Method and apparatus for encoding/decoding the colors of a point cloud representing a 3D object

1. A method, comprising:

obtaining an octree-based structure approximating a geometry of a point cloud, wherein the octree-based structure defines a set of points associated with the point cloud and comprises a leaf cube including a single point, the set of points corresponding to a representation of the point cloud at a first precision level;

adding at least one new point to the set of points defined by the octree-based structure, wherein the at least one new point is obtained by up-sampling recursively the single point, the at least one new point increasing the representation of the point cloud to a second precision level;

determining a color of the at least one new point based on a color of another point located around the at least one new point, wherein the other point is determined to be located around the at least one new point based on a determination that a distance between the other point and the at least one new point is below a threshold value; and

encoding color information indicating that a color of the single point is encoded in a bitstream and that the color of the at least one new point is not encoded in the bitstream.

2. The method of claim 1 , wherein the octree-based structure is determined by optimizing a trade-off between a bit-rate for encoding a candidate octree-based structure approximating points of the point cloud, and a distortion taking into account spatial distances between the points of the point cloud and points that are included in leaf cubes associated with leaf nodes of the candidate octree-based structure and approximate the points of the point cloud.

3. The method of claim 1 , further comprising obtaining at least one point of an inverse-projected point cloud.

4. The method of claim 3 , wherein a color of the at least one point of the inverse-projected point cloud is encoded in the bitstream and the color information also indicates that the color of the at least one point of the inverse-projected point cloud is encoded in the bitstream.

5. The method of claim 3 , wherein the inverse-projected point cloud is obtained by inverse-projecting at least one texture and depth images representative of a part of the point cloud.

6. A non-transitory computer readable medium comprising instructions which, when executed by a computing device, cause the computing device to carry out the method of claim 1 .

7. A method comprising:

obtaining, based on a bitstream, an octree-based structure approximating a geometry of a point cloud, wherein the octree-based structure defines a set of points associated with the point cloud and includes a leaf cube comprising a single point, the set of points corresponding to a representation of the point cloud at a first precision level;

adding at least one new point to the set of points defined by the octree-based structure, wherein the at least one new point is obtained by up-sampling recursively the single point, the at least one new point increasing the representation of the point cloud to a second precision level;

decoding color information included in the bitstream, wherein the color information indicates that a color of the single point is encoded in the bitstream and that a color of the at least one new point is not encoded in the bitstream; and

obtaining the color of the at least one new point from a color of another point located around the at least one new point, wherein the other point is determined to be located around the at least one new point based on a determination that a distance between the other point and the at least one new point is below a threshold value.

8. The method of claim 7 , further comprising obtaining at least one point of an inverse-projected point cloud from the bitstream.

9. The method of claim 8 , wherein when the color information also indicates that a color of the at least one point of the inverse-projected point cloud is encoded in the bitstream, the method further comprises obtaining the color of the at least one point of the inverse-projected point cloud from the bitstream.

10. The method of claim 8 , wherein the color of the at least one new point is obtained from the color of the other point located around the at least one new point and a color of the at least one point of the inverse-projected point cloud.

11. A non-transitory computer readable medium comprising instructions which, when executed by a computing device, cause the computing device to carry out the method of claim 7 .

12. A device, comprising electronic circuitry configured to:

obtain an octree-based structure approximating a geometry of a point cloud, wherein the octree-based structure defines a set of points associated with the point cloud and comprises a leaf cube including a single point, the set of points corresponding to a representation of the point cloud at a first precision level;

add at least one new point to the set of points defined by the octree-based structure, wherein the at least one new point is obtained by up-sampling recursively the single point, the at least one new point increasing the representation of the point cloud to a second precision level;

determine a color of the at least one new point based on a color of another point located around the at least one new point, wherein the other point is determined to be located around the at least one new point based on a determination that a distance between the other point and the at least one new point is below a threshold value; and

encode color information indicating that a color of the single point is encoded in a bitstream and that the color of the at least one new point is not encoded in the bitstream.

13. The device of claim 12 , wherein the octree-based structure is determined by optimizing a trade-off between a bit-rate for encoding a candidate octree-based structure approximating points of the point cloud, and a distortion taking into account spatial distances between the points of the point cloud and points which are included in leaf cubes associated with leaf nodes of the candidate octree-based structure and which approximate the points of the point cloud.

14. The device of claim 12 , wherein the electronic circuitry is further configured to obtain at least one point of an inverse-projected point cloud.

15. The device of claim 14 , wherein a color of the at least one point of the inverse-projected point cloud is encoded in the bitstream and the color information also indicates that the color of said at least one point of the inverse-projected point cloud is encoded in the bitstream.

16. The device of claim 14 , wherein the inverse-projected point cloud is obtained by inverse-projecting at least one texture and depth images representative of a part of the point cloud.

17. A device comprising electronic circuitry configured to:

obtain, based on a bitstream, an octree-based structure approximating a geometry of a point cloud, wherein the octree-based structure defines a set of points associated with the point cloud and includes a leaf cube comprising a single point, the set of points corresponding to a representation of the point cloud at a first precision level;

add at least one new point to the set of points defined by the octree-based structure, wherein the at least one new point is obtained by up-sampling recursively the single point, the at least one new point increasing the representation of the point cloud to a second precision level;

decode color information from the bitstream, wherein the color information indicates that a color of the single point is encoded in the bitstream and that the color of the at least one new point is not encoded in the bitstream; and

obtain the color of the at least one new point from a color of another point located around the at least one new point, wherein the other point is determined to be located around the at least one new point based on a determination that a distance between the other point and the at least one new point is below a threshold value.

18. The device of claim 17 , wherein the electronic circuitry is further configured to obtain at least one point of an inverse-projected point cloud from the bitstream.

19. The device of claim 18 , wherein when the color information also indicates that a color of the at least one point of the inverse-projected point cloud is encoded in the bitstream, the electronic circuitry is further configured to obtain the color of the at least one point of the inverse-projected point cloud from the bitstream.

20. The device of claim 18 , wherein the color of the at least one new point is obtained from the color of the other point located around the at least one new point and a color of the at least one point of the inverse-projected point cloud.