CSA Preface
Standards development within the Information Technology sector is harmonized with international standards development. Through the CSA Technical Committee on Information Technology (TCIT), Canadians serve as the Canadian Advisory Committee (CAC) on ISO/IEC Joint Technical Committee 1 on Information Technology (ISO/IEC JTC1) for the Standards Council of Canada (SCC), the ISO member body for Canada and sponsor of the Canadian National Committee of the IEC. Also, as a member of the International Telecommunication Union (ITU), Canada participates in the International Telegraph and Telephone Consultative Committee (ITU-T).
This Standard has been formally approved, without modification, by these Committees and has been approved as a National Standard of Canada by the Standards Council of Canada.
Scope
This part of ISO/IEC 16500 takes a practical approach to the specification of Information Representation. Just the information types that cannot be dispensed with in producing the set of DAVIC applications (viz. broadcast, movies on demand, home shopping, etc.) are specified. The approach taken in this part of ISO/IEC 16500 starts by defining the various mono-media information types. They include character, text, fonts, service information, audio, video, and graphics. Consistent with DAVIC principles, one tool is selected for the encoding of each information type. Multimedia components comprise one or more mono-media components. This part of ISO/IEC 16500 defines the way in which multimedia information is coded and exchanged. This includes the definition of a virtual machine and a set of APIs to support interoperable exchange of program code. Finally, this part of ISO/IEC 16500 defines a Reference Decoder Model for contents decoding which provides constraints on content. The major problem addressed by the model is to ensure interoperability of applications by specifying memory and behaviour constraints for contents decoding by a hypothetical STU, without specifying the internal design of an STU. An application built according to the reference decoder model will be an ISO/IEC 16500 conforming application and will successfully execute on a STU that is compliant to ISO/IEC 16500.
For each mono-media and multimedia component the coding format is specified, as well as applicable constraints for coding of the components. Three types of mono-media components are distinguished. Mono-media components which are included within other mono-media components, such as characters within text, are of type implied. Non- implied mono-media components that do not require synchronization with a time base at play back, are of type stand-alone. Finally, non-implied mono-media components of which the presentation may require synchronization with a time base are of type stream. This part of ISO/IEC 16500 defines which type each DAVIC defined mono-media component may take, and specifies that the coded representation of mono-media components of type stream are packetized in PES packets (for definition of PES packets refer to ISO/IEC 13818-1). PES packets permit (1) to include time stamps to support mutual synchronisation of multiple mono-media components in reference to a common time base and (2) to define timing and buffer behaviour in a common reference model for contents decoding. While there are various ways to deliver the mono-media and multimedia components to the STU, This part of ISO/IEC 16500 defines how the components are carried in an MPEG-2 Transport Stream.
DAVIC specifies a number of different profiles. In a specific profile there may be support of a subset of the mono-media components. Each STU that complies to a specific profile of DAVIC shall be capable of decoding and presenting each mono-media and multimedia component permitted within that profile.
This part of ISO/IEC 16500 also specifies methods for packaging of contents and metadata. The way in which content is packaged for delivery is independent of the way in which content data is delivered to the SPS (it may be delivered to a Service Provider either on physical media or over a transmission system). All programming content is represented in the DAVIC system as multimedia components. Multimedia components comprise one or more mono-media components coupled with the logical relationships between the mono-media components. The multimedia components will be created by content providers for input to the servers.
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