Variable rate coder.

A coder for transforming an input signal into a low bit rate digital signal, includes a plurality of coding means (101, 102, 10m) in each of which a number of output bits can be variably set, and each of which can carry out a predictive coding independently, and a plurality of prediction gain obtaining means (321, 322, 32m, 331, 332, 33m) each for obtaining a prediction gain in each of said plurality of coding means (101, 102, 10m). A bit rate calculating means (360) determines a plurality of successive numbers as said numbers of output bits of said plurality of coding means (101, 102, 10m), based on a required value of the signal-to-noise ratio of the coder and said prediction gains in said plurality of coding means (101, 102, 10m). A bit rate setting means (380, 156) sets said plurality of successive numbers in said plurality of coding means (101, 102, 10m) as said number of output bits, respectively, and an output selecting means (400, 500) selects an output of one of said plurality of coding means (101, 102, 10m), as the output of said coder, based on a predetermined standard.