Approximated Correlation Matrix and Pulse Prediction for Fast Algebraic Code-Excited LPC Speech Coders

With reducing computational complexity, an approximated correlation matrix of the vocal impulse response is proposed in algebraic-code-excited linear prediction (ACELP) coders. By exploring statistical characteristics, we only need to calculate a small portion of correlation coefficients before ACELP search procedure. If we further combine a pulse position prediction algorithm, we can reduce the arithmetic complexity in pre-computing autocorrelation matrix and the number of pulse position combinations with imperceptible degradation in speech quality performance. The proposed scheme can be applied to all ACELP coders such as ITU G.729 and G.723.1