Low power spectral band replication technology for the MPEG-4 audio standard

Spectral Band Replication (SBR) is the bandwidth extension technology for the MPEG-4 Audio Extension I standard. Its principle is based on mapping the low-frequency portion of an audio signal coded at low bitrate to the missing high-frequency region, and uses a small amount of information embedded in the audio bitstream to shape the energy envelop and tone to noise ratio of the mapped signals, such that they aurally resembles the high-frequency spectrum of the original signal, thereby deliver compact disc -like listening sensation to the listeners. Low Power SBR (LP-SBR) is a simplified version of the SBR technology that applies real-valued processing to all SBR modules, and applies aliasing reduction tools to suppress the resultant aliasing artifacts. LP-SBR requires 40% less computational cost compared to the original SBR. This paper describes the causes of aliasing artifacts and the principles behind the anti-aliasing solutions.