Abstract: An improved pitch searching time reducing method for a CELP vocoder using a Line Spectral Pair (LSP) frequency which is capable of significantly reducing the pitch search time by separating the speech signal using a first formant frequency of the line spectral pair of the digital type personal communication system, which includes the steps of computing a decimation interval of a pitch search interval using an LSP frequency of a first formant computed by a formant filter so as to compute a preparatory pitch of a given speech; determining a preparatory pitch to be used when searching a pitch by detecting a peak and a valley within each decimation interval; and computing a preparatory pitch by adapting a first formant frequency of an LSP computed by a formant filter with a decimation rate and performing a pitch search with respect to the obtained preparatory pitch.

Abstract: The present invention relates to the method to receive a speech signal, to perform a recognition weighting process on it, to synthesize a synthetic speech signal, to calculate an autocorrelation of the synthetic speech signal whose delay is a predetermined value and an autocorrelation whose delay is 0, to divide the square of the former by the latter, to calculate a pitch lag and a pitch filter coefficient by calculating only the part of a positive peak with skipping over the part of a negative peak by using the results from the dividing operation, and to calculate and output the pitch lag and the pitch filter coefficient by repeating the above process Thus, real-time implementation of CELP vocoder can be achieved.

Abstract: A method for processing an input speech signal to be applied to a CELP vocoder has the steps of obtaining preliminary pitch search intervals by a preprocessing autocorrelation expression from a pitch lag of a synthesized speech signal which is synthesized from a residual signal of the input speech signal; computing coefficients of pitch filter with respect to the preliminary pitches; searching a high interval in the autocorrelation; and removing the remaining interval other than the high interval in the pitch lag. Since the present invention proposes a speech processing method which uses only a high interval in autocorrelation of a voice waveform in pitch-searching, and where such a speech processing method is embodied in a CELP vocoder, total computation time of the CELP vocoder can be decreased 37% or more without lowering speech quality. Therefore, a digital signal processor, which is low in price and is slow in speed, can be embodied in a CELP vocoder.