Patent ID: 8195469

Claim:
A speech decoding device which decodes speech signals by using received feature parameters representing gain and representing spectral envelope characteristics, the device comprising: a voice/voice-less detecting circuit for detecting if said speech signals are classified in a period containing voice, denoted as a voice period, or in a period that does not contain voice, denoted as a voice-less period; and a voice-less decoding circuit for intermittently receiving said feature parameter representing spectral envelope characteristics to decode a current frame of the speech signals in said voice-less period, the voice-less decoding circuit performing said decoding by smoothing said feature parameter representing spectral envelope characteristics of said current frame and synthesizing said speech signals of said current frame based on a smoothed feature parameter representing spectral envelope characteristics of said current frame and said feature parameter representing a gain of said current frame, wherein said smoothing is performed by weighting a smoothed feature parameter representing spectral envelop characteristics of an immediately preceding frame and a feature parameter representing special envelope characteristics of said current frame and by adding the weighted smoothed feature parameter representing spectral envelope characteristics of said immediately preceding frame and the weighted feature parameter representing spectral envelope characteristics of said current frame, wherein a value of a weighting factor used in said smoothing is changed according to a number of frames which have been received in prior voice-less periods, and wherein when no feature parameter representing spectral envelope characteristics is received in said current frame, the smoothing is performed using said feature parameter representing spectral envelope characteristics received before the current frame in place of said feature parameter representing spectral envelope characteristics of said current frame.