Perceptual Enhancement for Fully Scalable Audio

MPEG-4 Scalable Lossless (SLS) coding is the latest released ISO international standard for scalable audio coding. Besides its function as an extension of MPEG-4 Advanced Audio Coding (AAC) perceptual audio coder, SLS has a "non-core mode" that is able to offer full scalability. The perceptual audio coder is absent in this mode and scalability is achieved through pure bit-plane coding. In this paper, a perceptually enhanced bit-plane coding method, namely Quad-level Bit-Plane Coding (QBPC) is proposed to enhance the perceptual quality of fully scalable audio at intermediate bitrates. With QBPC structure, the perceptual quality of fully scalable audio coded by SLS is significantly improved in a wide range of intermediate bitrates. Meanwhile this is achieved with trivial added overhead and complexity.