Metadata Resources

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:

• ISO/IEC 15938-1: Systems
• ISO/IEC 15938-2: Description Definition Language
• ISO/IEC 15938-3: Visual
• ISO/IEC 15938-4: Audio
• ISO/IEC 15938-5: Multimedia Description Schemes
• ISO/IEC 15938-6: Reference Software
• ISO/IEC 15938-7: Conformance testing

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 resources

General:

• MPEG-7 Home [Site hosted by the Fraunhofer-Gesellschaft]
• Shih-Fu Chang, Thomas Sikora and Atul Puri, "Overview of the MPEG-7 Standard," IEEE Transactions on Circuits and Systems for Video Technology, 11 (6), June 2001, 688-695.
• Rob Koenen and Fernando Pereira, "MPEG-7: a standardised description of audiovisual content," Signal Processing: Image Communication, 16, 2000, 5-13.
• E. Hartley, A.P. Parkes, "MPEG-7: relevance and applications to broadcasting," SMPTE Journal, 109, July 2000, 559-563.
• José M. Martínez, Rob Koenen and Fernando Pereira, "MPEG-7: the generic multimedia content description standard," (part 1) IEEE Multimedia, 9 (2), April-June 2002, 78-87.
• Frank Nack and Adam T. Lindsay, "Everything you wanted to know about MPEG-7 (part 1)," IEEE Multimedia, 6 (3), July-September 1999, 65-77.
• Frank Nack and Adam T. Lindsay, "Everything you wanted to know about MPEG-7 (part 2)," IEEE Multimedia, 6 (4), October-December 1999, 64-73.
• Jane Hunter, "MPEG-7: behind the scenes," D-Lib Magazine, 5 (9) September 1999.
http://www.dlib.org/dlib/september99/hunter/09hunter.html

MPEG-7 Description Definition Language:

• Jane Hunter, "An overview of the MPEG-7 Description Definition Language (DDL)," IEEE Transactions on Circuits and Systems for Video Technology, 11 (6), June 2001, 765-772.
• Jane Hunter and Frank Nack, "An overview of the MPEG-7 Description Definition Language (DDL) proposals," Signal Processing: Image Communication, 16, 2000, 271-293.
• Jane Hunter and Liz Armstrong, "A comparison of schemas for video metadata representation," Computer Networks, 31, 1999, 1431-1451.