A new bandwidth extension technology for MPEG Unified Speech and Audio Coding

In January 2012, MPEG finalized the new MPEG-D Unified Speech and Audio Coding (USAC) standard, which enables the coding of a variety of audio content at low bitrates. USAC provides low-bitrate coding by integrating a speech codec and an audio codec into a unified system. In USAC, Predictive Vector Coding (PVC) is added to Enhanced Spectral Band Replication (eSBR) to improve the subjective quality, especially for speech at low bitrates. For speech signals, there is generally a relatively high correlation between the spectral envelopes of low- and high-frequency bands. The PVC scheme exploits this by predicting the high-frequency envelopes from the low-frequency ones, with the coefficient matrices for the prediction being coded by means of vector quantization.