On synchronous coding

Novel synchronous coding schemes are introduced and relationships between optimal synchronous codes and Huffman codes are also discussed. Although the problem of existence of optimal synchronous codes has not been resolved yet, we show that any synchronous code can consider as an optimal synchronous code for some information source and that there always exist optimal synchronous codes for the information source with a dyadic probability distribution. Comparing with Huffman coding, the synchronous coding is used not only for statistical modeling but also for dictionary methods. Moreover, it is proven that breaking a synchronous code is NP-complete.