MPEG-7

Key takeaways

MPEG-7 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect MPEG-7 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of MPEG-7 from memory before moving on to harder problems.

Reference excerpt

MPEG-7 is a multimedia content description standard. It was standardized in ISO/IEC 15938 (Multimedia content description interface). This description will be associated with the content itself, to allow fast and efficient searching for material that is of interest to the user. MPEG-7 is formally called Multimedia Content Description Interface. Thus, it is not a standard which deals with the actual encoding of moving pictures and audio, like MPEG-1, MPEG-2 and MPEG-4. It uses XML to store metadata, and can be attached to timecode in order to tag particular events, or synchronise lyrics to a song, for example. It was designed to standardize:

a set of Description Schemes ("DS") and Descriptors ("D") a language to specify these schemes, called the Description Definition Language ("DDL") a scheme for coding the description The combination of MPEG-4 and MPEG-7 has been sometimes referred to as MPEG-47.

Introduction MPEG-7 is intended to complement the previous MPEG standards, by standardizing multimedia metadata -- information about the content, not the content itself. MPEG-7 can be used independently of the other MPEG standards - the description might even be attached to an analog movie. The representation that is defined within MPEG-4, i.e. the representation of audio-visual data in terms of objects, is however very well suited to what will be built on the MPEG-7 standard. This representation is basic to the process of categorization. In addition, MPEG-7 descriptions could be used to improve the functionality of previous MPEG standards. With these tools, we can build an MPEG-7 Description and deploy it. According to the requirements document,1 "a Description consists of a Description Scheme (structure) and the set of Descriptor Values (instantiations) that describe the Data." A Descriptor Value is "an instantiation of a Descriptor for a given data set (or subset thereof)." The Descriptor is the syntactic and semantic definition of the content. Extraction algorithms are inside the scope of the standard because their standardization is not required to allow interoperability.

Parts The MPEG-7 (ISO/IEC 15938) consists of different Parts. Each part covers a certain aspect of the whole specification.

Relation between description and content

An MPEG-7 architecture requirement is that description must be separate from the audiovisual content. On the other hand, there must be a relation between the content and description. Thus the description is multiplexed with the content itself. On the right side you can see this relation between description and content.

MPEG-7 tools

MPEG-7 uses the following tools:

Descriptor (D): It is a representation of a feature defined syntactically and semantically. It could be that a unique object was described by several descriptors. Description Schemes (DS): Specify the structure and semantics of the relations between its components, these components can be descriptors (D) or description schemes (DS). Description Definition Language (DDL): It is based on XML language used to define the structural relations between descriptors. It allows the creation and modification of description schemes and also the creation of new descriptors (D). System tools: These tools deal with binarization, synchronization, transport and storage of descriptors. It also deals with Intellectual Property protection. On the right side you can see the relation between MPEG-7 tools.

MPEG-7 applications There are many applications and application domains which will benefit from the MPEG-7 standard. A few application examples are:

Digital library: Image/video catalogue, musical dictionary. Multimedia directory services: e.g. yellow pages. Broadcast media selection: Radio channel, TV channel. Multimedia editing: Personalized electronic news service, media authoring. Security services: Traffic control, production chains... E-business: Searching process of products. Cultural services: Art-galleries, museums... Educational applications. Biomedical applications. Intelligent multimedia applications that leverage low-level multimedia semantics via formal representation and automated reasoning.

See also Exif ID3 Metadata standards MPEG-4 Part 11 – Scene description and application engine Multimedia information retrieval Query by humming

Limitations The MPEG-7 standard was originally written in XML Schema (XSD), which constitutes semi-structured data. For example, the running time of a movie annotated using MPEG-7 in XML is machine-readable data, so software agents will know that the number expressing the running time is a positive integer, but such data is not machine-interpretable (cannot be understood by agents), because it does not convey semantics (meaning), known as the "Semantic Gap." To address this issue, there were many attempts to map the MPEG-7 XML Schema to the Web Ontology Language (OWL), which is a structured data equivalent of the terms of the MPEG-7 standard (MPEG-7Ontos, COMM, SWIntO, etc.). However, these mappings did not really bridge the "Semantic Gap," because low-level video features alone are inadequate for representing video semantics. In other words, annotating an automatically extracted video feature, such as color distribution, does not provide the meaning of the actual visual content.

Compare Material Exchange Format (MXF), a container format for professional digital video and audio media defined by SMPTE.

References B.S. Manjunath (Editor), Philippe Salembier (Editor), and Thomas Sikora (Editor): Introduction to MPEG-7: Multimedia Content Description Interface. Wiley & Sons, April 2002 - ISBN 0-471-48678-7 Harald Kosch: Distributed Multimedia Database Technologies Supported by MPEG-7 and MPEG-21. CRC Press, January 2004 - ISBN 0-8493-1854-8 Giorgos Stamou (Editor) and Stefanos Kollias (Editor): Multimedia Content and the Semantic Web: Standards, Methods and Tools. Wiley & Sons, May 2005 - ISBN 0-470-85753-6 Hyoung-Gook Kim, Nicolas Moreau, and Thomas Sikora: MPEG-7 Audio and Beyond: Audio Content Indexing and Retrieval. Wiley & Sons, October 2005 - ISBN 0-470-09334-X

External links MPEG-7 Overview Archived 2010-02-14 at the Wayback Machine MPEG-7/-21 Community Portal

Illustrations

Worked examples

Example 1 — a first encounter with MPEG-7

Start with the simplest possible case. Write down what MPEG-7 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to MPEG-7 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about MPEG-7 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of MPEG-7

In research: MPEG-7 appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses MPEG-7 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: MPEG-7 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Digital container formats, ISO/IEC standards, MPEG, so understanding it makes those chapters shorter.
In everyday life: Look for MPEG-7 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study MPEG-7 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what MPEG-7 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain MPEG-7 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is MPEG-7 in simple terms?

MPEG-7 is a multimedia content description standard. It was standardized in ISO/IEC 15938 (Multimedia content description interface).

Why does MPEG-7 matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study MPEG-7?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on MPEG-7.