Angular mode for tree-based point cloud coding

A method of decoding a bitstream of compressed point cloud data to generate a reconstructed geometry of the point cloud, the point cloud having been acquired by means of a beam assembly comprising a set of beams, the geometry of the point cloud being defined in a tree structure having a plurality of nodes having parent-child relationships and representing a three-dimensional location of an object, the point cloud being located within a volumetric space recursively split into sub-volumes and containing points of the point cloud, wherein a volume is partitioned into a set of child sub-volumes, and wherein an occupancy bit associated with each respective child sub-volume indicates whether that respective child sub-volume contains at least one of the points, the method comprising,

• for a current node associated with a volume split into child sub-volumes:
• determining angular information for child sub-volumes or groups of child sub-volumes of the volume, the angular information being indicative of one or more elevation angles relative to a location associated with the beam assembly within the volumetric space;
• determining a context for decoding a representation of an occupancy pattern of the volume based on the angular information, the occupancy pattern indicating occupancy statuses of the child sub-volumes of the volume, wherein the occupancy pattern is a sequence of occupancy bits associated with the volume, wherein the context tracks an internal probability to be used in context-adaptive coding;
• and
• context-adaptively entropy decoding the bitstream to generate a reconstructed representation of the occupancy pattern using the determined context.

An encoder for encoding the geometry of a point cloud acquired by means of a beam assembly comprising a set of beams, to generate a bitstream of compressed point cloud data, the geometry of the point cloud being defined in a tree structure having a plurality of nodes having parent-child relationships and representing a three-dimensional location of an object, the point cloud being located within a volumetric space recursively split into sub-volumes and containing points of the point cloud, wherein a volume is partitioned into a set of child sub-volumes, and wherein an occupancy bit associated with each respective child sub-volume indicates whether that respective child sub-volume contains at least one of the points, the encoder comprising:

• a processor;
• a memory;
• and
• an encoding application containing instructions executable by the processor that, when executed, cause the processor to:
• for a current node associated with a volume split into child sub-volumes:
• determine an occupancy pattern for the volume based on occupancy statuses of the child sub-volumes of the volume, wherein the occupancy pattern is a sequence of occupancy bits associated with the volume;
• and
• context-adaptively entropy encode a representation of the occupancy pattern into the bitstream,
• wherein to context-adaptively entropy encode the occupancy pattern is to:
• determine angular information for child sub-volumes or groups of child sub-volumes of the volume, the angular information being indicative of one or more elevation angles relative to a location associated with the beam assembly within the volumetric space;
• determine a context for encoding the representation of the occupancy pattern based on the angular information, wherein the context tracks an internal probability to be used in context-adaptive coding;
• and
• entropy encode the representation of the occupancy pattern using the determined context.

A decoder for decoding a bitstream of compressed point cloud data to generate a reconstructed geometry of the point cloud, the point cloud having been acquired by means of a beam assembly comprising a set of beams, the geometry of the point cloud being defined in a tree structure having a plurality of nodes having parent-child relationships and representing a three-dimensional location of an object, the point cloud being located within a volumetric space recursively split into sub-volumes and containing points of the point cloud, wherein a volume is partitioned into a set of child sub-volumes, and wherein an occupancy bit associated with each respective child sub-volume indicates whether that respective child sub-volume contains at least one of the points, the decoder comprising:

• a processor;
• a memory;
• and
• a decoding application containing instructions executable by the processor that, when executed, cause the processor to:
• for a current node associated with a volume split into child sub-volumes:
• determine angular information for child sub-volumes or groups of child sub-volumes of the volume, the angular information being indicative of one or more elevation angles relative to a location associated with the beam assembly within the volumetric space;
• determine a context for decoding a representation of an occupancy pattern of the volume based on the angular information, the occupancy pattern indicating occupancy statuses of the child sub-volumes of the volume, wherein the occupancy pattern is a sequence of occupancy bits associated with the volume, wherein the context tracks an internal probability to be used in context-adaptive coding;
• and
• context-adaptively entropy decode the bitstream to generate a reconstructed representation of the occupancy pattern using the determined context.

A non-transitory processor-readable medium storing processor-executable instructions for decoding a bitstream of compressed point cloud data to generate a reconstructed geometry of the point cloud, the point cloud having been acquired by means of a beam assembly comprising a set of beams, the geometry of the point cloud being defined in a tree structure having a plurality of nodes having parent-child relationships and representing a three-dimensional location of an object, the point cloud being located within a volumetric space recursively split into sub-volumes and containing points of the point cloud, wherein a volume is partitioned into a set of child sub-volumes, and wherein an occupancy bit associated with each respective child sub-volume indicates whether that respective child sub-volume contains at least one of the points, wherein the instructions, when executed by a processor, cause the processor to:

• for a current node associated with a volume split into child sub-volumes:
• determine angular information for child sub-volumes or groups of child sub-volumes of the volume, the angular information being indicative of one or more elevation angles relative to a location associated with the beam assembly within the volumetric space;
• determine a context for decoding a representation of an occupancy pattern of the volume based on the angular information, the occupancy pattern indicating occupancy statuses of the child sub-volumes of the volume, wherein the occupancy pattern is a sequence of occupancy bits associated with the volume, wherein the context tracks an internal probability to be used in context-adaptive coding;
• and
• context-adaptively entropy decode the bitstream to generate a reconstructed representation of the occupancy pattern using the determined context.