New techniques in context modeling and arithmetic encoding

The PPM algorithm is known to be one of the most powerful data compression techniques. However, it uses a large amount of memory, and operates slowly. Several new techniques were explored which address the problems with PPM, at each order of context modeling: the DefSum (or deferred summation) order-0 coder, the ListLRU order-1 coder, the static Huffman order-1 coder, and the PPMCB high-order coder.