Patent ID: 6594626
Filing Date: 2003-07-15
Classification: G10L

Abstract:
A voice encoding apparatus for encoding a voice signal using an adaptive codebook and an algebraic codebook, comprising:a synthesis filter implemented using linear prediction coefficients obtained by subjecting an input signal, which is the result of sampling a voice signal at a predetermined speed, to linear prediction analysis in frame units in which each frame is composed of a fixed number of samples (=N); an adaptive codebook for preserving a pitch-period component of the past L samples of the voice signal and outputting N samples of periodicity signals successively delayed by one pitch; an algebraic codebook for dividing N sampling points constituting one frame into a plurality of pulse-system groups and, for all combinations obtained by extracting one sampling point from each of the pulse-system groups, successively outputting, as noise components, pulsed signals having a pulse of a positive or negative polarity at each extracted sampling point; a pitch-lag determination unit for adopting a pitch lag (first pitch lag) as pitch lag of a present frame, wherein this pitch lag specifies a periodicity signal for which the smallest difference will be obtained between said input signal and signals obtained by driving said synthesis filter by the periodicity signals output successively from the adaptive codebook, or for adopting a pitch lag (second pitch lag), found in a past frame, as pitch lag of the present frame; a pulsed-signal determination unit for determining a pulsed signal for which the smallest difference will be obtained between said input signal and signals obtained by driving said synthesis filter by the periodicity signal specified by the decided pitch lag and the pulsed signals output successively from the algebraic codebook; and signal output means for outputting said pitch lag, data specifying said pulsed signal and said linear prediction coefficients as a voice code.