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Data Broadcasting

Data Broadcasting. Ken McCann. Application Example - Internet via satellite. Delivery of web pages at up to 38 Mbit/s. DVB Return Channel. Return channel used for interactive services depends on the physical network, e.g.: Telecom modem via PSTN & ISDN for terrestrial or satellite TV

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Data Broadcasting

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  1. Data Broadcasting Ken McCann

  2. Application Example - Internet via satellite Delivery of web pages at up to 38 Mbit/s

  3. DVB Return Channel • Return channel used for interactive services depends on the physical network, e.g.: • Telecom modem via PSTN & ISDN for terrestrial or satellite TV • DVB/DAVIC modem for cable TV

  4. DVB Data Broadcasting • DVB Data Broadcasting standard, EN 301 192, provides a set of network-independent protocols optimised to different applications: • data piping • data streaming • multiprotocol encapsulation • data carousel • object carousel

  5. DVB Data Piping 0 1 0 0 1 1 0 0 1 0 1 0 1 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 • DVB Data Piping uses MPEG Transport Stream (TS) packets without any intermediate layer • provides non-synchronised end-to-end delivery of data through DVB networks • 188 byte packets with 184 byte payload • DVB descriptor to identify data pipe • Any other mechanism relies on the application

  6. Audio DVB Data Streaming Data Video • Based on the MPEG Packetised Elementary Stream (PES) construct that is used for video and audio: • Asynchronous data streams carry no timing information (e.g. RS232) • Synchronous data streams allow clock and data to be regenerated (e.g. E1, T1) • Synchronised data streams allow playback in sync. with video and audio

  7. Multiprotocol Encapsulation • Based on the MPEG section construct that is used for MPEG PSI and DVB SI: • optimised for Internet Protocol (IP) but can be used for any other network protocol • “datagrams” can be fragmented into multiple sections if they exceed maximum payload of a single section (4080 bytes)

  8. Data Carousel • Based on the MPEG Digital Storage Media Command and Control (DSMCC) data carousel • supports cyclic transmission of data modules to receivers • analogous to traditional Teletext • data is structured into Modules, Groups and SuperGroups • could be used for software download to receivers

  9. Object Carousel • Based on the MPEG DSMCC object carousel • supports cyclic transmission of structured groups of objects from broadcast server to client (receiver) • can download application, data files, data streams and trigger events • typically used to provide interactive services

  10. Conclusions • DVB data broadcasting specification provides a comprehensive set of network-independent protocols • capacity for data broadcasting can be traded against capacity for video and audio in a totally flexible manner

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