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This article mainly introduces what format mpeg-4 refers to, the article is very detailed, has a certain reference value, interested friends must read it!

Mpeg-4 is a set of compression coding standard for audio and video information, a compression format, the first edition was adopted in October 1998, and the second edition was adopted in December 1999. The main uses of the MPEG-4 format are Internet streaming, CD-ROMs, voice transmission (video calls), and television broadcasts.

MPEG-4 is a set of compression coding standard for audio and video information, which is formulated by the International Organization for Standardization (ISO) and the moving Image expert Group (MPEG) of the International Electrotechnical Commission (IEC). The first edition was adopted in October 1998 and the second edition in December 1999. The main uses of the MPEG-4 format are Internet streaming, CD-ROMs, voice transmission (video calls), and television broadcasts.

MPEG-4 includes most of the functions of MPEG-1 and MPEG-2 and the strengths of other formats, and adds and extends support for virtual reality modeling language (VRML,Virtual Reality Modeling Language), object-oriented synthetic files (including audio, video and VRML objects), and digital rights management (DRM) and other interactive functions. One of the more advanced features of MPEG-4 than MPEG-2 is that it no longer uses macro blocks for image analysis, but records the changes of individuals on the image, so although the image changes quickly and the bit rate is insufficient, the square picture will not appear.

MPEG-4 is an evolving standard made up of several sub-standards (part). The MPEG-4 compatibility advertised by companies' products often does not specify which sub-standards it is compatible with. The most important sub-standards are MPEG-4 Part 2 and MPEG-4 Part 10.

Because MPEG-4 is an open platform, companies and institutions can develop different formats according to MPEG-4 standards, so there are many video formats based on MPEG-4 technology in the market, such as WMV 9, Quick Time, DivX, Xvid and so on. Most of the features of MPEG-4 are left to developers to decide whether to adopt or not. This means that the functionality of the entire format is not necessarily fully covered by a program. Therefore, this format is called profile and level, which defines the set of functions when MPEG-4 is applied to different platforms.

Compared with MPEG1,MPEG2,MPEG4 with higher interactivity and flexibility, the standard of MPEG4 technology is to encode the content in the moving image, the specific coding object is the audio and video in the image, the term is "AV object", and the continuous AV objects can be combined together to form an AV scene. Therefore, the MPEG4 standard is developed around the coding, storage, transmission and combination of AV objects. Efficient coding, organization, storage and transmission of AV objects is the basic content of the MPEG4 standard.

The advantage of MPEG4 lies in its compression ratio (up to 4000). Because MPEG4 abandons the same elements and only deals with elements that have differences between image frames, the volume of composite multimedia files is greatly reduced. Coupled with its low bit rate, less core program space, enhanced computing capabilities, and strong communication application integration capabilities, MPEG4 has become the most important and standard format in the audio-visual digital video industry.

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