Point cloud data transmission device, point cloud data transmission method, point cloud data reception device and point cloud data reception method

1. A method of transmitting point cloud data, the method comprising:

acquiring the point cloud data;

encoding geometry information included in the point cloud data;

encoding attribute information included in the point cloud data; and

transmitting the encoded geometry information, the encoded attribute information, and signaling information,

wherein encoding the attribute information comprises:

generating LoDs (Levels of Detail) based on an octree structure, and

compressing the attribute information based on the LoDs,

wherein the octree structure is formed of depths,

wherein each of the depths includes a plurality of nodes,

wherein each of the plurality of nodes is an occupied node that includes one or more points or an unoccupied node that does not include any point,

wherein, based on an occupied node belonging to a LoD of the LoDs including two or more occupied child nodes, a first node of the two or more occupied child nodes is selected for an attribute value of the occupied node,

wherein a higher LoD of the LoDs includes points that belong to a lower LoD of the LoDs and includes points that do not belong to the lower LoD,

wherein each LoD includes points of at least one depth of the octree structure,

wherein the signaling information includes an attribute parameter set, and

wherein the attribute parameter set includes information for identifying the attribute parameter set and information related to a number of the LoDs.

2. The method of claim 1 , wherein encoding the geometry information comprises:

quantizing the geometry information;

generating the octree structure having an octal tree structure based on the quantized geometry information;

approximating the octree structure;

reconstructing the geometry information based on the generated octree structure and the approximated octree structure; and

entropy-encoding occupancy codes of the generated octree structure or the approximated octree structure and outputting a geometry bitstream.

3. An apparatus configured to transmit point cloud data, the apparatus comprising:

an acquirer configured to acquire the point cloud data;

a geometry encoder configured to encode geometry information included in the point cloud data;

an attribute encoder configured to encode attribute information included in the point cloud data; and

a transmitter configured to transmit the encoded geometry information, the encoded attribute information, and signaling information,

wherein the attributer encoder comprises:

a LoD (Levels of Detail) generator configured to generate LoDs based on an octree structure, and

a compressor configured to compress the attribute information based on the LoDs,

wherein the octree structure is formed of depths,

wherein each of the depths includes a plurality of nodes,

wherein each of the plurality of nodes is an occupied node that includes one or more points or an unoccupied node that does not include any point,

wherein, based on an occupied node belonging to a LoD of the LoDs including two or more occupied child nodes, a first node of the two or more occupied child nodes is selected for an attribute value of the occupied node,

wherein a higher LoD of the LoDs includes points that belong to a lower LoD of the LoDs and includes points that do not belong to the lower LoD,

wherein each LoD includes points of at least one depth of the octree structure,

wherein the signaling information includes an attribute parameter set, and

wherein the attribute parameter set includes information for identifying the attribute parameter set and information related to a number of the LoDs.

4. The apparatus of claim 3 , wherein the geometry encoder comprises:

a quantizer configured to quantize the geometry information;

an octree analyzer configured to generate the octree structure having an octal tree structure based on the quantized geometry information;

an approximation analyzer configured to approximate the octree structure;

a geometry reconstructor configured to reconstruct the geometry information based on the generated octree structure and the approximated octree structure; and

an arithmetic encoder configured to entropy-encode occupancy codes of the generated octree structure or the approximated octree structure and output a geometry bitstream.

5. A method of receiving point cloud data, the method comprising:

receiving the point cloud data and signaling information;

decoding geometry information included in the point cloud data based on the signaling information; and

decoding attribute information included in the point cloud data based on the signaling information,

wherein decoding the attribute information comprises:

generating LoDs (Levels of Detail) based on an octree structure, and

de-compressing the attribute information based on the LoDs,

wherein the octree structure is formed of depths,

wherein each of the depths includes a plurality of nodes,

wherein each of the plurality of nodes is an occupied node that includes one or more points or an unoccupied node that does not include any point,

wherein, based on an occupied node belonging to a LoD of the LoDs including two or more occupied child nodes, a first node of the two or more occupied child nodes is selected for an attribute value of the occupied node,

wherein a higher LoD of the LoDs includes points that belong to a lower LoD of the LoDs and includes points that do not belong to the lower LoD,

wherein each LoD includes points of at least one depth of the octree structure,

wherein the signaling information includes an attribute parameter set, and

wherein the attribute parameter set includes information for identifying the attribute parameter set and information related to a number of the LoDs.

6. The method of claim 5 , wherein decoding the geometry information comprises:

reconstructing the geometry information by regenerating the octree structure of a partial level or a full level based on occupancy codes included in the geometry information.

7. An apparatus configured to receive point cloud data, the apparatus comprising:

a receiver configured to receive the point cloud data and signaling information;

a geometry decoder configured to decode geometry information included in the point cloud data based on the signaling information; and

an attribute decoder configured to decode attribute information included in the point cloud data based on the signaling information,

wherein the attribute decoder comprises:

a LoD (Levels of Detail) generator configured to generate LoDs based on an octree structure, and

a decompressor configured to de-compress the attribute information based on the LoDs,

wherein the octree structure is formed of depths,

wherein each of the depths includes a plurality of nodes,

wherein each of the plurality of nodes is an occupied node that includes one or more points or an unoccupied node that does not include any point,

wherein, based on an occupied node belonging to a LoD of the LoDs including two or more occupied child nodes, a first node of the two or more occupied child nodes is selected for an attribute value of the occupied node,

wherein a higher LoD of the LoDs includes points that belong to a lower LoD of the LoDs and includes points that do not belong to the lower LoD,

wherein each LoD includes points of at least one depth of the octree structure,

wherein the signaling information includes an attribute parameter set, and

wherein the attribute parameter set includes information for identifying the attribute parameter set and information related to a number of the LoDs.

8. The apparatus of claim 7 , wherein the geometry decoder reconstructs the geometry information by regenerating the octree structure of a partial level or a full level based on occupancy codes included in the geometry information.