Analysis-by-synthesis linear predictive speech coding at 2.4 kbit/s

Novel 2.4-kb/s linear predictive speech coders based on the analysis-by-syntheses method are proposed. The introduction of a perceptually weighted distortion measure between the original speech and the reconstructed speech implicitly optimizes both the voiced/unvoiced decision and the pitch estimation/tracking. The coders are also shown to be more robust to background acoustic noises. The resultant speech quality is significantly enhanced by judicious parameter coding. Three excitation models are proposed and investigated. It is found that the model which selects the excitation signal from either a random sequence codebook or a pitch synthesizer produces the best perceived quality speech