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MPEG-4 is a standard used primarily to compress audio and video (AV) digital data. Introduced in late 1998, it is the designation for a group of audio and video coding standards and related technology agreed upon by the ISO/IEC Moving Picture Experts Group (MPEG). The uses for the MPEG-4 standard are web (streaming media) and CD distribution, conversation (videophone), and broadcast television, all of which benefit from compressing the AV stream.
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. AAC (Advanced Audio Codec) was standardized as an adjunct to MPEG-2 (as Part 7) before MPEG-4 was issued.
Most of the features included in MPEG-4 are left to individual developers to decide whether to implement them. 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."
MPEG-4 consists of several standards—termed "parts"—including the following:
- Part 1 (ISO/IEC 14496-1): Systems: Describes synchronization and multiplexing of video and audio. For example Transport stream.
- Part 2 (ISO/IEC 14496-2): Visual: A compression codec for visual data (video, still textures, synthetic images, etc.). One of the many "profiles" in Part 2 is the Advanced Simple Profile (ASP).
- Part 3 (ISO/IEC 14496-3): Audio: A set of compression codecs for perceptual coding of audio signals, including some variations of Advanced Audio Coding (AAC) as well as other audio/speech coding tools.
- Part 4 (ISO/IEC 14496-4): Conformance: Describes procedures for testing conformance to other parts of the standard.
- Part 5 (ISO/IEC 14496-5): Reference Software: Provides software for demonstrating and clarifying the other parts of the standard.
- Part 6 (ISO/IEC 14496-6): Delivery Multimedia Integration Framework (DMIF).
- Part 7 (ISO/IEC 14496-7): Optimized Reference Software: Provides examples of how to make improved implementations (e.g., in relation to Part 5).
- Part 8 (ISO/IEC 14496-8): Carriage on IP networks: Specifies a method to carry MPEG-4 content on IP networks.
- Part 9 (ISO/IEC 14496-9): Reference Hardware: Provides hardware designs for demonstrating how to implement the other parts of the standard.
- Part 10 (ISO/IEC 14496-10): Advanced Video Coding (AVC): A codec for video signals which is technically identical to the ITU-T H.264 standard.
- Part 11 (ISO/IEC 14496-11): Scene description and Application engine, also called BIFS; can be used for rich, interactive content with multiple profiles, including 2D and 3D versions.
- Part 12 (ISO/IEC 14496-12): ISO Base Media File Format: A file format for storing media content.
- Part 13 (ISO/IEC 14496-13): Intellectual Property Management and Protection (IPMP) Extensions.
- Part 14 (ISO/IEC 14496-14): MPEG-4 File Format: The designated container file format for MPEG-4 content, which is based on Part 12.
- Part 15 (ISO/IEC 14496-15): AVC File Format: For storage of Part 10 video based on Part 12.
- Part 16 (ISO/IEC 14496-16): Animation Framework eXtension (AFX).
- Part 17 (ISO/IEC 14496-17): Timed Text subtitle format.
- Part 18 (ISO/IEC 14496-18): Font Compression and Streaming (for OpenType fonts).
- Part 19 (ISO/IEC 14496-19): Synthesized Texture Stream.
- Part 20 (ISO/IEC 14496-20): Lightweight Scene Representation (LASeR).
- Part 21 (ISO/IEC 14496-21): MPEG-J Graphical Framework eXtension (GFX) (not yet finished - at "FCD" stage in July 2005, FDIS January 2006).
- Part 22 (ISO/IEC 14496-22): Open Font Format Specification (OFFS) based on OpenType (not yet finished - reached "CD" stage in July 2005)
- Part 23 (ISO/IEC 14496-23): Symbolic Music Representation (SMR) (not yet finished - reached "FCD" stage in October 2006)
Profiles are also defined within the individual "parts", so an implementation of a part is ordinarily not an implementation of an entire part.
MPEG-1, MPEG-2, MPEG-7 and MPEG-21 are other suites of MPEG standards.
MPEG-4 is patented proprietary technology. This means that, although the software to create and playback MPEG-4 videos may be readily available, hypothetically a license would be needed to use it legally. Patents covering MPEG-4 are claimed by over two dozen companies. There is no easy way to license MPEG-4 and a so-called MPEG Licensing Authority can license patents required for MPEG-4 visual techniques from a wide range of companies (audio is licensed separately). A one stop shop is currently not possible; these articles  claim that AT&T is trying to sue companies such as Apple over alleged MPEG-4 patent infringement. This AT&T action against Apple illustrates that it is hard to know which companies actually have patents covering MPEG-4.
Open source alternatives to encapsulate AV.
- Ogg - Created by the Xiph Foundation.
- See also OGM, which is a fork of Ogg.
- Matroska - .mkv & .mka files.
- NUT - Developed by the MPlayer team.
- x264 - H.264 (MPEG-4 part 10) implementation.
- Xvid - MPEG-4 part 2 codec, compatible with DivX.
- FFmpeg codecs - codecs in the libavcodec library from the FFmpeg project (FFV1, Snow, MPEG-1, MPEG-2, MPEG-4 part 2, MSMPEG-4, H.264, WMV2, SVQ3, MJPEG, HuffYUV, Indeo and others).
- Tarkin - an experimental lossy video codec under development by the Xiph.org Foundation based on 3-D wavelet compression
- Lagarith - lossless video codec
- Theora - Based on VP3, part of the Ogg Project.
- Dirac - Wavelet based codec created by the BBC.
- Huffyuv - Lossless codec from BenRG.
- FLAC - Lossless compression.
- iLBC - Low bitrate voice compression.
- Musepack - Lossy compression; an attempt to replicate the MP3 format.
- Speex - Low bitrate compression, primarily voice.
- TTA - Lossless compression
- Vorbis - Lossy compression; developed by Xiph.org.
- WavPack - Hybrid lossy/lossless
- MPEG-4 Structured Audio
- MPEG-4 SLS
Links from the main article
- ^ MPEG Licensing Authority
- ^ engadget.com article
- ^ theinquirer.net article
- ^ pcmag.com article
- MPEG-4: The Next Generation
- MPEG-4 Audio: AAC
- MPEG Industry Forum MPEG-4 page
- Moving Picture Experts Group (MPEG) Official Website
- JM MPEG-4 Reference Code
- MPEG-4 simplified
- MPEG-4 SP/ASP Video Codecs Comparison
- Free MPEG-4 converting tool
- Streamable Mpeg-4 Conversion guide
- MPEG-4 part 20: LASeR
- MPEG-4 Video Compression Guide