Efficient vector quantisation of LPC parameters for noisy channels
Line spectral pairs (LSP) are, because of their advantageous properties, commonly used to represent the spectral information in a linear predictive (LP) speech coder. However, the quantised spectrum is relatively sensitive to channel errors. This paper describes a robust quantiser for LSPs transmitted over noisy waveform channels, based on an optimisation of the source coder over the modulation scheme. Modulation organized vector quantisation, MOR-VQ, jointly optimises a codebook and its index assignment, governed by the defined modulation symbol constellation. The system closely follows the optimum performance theoretically available (OPTA). Moreover, the MOR-VQ scheme allows for efficient codebook search strategies.<<ETX>>