Pitch-orthogonal code-excited LPC

An algorithm is proposed for the purpose of removing the coding redundancy between the adaptive codebook, or pitch, and the stochastic codebook, in a standard CELP (code-excited linear predictive) speech coder, allowing the calculation of an optimum two-vector gain set using sequential one-vector quantizers. This is done by orthogonalizing tile unweighted stochastic codebook to a codebook redundancy vector produced by backward-filtering the selected pitch vector. Using this algorithm, it is possible to design a reasonable-quality speech coder using the computationally-minimal hexagonal lattice algebraic codebook, or a high-quality embedded coder using multistage vector excitation