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:

partitioning transform coefficients associated with compressed point cloud data into one or more sets;

determining set-index values of the partitioned transform coefficients, wherein the determining comprises determining the set-index values from an aggregated super-symbol;

determining symbol-index values of the partitioned transform coefficients; and

generating decompressed point cloud data based on the set-index values and the symbol-index values.

2. The method of claim 1 , wherein the partitioning of the transform coefficients comprises decomposing the transform coefficients associated with the compressed point cloud data to determine the set-index values and the symbol-index values, the symbol index-values specifying locations of the transform coefficients within a set.

3. The method of claim 1 , wherein generating the aggregated super-symbol comprises:

determining a maximum set-index value from the set-index values associated with children of a same patent node in an octree associated with point cloud data;

entropy-coding the maximum set-index value based on the maximum set-index value being not zero; and

aggregating a plurality of the set-index values together to entropy-code one or more groups of set-index values based on the maximum set-index value being small.

4. The method of claim 1 , wherein generating the aggregated super-symbol comprises:

determining a maximum set-index value from the set-index values associated with children of a same patent node in an octree associated with point cloud data;

entropy-coding the maximum set-index value based on the maximum set-index value being not zero;

entropy-coding an alpha value with a 255-symbol alphabet; and

aggregating a plurality of the set-index values together to entropy-code one or more groups of set-index values based on a sibling occupancy value index of the octree being smaller than the maximum set-index value.

5. 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.

6. The method of claim 1 , 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.

7. The method of claim 6 , wherein the one or more alphabet-partition types are used for one or more level-of-detail layers corresponding to the transform coefficients.

8. The method of claim 6 , wherein the one or more alphabet-partition types are used for one or more inverse quantization parameters based on quantization of the transform coefficients.

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

10. 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:

partitioning code configured to cause the at least one processor to partition transform coefficients associated with compressed point cloud data into one or more sets;

first determining code code configured to cause the at least one processor to determine set-index values of the partitioned transform coefficients, wherein the determining comprises determining the set-index values from an aggregated super-symbol;

second determining code configured to cause the at least one processor to determine symbol-index values of the partitioned transform coefficients; and

decompressing code configured to cause the at least one processor to generate decompressed point cloud data based on the set-index values and the symbol-index values.

11. The apparatus of claim 10 , wherein the partitioning of the transform coefficients comprises decomposing the transform coefficients associated with the compressed point cloud data to determine the set-index values and the symbol-index values, the symbol index-values specifying locations of the transform coefficients within a set.

12. The apparatus of claim 10 , wherein generating the aggregated super-symbol comprises:

determining a maximum set-index value from the set-index values associated with children of a same patent node in an octree associated with point cloud data;

entropy-coding the maximum set-index value based on the maximum set-index value being not zero; and

aggregating a plurality of the set-index values together to entropy-code one or more groups of set-index values based on the maximum set-index value being small.

13. The apparatus of claim 10 , wherein generating the aggregated super-symbol comprises:

determining a maximum set-index value from the set-index values associated with children of a same patent node in an octree associated with point cloud data;

entropy-coding the maximum set-index value based on the maximum set-index value being not zero;

entropy-coding an alpha value with a 255-symbol alphabet; and

aggregating a plurality of the set-index values together to entropy-code one or more groups of set-index values based on a sibling occupancy value index of the octree being smaller than the maximum set-index value.

14. The apparatus of claim 10 , 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.

15. The apparatus of claim 10 , 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.

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

partition transform coefficients associated with compressed point cloud data into one or more sets;

determine set-index values of the partitioned transform coefficients, wherein the determining comprises determining the set-index values based on an aggregated super-symbol;

determining symbol-index values of the partitioned transform coefficients; and

generating decompressed point cloud data based on the set-index values and the symbol-index values.

17. The computer-readable medium of claim 16 , wherein the partitioning of the transform coefficients comprises decomposing the transform coefficients associated with the compressed point cloud data to determine the set-index values and the symbol-index values, the symbol index-values specifying locations of the transform coefficients within a set.

18. The computer-readable medium of claim 16 , wherein generating the aggregated super-symbol comprises:

determining a maximum set-index value from the set-index values associated with children of a same patent node in an octree associated with point cloud data;

entropy-coding the maximum set-index value based on the maximum set-index value being not zero; and

aggregating a plurality of the set-index values together to entropy-code one or more groups of set-index values based on the maximum set-index value being small.

19. The computer-readable medium of claim 16 , wherein generating the aggregated super-symbol comprises:

determining a maximum set-index value from the set-index values associated with children of a same patent node in an octree associated with point cloud data;

entropy-coding the maximum set-index value based on the maximum set-index value being not zero;

entropy-coding an alpha value with a 255-symbol alphabet; and

aggregating a plurality of the set-index values together to entropy-code one or more groups of set-index values based on a sibling occupancy value index of the octree being smaller than the maximum set-index value.

20. The computer-readable medium of claim 16 , 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.