MPEG-4

From Hydrogenaudio Knowledgebase
Revision as of 00:29, 18 October 2004 by 80.218.58.217 (talk)
The printable version is no longer supported and may have rendering errors. Please update your browser bookmarks and please use the default browser print function instead.

MPEG-4, introduced in 1998, is the designation for a group of audio and video coding standards agreed upon by MPEG (Moving Picture Experts Group). MPEG-4 is primarily designed to handle low bit rate content, from 4800 bit/s to approximately 4 Mbit/s. The primary uses for the MPEG-4 standard are web (streaming media) and CD distribution, conversational (videophone) uses, and broadcast television.

MPEG-4 absorbs many of the features of MPEG-1 and MPEG-2, adding new features such as (extended) VRML support for 3D rendering, object-oriented composite files (including audio, video and VRML objects), support for Digital Rights Management and various types of interactivity.

Most of the features included in MPEG-4 are left to individual developers to implement. This means that there are very few complete implementations of the MPEG-4 standard. Anticipating this, the developers added the concept of "Profiles," allowing various capabilities to be grouped together.

MPEG-4 consists of several standards—termed "Layers"—as follows.

  • Layer 1 describes synchronization and multiplexing of video and audio.
  • Layer 2 is a compression codec for video signals.
  • Layer 3 is a compression codec for perceptual coding of audio signals.
  • Layer 4 describes procedures for testing compliance.
  • Layer 5 describes systems for Software simulation.
  • Layer 6 describes Delivery Multimedia Integration Framework (DMIF).
  • Layer 10 is an advanced codec for video signals also called H.264.

The designated container for MPEG-4 content is MP4, which was also defined within MPEG-4.

MPEG-7 and MPEG-21 serve other purposes.

See