1、MPEG-7 Overview-part 21ReviewnDescriptor(D)-對內容的特徵作定義。-通常用以描述low-level features。nDescription 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。2Review(contd.)nD、DS與DDL之關係圖如下:DDDDSDSDDDDSDDL3DDL(Description Definition Language)nThe DDL defines the syntactic rules to express a
2、nd combine DSs and Ds.nThe DDL is not a modeling language but a schema language to represent the results of modeling audiovisual data,i.e.DSs and Ds.nIn March 2000,MPEG was decided to adopt XML Schema Language as the MPEG-7 DDL.4DDL(contd.)nHowever,XML Schema language has not been designed specifica
3、lly for AV content,certain extensions have been necessary.Array and matrix datatypes Built-in primitive time datatypes5BiMnXML has not been designed to deal ideally in a real-time,constrained and streamed environment.nTo overcome it,MPEG-7 Systems defines a generic framework to facilitate the carria
4、ge and processing of MPEG-7 descriptions:BiM(Binary Format for MPEG-7).6BiM(contd.)nThe 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
5、 depicted below:Fig.Different streaming strategies of the same XML file7MPEG-7 TerminalnThe entity that makes use of the coded representations of the multimedia content description is referred to as the“terminal”.nThe terminal has three main architectural layers:application layer system layer delive
6、ry layer8MPEG-7 Terminal(contd.)nAn MPEG-7 terminal consumes description streams and outputs a representation of the description called the current description tree.nDescription streams consist of Access Units(AUs).textual description stream binary description stream9MPEG-7 Terminal(contd.)nAn AU is
7、 composed of any number of Fragment Update(FU)Units,each of which is extracted in sequence by the fragment update component extractor.nEach FU unit consists of:a FU command a FU context a FU payload10MPEG-7 Terminal(contd.)11Reference Software:the eXperimentation ModelnThe XM software is the frame w
8、ork for the for all the reference code of the MPEG-7 standard.nThe XM software has only a command line interface,which does not allow any interaction during run-time.nThe modules of the XM software are designed in a way,that all modules are using specified interfaces.12Reference Software:the eXperim
9、entation Model(contd.)nWithin the XM software framework,applications are related to one particular descriptor or description scheme.Server(or extraction)applications Client applications13Application types in the XM softwarenExtraction from Media 14Application types in the XM software(contd.)nSearch&
10、Retrieval Application15Application types in the XM software(contd.)nMedia Transcoding Application16Application types in the XM software(contd.)nDescription Filtering Application17The MPEG-7 key application modelnApplications,which are implemented in the XM software are also called key applications.n
11、The inputs and outputs of key applications are:18Key applications vs.real world applicationsnIn general,combining the key applications will form complex applications.19MPEG-7 Conformance TestingnMPEG-7 Conformance Testing includes the guidelines and procedures for testing conformance of MPEG-7 imple
12、mentations.nThere are two kinds of conformance testing:conformance testing for descriptions conformance testing for terminals20MPEG-7 Conformance Testing(contd.)nThe objective of the conformance testing of descriptions is to check the syntactic compliance with ISO/IEC IEC 15938 parts 1 5.21MPEG-7 Conformance Testing(contd.)nThe 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.22
