MPEG-D is a group of standards for audio coding formally known as ISO/IEC 23003 - MPEG audio technologies, published since 2007. MPEG-D consists of four parts: MPEG-D Part 1: MPEG Surround (a.k.a. Spatial Audio Coding) MPEG-D Part 2: Spatial Audio Object Coding (SAOC) MPEG-D Part 3: Unified speech and audio coding MPEG-D Part 4: Dynamic Range Control MPEG-D Part 5: Uncompressed audio in MPEG-4 File Format See also ISO/IEC JTC 1/SC 29 References ISO/IEC standards Audio codecs MPEG