Patent ID: 8433563

Claim:
A method comprising: receiving a speech signal; from the speech signal, deriving a spectral envelope signal representative of a source-filter model and a first remaining signal representative of a modelled source signal, the first remaining signal comprising a plurality of successive portions having a degree of periodicity and being derived using two or more parameters of the source-filter model; deriving a second remaining signal from the first remaining signal by, at intervals during encoding of said speech signal: exploiting a correlation between ones of said portions to generate a predicted version of a later of said portions from a stored version of an earlier of said portions, and using the predicted version of the later of said portions to remove an effect of said periodicity from the first remaining signal; and transmitting an encoded signal representing said speech signal based on the spectral envelope signal, said correlations, and the second remaining signal; wherein the method further comprises, at one or more of said intervals, transforming the stored version of the earlier portion of the first remaining signal prior to generating the predicted version of the respective later portion by updating the stored version of the earlier of said portions using updated versions of the two or more parameters of the source-filter model.