One of the many audio compression schemes used in consumer devices is Advanced Audio Coding (AAC), which is a ‘lossy’ compression and encoding scheme. Low-complexity AAC, or AAC-LC, is used for low bit-rate applications, such as internet streaming and was standardized as a profile of MPEG-2 Audio in 1997 (MPEG-2 AAC-LC). MPEG-4 AAC-LC, which was defined in 1999, also included Perceptual Noise Substitution (PNS). Spectral Band Replication (SBR), invented by Coding Technologies, was added to the MPEG-4 standard in 2003.This is now called HE-AAC v1 and is also known as aacPlus v1, eAAC+, AAC++, or enhanced AAC+. In 2004, a Parametric Stereo (PS) coding tool was added to the standard, which has since then been called MPEG-4 HE-AAC v2 (or aacPlus v2).
We typically find AAC-LC and aacPlus v2 (HE-AAC v2) used in applications such as digital radio, broadcast, internet streaming, high-quality audio recording, and in consumer devices such as digital TV, set-top boxes, digital video cameras, tablets, and media players. Therefore, audio processors need to provide best-in-class solutions for these standards.