Telefonaktiebolaget LM Ericsson (publ)
Methods, encoder and decoder for handling line spectral frequency coefficients

Abstract:

A method and apparatus for handling input Line Spectral Frequency, LSF, coefficients. The method comprises determining LSF residual coefficients as first compressed LSF coefficients subtracted from the input LSF coefficients, and transforming the LSF residual coefficients into a warped domain. One of a plurality of gain-shape coding schemes is applied on the transformed LSF residual coefficients in order to achieve gain-shape coded LSF residual coefficients, where the plurality of gain-shape coding schemes have mutually different trade-offs in one or more of gain resolution and shape resolution for one or more of the transformed LSF residual coefficients. A representation of the first compressed LSF coefficients, the gain-shape coded LSF residual coefficients, and information on the applied gain-shape coding scheme are transmitted over a communication channel to a decoder.