PURPOSE: To provide a high-quality speech message encoding and decoding method which is reduced in complicated calculation and a synchronization system between an encoding device and a decoding device which can accurately and efficiently extract control information and speech information.

CONSTITUTION: The speech message encoding and decoding method which processes sample permutations consists of a step of gain control 102 in which respective code vectors are brought under gain control in a backward adaptive gain controller body 145 and discriminated with corresponding indexes, a step in which corresponding code vector candidates are generated by filtering the gain-controlled code vectors in synthesizing filters 103 and 104 featured with filter parameters, a step in which the parameters of the synthesizing filters are adjusted in response to the input sample permutations, a step in which the sequential sample permutations are compared with the code vector candidates, and a step in which (i) the index of the code vector candidate having the shortest distance from each permutation and (ii) the parameters of the synthesizing filters are outputted.