Context determination for planar mode in octree-based point cloud coding

A method of decoding a bitstream of compressed point cloud data to produce a reconstructed point cloud representing a three-dimensional location of a physical 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 first set of child sub-volumes and a second set of child sub-volumes, the first set of child sub-volumes being positioned in a first plane and the second set of child sub-volumes being positioned in a second plane parallel to the first plane, 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, both the first plane and the second plane being orthogonal to an axis, the method comprising:

• reconstructing the points of the point cloud by reconstructing the occupancy bits by
• entropy decoding from the bitstream a planar mode flag that indicates whether the volume is planar, wherein the volume is planar if all child sub-volumes containing at least one point are positioned in either the first set or the second set, wherein entropy decoding includes determining a context for decoding the planar mode flag based, in part, on one or more of:
• (a) whether a parent volume containing the volume is planar in occupancy,
• (b) occupancy of a neighbouring volume at a parent depth, the neighbouring volume being adjacent the volume and having a face in common with the parent volume, or
• (c) a distance between the volume and a closest already-coded occupied volume at a same depth as the volume and having a same position on the axis as the volume;
• and
• reconstructing occupancy bits for the child sub-volumes.

An encoder for encoding a point cloud to generate a bitstream of compressed point cloud data 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 first set of child sub-volumes and a second set of child sub-volumes, the first set of child sub-volumes being positioned in a first plane and the second set of child sub-volumes being positioned in a second plane parallel to the first plane, 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, both the first plane and the second plane being orthogonal to an axis, the encoder comprising:

• a processor;
• memory;
• and
• an encoding application containing instructions executable by the processor that, when executed, cause the processor to:
• determine whether the volume is planar based on whether all child sub-volumes containing at least one point are positioned in either the first set or the second set;
• entropy encode in the bitstream a planar mode flag to signal whether the volume is planar, wherein entropy encoding includes determining a context for coding the planar mode flag based, in part, on one or more of:
• (a) whether a parent volume containing the volume is planar in occupancy,
• (b) occupancy of a neighbouring volume at a parent depth, the neighbouring volume being adjacent the volume and having a face in common with the parent volume, or
• (c) a distance between the volume and a closest already-coded occupied volume at a same depth as the volume and having a same position on the axis as the volume;
• encode occupancy bits for at least some of the child sub-volumes;
• and
• output the bitstream of compressed point cloud data.

A decoder for decoding a bitstream of compressed point cloud data to produce a reconstructed point cloud representing a three-dimensional location of a physical 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 first set of child sub-volumes and a second set of child sub-volumes, the first set of child sub-volumes being positioned in a first plane and the second set of child sub-volumes being positioned in a second plane parallel to the first plane, 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, both the first plane and the second plane being orthogonal to an axis, the decoder comprising:

• a processor;
• memory;
• and
• a decoding application containing instructions executable by the processor that, when executed, cause the processor to reconstruct the points of the point cloud by reconstructing the occupancy bits by:
• entropy decoding from the bitstream a planar mode flag that indicates whether the volume is planar, wherein the volume is planar if all child sub-volumes containing at least one point are positioned in either the first set or the second set, wherein entropy decoding includes determining a context for decoding the planar mode flag based, in part, on one or more of:
• (a) whether a parent volume containing the volume is planar in occupancy,
• (b) occupancy of a neighbouring volume at a parent depth, the neighbouring volume being adjacent the volume and having a face in common with the parent volume, or
• (c) a distance between the volume and a closest already-coded occupied volume at a same depth as the volume and having a same position on the axis as the volume;
• and
• reconstructing occupancy bits for the child sub-volumes.

A non-transitory processor-readable medium storing processor-executable instructions to encode a point cloud to generate a bitstream of compressed point cloud data 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 first set of child sub-volumes and a second set of child sub-volumes, the first set of child sub-volumes being positioned in a first plane and the second set of child sub-volumes being positioned in a second plane parallel to the first plane, 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, both the first plane and the second plane being orthogonal to an axis, wherein the processor-executable instructions, when executed by a processor, are to cause the processor to:

• determine whether the volume is planar based on whether all child sub-volumes containing at least one point are positioned in either the first set or the second set;
• entropy encode in the bitstream a planar mode flag to signal whether the volume is planar, wherein entropy encoding includes determining a context for coding the planar mode flag based, in part, on one or more of:
• (a) whether a parent volume containing the volume is planar in occupancy,
• (b) occupancy of a neighbouring volume at a parent depth, the neighbouring volume being adjacent the volume and having a face in common with the parent volume, or
• (c) a distance between the volume and a closest already-coded occupied volume at a same depth as the volume and having a same position on the axis as the volume;
• encode occupancy bits for at least some of the child sub-volumes;
• and
• output the bitstream of compressed point cloud data.

A non-transitory processor-readable medium storing processor-executable instructions to decode a bitstream of compressed point cloud data to produce a reconstructed point cloud representing a three-dimensional location of a physical 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 first set of child sub-volumes and a second set of child sub-volumes, the first set of child sub-volumes being positioned in a first plane and the second set of child sub-volumes being positioned in a second plane parallel to the first plane, 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, both the first plane and the second plane being orthogonal to an axis, wherein the processor-executable instructions, when executed by a processor, cause the processor to:

• reconstruct the points of the point cloud by reconstructing the occupancy bits by:
• entropy decoding from the bitstream a planar mode flag that indicates whether the volume is planar, wherein the volume is planar if all child sub-volumes containing at least one point are positioned in either the first set or the second set, wherein entropy decoding includes determining a context for decoding the planar mode flag based, in part, on one or more of:
• (a) whether a parent volume containing the volume is planar in occupancy,
• (b) occupancy of a neighbouring volume at a parent depth, the neighbouring volume being adjacent the volume and having a face in common with the parent volume, or
• (c) a distance between the volume and a closest already-coded occupied volume at a same depth as the volume and having a same position on the axis as the volume;
• and
• reconstructing occupancy bits for the child sub-volumes.