Coding of UV coordinates

1. A method of processing UV coordinates of a three-dimensional (3D) mesh, the method comprising:

receiving the UV coordinates of the 3D mesh, the UV coordinates being two-dimensional (2D) texture coordinates that include U coordinates in a first axis and V coordinates in a second axis, and being mapped to vertices of the 3D mesh;

separating (i) the U coordinates from the UV coordinates into a first 2D array and (ii) the V coordinates from the UV coordinates into a second 2D array that is different from the first 2D array according to a predefined scanning order;

processing the U coordinates and the V coordinates of the 3D mesh separately based on at least one of a quantization process, and a transformation process, the quantization process being configured to convert the UV U coordinates and the V coordinates into a plurality of indicators, the transformation process being configured to convert the U coordinates and the V coordinates from a spatial domain into a transform domain; and

performing compression on the processed UV U coordinates and the processed V coordinates of the 3D mesh.

2. The method of claim 1 , wherein the processing is based on the quantization process, and the processing further comprises one of:

applying a linear scalar quantization to the U coordinates and the V coordinates of the UV coordinates respectively by dividing the U coordinates with a first scalar factor and the V coordinates with a second scalar factor; and

applying a vector quantization to a plurality of UV pairs of the UV coordinates, each UV pair of the plurality of UV pairs including a respective U coordinate and a respective V coordinate and being represented by an indicator to a vector dictionary of the vector quantization.

3. The method of claim 1 , wherein

the performing the compression further comprises:

performing the compression on the U coordinates of the UV coordinates in the first 2D array; and

performing the compression on the V coordinates of the UV coordinates in the second 2D array.

4. The method of claim 1 , wherein:

the processing is based on the transformation process, and the processing further comprises:

performing the transformation process on a plurality of UV pairs of the UV coordinates based on one of an invertible transform, a Haar transform, or a linear decorrelation transform, each UV pair of the plurality of UV pairs including a respective U coordinate and a respective V coordinate of the UV coordinates; and

generating first channel information based on the transformed U coordinates of the plurality of UV pairs of the UV coordinates and second channel information based on the transformed V coordinates of the plurality of UV pairs of the UV coordinates; and

the performing the compression further comprises:

performing the compression on the first channel information of the UV coordinates; and

performing the compression on the second channel information of the UV coordinates.

5. The method of claim 1 , wherein the performing the compression on the UV coordinates further comprises:

performing one of an image/video compression or an integer compression on the UV coordinates.

6. The method of claim 1 , further comprising:

predicting values of the U coordinates of the UV coordinates based on values of prior coded U coordinates and generating a list of prediction residues of the U coordinates; and

predicting values of the V coordinates of the UV coordinates based on values of prior coded V coordinates and generating a list of prediction residues of the V coordinates.

7. The method of claim 6 , further comprising:

performing a first mapping operation on the list of the prediction residues of the U coordinates to generate a list of non-negative integers of the U coordinates; and

performing a second mapping operation on the list of the prediction residues of the V coordinates to generate a list of non-negative integers of the V coordinates.

8. The method of claim 7 , further comprising:

performing a first bit packing process on the list of the non-negative integers of the U coordinates to generate a list of bits of the U coordinates; and

performing a second bit packing process on the list of the non-negative integers of the V coordinates to generate a list of bits of the V coordinates.

9. The method of claim 8 , wherein:

the performing the compression includes performing the compression on at least one of the list of the prediction residues of the U coordinates, the list of the prediction residues of the V coordinates, the list of the non-negative integers of the U coordinates, the list of the non-negative integers of the V coordinates, the list of bits of the U coordinates, or the list of bits of the V coordinates, and

the compression is performed based on one of an entropy coding, a variable length coding, a Huffman coding, or an arithmetic coding.

10. The method of claim 1 , wherein the performing the compression further comprises:

performing a lossy compression on the UV coordinates to generate lossy compression residues of the UV coordinates based on one of a lossy image/video codec and a lossy integer compression; and

performing a lossless compression on the lossy compression residues of the UV coordinates based on one of a lossless image/video codec and a lossless integer compression.

11. An apparatus for processing UV coordinates of a three-dimensional (3D) mesh, comprising:

processing circuitry configured to:

receive the UV coordinates of the 3D mesh, the UV coordinates being two-dimensional (2D) texture coordinates that include U coordinates in a first axis and V coordinates in a second axis, and being mapped to vertices of the 3D mesh;

separate (i) the U coordinates from the UV coordinates into a first 2D array and (ii) the V coordinates from the UV coordinates into a second 2D array that is different from the first 2D array according to a predefined scanning order;

process the UV coordinates of the 3D mesh based on at least one of a quantization process, and a transformation process, the quantization process being configured to convert the U coordinates and the V coordinates into a plurality of indicators, the transformation process being configured to convert the U coordinates and the V coordinates from a spatial domain into a transform domain; and

perform compression on the processed U coordinates and the processed V coordinates of the 3D mesh.

12. The apparatus of claim 11 , wherein the processing circuitry is configured to process the UV coordinates based on the quantization process by performing one of:

a linear scalar quantization that is applied to the U coordinates and the V coordinates of the UV coordinates respectively by dividing the U coordinates with a first scalar factor and the V coordinates with a second scalar factor; and

a vector quantization that is applied to a plurality of UV pairs of the UV coordinates, each UV pair of the plurality of UV pairs including a respective U coordinate and a respective V coordinate and being represented by an indicator to a vector dictionary of the vector quantization.

13. The apparatus of claim 11 , wherein the processing circuitry is configured to:

perform the compression on the U coordinates of the UV coordinates in the first 2D array; and

perform the compression on the V coordinates of the UV coordinates in the second 2D array.

14. The apparatus of claim 11 , wherein the processing circuitry is configured to:

perform the transformation process on a plurality of UV pairs of the UV coordinates based on one of an invertible transform, a Haar transform, or a linear decorrelation transform, each UV pair of the plurality of UV pairs including a respective U coordinate and a respective V coordinate of the UV coordinates;

generate first channel information based on the transformed U coordinates of the plurality of UV pairs of the UV coordinates and second channel information based on the transformed V coordinates of the plurality of UV pairs of the UV coordinates;

perform the compression on the first channel information of the UV coordinates; and

perform the compression on the second channel information of the UV coordinates.

15. The apparatus of claim 11 , wherein the processing circuitry is configured to:

perform one of an image/video compression or an integer compression on the UV coordinates.

16. The apparatus of claim 11 , wherein the processing circuitry is configured to:

predict values of the U coordinates of the UV coordinates based on values of prior coded U coordinates and generate a list of prediction residues of the U coordinates; and

predict values of the V coordinates of the UV coordinates based on values of prior coded V coordinates and generate a list of prediction residues of the V coordinates.

17. The apparatus of claim 16 , wherein the processing circuitry is configured to:

perform a first mapping operation on the list of the prediction residues of the U coordinates to generate a list of non-negative integers of the U coordinates; and

perform a second mapping operation on the list of the prediction residues of the V coordinates to generate a list of non-negative integers of the V coordinates.

18. The apparatus of claim 17 , wherein the processing circuitry is configured to:

perform a first bit packing process on the list of the non-negative integers of the U coordinates to generate a list of bits of the U coordinates; and

perform a second bit packing process on the list of the non-negative integers of the V coordinates to generate a list of bits of the V coordinates.

19. The apparatus of claim 18 , wherein:

the processing circuitry is configured to perform the compression on at least one of the list of the prediction residues of the U coordinates, the list of the prediction residues of the V coordinates, the list of the non-negative integers of the U coordinates, the list of the non-negative integers of the V coordinates, the list of bits of the U coordinates, or the list of bits of the V coordinates, and

the compression is performed based on one of an entropy coding, a variable length coding, a Huffman coding, or an arithmetic coding.

20. The apparatus of claim 11 , wherein the processing circuitry is configured to:

perform a lossy compression on the UV coordinates to generate lossy compression residues of the UV coordinates based on one of a lossy image/video codec and a lossy integer compression; and

perform a lossless compression on the lossy compression residues of the UV coordinates based on one of a lossless image/video codec and a lossless integer compression.