Low bitrate audio coding - state-of-the-art, challenges and future directions

Perceptual encoding of high-quality audio has found its way to many applications including digital radio, electronic music distribution (EMD) systems and portable audio devices. An overview on the basics of high-quality low-bitrate audio coding is followed by a look into currently widely used and newer, state-of-the-art coding systems like MP3 and MPEG-2 advanced audio coding (AAC). The rapid deployment of older (1992) technologies (like MP3) followed by the news of new and improved algorithms (like AAC) raises questions about future improvements. The paper analyses some candidates for such improvements and provides a view of some current research activities.