Fast compression with a static model in high-order entropy

We report on a simple encoding format called wzip for decompressing block-sorting transforms, such as the Burrows-Wheeler transform (BWT). Our compressor uses the simple notions of gamma encoding and RLE, organized with a wavelet tree, to achieve a slightly better compression ratio than bzip2 in less time. In fact, our compression/decompression time is dependent on H/sub h/, the hth order empirical entropy. This relationship of performance to the compressibility of data is a key new idea among compression algorithms. Another key contribution of our compressor is its simplicity. Our compressor can also operate as a full-text index with a small amount of data, while still preserving backward compatibility with just the compressor.