Editing MPEG-4 (section)

==Background==
MPEG-4 absorbs many of the features of [[MPEG-1]] and [[MPEG-2]] and other related standards, adding new features such as (extended) [[VRML]] support for 3D rendering, object-oriented composite files (including audio, video and VRML objects), support for externally specified [[digital rights management]] and various types of interactivity. [[Advanced Audio Coding|AAC (Advanced Audio Coding)]] was standardized as an adjunct to MPEG-2 (as Part 1) before MPEG-4 was issued.

MPEG-4 is still an evolving standard and is divided into a number of parts. Companies promoting MPEG-4 compatibility do not always clearly state which "part" level compatibility they are referring to. The key parts to be aware of are [[MPEG-4 Part 2]] (including Advanced Simple Profile, used by codecs such as [[DivX]], [[Xvid]], [[Nero Digital]], [[RealMedia]], [[3ivx]], [[H.263]] and by [[QuickTime]] 6) and [[MPEG-4 part 10]] (MPEG-4 AVC/[[H.264]] or Advanced Video Coding, used by the [[x264]] encoder, Nero Digital AVC, QuickTime 7, [[Flash Video]], and [[high-definition video]] media like [[Blu-ray Disc]]).

Most of the features included in MPEG-4 are left to individual developers to decide whether or not to implement. This means that there are probably no complete implementations of the entire MPEG-4 set of standards. To deal with this, the standard includes the concept of "profiles" and "levels", allowing a specific set of capabilities to be defined in a manner appropriate for a subset of applications.

Initially, MPEG-4 was aimed primarily at low-[[bit-rate]] video communications; however, its scope as a multimedia coding standard was later expanded. MPEG-4 is efficient across a variety of bit rates ranging from a few kilobits per second to tens of megabits per second. MPEG-4 provides the following functions:
* Improved coding efficiency over MPEG-2<ref>{{cite journal |last1=Wiegand |first1=T |author-link1=Thomas Wiegand |last2=Sullican |first2=G J |last3=Bjontegaard |first3=G |last4=Luthra |first4=A |title=Overview of the H.264/AVC video coding standard |journal=IEEE Transactions on Circuits and Systems for Video Technology |date=2003 |volume=13 |issue=7 |pages=560–576 |doi=10.1109/TCSVT.2003.815165 }}</ref>
* Ability to encode mixed media data (video, audio, speech)
* Error resilience to enable robust transmission
* Ability to interact with the audio-visual scene generated at the receiver