Caio César Viel

CastFlow: Clean-slate multicast approach using in-advance path processing in programmable networks

Multipoint communication is an important requirement for many types of applications such as videoconferencing, IPTV and online radio. However, the division of Internet in autonomous systems hinders the widespread adoption of traditional multicast protocols, which, for using distributed algorithms, delay the group control events processing. This paper proposes a multicast clean-slate approach logically centralized based on programmable networks and anticipated processing for all routes from each possible source, aiming to reduce event delays. A prototype was implemented based on OpenFlow technology. In addition, extensive evaluation was performed and results show promising delays comparable to the requirements of multipoint applications.

WebNCL: a web-based presentation machine for multimedia documents

Presentation machines for multimedia declarative languages especially the ones related with Interactive Digital TV (iDTV) and Internet Protocol TV (IPTV) are usually embedded in devices and strongly coupled with the platforms when native code and API for the devices platform are used. Since much of the complexity to implement presentation machines lies on presenting and controlling different types of media (video, audio, image, text), and given that most of the modern browsers natively support those requirements, it becomes interesting to implement presentation machines using Web technologies to reduce their coupling with platforms. In this paper we discuss the advantages of a presentation machine for declarative multimedia languages implemented on top of Web technologies. As a proof of concept we implemented the WebNCL, a lightweight NCL presentation machine based on the web technologies stack (HTML 5/ JavaScript/ CSS). By using WebNCL, NCL documents can be presented in any device that has a HTML5 compatible browser, such as tablets, smartphones, smart TVs and PCs.

Multimedia multi-device educational presentations preserved as interactive multi-video objects

The capture of lectures or similar presentations is of interest for several reasons. From the attendees perspective, students may use the recordings when working on homework assignments or preparing for exams, or to watch the contents of a missed class. From the instructors perspective, a captured lecture may be evaluated, recaptured for improvements, or reused as complementary learning material. Moreover, captured lectures may be a valuable resource for e-learning and distance education courses. In this paper we detail the design rationale associated with the development of a prototype platform for the ubiquitous capture of live presentations and their transformation into a corresponding interactive multi-video object. Our approach includes capturing important context information which, when incorporated into the multimedia object, enables one to interact with the recorded lecture in novel dimensions. We tested our prototype by using case studies involving instructors and students, which allowed us to identify important features and novel uses for the platform.

Multimedia presentation integrating interactive media produced in real time with high performance processing

Sophisticated interactive animation may be an interesting element to compose a multimedia document. However, potential demand for high performance computing can make this option impractical in digital interactive TV and mobile device environments, due to computing power restrictions of these platforms. In previous work we proposed a solution to overcome such restrictions based on video streaming. Moving forward the solution, it is described in this paper how to take advantage of media-agnostic characteristic, when present in the multimedia presentation machine, to manage this new type of media in multimedia documents. As a proof of concept we extended and tested an NCL presentation engine to add suport to this new type of media.

Go beyond boundaries of iTV applications

The development of multimedia applications that require the manipulation and the synchronization of multiple media and the handling of different types of user interactions usually requires specialized knowledge in imperative languages. Declarative languages have been proposed in order to make this task easier, especially when applications are restricted to certain classes, as it is the case of Interactive TV applications in which user interactions are restricted to a few simple models. However, those simple models may be too simple when documents are reused in other platforms: for instance, when watching a video most web users expect an interactive timeline to be available --- which is not the case in interactive TV videos. This paper presents a component-based approach to the enrichment of declarative languages for multimedia so that desirable user-media interactions are made possible at the same time that the original ease of authoring is maintained. We detail the components and present a corresponding proof-of-concept prototype. We also discuss design decisions associated with the development of the components, which should be useful in further extensions.

Design Solutions for Interactive Multi-video Multimedia Learning Objects

The increasing popularity of distance education courses, including Massive Open Online Courses (MOOCs), creates a demand for the production of quality video-based educational material. In order to reduce the costs involved in the production of video lectures, several researchers have investigated alternatives for capture and access systems which automatically capture lecture contents to generate corresponding video lectures. We also developed a system for this purpose; however our system generates Interactive Multimedia Learning Objects (iMLO) instead of a traditional (linear) video lecture. The iMLO’s features and its interface are important issues for the development of the capture and access system. Interface aspects, such as which are proper ways to present content for users and which navigation facilities are more useful, are distinctive requirements and may impact the user experience. In this paper we present a novel design for the iMLOs which results from an evolution process supported by feedbacks from the main stakeholders: students and lecturers. The feedbacks have been acquired by analyzing the interaction of students with the iMLOs in real scenarios. Based on these feedbacks, we have identified several design implications. We present the proposed interfaces and proof-of-concepts implementations and report lessons learned during the development of the final design solution, which can guide other designers in the conception of new iMLOs. The whole process is documented by means of Design Rationale.

Self-Service Classroom Capture Generating Interactive Multivideo Objects

The capture of lectures for the generation of associated videos is mainstream in several locations. Alternative approaches include the capture of real lectures or studio-produced ones, the latter designed with the only purpose of generating the associated videos. The amount of control offered to instructors during the capture process varies from system to system. In cases in which the lectures are delivered in classrooms while regular classes take place, the capture may occur according to programmed schedules which are unaware of the presence of the instructor in the classroom, and may start before the instructor is in place and may end before the instructor concludes the lecture – the latter occurring when the instructor passes the scheduled time, a situation which is not uncommon in traditional courses. In cases in which the lectures are delivered in studios, the capture is usually directed by professionals that control start and ending times and orient the instructor to look at specific cameras, for instance. We built a prototype system that offers instructors facilities to control the starting and ending times of multiple segments so that the overall exposition is transformed into a corresponding interactive multivideo object, exploiting the multimodal and multi-device nature of the presentation. After a brief overview of our prototype, in this paper we present the document-based workflow which underlies the processes of capture, generation and presentation that offer instructors a self-service alternative to control the generation of a multimedia object composed of synchronized videos, audio, images and context information associated to the lecture. We illustrate the utility of the approach by summarizing data relative to the use of our prototype by a group of instructors.