Techniques and apparatus for inter-channel prediction and transform for point-cloud 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 encoded bitstream corresponding to a point cloud;

determining whether the encoded bitstream was encoded using an inter-channel tool for inter-channel decorrelation;

based on determining that the encoded bitstream was encoded using the inter-channel tool, decoding the encoded bitstream using the inter-channel tool to reconstruct an attribute signal corresponding to the point cloud; and

reconstructing the point cloud using the reconstructed attribute signal,

wherein the decoding the encoded bitstream using the inter-channel tool comprises:

obtaining a reconstructed residual for a first color channel; and

obtaining a reconstructed residual for second color channel using the reconstructed residual for the first color channel.

2. The method of claim 1 , wherein the inter-channel tool comprises an in loop color-residual transform.

3. The method of claim 2 , wherein the in loop color-residual transform comprises a YCoCg-R transform.

4. The method of claim 1 , wherein the inter-channel tool comprises an inter-channel color-residual predictor.

5. The method of claim 1 , wherein the encoded bitstream is determined to be encoded using the inter-channel tool based on a flag signaled in the encoded bitstream.

6. The method of claim 5 , wherein the flag is set in the encoded bitstream based on at least one from among a difference between values of color channels of neighboring points, or a difference between reconstructed residual values of the color channels of the neighboring points.

7. The method of claim 1 , further comprising:

obtaining a reconstructed lifting coefficient for a first color channel; and

obtaining a reconstructed lifting coefficient for second color channel based on the reconstructed lifting coefficient for the first color channel.

8. The method of claim 1 , wherein the first color channel comprises a green color channel, and

wherein the second color channel comprises one from among a red color channel and a blue color channel.

9. The method of claim 1 , wherein the reconstructed residual for the first color channel is obtained based on at least one reconstructed neighbor sample.

10. 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:

first obtaining code configured to cause the at least one processor to obtain an encoded bitstream corresponding to a point cloud;

determining code configured to cause the at least one processor to determine whether the encoded bitstream was encoded using an inter-channel tool for inter-channel decorrelation;

decoding code configured to cause the at least one processor to, based on determining that the encoded bitstream was encoded using the inter-channel tool, decode the encoded bitstream using the inter-channel tool to reconstruct an attribute signal corresponding to the point cloud; and

reconstructing code configured to cause the at least one processor to reconstruct the point cloud using the reconstructed attribute signal,

wherein the decoding code comprises:

second obtaining code configured to cause the at least one processor to obtain a reconstructed residual for a first color channel; and

third obtaining configured to cause the at least one processor to obtain a reconstructed residual for second color channel using the reconstructed residual for the first color channel.

11. The apparatus of claim 10 , wherein the inter-channel tool comprises an in loop color-residual transform.

12. The apparatus of claim 11 , wherein the in loop color-residual transform comprises a YCoCg-R transform.

13. The apparatus of claim 10 , wherein the inter-channel tool comprises an inter-channel color-residual predictor.

14. The apparatus of claim 10 , wherein the encoded bitstream is determined to be encoded using the inter-channel tool based on a flag signaled in the encoded bitstream.

15. The apparatus of claim 14 , wherein the flag is set in the encoded bitstream based on at least one from among a difference between values of color channels of neighboring points, or a difference between reconstructed residual values of the color channels of the neighboring points.

16. The apparatus of claim 10 , wherein the computer program code further comprises:

fourth obtaining code configured to cause the at least one processor to obtain a reconstructed lifting coefficient for a first color channel; and

fifth obtaining code configured to cause the at least one processor to obtain a reconstructed lifting coefficient for second color channel based on the reconstructed lifting coefficient for the first color channel.

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 encoded bitstream corresponding to a point cloud;

determine whether the encoded bitstream was encoded using an inter-channel tool for inter-channel decorrelation;

based on determining that the encoded bitstream was encoded using the inter-channel tool, decode the encoded bitstream using the inter-channel tool to reconstruct an attribute signal corresponding to the point cloud; and

reconstruct the point cloud using the reconstructed attribute signal,

wherein the decoding of the encoded bitstream using the inter-channel tool comprises:

obtaining a reconstructed lifting coefficient for a first color channel; and

obtaining a reconstructed lifting coefficient for second color channel using the reconstructed lifting coefficient for the first color channel.

18. The non-transitory computer-readable medium of claim 17 , wherein the inter-channel tool comprises an in loop color-residual transform.

19. The non-transitory computer-readable medium of claim 17 , wherein the inter-channel tool comprises an inter-channel color-residual predictor.

20. The non-transitory computer-readable medium of claim 17 , wherein the one or more instructions are further configured to cause the one or more processor to:

obtain a reconstructed lifting coefficient for a first color channel; and

obtain a reconstructed lifting coefficient for second color channel based on the reconstructed lifting coefficient for the first color channel.