a probability distribution from among a plurality of probability distributions, wherein the selecting is based on occupancy data for a plurality of nodes neighbouring the current node;
• entropy encode the occupancy pattern based on the selected probability distribution to produce encoded data for the bitstream;
• and
• update the selected probability distribution based on the occupancy pattern.

A method of decoding a bitstream of compressed point cloud data to produce a reconstructed point cloud, the point cloud being defined in a tree structure having a plurality of nodes having parent-child relationships and that represent the geometry of a volumetric space recursively split into sub-volumes and containing the points of the point cloud, the method comprising:

• for a current node associated with a sub-volume split into further sub-volumes, each further sub-volume corresponding to a child node of the current node,
• selecting a probability distribution from among a plurality of probability distributions, wherein the selecting is based on occupancy data for a plurality of nodes neighbouring the current node;
• entropy decoding the bitstream based on the selected probability distribution to produce a reconstructed occupancy pattern for the current node signaling occupancy of the child nodes;
• and
• updating the selected probability distribution based on the reconstructed occupancy pattern.

A decoder for decoding a bitstream of compressed point cloud data to produce a reconstructed point cloud, the point cloud being defined in a tree structure having a plurality of nodes having parent-child relationships and that represent the geometry of a volumetric space recursively split into sub-volumes and containing the points of the point cloud, the decoder comprising:

• a processor;
• memory;
• and
• a decoding application containing instructions executable by the processor that, when executed, are to cause the processor to:
• for a current node associated with a sub-volume split into further sub-volumes, each further sub-volume corresponding to a child node of the current node,
• select a probability distribution from among a plurality of probability distributions, wherein the selecting is based on occupancy data for a plurality of nodes neighbouring the current node;
• entropy decode the bitstream based on the selected probability distribution to produce a reconstructed occupancy pattern for the current node signaling occupancy of the child nodes;
• and
• update the selected probability distribution based on the reconstructed occupancy pattern.