EXPLORING T-LEARNING IN THE MHP CONTEXT A. Gil, J.J. Pazos, C. López, M. Ramos, J.C. López, R.F. Rodríguez Depto. de Enxeñería Telemática, ETSE de Telecomunicación Campus Universitario s/n, University of Vigo (Spain)
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ABSTRACT In this paper, an ongoing experimental project relating distance education and interactive digital TV is presented. In last years, a lot of expectations and problems have risen around both fields separately and, in this project, we explore synergies that will provide mutual advantages: a wider market for distance learning and a value-added application for digital TV. Moreover, this work is an excellent test bed to test MHP capabilities to support these kind of services. KEYWORDS T-learning, Interactive Digital TV, DVB, MHP.
1. INTRODUCTION In last years, the world of TV is enrolled in the deepest transformation since birth: the change from analogical to digital. This transformation affects every stage of the broadcast chain, from content generation and representation to decoding and visualization in the user’s receiver. This new technology offers important advantages: more quality in audio and video, more space for TV channels, the possibility of implementing interactive contents, access to telematic services like Internet (Gil et al, 2002), etc. However, the framework to achieve this new scenery is not cheap in any way, as most of the equipment must be replaced and content generation is more complex and expensive. These costs must be finally paid by users, but content providers do not find the value-added applications the users are willing to pay for. Besides, the digitalization process requires g the TV set in a computing platform and this entails compatibility problems not remembered by the broadcast operators. These compatibility issues must be resolved as soon as possible to guarantee users a stable scenery and to achieve a market size big enough for the operators to recover the investments in a short term. The most important regulator body in this field, the Digital Video Broadcasting consortium (DVB), has published a new standard to normalize the computing platform needed to decode the digital transport stream and generate the TV signal. This new standard, called Multimedia Home Platform (MHP) (DVB Corsortium, 2001), specifies every issue involved in the definition of an execution context for the running applications that implement the interactive services abovementioned. Leaving apart technical problems, mainly related to the huge amount of resources that the MHP SetTop boxes require compared to current decoders, this standard will provide digital TV applications with a compatible environment to run, permitting them to abstract from the hardware technology underneath (Lopez-Ardao et al., 2002). In the other side, teleeducation systems have been gaining more and more interest in developed countries. These systems allow a continuous learning and training, which overcomes the main lacks of traditional learning media. Nowadays, continuous training is widely considered as the best way to maintain a region’s competitiveness, especially in our increasingly globalized world. Governments in the EU are more and more concerned in searching more accessible teleeducation systems for citizens. It is necessary to develop courses and reach the highest number of people. Digital TV, which makes possible a flexible and powerful broadcasting of interactive courses, may be the best media to broadcast this kind of training (PJB, 1999). This communication describes a project around the unexplored world of distance learning by means of interactive digital TV applications. In this work, the possibilities of MHP for implementing a system to broadcast interactive courses are explored. Also, the specific differences between this media and Internet are studied to find the appropriated adaptations in contents and procedures.
2. THE SYSTEM DESIGN The introduction of tele-education systems in Internet has undergone an important growing rate in last years, especially after WWW expansion. The huge activity of universities and companies has consolidated several models around the distribution of information and student monitoring. Today, actors involved in this scenery face a tough normalization task that will permit costs optimization and content reuse. But, it can be said that the formats of the courses, the execution processes and the equipment used (hardware and software) have reached an important degree of maturity, with a level of knowledge and experience that minimizes the unknown technical factors in this business. On the contrary, the development of these systems in the TV media is in the initial phase of study of the technical capabilities of the medium to support such services. But, even in this initial stage, a set of critical differences is observed, which require an adaptation work: • TV users have a lower level of preparation and predisposition to learn new technologies than Internet users. Besides, the way to access information in TV is traditionally passive, unlike the more active role that Internet users use to play. • The information distribution mechanism of digital TV is much more complex than the Internet model, principally by the packing of the course information and the signaling of the transport stream. • The data formats of the Internet courses have text and graphics as a central axis, while TV should promote audio and video in a natural way. In any case, the greater level of fluidity present in the contents in this media demands a greater interrelation among contents and a temporal reference. • The running platform (SetTop box) largely differs from a personal computer: more recent and unstable, lower resolution in presentation devices, less computing power, less local storage, etc. For these reasons, the architecture of a system to create, distribute and execute learning courses by digital TV is still an open field, with multiples incognitos to resolve. In the project described in this communication, we explore approximations to the resolution of these problems (and the definition of adaptations from Internet experiences) in the context of the normalization of digital TV by means of MHP. To study the abovementioned problems, in this project we work in the definition and implementation of several elements involved in the framework to create and distribute a course of these characteristics (fig. 1). These elements are: the structure and composition of a course (formats, contents sequence, contents interrelation and information signaling); the applications needed to support the creation and managing of courses; and, last, the course execution system in the SetTop box. Figure 1. System architecture to create, manage, distribute and execute courses by digital TV
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1. The courses: Our first goal in this task was the definition of the master structure and catalogue of contents of a course designed for being broadcasted in a digital TV channel. In a first place, we specified the different formats of information that can be used by designers of courses, taking the media characteristics into account (video, audio, text, images, graphics, software applications to provide animations and interaction, etc.). This specification of contents includes a formal declaration of the possibilities to sequence the information all along the course and the permitted interrelations among the different formats. Each piece of information has a set of possibilities to interact with the others, depending on the events it can produce (in an active behavior) or signal (in a passive role), its invocation capabilities or the ability to reference other agents in the system. This task involves the evaluation of adequacy to the TV characteristics of new information formats as MPEG-4 or MPEG-7 (MPEG, 2002), not quite used in e-learning yet. This process of specification of contents and their capabilities is being reflected in the definition of a markup language, based on XML, to describe the structure and contents of a course, that will serve as mechanism to declare the course configuration independently of the hardware and software used to distribute and execute the course. 2. The supporting tools. A multimedia course system as the one described here involves a large richness of content formats and interrelation capabilities. Besides, the technological complexity of the execution platform (demanding a precise and detailed signaling) makes a course to require a huge volume of metainformation. In addition, the information belonging to a course must respect a number of limitations derived from the capabilities of the representation device. Last, the main characteristic of this new TV (the availability of software applications to implement interactivity and active behaviors) demands applications to respect a number of restrictions depending on the standard used. In the MHP case, the downloaded applications (known as DVB-J applications or Xlets) must obey a set of restrictions related to the usage of a specific API, the implementation of a lifecycle or the use of an specific system to communicate with the system software of the SetTop box. All these technological determining factors go beyond of the tasks that it is reasonable to demand to content designers. So, in any system of this complexity is necessary to provide software tools to support the creation of the courses. These tools free designers from these tough tasks and permit them to concentrate in the contents, their sequence and interrelation from a functional perspective. In this project, we are working in the design and development of a tool with such characteristics, that provides support in the abovementioned tasks: content declaration (with interrelations), automatic checking of restrictions existing in the model, automatic generation of software applications following the MHP guidelines, integration and information packing, automatic generation of the configuration files needed to signal the course information, management of the courses, etc. 3. The execution subsystem. The set of information defined in the first point, generated and packed by the support tool of the second point, will be received in the SetTop box through an object carrousel, as defined in the DVB-MHP standards. The approximation followed in our work is that, once there, this information will be represented and executed by a software application in charge of the coordination of course execution (the courses manager in the figure). This middleware is specifically designed to manage the information formats defined in the project, but, in near future, it will include mechanisms to actualize that set of information contents. This execution software is closely linked to the configuration files and signaling mechanisms used to express the sequence of the course contents. This middleware software in charge of the course execution in the SetTop box is implemented by an autostart MHP application, periodically transmitted through the data channel of the TV service used to broadcast the course. This DVB-J application accesses all course configuration files in order to obtain the information to locate all the objects of the course inside the transport stream and to coordinate their execution and representation. Besides, it also coordinates the interaction with the user and the communication (through the return channel) with a central service in charge to monitor students. This execution environment is nowadays running in a prototype of a MHP receiver developed in a previous work of this research group funded by the EU through a FEDER project. In addition to these principal elements, some optional modules exist that provide additional functionalities:
A. Information storage in the hard disk of the local receiver. This possibility, usually contemplated in Personal Video Recorders, permits to set particular characteristics depending on the user, store the course material for later access, follow the course in a non-linear way, etc. For these functionalities, an interesting work is being developed in the TV-Anytime Forum (TV-Anytime, 2002), which is being integrated in our work. B. Usage of the return channel. Mainly, we use or plan to use the return channel in four ways: a) Student tutorship: the student can communicate with teachers to consult. b) Evaluation: In addition to a local evaluation, the interaction provided by the return channel permits teachers to monitor students. c) Conversation. Online discussion forums can be created involving teachers and students. d) Additional consultations. Internet access through this channel provides the possibility to access additional information sources about any subject. These sources can be provided by the teacher or freely searched by students. To implement each one of these functionalities, there exists a corresponding module that interacts with the courses manager (fig. 1).
3. CONCLUSION In this communication, we have presented an ongoing project that integrates two important fields as distance education and the new interactive digital TV. We foresee three important advantages that can be derived from the results of works in this field. First, a new market is opened for the distance learning business. With these kind of systems, courses and contents can be offered to people without computers, Internet access or knowledge to manage these kind of tecnologies. Second, a new interactive application is developed for digital TV, where new ideas about enhanced contents are needed to increase the number of users (payers). And third, this project is an interesting benchmark to test the adequacy of MHP to implement a compatible and efficient platform for running software applications downloaded in the transport stream.
ACKNOWLEDGEMENT This work is partially based on a previous work funded by spanish R&D Project number 1FD97-1195 (cofinanced with FEDER funds)
REFERENCES Gil, A. et al., 2002. Surfing the WEB on TV: the MHP approach. Proceedings of IEEE International Conference on Multimedia and Expo. Lausanne, Switzerland. DVB Corsortium. 2001. The Multimedia Home Platform 1.1. http://www.mhp.org. GRIS, 2001. GRIS research group. Sistema de recepción digital multimedia, http://mhp.det.uvigo.es. University of Vigo López-Ardao, J.C. et al., 2002. Experiences from implementing a MHP receiver. Proceedings of International Symposium on Video/Image Processing and Multimedia Communications. Zadar, Croatia. MPEG, 2002. Motion Picture Experts Group, http://mpeg.cselt.it PJB associates, 1999. Development of satellite and terrestrial digital broadcasting systems and services and implications for education and training. http://www.pjb.co.uk. TV-Anytime, 2002. The TV-Anytime Forum, http://www.tv-anytime.org
