DYNAMIC CODEBOOK FOR EFFICIENT SPEECH CODING BASED ON ALGEBRAIC CODES

摘要

The present invention relates to a method and device for conducting a search in a codebook. This codebook consists of a set of pulse amplitude/position combinations each defining a number L of positions p and comprising both zero-amplitude pulses and non-zero-amplitude pulses assigned to respective positions p = 1, 2, ...L of the combination. Also, each non-zero-amplitude pulse assumes one of q possible amplitudes. According to the method, a subset of combinations is pre-selected from the codebook, and the search is limited to this subset to reduce complexity thereof. To pre-select the subset, an amplitude/position function is pre-established in relation to the sound signal. Pre-establishing the amplitude/position function includes pre-assigning one of the q possible amplitudes to each position p by (i) processing the sound signal to produce a backward-filtered target signal D and a pitch-removed residual signal R', (ii) calculating an amplitude estimate vector B in response to the signals D and R', and (iii) for each position p, quantizing an amplitude estimate Bp of the vector B to obtain the amplitude to be selected for that particular position p.