Víctor G. García

User behavior analysis of a video-on-demand service with a wide variety of subjects and lengths

This paper presents the analysis performed on the www.lne.es video-on-demand service (LNE TV), which is part of the digital version of one of the most important newspapers in Spain. Its principal special characteristic is the wide range of subjects (news, music, culture, tourism, nature, sports, etc) and lengths of the offered contents (from 2 minutes to 2 hours), which make it an interesting case study. Elements about user behavior have been analyzed such as session analysis; delivered time, pause distribution, jumps length, etc. The study points out interesting results about length dependence, interactions appearing, popularity of the videos, etc., which are compared with the results obtained in previous works, generally developed on educational environments (services or users). A behavior user model has been performed using the results of the analyses. This model is oriented to services with different types of information and lengths for the videos. This study has been performed thanks to an access log database with more than 150,000 requests of almost 900 videos stored over a period of 4 years. The conclusions of the study are essential to improve the service configuration and content selection. Moreover, they can be used to develop service models for video-on-demand services, which can help administrators to predict future situations and avoid performance problems.

Statistical characterization of a real video on demand service: User behaviour and streaming-media workload analysis

Abstract The video on demand service characterized in this article has surpassed 4 years of service, and the access log database stores information of more than 160,000 reproductions and 900 videos. The wide variety of subjects, the range of content lengths and a frequent update of contents (several new videos every day), clearly differentiate this study from other previous research limited to specific users, subjects or environments. We present a statistical study of user behaviour and streaming traffic, analyzing session characteristics, mistaken reproductions, amount of media delivered, number and length of pauses and jumps in the reproduction, popularity and daily access profile. The results of the analysis will allow us to develop simulation models and workload generators to evaluate different scenarios and situations of the service.

Analysis and modeling of traffic on a hybrid fiber-coax network

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 networks 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.

Probabilistic analysis and interdependence discovery in the user interactions of a video news on demand service

Accurate workload prediction in multimedia systems requires a description of both its probabilistic properties and the interdependence between the variables of the system. This paper analyzes the interactions of the users of a news and entertainment video-on-demand service (LNE TV, http://tv.lne.es) during six months of activity. The analysis was performed using information extracted from the server logs, analyzing more than 300,000 requests for almost 1500 videos. The type of content on the site and the structure of LNE TV, which is similar to most Internet news services supported by a traditional newspaper, make this work an interesting case study, and the results can be easily extrapolated to similar audio/video streaming services. This paper shows that client interactivity in multimedia systems has the dependence structure of a stochastic process. In previous work, this type of study has been carried out in a single variable, whereas the user interactions in actual multimedia systems are multivariate. In this context, we have used copulas to create distributions to model correlated data. In our study, we model user interactions depending on their marginal univariate distributions and their correlation coefficient with the length of the videos.

Popularity analysis of a video-on-demand service with a great variety of content types: influence of the subject and video characteristics

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.

Evaluation of Virtual Keyboards for Interactive Digital Television Applications

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.

Analysis Tool for a Video-on-Demand Service Based in Streaming Technology

This paper describes the tool developed in order to analyse a video-on-demand streaming service. The aim of this work is to provide a powerful system to help both the service providers and the communication operators to configure this sort of services. Distributing the contents, developing redistribution routes, creating new contents in the most popular subjects and increasing or decreasing the length of information depending on the subscribers’ behaviour can improve the quality of the service. However, these decisions must be taken based in service performance. This tool tries to fill the gap in this field and provide the necessary analysis to configure these services. The quality of the tool has been evaluated by the www.lne.es, which is one of the most successful digital news sites in Spain. Its multimedia section offers a large number of videos on demand with several subjects, lengths and qualities. During the last months an analysis process has been performed to improve the service by using this analysis tool. This work is included in a project about analysis, modelling and configuring of interactive multimedia services.

Multivariate distributions for workload generation in video on demand systems

In this letter we present an analysis of workload in a real video on demand service with the objective of generating more accurate input data for simulation models. As well as statistically characterizing key aspects in the server workload of the multimedia system, we consider their statistical dependencies.We propose a procedure to generate multivariate distributions using normal copulas in the video on demand system. Results show that the proposed method fits exactly the statistical distributions to the empirical data and matches the real correlation coefficients matrix.

Evaluation of Video Server Capacity with Regard to Quality of the Service in Interactive News-On-Demand Systems

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 the 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 the 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.

Popularity analysis of a video-on-demand service in a digital newspaper: influence of the subject, video characteristics and new content publication policy

This paper presents the popularity analysis performed on the www.lne.es video-on-demand service. Its principal special characteristics are the wide range of subjects, the type of contents offered and the daily introduction of several new videos. All of this and its similarity with the majority of the digital news services make it an interesting case study. The analysis pays attention to all the elements which can influence content popularity such as the subject, the video characteristics and the new content introduction policy. Moreover, the results are checked in different timescales and periods of time.