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Web over DTV
Cost-attractive service through DVB:
Transmission of extra data in Web format
Web over DTV is a simple and cost-attractive solution for distributing Internet
resources among TV viewers, for example, and for allowing TV providers to
offer additional services with their programs. This service can be implemented by
means of the Rohde & Schwarz DTV IP Inserter and DTV Web Carousel software.
The underlying principle is to insert selected Internet data in IP format into the
MPEG2 data stream of a DVB transmitter for broadcasting together with the TV
signal via an antenna. The recipient can store this information in his PC and view
it using a standard Web browser.
DTV IP Inserter
The DTV IP Inserter (FIG) allows transmission
of additional data in Internet
format (IP) with the DVB MPEG2 data
stream. The DVB broadcaster can now
offer an extra service to provide many
viewers with the data. Transmission of
these additional data is not subject to
any restrictions and does not change the
data rate of the programs contained in
the transport stream, consisting of video,
audio and service information. This is
possible by utilizing unused resources
(null packets) in the transport stream. A
packet detector in DTV IP Inserter DIP
identifi es the null packets inserted in the
transport stream for stuffi ng, which are
18 News from Rohde & Schwarz Number 166 (2000/I)
then exchanged for IP packets and thus
effectively utilized. Additional data can
be inserted after the MPEG encoder or
multiplexer by the multiprotocol encapsulation
method defi ned for DVB.
If the available transmission data rate
is constant, the DTV IP Inserter directly
follows the MPEG encoder (see block
diagram) and the variable part of the
video and audio data is supplemented
with additional data to form a fi xed
data rate. The clear advantage for
program providers is the optimum utilization
of the data rate. To make use of
the resources available in the transport
stream, the DTV IP Inserter is located
after the multiplexer.
DTV Web Carousel
Convenient use of the resources provided
by the DTV Inserter is ensured by
the DTV Web Carousel system solution.
This software allows to transmit
selected Internet pages via DVB to
stationary and mobile subscribers and
to view these pages after reception
with a common Web browser.
Web Carousel sends the data without
request, which exactly corresponds
to the push principle used in teletext for
example. The sense of transmission is
unidirectional, communication is from
transmitter to receiver.