MPEG-4
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MPEG-4 is a collection of methods defining compression of audio and visual (AV) digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group (MPEG) under the formal standard ISO/IEC 14496. Uses of MPEG-4 include compression of AV data for web (streaming media) and CD distribution, voice (telephone, videophone) and broadcast television applications.
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.
MPEG-4 is still a developing 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 and 3ivx and by Quicktime 6) and MPEG-4 part 10 (MPEG-4 AVC/H.264 or Advanced Video Coding, used by the x264 codec, by Nero Digital AVC, by Quicktime 7, and by next-gen DVD formats like HD DVD and Blu-ray Disc).
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.
Initially, MPEG-4 was aimed primarily at low bit-rate video communications; however, its scope was later expanded to be much more of a multimedia coding standard. 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 functionalities:
- Improved coding efficiency
- 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
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[edit] Overview
MPEG-4 provides a series of technologies for developers, for various service-providers and for end users.
- MPEG-4 enables different developers to create objects possessing better abilities of adaptability and flexibility to improve the quality of such services and technologies as digital television, animation graphics, World Wide Web and their extensions. This standard enables developers to control their content better and to fight more effectively against copyright violations.
- Various network providers can use MPEG-4 for data transparency. With the help of standard procedures such data can be interpreted and transformed into various signals compatible with any available network.
- The MPEG-4 format provides the end users with a wide range of interaction with various animated objects.
- Standardized Digital Rights Management signaling, otherwise known in the MPEG community as Intellectual Property Management and Protection (IPMP).
The MPEG-4 format can perform various functions, among which might be the following:
- Multiplexes and synchronizes data, associated with media objects, in such a way that they could be transported further via network channels.
- Interaction with the audio-visual scene, which is formed on the side of the receiver.
[edit] Profiles and Levels
MPEG-4 provides a large and rich set of tools for encoding. Subsets of the MPEG-4 tool sets have been provided for use in specific applications. These subsets, called 'Profiles', limit the size of the tool set a decoder is required to implement.[1] In order to restrict computational complexity, one or more 'Levels' are set for each Profile.[1] A Profile and Level combination allows:[1]
- A codec builder to implement only the subset of the standard he needs, while maintaining interworking with other MPEG-4 devices that implement the same combination.[1]
- Checking whether MPEG-4 devices comply with the standard, referred to as conformance testing.[1]
[edit] MPEG-4 parts
MPEG-4 consists of several standards—termed "parts"—including the following:
| Part | Number | Title | Description |
|---|---|---|---|
| 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("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 Application 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.
[edit] Licensing
MPEG-4 contains patented technologies that require licensing in countries that acknowledge software patents. Patents covering MPEG-4 are claimed by over two dozen companies. The MPEG Licensing Authority[2] licenses patents required for MPEG-4 Part 2 Visual from a wide range of companies (audio is licensed separately) and lists all of its licensors and licensees on the site. New licenses for MPEG-4 System patents are under development[3] and no new licenses are being offered while holders of its old MPEG-4 Systems license are still covered under the terms of that license for the patents listed (MPEG LA – Patent List).
AT&T is trying to sue companies such as Apple Inc. over alleged MPEG-4 patent infringement.[4] The terms of Apple's Quicktime 7 license for users[5] describes in paragraph 14 the terms under Apple's existing MPEG-4 System Patent Portfolio license from MPEGLA.
[edit] See also
[edit] References
- ^ a b c d e RFC 3640, p.31
- ^ MPEG Licensing Authority – MPEG-4 Visual: Introduction
- ^ MPEG Licensing Authority – MPEG-4 Systems: Introduction
- ^ "AT&T Warns Apple, Others, Of Patent Infringement". PC Magazine. February 9, 2006. http://www.pcmag.com/article2/0,1895,1923218,00.asp. Retrieved on 2007-08-10.
- ^ Apple Quicktime 7 Software License (PDF)
[edit] External links
- MPEG-4: The Next Generation
- MPEG-4 Audio: AAC
- MPEG Industry Forum (MPEGIF) MPEG-4 page
- MPEG Industry Forum (MPEGIF) MPEG-4 White Paper
- Moving Picture Experts Group (MPEG) Official Website
- JM MPEG-4 AVC /H.264 Reference Code
- OpenIPMP: Open Source DRM Project for MPEG-4
- MPEG-4 part 20: LASeR
- Encoder/Decoder for .NET Framework
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