Patent ID: 6377915
Filing Date: 2002-04-23
Classification: G10L

Abstract:
A speech decoding method for reproducing a speech signal from a speech information bit stream which is a coded output of the speech signal that has been encoded by a linear prediction analysis and synthesis type speech encoder, said speech decoding method comprising the steps of:separating spectral envelope information, voiced/unvoiced discriminating information, pitch period information and gain information from said speech information bit stream, whereby forming a plurality of separated informations, and decoding each separated information; obtaining a spectral envelope amplitude from said spectral envelope information, and identifying a frequency band having a largest spectral envelope amplitude among a predetermined number of frequency bands each having a predetermined frequency bandwidth divided on a frequency axis for generating a mixed excitation signal; determining a mixing ratio for each of said predetermined number of frequency bands, based on said identified frequency band and said voiced/unvoiced discriminating information and using said mixing ratio to mix a pitch pulse generated in response to said pitch period information and white noise with reference to a predetermined mixing ratio table that has previously been stored; producing a mixing signal for each of said predetermined number of frequency bands based on said determined mixing ratio, and then producing said mixed excitation signal by summing all of said mixing signals of said predetermined number of frequency bands; and producing a reproduced speech by adding said spectral envelope information and said gain information to said mixed excitation signal.