Transcript DVB Data Broadcasting

Data Broadcasting
Ken McCann
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Application Example - Internet via satellite
Delivery of web pages
at up to 38 Mbit/s
18" dish
User PC
DVB Card
Leased line
Satellite
Operator
The Net
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Service
Provider
Information
Provider
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
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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
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DVB Data Piping
0100110010
1011001011
0100110010
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
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Audio
Data
DVB Data Streaming
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
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TCP/ IP
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)
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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
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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
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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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