Method for quantizing speech coder parameters

Method of encoding and decoding speech for voice communications using a vocoder with very low bit rate comprising an analysis part for the encoding and transmission of the parameters of the speech signal and a synthesis part for the reception and decoding of the transmitted parameters, and the rebuilding of the speech signal through the use of linear predictive synthesis filters of the type analyzing the parameters, describing the pitch, the voicing transition frequency, the energy, and the spectral envelope of the speech signal, by subdividing the speech signal into successive frames of given length, the method comprising assembling the parameters on N consecutive frames to form a super-frame, making a vector quantization of the transition frequencies of the voicing during each super-frame, transmitting without deterioration only the most frequent configurations and replacing the least frequent configurations by the configuration that is the nearest in terms of absolute error among the most frequent configurations, encoding the pitch in carrying out a scalar quantization of only one value of the pitch for each super-frame, encoding the energy in selecting only a reduced number of values in assembling these values in sub-packets quantized by vector quantization, the non-transmitted energy values being recovered in the synthesis part by interpolation or extrapolation from transmitted values, encoding, by vector quantization, the spectral envelope parameters for the encoding of the linear predictive synthesis filters in selecting only a determined number of filters, the untransmitted parameters being rebuilt by interpolation or extrapolation from the parameters of the transmitted filters.