Adaptive Bandwidth Extension of Low Bitrate Compressed Audio Based on Spectral Correlation

Abstract

Application scenarios constraints of most low bit rate compression schemes lead to audio signals of low bandwidth and, inevitable, of low perceptual audio quality. Audio bandwidth extension (BWE) methods solve this problem by reconstructing the high frequency spectrum of a degraded signal based on information from the low frequency part. LPC-based BWE may represent the coarse spectral envelope, but it is difficulty to modulate finer spectrum. A novel adaptive bandwidth extension method is proposed for effective high frequency regeneration in audio coding, which is adaptive switch between LPC-based and FFT-based BWE base upon the spectral correlation. The presented FFT-based BWE reconstructs the high frequency part by information of the low frequency, and spectral envelope is adjusted by gain between high and low frequency in FFT domain. The performance gain of the proposed adaptive BWE approach increases and is superior to LPC-based and FFT-based BWE respectively.