| 摘要 |
PROBLEM TO BE SOLVED: To excellently encode a speech signal even in noisy environment and to obtain a speech signal of high sound quality by providing a gain control means which increases and decreases the gain of both or one of a probability code book and an adaptive code book according to the decision result of a speech decision means and the analytic result of a pitch periodicity analyzing means. SOLUTION: On the basis of spectrum parameters obtained by analyzing an input signal by an LPC analyzer 16, a composing filter 8 puts together signals outputted from the probability code book 4 and the adaptive code book 1 and an error evaluation unit 14 outputs codes corresponding to the delay of the adaptive code book 1 minimizing the distortion of the composite signal, the indexes of the probability code book 4, and respective gains. According to the decision result of a speech decision unit 11 and the analytic result of the pitch periodicity analyzer 10, the gains of the probability code book 4 and adaptive code book 1 are increased and decreased by a gain controller 15. |
