High quality scalable audio codec
Mi‐Young Kim, Eunmi Oh, Junghoe Kim · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2007
The MPEG-4 BSAC (Bit Sliced Arithmetic Coding) is a fine-grain scalable codec with layered structure which consists of a single base-layer and several enhancement layers. The scalable functionality allows us to decode the subsets of a full bitstream and to deliver audio contents adaptively under conditions of heterogeneous network and devices, and user interaction. This bitrate scalability can be provided at the cost of high frequency components. It means that the decoded output of BSAC sounds muffled as the transmitted layers become less and less due to deprived conditions of network and devices. The goal of the proposed technology is to compensate the missing high frequency components, while maintaining the fine grain scalability of BSAC. This paper describes the integration of SBR (Spectral Bandwidth Replication) tool to existing MPEG-4 BSAC. Listening test results show that the sound quality of BSAC is improved when the full bitstream is truncated for lower bitrates, and this quality is comparable to that of BSAC using SBR tool without truncation at the same bitrate.