a method and apparatus for processing an input signal for transmission and / or storage , uses an analysis filter bank to decompose the signal into sub - band signals which are used to modulate a plurality of carriers . the carriers are combined into a single encoded signal for transmission / storage . the encoder / decoder is especially applicable to telecommunications systems and recording systems . the analysis filter bank may comprise a multiresolution filter , such as an octave band filter bank implementing discrete wavelet transform . the modulation may comprise double - sideband , single sideband , quadrature amplitude modulation , and so on . where the input signal is analog , the carriers may be modulated directly by the sub - band signals . where the input signal is digital , however , the sub - band signals are interpolated , all to the same rate , and then used to modulate the carriers . the corresponding decoder extracts the modulated carrier signals , demodulates them , decimates them and then synthesizes them to reconstruct the original input signal . one or more of the sub - bands , especially at the higher frequencies , may be discarded . discrete wavelet transformation is applied to segments of the digital signal .