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Enhanced Accuracy of the Tonality Measure and Control Parameter Extraction Modules in MPEG-4 HE-AAC
This paper investigates possible enhancements of the high efficiency-advanced audio coding (HE-AAC) encoder, with focus on the spectral band replication modules. The HE-AAC encoder generates side information, including control parameters, that characterizes the energy distribution across time and frequency as well as tonal and noise components, to ensure perceptually coherent regeneration of the high band at the decoder. The accuracy of the encoder's tonality measure and control parameter extraction modules is analyzed, leading to the proposal of an alternative approach employing sinusoidal analysis, which offers enhanced estimation of tonal and noise energy levels, as well as an improved control parameter extraction procedure. Comparative performance evaluation of the standard and modified encoders, on a set of audio signals demonstrates the perceptual impact of estimation inaccuracy on the regenerated high band quality, and identifies the type of audio where it causes meaningful degradation.
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