MPEG-4

MPEG-4

MPEG-4 is a set of compression coding standards for audio and video information, established by the Moving Picture Experts Group (MPEG) under the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). The first version was approved in October 1998, and the second version in December 1999. The main applications of the MPEG-4 format are online streaming, DVDs, voice transmission (video telephony), and television broadcasting.

MPEG-4 includes most functions of MPEG-1 and MPEG-2, along with strengths from other formats, adding support for Virtual Reality Modeling Language (VRML), object-oriented composite files (including audio, video, and VRML objects), as well as Digital Rights Management (DRM) and other interactive features. One of the advanced features of MPEG-4 compared to MPEG-2 is that it no longer uses macroblocks for image analysis, instead recording changes on individual pixels. Therefore, even when the image changes rapidly and the bitrate is insufficient, blocky artifacts do not appear.

Since MPEG-4 is an open platform, companies and organizations can develop different standards based on the MPEG-4 standard, leading to the emergence of many video formats based on MPEG-4 technology in the market, such as WMV 9, QuickTime, DivX, Xvid, and others. Most functions of MPEG-4 are left for developers to decide whether to adopt. This means that the entire format's functionality may not be fully encompassed by a single program. Thus, this format has what is known as profiles and levels, defining the set of functions for MPEG-4 applications across different platforms.

MPEG-4 consists of a series of sub-standards, referred to as parts, which include the following sections:

• Part 1 (ISO/IEC 14496-1): Systems: Describes the control, synchronization, and multiplexing methods of video and audio data streams.
• Part 2 (ISO/IEC 14496-2): Video: Defines a codec for various visual information (including natural video, still textures, computer-generated graphics, etc.). (For example, XviD encoding falls under MPEG-4 Part 2).
• Part 3 (ISO/IEC 14496-3): Audio: Defines a set of codecs for encoding various audio signals, including several variations of Advanced Audio Coding (AAC) and other audio/speech encoding tools.
• Part 4 (ISO/IEC 14496-4): Conformance: Defines the procedure for testing conformance to other parts of this standard.
• Part 5 (ISO/IEC 14496-5): Reference Software: Provides software for demonstrating the functionalities of other parts of this standard.
• Part 6 (ISO/IEC 14496-6): Delivery Multimedia Integration Framework (DMIF).
• Part 7 (ISO/IEC 14496-7): Optimized Reference Software: Provides examples of optimizations for implementations (here referring to Part 5).
• Part 8 (ISO/IEC 14496-8): Transport of MPEG-4 Content Over IP Networks: Defines the methods for transmitting MPEG-4 content over IP networks.
• Part 9 (ISO/IEC 14496-9): Reference Hardware: Provides design solutions for demonstrating how to implement the functionalities of other parts of this standard in hardware.
• Part 10 (ISO/IEC 14496-10): Advanced Video Coding (AVC): Defines a video codec. AVC and XviD both fall under MPEG-4 encoding, but AVC, which is part of MPEG-4 Part 10, is more advanced in technical features than XviD, which belongs to MPEG-4 Part 2. Additionally, it aligns with the ITU-T H.264 standard, hence also referred to as H.264.
• Part 12 (ISO/IEC 14496-12): ISO-based Media File Format: Defines 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: Defines a video file format for storing MPEG-4 content based on Part 12.
• Part 15 (ISO/IEC 14496-15): AVC File Format: Defines a file format for storing video content from Part 10 based on Part 12.
• Part 16 (ISO/IEC 14496-16): Animation Framework Extension (AFX).
• Part 17 (ISO/IEC 14496-17): Synchronized Text Subtitle Format.
• Part 18 (ISO/IEC 14496-18): Font Compression and Streaming (for Open Font Format).
• 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 Extensions for Rendering.
• Part 22 (ISO/IEC 14496-22): Open Font Format.
• Part 23 (ISO/IEC 14496-23): Symbolic Music Representation.
• Part 24 (ISO/IEC 14496-24): Audio and Systems Interaction.
• Part 25 (ISO/IEC 14496-25): 3D Graphics Compression Model.
• Part 26 (ISO/IEC 14496-26): Audio Conformance: Defines methods for testing audio data against ISO/IEC 14496-3 for conformance.
• Part 27 (ISO/IEC 14496-27): 3D Graphics Conformance: Defines methods for testing 3D graphics data against ISO/IEC 14496-11:2005, ISO/IEC 14496-16:2006, ISO/IEC 14496-21:2006, and ISO/IEC 14496-25:2009 for conformance.

Profiles are defined within each part, so an implementation for a given part is often not a complete implementation of that part.

• Content of this article is excerpted from Wikipedia