Research On Digital Television Program's Interactive Technology With Ginga-NCL

Interactive digital television is the necessary method by which the broadcast television system's digital process can fast and completely evolute nowadays.The most critical condition of the interactive digital televion's promotion and popularization is the support of the well interactive application.The three major international middleware standards MHP,DASE and ARIB use Java technology as their core interactive technology.The interactive technology based on Java lacks of flexibility and Extensibility, greatly hindering the expansion of the interactive business.Ginga is the middleware standard of terrestrial digital TV in Brazil.Its declarative environment Ginga-NCL is the context of the interactive application,using a XML application technology as its core interactive technology.Comparing and analyzing the interactive technologies adopted by the three major middleware standards,the digital televison program's interactive technologies suiting Ginga-NCL environment are researched.In order to overcome the disadvantage that the Java technology is inefficient and hard to extend the application in anthoring phase,the extensibility of the XML technology is adopted to modify and extend some NCL entities,as a result,it separates the media content and the synchronization relationship completely,enabling the anthoring process efficient, conveniency and extensible.In order to transferring the application with deep directory,the DSM-CC object carousel is adopted and a locating technology is designed ,making the transferring of the interactive program's data and logic constructure conveniency.The designation and realization of modules in the presentation engine manager guarantees that the Ginga-NCL environment in the back end can run smoothly,and the extraction of interactive application information from object carousel is realized.Many interactive programs need the function of live updating,in order to fulfill the requirement,two key technologies are adopted and developed:The DOM technology is implemented to parse the NCL document,so the NCL entites can be live updated.In the other hand,based on the stream event mechanism of object carousel,defining a set of live editing command and defining a data structure"stream event descriptor"as the transferring carrier realizes that the live editing action in the front end can at the same time appears in the counterpart of the presenting program in the back end.According to the emulational tool's emulating result,the space and temporal synchronization between program's media objects and the responsion of the user's interactive input in the back end basically in line with the anthoring intention in the front end.The extraction of file system and live editing commands from object carsousel is emulated using the procedure coded and the result is basically fit the target. Flexibility and Extensibility of this system is obvious from the process of emulating.