Recent advances in perceptual audio coding are strongly based on the concept of bandwidth extension. Most techniques implementing bandwidth extension require an analysis/synthesis filter bank in addition to that used by the associated perceptual audio coder, with a clear penalty in system complexity and coding delay. In this paper we present Accurate Spectral Replacement (ASR) as one of a new class of bandwidth extension techniques applied directly to the high frequency representation of the signal. ASR is based on a suitable decomposition of the MDCT filter bank, and implements synthesis of sinusoidal components with an accuracy much higher than the natural frequency resolution of the MDCT. The ASR technique is described, its performance is assessed with both synthetic and natural audio signals, and its main areas of application are addressed.
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