Spectral coding by LSP frequencies—scalar and segmented VQ-methods

Abstract

Line spectrum pairs (LSP) is one interesting way of representing the filter parameters of a linear production model. In particular, LSPs have been used for quantisation, i.e. for the spectral coding problem of speech coding. The concept of close-to-optimal search strategies, as well as optimal quantiser design, is discussed for the case of LSP-based quantisation. Previous scalar approaches are generalised to a vectorial treatment by carefully selecting a VQ technique that can provide robust results with low complexity. Simulation results are presented both for the scalar and for the vectorial case, showing that a two-dimensional VQ approach can provide substantial bit savings in realistic cases.