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Abstract

A codebook is searched in view of encoding a sound signal. This codebook consists of a set of pulse amplitude/position combinations each defining L different positions and comprising both zero-amplitude pulses and non-zero-amplitude pulses assigned to respective positions p=1, 2, . . . L of the combination, wherein each non-zero-amplitude pulse assumes at least one of q possible amplitudes. To reduce the search complexity, a subset of pulse amplitude/position combinations from the codebook is pre-selected in relation to the sound signal, and only this subset of combinations is searched. The pre-selection of the subset of combinations consists of pre-establishing, in relation to the sound signal, a function S.sub.p between the respective positions p=1, 2, . . . L and the q possible amplitudes, the search being limited to the combinations of the codebook having non-zero-amplitude pulses which respect the pre-established function. The function can be pre-established by pre-assigning one of the q possible amplitudes to each position p, the pre-established function being respected when the non-zero-amplitude pulses of a combination each have an amplitude equal to the amplitude S.sub.p pre-assigned to the position p of that pulse.

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