METHOD OF TRANSMITTING, AT LOW THROUGHPUT, A SPEECH SIGNAL BY CELP CODING, AND CORRESPONDING SYSTEM

A method is provided for transmitting a digital speech signal at low throughput. Coding is performed by code excited linear prediction in order to generate a code signal, a waveform being represented by an initial vector (O) of dimension L, from a filter for synthesizing by a reference waveform selected from a dictionary of reference vectors (v), relating to a criterion of minimum deviation min .parallel..chi.-H.v.parallel..sup.2, .chi. representing a target vector through perceptual weighting of the initial vector (O). A dictionary (Y) factorized as a product of basis vectors yi of n-ary form, which are corrected by a scale factor .gamma.i of distribution of the excitation energy, and a dictionary G(y) of gains gk, are established to represent the dictionary of the reference vectors (v), vk, i=gk..gamma..yi. The criterion is established by calculating C(gk, .gamma.i.yi)=2gk<.chi..vertline.H..gamma.i.yi>-gk.sup.2 formed of the scalar products and perceptual energies. To the initial vector (O) is assigned the optimal reference vector vk*, i*=gk*..gamma.i.yi represented by just the index values k*, i*.