ANALYSIS-BY-SYNTHESIS 2,4 KBPS LINEAR PREDICTIVE SPEECH CODEC

A linear predictive speech codec arrangement including: a spectrum synthesizer for providing reconstructed speech generation in response to excitation signals; a distortion analyzer for comparing the reconstructed speech with an original speech, and providing a distortion analysis signal in response to such comparison; and an excitation model circuit for providing excitation signals to the spectrum synthesizer, with the excitation model circuit receiving and utilizing the distortion analysis signal in an analysis-by-synthesis operation, for determining ones of excitation signals which provide an optimal reconstructed speech. The excitation model circuit can include: a voiced excitation generator and a Gaussian noise generator, both of which should optimally provide a plurality of available excitation signal models. The voiced excitation generator and Gaussian noise generator can be in the form of a codebook of a plurality of possible pulse trains and Gaussian sequences, respectively, or alternatively, the voiced excitation generator can be in the form of a first order pitch synthesizer. The optimal excitation signal and/or the pitch value and the pitch filter coefficient are determined using an analysis-by-synthesis technique.