Talkodare som utnyttjar syntes-analysteknik, och som omfattar pulsaktivering

摘要

In an analysis-by-synthesis coder, the original speech signal undergoes small time shifts to match in time the signal to be coded with the replica produced by the long term synthesis filter. The shift is determined at each subframe by an exhaustive search within a range of possible values so as to minimize the error signal energy. Once the optimal shift has been determined, the optimal excitation is searched for. The excitation is chosen in a codebook containing words with very few pulses arranged in a deterministic structure, which words are all obtained from a limited number of key words. The deterministic codebook structure allows a fast search for the optimal excitation, without need of storing the codebook and actually performing the synthesis filterings of the candidate excitations.