Arithmetic coding into fixed-length codewords

Arithmetic coding is known to be optimal in compressing strings of independent symbols, the probabilities of which are given. However the method has some disadvantages that the present variant tries to overcome. The idea here is to apply arithmetic coding piecewise, by cutting the process regularly. The result consists of fixed-length sequences of bits, representing variable-length substrings of the source. For implementation reasons, the bit sequences are composed of machine words, allowing one to use basic arithmetic efficiently. The compression gain approaches the optimum when the sequence size is increased