MPEG-4
MPEG-4, introduced1998, isdesignation forgroupaudiovideo coding standards agreed upon by MPEG (Motion Pictures Coding Experts Group). MPEG-4primarily designedhandle low bit-rate content, from 4800 bit/sapproximately 4 Mbit/s. The primary uses forMPEG-4 standardweb (streaming media)CD distribution, conversational (videophone) uses,broadcast television.
MPEG-4 absorbs many offeaturesMPEG-1MPEG-2, adding new features such as (extended) VRML support3D rendering, object-oriented composite files (including audio, videoVRML objects), supportDigital Rights Managementvarious typesinteractivity.
Most offeatures includedMPEG-4leftindividual developersimplement. This means that therevery few complete implementations ofMPEG-4 standard. Anticipating this,developers addedconcept"Profiles," allowing various capabilitiesbe grouped together.
MPEG-4 consistsseveral standards—termed "Layers"—as follows.
- Layer 1 describes synchronizationmultiplexingvideoaudio.
- Layer 2 iscompression codecvideo signals.
- Layer 3 iscompression codecperceptual codingaudio signals.
- Layer 4 describes procedurestesting compliance.
- Layer 5 describes systemsSoftware simulation.
- Layer 6 describes Delivery Multimedia Integration Framework (DMIF).
