Three-dimensional data encoding method, three-dimensional data decoding method, three-dimensional data encoding device, and three-dimensional data decoding device

1. A three-dimensional data encoding method of encoding a plurality of three-dimensional points each having geometry information, the method comprising:

classifying each of the plurality of three-dimensional points into any of a plurality of layers including a first layer, a second layer, and a third layer; and

arithmetic-encoding geometry information of a current three-dimensional point among the plurality of three-dimensional points, the arithmetic encoding being performed (i) with reference to a first encoding table when the current three-dimensional point is at the first layer, (ii) with reference to a second encoding table not dependent on the first encoding table when the current three-dimensional point is at the second layer, and (iii) with reference to a third encoding table dependent on the first encoding table when the current three-dimensional point is at the third layer.

2. The three-dimensional data encoding method according to claim 1 ,

wherein the first encoding table and the second encoding table are different from each other.

3. The three-dimensional data encoding method according to claim 1 ,

wherein the classifying is performed based on the geometry information to cause a higher layer among the plurality of layers to have a longer distance between three-dimensional points belonging to the higher layer.

4. The three-dimensional data encoding method according to claim 1 ,

wherein the first layer is higher than the second layer among the plurality of layers,

the arithmetic-encoding is performed with reference to a first encoding table when the current three-dimensional point is at a layer higher than a first threshold layer among the plurality of layers.

5. The three-dimensional data encoding method according to claim 1 ,

wherein the first layer is higher than the second layer among the plurality of layers, and

the arithmetic-encoding includes:

arithmetic-encoding geometry information of all of three-dimensional points at the first layer;

initializing the first encoding table after the arithmetic-encoding of the geometry information; and

arithmetic-encoding geometry information of three-dimensional points at a layer next to the first layer with reference to the first encoding table initialized in the initializing.

6. The three-dimensional data encoding method according to claim 5 ,

wherein the arithmetic-encoding is performed sequentially from a higher layer among the plurality of layers,

when the current three-dimensional point is at a layer higher than a second threshold layer, initializing the first encoding table, and arithmetic-encoding the geometry information of the current three-dimensional point with reference to the first encoding table initialized in the initializing; and

when the current three-dimensional point is at a layer equal to or lower than the second threshold layer, arithmetic-encoding the geometry information of the current three-dimensional point with reference to the second encoding table.

7. The three-dimensional data encoding method according to claim 5 ,

wherein the second encoding table is generated by initializing the first encoding table.

8. A three-dimensional data decoding method of decoding a plurality of encoded three-dimensional points each having geometry information, the method comprising:

obtaining each of the plurality of encoded three-dimensional points classified into any of a plurality of layers including a first layer, a second layer, and a third layer; and

arithmetic-decoding geometry information of a current three-dimensional point among the plurality of encoded three-dimensional points included in a bit stream, the arithmetic decoding being performed (i) with reference to a first decoding table when the current three-dimensional point is at the first layer, (ii) with reference to a second decoding table not dependent on the first decoding table when the current three-dimensional point is at the second layer, and (iii) with reference to a third decoding table dependent on the first decoding table when the current three-dimensional point is at the third layer.

9. The three-dimensional data decoding method according to claim 8 ,

wherein the first decoding table and the second decoding table are different from each other.

10. The three-dimensional data decoding method according to claim 8 ,

wherein the classifying is performed based on the geometry information to cause a higher layer among the plurality of layers to have a longer distance between three-dimensional points belonging to the higher layer.

11. The three-dimensional data decoding method according to claim 8 ,

wherein the first layer is higher than the second layer among the plurality of layers,

the arithmetic-decoding is performed with reference to a first decoding table when the current three-dimensional point is at a layer higher than a first threshold layer among the plurality of layers.

12. The three-dimensional data decoding method according to claim 8 , wherein the first layer is higher than the second layer among the plurality of layers, and the arithmetic-decoding includes:

arithmetic-decoding geometry information of all of three-dimensional points at the first layer;

initializing the first decoding table after the arithmetic-decoding of the geometry information; and

arithmetic-decoding geometry information of three-dimensional points at a layer next to the first layer with reference to the first decoding table initialized in the initializing.

13. The three-dimensional data decoding method according to claim 12 ,

wherein the arithmetic-decoding is performed sequentially from a higher layer among the plurality of layers,

when the current three-dimensional point is at a layer higher than a second threshold layer, initializing the first decoding table, and arithmetic-decoding the geometry information of the current three-dimensional point with reference to the first decoding table initialized in the initializing; and

when the current three-dimensional point is at a layer equal to or lower than the second threshold layer, arithmetic-decoding the geometry information of the current three-dimensional point with reference to the second decoding table.

14. The three-dimensional data decoding method according to claim 12 ,

wherein the second decoding table is generated by initializing the first decoding table.

15. A three-dimensional data encoding device that encodes a plurality of three-dimensional points each having geometry information, the device comprising:

a processor; and

a memory, wherein

by using the memory, the processor performs:

classifying each of the plurality of three-dimensional points into any of a plurality of layers including a first layer, a second layer, and a third layer; and

arithmetic-encoding geometry information of a current three-dimensional point among the plurality of three-dimensional points, the arithmetic encoding being performed (i) with reference to a first encoding table when the current three-dimensional point is at the first layer, (ii) with reference to a second encoding table not dependent on the first encoding table when the current three-dimensional point is at the second layer, and (iii) with reference to a third encoding table dependent on the first encoding table when the current three-dimensional point is at the third layer.

16. A three-dimensional data decoding device that decodes a plurality of encoded three-dimensional points each having geometry information, the device comprising:

a processor; and

a memory, wherein

by using the memory, the processor performs:

obtaining each of the plurality of encoded three-dimensional points classified into any of a plurality of layers including a first layer, a second layer, and a third layer; and

arithmetic-decoding geometry information of a current three-dimensional point among the plurality of encoded three-dimensional points included in a bit stream, the arithmetic decoding being performed (i) with reference to a first decoding table when the current three-dimensional point is at the first layer, (ii) with reference to a second decoding table not dependent on the first decoding table when the current three-dimensional point is at the second layer, and (iii) with reference to a third decoding table dependent on the first decoding table when the current three-dimensional point is at the third layer.

17. The three-dimensional data encoding method according to claim 1 , wherein

an occurrence probability in the first encoding table is different from an occurrence probability in the second encoding table.

18. The three-dimensional data decoding method according to claim 8 , wherein

an occurrence probability in the first decoding table is different from an occurrence probability in the second decoding table.