- Company: MPEG/Infocomm Research (I2R)
- Whitepaper: http://mpeg.chiariglione.org/technologies/mpeg-4/mp04-sls/index.htm
- Reference Software: http://standards.iso.org/ittf/PubliclyAvailableStandards/c052968_ISOIEC_14496-5_2001_Amd_10_2007_Cor_3_2009_Reference_Software.zip
- Samples: sls* files at ftp://mpaudconf:firstname.lastname@example.org/mpeg4audio-conformance/compressedMp4/
- Specification: ISO/IEC 14496-3:2009 (Draft)
SLS is MPEG-4's hybrid lossless audio codec. It uses a standard MPEG-4 GA core layer. Valid cores include AAC-LC, AAC Scalable (without LTP), ER AAC LC, ER AAC Scalable, and ER BSAC. It can also operate without a core layer. The core layer is decoded with a fixed integer approximation. Then one of more Lossless enhancement layers may be added. Lossless enhancement layers are entropy coded with either Bit-Plane Golomb Codes (BPGC) or Context Based Arithmetic Codes (CBAC) and Low Energy Mode Codes (LEMC). SLS can also oversample the core coder by up to a factor of 2 or 4.
The pre-standardized name for SLS was Advanced Audio Zip (AAZ).
- Company: MPEG/Fraunhofer/Infocomm Research (I2R)
- Homepage: http://www.iis.fraunhofer.de/EN/bf/amm/projects/lossless/
- Specification: ISO/IEC 14496-3:2009/Amd.1 (Draft)
The HD-AAC Profile is a limited subset of MPEG-4 SLS in an effort to gain commercial adoption. HD-AAC limits SLS to an AAC-LC core and BPGC with LEMC entropy coding.