Perceptual quantisation of LPC excitation parameters

Abstract

A new approach to wideband digital audio compression at 64 kbit/s is presented. This LPC coder features a sinusoidal excitation model and adaptive bit-allocation based on a mask-to-noise ratio perceptual measure. Owing to its localised spectral sensitivity, sinusoidal excitation representation can be shown to provide an ideal framework for incorporating an estimated masking threshold in the design of noise spectral shaping. Quantisation of LPC and excitation parameters is also examined. Simulation results indicate that sine waves are preferred to spectrally flat signals for use in excitation modelling, because in the former the estimated masking threshold can be more precisely implemented in the distribution of quantisation noise.