MPEG-4 SLS, or
MPEG-4 Scalable to Lossless as per
ISO/
IEC 14496-3:2005/Amd 3:2006 (
Scalable Lossless Coding), is an extension to the
MPEG-4 Part 3 (
MPEG-4 Audio) standard to allow
lossless audio compression scalable to
lossy MPEG-4 General Audio coding methods (e.g. variations of
AAC). It was developed jointly by the Institute for Infocomm Research (I
2R) and
Fraunhofer, which commercializes its implementation of a limited subset of the standard under the name of
HD-AAC. Standardization of the HD-AAC profile for MPEG-4 Audio is under development (as of September 2009).