| 摘要 |
PROBLEM TO BE SOLVED: To obtain excellent speech quality even when the bit rate is lowered by finding the position where predetermined conditions are met by a sound source quantization part, and searching for the best position in the search range of positions of pulses representing a sound source signal on the basis of the found position. SOLUTION: A spectrum parameter calculating circuit 200 finds spectrum parameters from an input speech signal and quantizes them. An adaptive code book circuit 300 finds delay corresponding to a pitch cycle from the speech signal and calculates a pitch prediction signal to predict a pitch. Then a sound source quantizing circuit 350 constitutes a sound source signal of the speech signal with M pulses whose amplitudes are not zero, finds the sample position corresponding to a pulse position where the predetermined conditions are met for the pitch prediction signal, and sets a range of a search for the position of a pulse on the basis of a position which is shifted from the found sample position by a predetermined number of samples, thereby searching for and outputting the best position for the set range. |
