A perceptually enhanced Scalable-to-Lossless audio coding scheme and a trellis-based approach for its optimization
Scalable-to-Lossless (SLS) audio compression, as standardized by MPEG, provides a lossy base layer compatible with the Advanced Audio Coding (AAC) format, ensuring state-of-the-art quality in the base layer, and additional fine grained enhancements that eventually provide a lossless compressed version of the signal. While SLS offers highly efficient lossless compression, the perceptual quality of its intermediate lossy layers has been observed to be suboptimal. This paper proposes a modified SLS audio coding scheme that provides enhanced perceptual quality at an intermediate bit-rate, at the expense of an additional parameter per frequency band as side-information. This scheme when coupled with a trellis-based optimization algorithm is demonstrated to outperform, in terms of quality at the intermediate bit-rate, both standard SLS and a recent perceptually enhanced variant, with minimal degradation in lossless coding performance.