Move To Front Transform

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The move-to-front transform (or MTF) is an encoding of data (typically a stream of bytes) designed to improve the performance of entropy encoding techniques of compression. When efficiently implemented, it is fast enough that its benefits usually justify including it as an extra step in data compression algorithms.The main idea is that each symbol in the data is replaced by its index in the stack of "recently used symbols". For example, long sequences of identical symbols are replaced by as many zeroes, whereas when a symbol that has not been used in a long time appears, it is replaced with a large number. Thus at the end the data is transformed into a sequence of integers; if the data exhibits a lot of local correlations, then these integers tend to be small.