Abstract: A method is disclosed for encoding and decoding an input signal representative of video or audio information. A form of the encoding includes the following steps: processing the input signal to produce a sequence of vectors representative of the input signal; implementing a lattice vector quantization procedure on individual vectors of the sequence to identify a lattice point of a lattice that is closest to the individual vector and to obtain an index value representative of a labelling of the identified lattice point, the lattice vector quantization procedure including a multi-level allocation of groups of reserved indices, and selection of the index value for the individual vector within a group of reserved indices. The index signals representative of the index values are stored and then recovered for decoding, or transmitted before decoding. The decoding is operative to obtain a recovered sequence of vectors, and the sequence of vectors can be processed to produce an output signal.