On the use of adaptive media playout for inter-destination synchronization

[EN] Inter-Destination Multimedia Synchronization (IDMS) is essential in most of the emerging social multimedia applications. In this paper we present a novel Adaptive Media Playout (AMP) scheme that aims to acquire an overall synchronization status between distributed receivers by means of smoothly adjusting their playout timing. Simulation results show that the proposed solution minimizes long-term playout discontinuities (skips and/or pauses) which are subjectively more annoying to users than small variations in the media playout rate.This work was supported by the Universitat Politecnica de Valencia (UPV), under its R&D Support Program in the PAID-01-10 Project, and by Generalitat Valenciana, under its R&D Support Program in the GV 2010/009 Project.Montagud, M.; Boronat, F. (2011). On the use of adaptive media playout for inter-destination synchronization. IEEE Communications Letters. 15(9):863-865. https://doi.org/10.1109/LCOMM.2011.061611.110072S86386515

Enhanced adaptive RTCP-based inter-destination multimedia synchronization approach for distributed applications

[EN] Newer social multimedia applications, such as Social TV or networked multi-player games, enable independent groups (or clusters) of users to interact among themselves and share services within the context of simultaneous media content consumption. In such scenarios, concurrently synchronized playout points must be ensured so as not to degrade the user experience on such interaction. We refer to this process as Inter-Destination Multimedia Synchronization (IDMS). This paper presents the design, implementation and evaluation of an evolved version of an RTCP-based IDMS approach, including an Adaptive Media Playout (AMP) scheme that aims to dynamically and smoothly adjust the playout timing of each one of the geographically distributed consumers in a specific cluster if an allowable asynchrony threshold between their playout states is exceeded. For that purpose, we previously had also to develop a full implementation of RTP/RTCP protocols for NS-2, in which we included the IDMS approach as an optional functionality. Simulation results prove the feasibility of such IDMS and AMP proposals, by adopting several dynamic master reference selection policies, to maintain an overall synchronization status (within allowable limits) in each cluster of participants, while minimizing the occurrence of long-term playout discontinuities (such as skips/pauses) which are subjectively more annoying and less tolerable to users than small variations in the media playout rate.This work has been financed, partially, by Universitat Politecnica de Valencia (UPV), under its R&D Support Program in PAID-05-11-002-331 Project and in PAID-01-10. Authors also would like to thank the anonymous reviewers that helped to significantly improve the quality of the paper with their constructive comments.Montagud, M.; Boronat, F. (2012). Enhanced adaptive RTCP-based inter-destination multimedia synchronization approach for distributed applications. Computer Networks. 56(12):2912-2933. https://doi.org/10.1016/j.comnet.2012.05.00329122933561

Berezinskii-Kosterlitz-Thouless transition in two-dimensional dipolar stripes

A two-dimensional quantum system of dipoles, with a polarization angle not perpendicular to the plane, shows a transition from a gas to a stripe phase. We have studied the thermal properties of these two phases using the path-integral Monte Carlo (PIMC) method. By simulating the thermal density matrix, PIMC provides exact results for magnitudes of interest such as the superfluid fraction and the one-body density matrix. As it is well known, in two dimensions the superfluid-to-normal phase transition follows the Berezinskii-Kosterlitz-Thouless (BKT) scenario. Our results show that both the anisotropic gas and the stripe phases follow the BKT scaling laws. At fixed density and increasing the tilting angle, the transition temperature decreases in going from the gas to the stripe phase. Superfluidity in the perpendicular direction to the stripes is rather small close to the critical temperature but it becomes larger at lower temperatures, mainly close to the transition to the gas. Our results are in qualitative agreement with the supersolidity observed recently in a quasi-one-dimensional array of dipolar droplets.Postprint (published version

Checking bisimilarity for attributed graph transformation

Borrowed context graph transformation is a technique developed by Ehrig and Koenig to define bisimilarity congruences from reduction semantics defined by graph transformation. This means that, for instance, this technique can be used for defining bisimilarity congruences for process calculi whose operational semantics can be defined by graph transformation. Moreover, given a set of graph transformation rules, the technique can be used for checking bisimilarity of two given graphs. Unfortunately, we can not use this ideas to check if attributed graphs are bisimilar, i.e. graphs whose nodes or edges are labelled with values from some given data algebra and where graph transformation involves computation on that algebra. The problem is that, in the case of attributed graphs, borrowed context transformation may be infinitely branching. In this paper, based on borrowed context transformation of what we call symbolic graphs, we present a sound and relatively complete inference system for checking bisimilarity of attributed graphs. In particular, this means that, if using our inference system we are able to prove that two graphs are bisimilar then they are indeed bisimilar. Conversely, two graphs are not bisimilar if and only if we can find a proof saying so, provided that we are able to prove some formulas over the given data algebra. Moreover, since the proof system is complex to use, we also present a tableau method based on the inference system that is also sound and relatively complete.Postprint (published version

Analysis, Deployment, and Evaluation of the Use of Network Simulation as a Learning Resource

This paper analyzes the benefits of using network simulation as a learning resource in the educational area of Telematics Engineering. Accordingly, a (students skills) practice program, which can be done using either network simulation or real equipment, has been introduced in the core subject Telematics Architectures and Networks (TAN) of the second year of the bachelor s degree in Telecommunications Systems, Sound, and Image Engineering. The satisfactory evaluation of this innovative teaching methodology is proved by the rating of the surveys answered by the students after the course completion.Montagud, M.; Boronat Segui, F. (2014). Analysis, Deployment, and Evaluation of the Use of Network Simulation as a Learning Resource. Rita -IEEE. 9(3):82-90. doi:10.1109/RITA.2014.2340011S82909

Gapped spectrum in pair-superfluid bosons

We study the ground state of a bilayer system of dipolar bosons with dipoles oriented by an external field perpendicularly to the two parallel planes. By decreasing the interlayer distance, for a fixed value of the strength of the dipolar interaction, the system undergoes a quantum phase transition from an atomic to a pair superfluid. We investigate the excitation spectrum on both sides of this transition by using two microscopic approaches. Quantum Monte Carlo methods are employed to obtain the static structure factors and intermediate scattering functions in imaginary time. The dynamic response is calculated using both the correlated basis functions (CBF) method and the approximate inversion of the Laplace transform of the quantum Monte Carlo imaginary time data. In the atomic phase, both the density and spin excitations are gapless. However, in the pair-superfluid phase a gap opens in the excitation energy of the spin mode. For small separation between layers, the minimal spin excitation energy equals the binding energy of a dimer and is twice the gap value.Postprint (author's final draft

A customizable open-source framework for measuring and equalizing e2e delays in shared video watching

[EN] Low-latency and media sync are essential requirements to enable interactive multi-party services, such as Social TV. In this work, we present an open-source and customizable framework that allows measuring end-to-end (e2e) video delays and provides support for different types of media sync, including Inter-Destination Media Sync (IDMS). This framework can be used by researchers to investigate the suitability of different techniques for optimizing the system performance in terms of e2e delays and media sync.This work has been funded, partially, by UPV under its R&D Support Program in PAID-01-10 Project and by CWI under EU/FP7 REVERIE Project (ICT-2011-7-287723).Montagud, M.; Boronat, F.; Cesar, P. (2014). A customizable open-source framework for measuring and equalizing e2e delays in shared video watching. ACM. 95-96. https://doi.org/10.6084/m9.figshare.1032656S959

Droplets of trapped quantum dipolar bosons

Strongly interacting systems of dipolar bosons in three dimensions confined by harmonic traps are analyzed using the exact path integral ground-state Monte Carlo method. By adding a repulsive two-body potential, we find a narrow window of interaction parameters leading to stable ground-state configurations of droplets in a crystalline arrangement. We find that this effect is entirely due to the interaction present in the Hamiltonian without resorting to additional stabilizing mechanisms or specific three-body forces. We analyze the number of droplets formed in terms of the Hamiltonian parameters, relate them to the corresponding s-wave scattering length, and discuss a simple scaling model for the density profiles. Our results are in qualitative agreement with recent experiments showing a quantum Rosensweig instability in trapped Dy atoms.Peer ReviewedPostprint (published version

Web-based Platform for Subtitles Customization and Synchronization in Multi-Screen Scenarios

[EN] This paper presents a web-based platform that enables the customization and synchronization of subtitles on both single- and multi-screen scenarios. The platform enables the dynamic customization of the subtitles format (font family, size, color...) and position according to the users preferences and/or needs. Likewise, it allows configuring the number of subtitles lines to be presented, being able to restore the video playout position by clicking on a specific one. It also allows the simultaneous selection of various subtitle languages, and applying a delay offset to the presentation of subtitles. All these functionalities can also be available on (personal) companion devices, allowing the presentation of subtitles in a synchronized manner with the ones on the main screen and their individual customization. With all these functionalities, the platform enables personalized and immersive media consumption experiences, contributing to a better language learning, social integration and an improved Quality of Experience (QoE) in both domestic and multi-culture environments.This work has been funded, partially, by the Fondo Europeo de Desarrollo Regional (FEDER) and the Spanish Ministry of Economy and Competitiveness, under its R&D&I Support Program, in project with Ref. TEC2013- 45492-R, and by Fundación Española para la Ciencia y Tecnología (FECYT) , in project with Ref. FCT-15-9579Montagud, M.; Boronat, F.; González, J.; Pastor, J. (2017). Web-based Platform for Subtitles Customization and Synchronization in Multi-Screen Scenarios. ACM Digital Library. 81-82. https://doi.org/10.1145/3084289.3089913S8182M. Armstrong, et al., "Understanding the Diverse Needs of Subtitle Users in a Rapidly Evolving Media Landscape", IBC 2015, Amsterdam, September 2015.A. Brown, et al, "Dynamic Subtitles: The User Experience". ACM TVX '15, pp. 103--112, Brussels (Belgium), June 2015.Y. Hu, et al. "Speaker-Following Video Subtitles", TOMCCAP, 11, 2, Article 32, 17 pages, January 2015.M. Montagud, et al., "Use of Web Components to Develop Interactive, Customizable and Multi-Device Video Consumption Platforms", Applications and Usability of Interactive TV, Springer, V.605, 2016.A. Rodriguez, et al., "Subtitle Synchronization across Multiple Screens and Devices", Sensors, 12(7), 87108731, June 2012