MPEG-4 Part 3 or MPEG-4 Audio (formally ISO/IEC 14496-3) is the third part of the ISO/IEC MPEG-4 international standard developed by Moving Picture Experts Group. It specifies audio coding methods. The first version of ISO/IEC 14496-3 was published in 1999. The MPEG-4 Part 3 consists of a variety of audio coding technologies – from lossy speech coding (HVXC, CELP), general audio coding (AAC, TwinVQ, BSAC), lossless audio compression (MPEG-4 SLS, Audio Lossless Coding, MPEG-4 DST), a Text-To-Speech Interface (TTSI), Structured Audio (using SAOL, SASL, MIDI) and many additional audio synthesis and coding techniques. MPEG-4 Audio does not target a single application such as real-time telephony or high-quality audio compression. It applies to every application which requires the use of advanced sound compression, synthesis, manipulation, or playback. MPEG-4 Audio is a new type of audio standard that integrates numerous different types of audio coding: natural sound and synthetic sound, low bitrate delivery and high-quality delivery, speech and music, complex soundtracks and simple ones, traditional content and interactive content. Versions Subparts MPEG-4 Part 3 contains following subparts: Subpart 1: Main (list of Audio Object Types, Profiles, Levels, interface to ISO/IEC 14496-1, MPEG-4 Audio transport stream, etc.) Subpart 2: Speech coding – HVXC (Harmonic Vector eXcitation Coding) Subpart 3: Speech coding – CELP (Code Excited Linear Prediction) Subpart 4: General Audio Coding (GA) (Time/Frequency Coding) – AAC, TwinVQ, BSAC Subpart 5: Structured Audio (SA) Subpart 6: Text to Speech Interface (TTSI) Subpart 7: Parametric Audio Coding – HILN (Harmonic and Individual Line plus Noise) Subpart 8: Technical description of parametric coding for high quality audio (SSC, Parametric Stereo) Subpart 9: MPEG-1/MPEG-2 Audio in MPEG-4 Subpart 10: Technical description of lossless coding of oversampled audio (MPEG-4 DST – Direct Stream Transfer) Subpart 11: Audio Lossless Coding (ALS) Subpart 12: Scalable Lossless Coding (SLS) MPEG-4 Audio Object Types MPEG-4 Audio includes a system for handling a diverse group of audio formats in a uniform manner. Each format is assigned a unique Audio Object Type to represent it. Object Type is used to distinguish between different coding methods. It directly determines the MPEG-4 tool subset required to decode a specific object. The MPEG-4 profiles are based on the object types and each profile supports a different list of object types. Audio Profiles The MPEG-4 Audio standard defines several profiles. These profiles are based on the object types and each profile supports different list of object types.