1. A method for encoding an input signal, said method including the steps of: generating a reconstructed signal from past signal segments of said input signal; extracting model parameters from said reconstructed signal; adding at least one first distribution model with which the extracted model parameters are associated and at least one fixed distribution model, wherein weighting coefficients are affected to each of these distribution models, for obtaining a combined distribution model; encoding a current signal segment of said input signal into a sequence of coded data using said combined distribution model; and generating a bit stream including said sequence of coded data and information about said combined distribution model corresponding to said current signal segment.