Techniques and apparatus for lossless lifting for attribute coding

1. A method of point cloud attribute coding, the method being performed by at least one processor, and the method comprising:

obtaining an attribute signal corresponding to a point cloud;

determining whether lossless lifting is enabled;

based on determining that lossless lifting is enabled, modifying at least one from among a plurality of quantization weight and a plurality of lifting coefficients;

checking a bitplane of a lifting coefficient of the plurality of lifting coefficients to determine if the bitplane is larger than a corresponding quantization step size of the bitplane,

setting a significance bit based on a result of the determining;

decomposing the attribute signal into a plurality of detail signals and a plurality of approximation signals based on the modified at least one from among the plurality of quantization weights and the plurality of lifting coefficients;

generating a bitstream representing the point cloud based on the plurality of detail signals and the plurality of approximation signals; and

transmitting the bitstream.

2. The method of claim 1 , wherein the lossless lifting is determined to be enabled based on a lossless lifting flag.

3. The method of claim 1 , wherein the modifying further comprises rounding each of the plurality of quantization weights to be a multiple of a predetermined weight constant.

4. The method of claim 1 , wherein the modifying further comprises rounding each of the plurality of lifting coefficients to be a multiple of a predetermined lifting constant.

5. The method of claim 1 , wherein based on determining that the bitplane is larger than the corresponding quantization step size, the significance bit is set to indicate that the bitplane is significant.

6. The method of claim 1 , further comprising:

based on a previous bitplane being determined to be significant, setting a refinement bit based on a value of a bit representing the bitplane.

7. The method of claim 1 , wherein the attribute signal relates to a reflectance of the point cloud.

8. The method of claim 1 , wherein the attribute signal relates to a color of the point cloud.

9. An apparatus for point cloud attribute coding, the apparatus comprising:

at least one memory configured to store computer program code; and

at least one processor configured to access the at least one memory and operate according to the computer program code, the computer program code comprising:

obtaining code configured to cause the at least one processor to obtain an attribute signal corresponding to a point cloud;

determining code configured to cause the at least one processor to determine whether lossless lifting is enabled;

modifying code configured to cause the at least one processor to, based on determining that lossless lifting is enabled, modify at least one from among a plurality of quantization weight and a plurality of lifting coefficients;

checking code configured to cause the at least one processor to check a bitplane of a lifting coefficient of the plurality of lifting coefficients to determine if the bitplane is larger than a corresponding quantization step size of the bitplane, and

first setting code configured to cause the at least one processor to set a significance bit based on a result of the determining;

decomposing code configured to cause the at least one processor to decompose the attribute signal into a plurality of detail signals and a plurality of approximation signals based on the modified at least one from among the plurality of quantization weights and the plurality of lifting coefficients;

generating code configured to cause the at least one processor to generate a bitstream representing the point cloud based on the plurality of detail signals and the plurality of approximation signals; and

transmitting code configured to cause the at least one processor to transmit the bitstream.

10. The apparatus of claim 9 , wherein the lossless lifting is determined to be enabled based on a lossless lifting flag.

11. The apparatus of claim 9 , wherein the modifying code is further configured to cause the at least one processor to round each of the plurality of quantization weights to be a multiple of a predetermined weight constant.

12. The apparatus of claim 9 , wherein the modifying code is further configured to cause the at least one processor to round each of the plurality of lifting coefficients to be a multiple of a predetermined lifting constant.

13. The apparatus of claim 9 , wherein based on determining that the bitplane is larger than the corresponding quantization step size, the significance bit is set to indicate that the bitplane is significant.

14. The apparatus of claim 9 , further comprising:

second setting code configured to cause the at least one processor to, based on a previous bitplane being determined to be significant, set a refinement bit based on a value of a bit representing the bitplane.

15. The apparatus of claim 9 , wherein the attribute signal relates to a reflectance of the point cloud.

16. The apparatus of claim 9 , wherein the attribute signal relates to a color of the point cloud.

17. A non-transitory computer-readable medium storing instructions, the instructions comprising: one or more instructions that are configured to, when executed by one or more processors of a device for point cloud attribute coding, cause the one or more processors to:

obtain an attribute signal corresponding to a point cloud;

determine whether lossless lifting is enabled;

based on determining that lossless lifting is enabled, modify at least one from among a plurality of quantization weight and a plurality of lifting coefficients;

check a bitplane of a lifting coefficient of the plurality of lifting coefficients to determine if the bitplane is larger than a corresponding quantization step size of the bitplane;

set a significance bit based on a result of the determining;

decompose the attribute signal into a plurality of detail signals and a plurality of approximation signals based on the modified at least one from among the plurality of quantization weights and the plurality of lifting coefficients;

generate a bitstream representing the point cloud based on the plurality of detail signals and the plurality of approximation signals; and

transmit the bitstream.

18. The non-transitory computer-readable medium of claim 17 , wherein the lossless lifting is determined to be enabled based on a lossless lifting flag.