Variable Bit-Length Reiterative Lossless Compression System and Method

Abstract

A computer-implemented method of performing lossless compression of a digital data set uses an iterative compression process in which the number of symbols N and bit length per symbol n may vary on successive iterations. The process includes analyzing at least a part of the data set to establish a partition thereof into N symbols of symbol length n, and to determine whether the N symbols can be further compressed, and, if so, a model to be used in encoding the N symbols.

What is claimed is: 
     
         1 . A computer-implemented method for decompressing a digital data set compressed using a variable bit-length reiterative lossless compression method, the compressed digital data set including a set of partitions, the method comprising:
 performing a decompression process including:   for each partition in the compressed digital data set,
 examining a partition header for the partition to determine if its data is compressed or uncompressed and if the partition is the last partition; 
 if the partition's data is determined to be compressed, 
 retrieving from the partition header a value of little-n for the partition and a value identifying the model; 
 if the partition is determined to be the last partition, retrieving from the header a number of bits in the last decompressed symbol from the partition that must be discarded; 
 decoding the partition data using the model identified for the partition and the value of little-n for the partition and storing the decoded partition data in a decompression store; 
 if the partition's data is determined to be uncompressed, 
 retrieving from the partition header a value indicating the number of bits of uncompressed data in the partition; 
 using the value indicating the number of bits of uncompressed data in the partition, copying the partition's data to the decompression store; 
 if an endpoint condition has not been reached, then substituting the contents of the decompression store for the compressed digital data set and repeating the decompression process; 
 otherwise, providing an output from the decompression store.