| 摘要 |
PURPOSE:To encode a waveform at an encoding speed of about 2.4Kb/S and to improve a speech with a low encoding speed like this by representing sound source information with a pulse train of plural polar pulses which are equal in interval and amplitude and have the degree in freedom only for the phases and polarities of the pulses. CONSTITUTION:An impulse response calculator 14 calculates the impulse response of all polar filters defined with an a parameter, obtained by converting an LSP coefficient obtained by taking an LPC analysis of an input speech signal by an LSP analyzer 3 by analytic frames and outputting the result, by time slots of each sample of the analytic frame, an autocorrelation calculator 18 calculates its autocorrelation coefficient series, and a cross-correlation calculator 16 calculates the cross-correlation coefficient series between an isolated waveform corresponding to the analytic frame of the input speech signal and the impulse response. A maximum series retrieving unit 20 determines the phase of the retrieval output pulse train Bi consisting of the equal-interval and equal-amplitude polar pulses and the polarity of each polar pulse so that the composite waveform of the autocorrelation coefficient series corresponding to each polar pulse is most similar to the waveform of the cross-correlation coefficient series, and outputs them as sound source information. |
