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MPEG-7 Overview - part 2

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Review Descriptor (D) - 對內容的特徵作定義。 - 通常用以描述 low-level features 。 Description Scheme (DS) - 通常用以描述 high-level features 。 - DS 和 D 的區別是： D 僅包含基本的資料類型，而 DS

可 同時包含 D 與 DS 。

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Review (contd.) D 、 DS 與 DDL 之關係圖如下 :

D D D

DS DS

D D D

DS

DDL

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DDL (Description Definition

Language)

The DDL defines the syntactic rules to express and combine DSs and Ds.

The DDL is not a modeling language but a schema language to represent the results of modeling audiovisual data, i.e. DSs and Ds.

In March 2000, MPEG was decided to adopt XML Schema Language as the MPEG-7 DDL.

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DDL (contd.) However, XML Schema language has

not been designed specifically for AV

content, certain extensions have been

necessary. ․Array and matrix datatypes ․Built-in primitive time datatypes

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BiM XML has not been designed to deal

ideally in a real-time, constrained and streamed environment.

To overcome it, MPEG-7 Systems defines a generic framework to facilitate the carriage and processing of MPEG-7 descriptions:

BiM (Binary Format for MPEG-7).

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BiM (contd.) The features of BiM are : ․BiM binary format is not dedicated to any

specific XML language. ․BiM is a schema oriented encoding scheme. ․BiM is a pre-parsed format ․BiM allows a parameterized transmission of

XML document, like depicted below :

Fig. Different streaming strategies of the same XML file

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MPEG-7 Terminal The entity that makes use of the coded

representations of the multimedia content description is referred to as the “terminal”.

The terminal has three main architectural layers :

․application layer ․system layer ․delivery layer

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MPEG-7 Terminal (contd.) An MPEG-7 terminal consumes

description streams and outputs a representation of the description called the current description tree.

Description streams consist of Access Units (AUs).

․textual description stream ․binary description stream

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MPEG-7 Terminal (contd.) An AU is composed of any number of

Fragment Update (FU) Units, each of which is extracted in sequence by the fragment update component extractor.

Each FU unit consists of : ․a FU command ․a FU context ․a FU payload

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MPEG-7 Terminal (contd.)

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Reference Software: the eXperimentation Model

The XM software is the frame work for the for all the reference code of the MPEG-7 standard.

The XM software has only a command line interface, which does not allow any interaction during run-time.

The modules of the XM software are designed in a way, that all modules are using specified interfaces.

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Reference Software: the eXperimentation Model (contd.)

Within the XM software framework, applications are related to one particular descriptor or description scheme.

․Server (or extraction) applications ․Client applications

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Application types in the XM software

Extraction from Media

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Application types in the XM software(contd.)

Search & Retrieval Application

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Application types in the XM software(contd.)

Media Transcoding Application

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Application types in the XM software(contd.)

Description Filtering Application

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The MPEG-7 key application model

Applications, which are implemented in the XM software are also called key applications.

The inputs and outputs of key applications are:

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Key applications vs. real world applications

In general, combining the key applications will form complex applications.

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MPEG-7 Conformance Testing

MPEG-7 Conformance Testing includes the guidelines and procedures for testing conformance of MPEG-7 implementations.

There are two kinds of conformance testing :

․conformance testing for descriptions ․conformance testing for terminals

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MPEG-7 Conformance Testing(contd.)

The objective of the conformance testing of descriptions is to check the syntactic

compliance with ISO/IEC IEC 15938 parts 1 – 5.

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MPEG-7 Conformance Testing(contd.)

The conformance testing for terminal involves the comparison of the result of processing a description using a reference terminal against the result using the test terminal.