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4.1.4 SPS-SCS delivery system
This system defines a model for transferring audio and video information from service provider system to
service consumer system. This system consists of 1) Service related control - Supports for SL0, SL1 and
SL2 related control functionality, 2) Network related control - Supports for network configuration (SL3),
connection setup and termination, and information routing, 3) Core network - represents a high speed
digital network and provides a means for accepting and transmitting information flow in an error free
manner, and 4) Access network - This comprises of: a) access node, which is responsible for processing
information flow for transport through a distribution network, b) Distribution network, which provides for
transport medium for delivering information from source to destination, and c) Network termination,
serves as a bridge for the system for adaptation of information flow from one network configuration to
another.
5. Scope of MHEG-5 in DAVIC
DAVIC 1.0 requires MHEG-5 as a run-time environment (RTE) for STB, it does not require that all
implementations of MHEG-5 for STBs provide for complete MHEG-5 implementations. It identifies all
required MHEG-5 specifications. In addition to the above, DAVIC requires RTE to use a standard set of
user input events, connection management, standard set of RPC interfaces, persistent name spaces and
standard encoding of content data. In addition this, DAVIC defines the MHEG-5 to DSM-CC U-U
mapping in terms of name-space mapping, high-level API for object and content references. By defining
all these requirements conformance is achieved. Using MHEG-5 on the STB provides for the highest
degree of platform independence and interoperability.
6. Integration with the WWW
MHEG-5 supports text objects encoded using HTML, and also supports URL-based addressing of objects.
When ever an HTML content is referenced through an MHEG-5 hypertext object, the corresponding
WWW service provider is identified and the object is retrieved from the web, packaged as a new scene
with hypertext ingredient and delivered to the MHEG-5 engine. The engine does some processing on this
new scene object and then presents it to the user. Figure 3 shows how a DAVIC STB system can interact
with a WWW server to gain access to the WWW.
WWW
MHEG5
Engine
MHEG5
Objects
Content
Service
Service Provider System
Delivery Network
(ATM)
Access
Access Network
(MPEG2 TP)
Figure 3: DAVIC-STB used in a gateway to WWW
Set Top Box
Figure 4 shows the DSM-CC message flows. Here the STU uses the U-U interface to communicate with
the WWW server which uses the DSM-CC download protocol to transfer HTML content The scenario
shown here is flow controlled and it is through the U-U messaging the STU and server decide upon
window size for download and other download requirements before using the download protocol to
retrieve the HTML object.