20-10-2012, 11:46 AM
An Introduction to MPEG-1, MPEG-2, MPEG-4, MPEG-7 & MPEG-21
Introduction_MPEG.pdf (Size: 379.72 KB / Downloads: 37)
Introduction
The Moving Picture Experts Group (MPEG) was established by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). The MPEG group is responsible for the development of a range of standards and technical reports relating to video, audio and multmedia content. This working paper will begin by discussing MPEG-1, which relates to the coding of moving pictures and audio, followed by MPEG-2, which evolved from MPEG-1 but enables the encoding of video at higher speeds. MPEG-4, which deals with the coding of multimedia content and MPEG-7 which standardises a method for describing multimedia content are then discussed, followed by MPEG-21, which is a technical report aimed at providing a multimedia framework.
Part 2 Video
This part of the specification describes the coded representation for the compression of video sequences.
The basic idea of MPEG video compression is to discard any unnecessary information i.e. an MPEG-1 encoder by analyses:
•how much movement there is in the current frame compared to the previous frame
•what changes of colour have taken place since the last frame
•what changes in light or contrast have taken place since the last frame
•what elements of the picture have remained static since the last frame
The encoder then looks at each individual pixel to see if movement has taken place, if there has been no movement, the encoder stores an instruction to say to repeat the same frame or repeat the same frame, but move it to a different position.
Aims & Features
MPEG-4 aims to enable:
•Interoperability of products from different vendors.
•Authors to have greater re-usability and flexibility with multimedia content produced.
•Improvement in the management of Intellectual Property Rights.
•Transparent information for network service providers.
•Greater interactivity for end users. Users and content authors can manipulate rich media content (both natural and synthetic). The limits of interactivity are set by the author. Users can have the ability to:
oChange their viewing or listening point in the scene, e.g. by navigation through a scene
oDrag objects in the scene to a different position