Techniques and apparatus for alphabet-partition coding of transform coefficients for point cloud compression

1. A method of point cloud coefficient decoding, the method being performed by at least one processor, comprising:

receiving compressed point cloud data based on set-index values and symbol-index values;

entropy-decoding the set-index values based on the compressed point cloud data;

bypass-decoding the symbol-index values based on the compressed point cloud data; and

combining the set-index values and symbol-index values into transform coefficients associated with cloud point data.

2. The method of claim 1 , wherein frequency values associated with the transform coefficients are stored in a cache or frequency-sorting based lookup table in a descending order, wherein a lowest set-index value is assigned to a transform coefficient having a greatest frequency value.

3. The method of claim 1 , wherein the symbol-index value indicates a location of the transform coefficient in a set; and wherein the symbol-index values and the set-index values are signaled to indicate an alphabet-partition having associated boundary values based on one or more alphabet-partition types shared between an encoder and a decoder.

4. The method of claim 3 , wherein the one or more alphabet-partitioning types are used for one or more level-of-detail layers corresponding to the transform coefficients.

5. The method of claim 3 , wherein the one or more alphabet-partitioning types are used for one or more quantization parameters based on quantization of the transform coefficients.

6. The method of claim 3 , wherein the one or more alphabet-partitioning types are used for one or more layers of scalability for signal-to-noise ratio-scalable coding based on correlations between the transform coefficients.

7. The method of claim 1 , wherein the set-index values are decoded by multi-symbol arithmetic coding.

8. An apparatus for point cloud coefficient decoding, 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:

receiving code configured to cause the at least one processor to receive compressed point cloud data based on set-index values and symbol-index values;

entropy-decoding code configured to cause the at least one processor to entropy-decode the set-index values based on the compressed point cloud data;

bypass-decoding code configured to cause the at least one processor to bypass-decode the symbol-index values based on the compressed point cloud data; and

combining code configured to cause the at least one processor to combine the set-index values and symbol-index values into transform coefficients associated with cloud point data.

9. The apparatus of claim 8 , wherein frequency values associated with the transform coefficients are stored in a cache or frequency-sorting based lookup table in a descending order, wherein a lowest set-index value is assigned to a transform coefficient having a greatest frequency value.

10. The apparatus of claim 8 , wherein the symbol-index value indicates a location of the transform coefficient in a set; and wherein the symbol-index values and the set-index values are signaled to indicate an alphabet-partition having associated boundary values based on one or more alphabet-partition types shared between an encoder and a decoder.

11. The apparatus of claim 10 , wherein the one or more alphabet-partitioning types are used for one or more level-of-detail layers corresponding to the transform coefficients.

12. The apparatus of claim 10 , wherein the one or more alphabet-partitioning types are used for one or more quantization parameters based on quantization of the transform coefficients.

13. The apparatus of claim 10 , wherein the one or more alphabet-partitioning types are used for one or more layers of scalability for signal-to-noise ratio-scalable coding based on correlations between the transform coefficients.

14. The apparatus of claim 8 , wherein the set-index values are decoded by multi-symbol arithmetic coding.

15. A non-transitory computer-readable storage medium storing instructions configured to cause at least one processor to:

receive compressed point cloud data based on set-index values and symbol-index values;

entropy-decode the set-index values based on the compressed point cloud data;

bypass-decode the symbol-index values based on the compressed point cloud data; and

combine the set-index values and symbol-index values into transform coefficients associated with cloud point data.

16. The computer-readable medium of claim 15 , wherein frequency values associated with the transform coefficients are stored in a cache or frequency-sorting based lookup table in a descending order, wherein a lowest set-index value is assigned to a transform coefficient having a greatest frequency value.

17. The computer-readable medium of claim 15 , wherein the symbol-index value indicates a location of the transform coefficient in a set; and wherein the symbol-index values and the set-index values are signaled to indicate an alphabet-partition having associated boundary values based on one or more alphabet-partition types shared between an encoder and a decoder.

18. The computer-readable medium of claim 17 , wherein the one or more alphabet-partitioning types are used for one or more level-of-detail layers corresponding to the transform coefficients.

19. The computer-readable medium of claim 17 , wherein the one or more alphabet-partitioning types are used for one or more quantization parameters based on quantization of the transform coefficients.

20. The computer-readable medium of claim 17 , wherein the one or more alphabet-partitioning types are used for one or more layers of scalability for signal-to-noise ratio-scalable decoding based on correlations between the transform coefficients.