Speech encoder with features extracted from current and previous frames

Claim 1

A speech signal encoder device comprising: segmenting means for segmenting an input speech signal into original speech frames at a predetermined frame period; deciding means for using said original speech frames in deciding a predetermined number of modes of said original speech frames to produce decided mode results; weighting means for perceptually weighting said original speech frames into weighted speech frames; and encoding means for encoding said input speech signal into codes at said frame period and in response to said modes to produce said decided mode results and said codes as an encoder device output signal, wherein said deciding means makes use, in deciding a current mode of said modes for each current speech frame segmented from said input speech signal at said frame period, of feature quantities of at least one kind extracted from said current speech frame and a previous speech frame segmented at least one frame period prior to said current speech frame and of a previous mode decided at least one frame period prior to said current mode. wherein said deciding means uses said weighted speech frames in deciding said modes, wherein said feature quantities are rates of variation with time in said feature quantities, said speech signal encoder device further comprising: means for extracting each of primary quantities of said feature quantities from said current speech frame, wherein said deciding means comprises: means for extracting said rates of variation from said current and said previous speech frames as secondary quantities of said feature quantities; and mode deciding means for deciding said current mode in response to said primary and said secondary quantities and said previous mode.