MPEG-4 SLS (SLS) is the 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 bit-rate scalability up to fully lossless reconstruction at bit-depths and sampling rates used in high-resolution audio.
Primephonic uses an enhanced (implementation of the) non-core version of MPEG-4 SLS (SLS stand-alone mode) without an AAC core codec. Developed in conjunction with bit-rate adaptive streaming, it enables 16/24-bit audio streaming to take maximum advantage of bandwidth available to deliver superior music fidelity and optimize bandwidth usage.
In cloud-based music streaming services, the bandwidth conditions can vary dramatically over different access network technologies. As a result, current streaming services (Tidal, Spotify, Apple Music, Google Music, Deezer, Napster, others) store the same audio content at a variety of bit-rate qualities (and formats) in content origin at the server-side.
In contrast, MPEG-4 SLS enables a one-file solution to meet these requirements. Adaptive streaming servers make use of the fine-grain bit-rate layers (0.4 Kbps increments) in the audio bitstream to truncate and deliver scalable audio frames, responding dynamically to QoS variations in each user's (music player) network. This results in real-time bit-rate scalability in Internet audio streaming that feeds several channels of different bandwidth capacity (with variable QoS conditions). Users need not choose between low-quality and high-quality music as adaptive streaming servers deliver the best musical experience possible in light of bandwidth availability and the (audio) source.