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Enhanced Television ,ETV,, provides a way in
which interactive TV applications may be deployed to legacy set-top-boxes,
such as the Motorola DCT 2000, the Scientific-Atlanta Explorer 2000 and
many of the subsequent models. ETV applications are expected to run on
OCAP set-top-boxes as well.
ETV was specified by CableLabs in response to direction by its MSO members who wanted to deploy interactive applications on the above "thin clients". It is estimated that there are at least 15 million DCT2000 at subscribers' homes currently, so this set-top-box population is clearly significant. ETV applications are set-out in an ETV Binary Interchange Format (EBIF), for use in decoding and rendering ETV constructs on the TV screen. Applications consist of a collection of one or more partitions containing resources and programmatic data. ETV applications are interpreted by a User Agent, which needs to be implemented on a variety of deployed set-top-boxes. It is important to note that ETV is supplemental to OCAP. Infact, ETV applications can be supported on OCAP platforms by use of an User Agent implemented as an OCAP application. In terms of transmission from the headend, ETV requires a number of additions to a standard MPEG-2 transport stream. These include two new descriptors in the PMT, an EISS Table (ETV integrated signaling stream) containing three additional descriptors and a Data Carousel for carriage of the application. The carousel is either a DSM-CC Data Carousel or an Alternative Constrained Data Carousel (DigiCypherII) where the section size is limited to less than 1KB. The DSM-CC Data Carousel is required for Scientific-Atlanta set-to-boxes running ETV user agents and DigiCypherII is required for Motorola DCTs. TSBroadcaster is available with ETV stream output. It is typically supplied running on a TSPlayer system configured with two ASI cards. These outputs provide OCAP and ETV transport streams respectively. [View screen shot of TSBroadcaster ETV Application Page]. Since ETV applications are generally use a small memory footprint, this makes them particularly suitable for injection into 30-second spot commercials. UniSoft is working currently with a number of partners to allow easy generation of ETV ads. For ETV application testing, it should be noted that the XAV application validator supports ETV application conformance testing. |
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