Patent ID: 7716045

Claim:
A method of coding and decoding speech for voice communications using a vocoder with very low bit rate comprising an analysis part for the coding and the transmission of the parameters of the speech signal, such as the voicing information per sub-band, the pitch, the gains, the LSF spectral parameters and a synthesis part for the reception and the decoding of the parameters transmitted and the reconstruction of the speech signal comprising executing the following steps on an audio processor: grouping together the voicing parameters, pitch, gains, LSF coefficients over N consecutive frames to form a superframe, performing a vector quantization of the voicing information for each superframe by formulating a classification using the information on the chaining in terms of voicing existing over a sub-multiple of N consecutive elementary frames, the voicing information makes it possible specifically to identify classes of sounds for which the allocation of the bit rate and the associated dictionaries will be optimized, the classification is performed on voicing classes over a horizon of 2 elementary frames, the classes are 6 in number and include: a 1 st class comprising two consecutive unvoiced frames (UU); a 2 nd class comprising an unvoiced frame followed by a voiced frame (UV); a 3 rd class comprising a voiced frame followed by an unvoiced frame (VU); a 4 th class comprising two consecutive voiced frames with at least one weak voicing frame and the other frame being of greater or equal voicing (VV 4 ); a 5 th class comprising two consecutive voiced framed with at least one mean voicing frame and the other frame being of greater or equal voicing (VV 2 ); and a 6 th class comprising two consecutive voiced frames wherein each of the frames is strongly voiced and only a last sub band may be unvoiced (VV 3 ); coding the pitch, the gains and the LSF coefficients by using the classification obtained.