MPEG-7 - Multimedia Content Description Interface
MPEG-7, the Multimedia Content Description Interface, is part of a family of standards developed by the Moving Picture Experts Group (MPEG) - a working group (JTC1/SC29/WG11) of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). MPEG are responsible for the development of standards for the coded representation of digital video and audio. While other MPEG standards (e.g., MPEG-1, MPEG-2 and MPEG-4) have focused on the coded representation of audio-visual content, MPEG-7 is primarily concerned with information about content, i.e., metadata.
Development of MPEG-7 began in October 1996. It was motivated by the need to extract or manipulate information from large collections of multimedia content, e.g. the outputs of video surveillance or Internet live feeds. The standard is intended for use in a variety of applications, including the broadcast media, digital libraries, e-commerce and multimedia directory services, and covers still images, graphics, three dimensional models, audio, speech, video, and combinations of them. Nack & Lindsay have said that the ultimate aim of MPEG-7 was to make audio-visual material as searchable as text.
The basic concepts used in MPEG-7 are 'Descriptors' (that define the syntax and the semantics of each feature or metadata element) and 'Description Schemes' that specify the structure and semantics of the relationships between components. In addition, MPEG-7 specifies a 'Description Definition Language' (DDL) that provides a syntax for the express, combine, extend and refine Descriptors and Description Schemes. This is based on the XML Schema language. MPEG-7 Descriptors are intended to apply at different levels of abstraction, e.g. from low-level visual features like shape, size, texture and colour to high level 'semantic' information, e.g. about abstract concepts, events, genres, etc. These can then be associated with other metadata (Descriptors and Descriptor Schemes) about the coding schemes used (e.g. MPEG-2), conditions of access, rating information, context, etc.
The MPEG-7 specification is formally known as ISO/IEC 15938 (Information technology -- Multimedia content description interface) and is organised into seven parts:
MPEG-7 Part 3 specifies a set of standardised low-level Descriptors and Description Schemes for visual content, e.g., the shape of objects, object size, colour, texture, motion, etc.
MPEG-7 Description Definition Language:
Maintained by: Michael Day of UKOLN.
Last updated: 22-May-2002.
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