The development of the technologies behind Interactive Digital Television (IDTV) services has produced a new type of audience. Traditional viewers now become users as they may play an active role in front of the TV, for example, by choosing a video to be played on demand or by introducing text on an IDTV application. In these services, interactions need to be performed with a remote control, currently the main interaction device, or other devices such as keyboards or mice, which are not very popular in this environment. Nevertheless, although remote controls are essential tools for IDTV services, they are very limited when it comes to writing text. Thus, this study evaluated different alternatives to introduce text on an IDTV application with a remote control. A heterogeneous group of people was selected to write predefined sentences in Spanish in a test environment using three virtual keyboard layouts and the multitap mechanism. Their performance and subjective impressions reveal weaknesses and strengths of the evaluated methods. The article draws important conclusions about the usage of remote controls in IDTV applications, not only for the design of new applications but also for the research of new techniques to introduce text.

This paper presents the popularity analysis performed on the www.lne.es video-on-demand service, which is part of the digital version of one of the most important newspapers in Spain. Its most special characteristics are the wide range of subjects (events, music, culture, tourism, nature, sports, etc) and the type of contents offered (long life, seasonal, etc), which make it an interesting case study. The analysis pays attention to the influence of the subject and the video characteristics on the popularity. Moreover, the results are checked for short and long periods of time. This study has been performed thanks to a log database with more than 170,000 requests of almost 1000 videos stored over a period of 4 years.

This paper presents the study carried out on the data traffic collected on the network of a cable operator based on hybrid fiber-coax technology, and the subsequent simulation model developed to predict the bandwidth requirements of the network channels. The paper starts with the analysis of the traffic measurements, taken over two periods of time in one year, on all the network's channels. This analysis identifies the main characteristics of the traffic, as well as some relationships between network parameters and their persistence over time. The paper proceeds to present the development of a simulation model, which represents the cable network. This model is built from the results of the traffic analysis and network parameters. The major challenge of this model is to predict the traffic on each channel of the cable network, related to parameters of the network configuration, such as the number of assigned subscribers to the channel and the time of day. To reach this goal, the simulation model has been developed with a modular structure, which gives it flexibility to adapt to changes in the network. The process followed involves the establishment of a traffic model, a system model, and finally, the validation of the results.

A key issue in any system for distribution of continuous media-on-demand is the capacity of the system with regard to quality of the service specifications, that is, the number of simultaneous streams the system can provide until degradation of quality of reproduction and interactivity perceived by the users. This work presents the evaluation of interactive video-on-demand systems, with special attention to limitations caused by the video server. The evaluation is based on a set of metrics designed to determine the number of streams a video server can support under specific requirements of quality of the service as perceived by the users. To validate the utility of these metrics, a prototype of a news-on-demand service has been built and the load for this kind of systems has been characterised. In addition, a load generator which emulates the concurrent access of several users to the system has been built. The evaluation establishes the relationship between the video server limitations and the quality of the service perceived by the users.

Real-time distribution of continuous media on demand is a natural step in the evoluation of internet services. Here, we briefly present an interactive talks-on-demand service currently integrated in a digital newspaper. Low cost, high availability and high performance are features of the system supporting the service.