794 resultados para Scalable video


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This study compares interpreter-mediated face-to-face Magistrates Court hearings with those conducted through prison video link in which interpreters are located in court and non- English-speaking defendants in prison. It seeks to examine the impact that the presence of video link has on court actors in terms of interaction and behaviour. The data comprises 11 audio-recordings of face-to-face hearings, 10 recordings of prison video link hearings, semistructured interviews with 27 court actors, and ethnographic observation of hearings as viewed by defendants in Wormwood Scrubs prison in London. The over-arching theme is the pervasive influence of the ecology of the courtroom upon all court actors in interpretermediated hearings and thus on the communication process. Close analysis of the court transcripts shows that their relative proximity to one another can be a determinant of status, interpreting role, mode and volume. The very few legal protocols which apply to interpretermediated cases (acknowledging and ratifying the interpreter, for example), are often forgotten or dispensed with. Court interpreters lack proper training in the specific challenges of court interpreting, whether they are co-present with the defendant or not. Other court actors often misunderstand the interpreter’s role. This has probably come about because courts have adjusted their perceptions of what they think interpreters are supposed to do based on their own experiences of working with them, and have gradually come to accept poor practice (the inability to perform simultaneous interpreting, for example) as the norm. In video link courts, mismatches of sound and image due to court clerks’ failure to adequately track current speakers, poor image and sound quality and the fact that non-English-speaking defendants in pre-and post-court consultations can see and hear interpreters but not their defence advocates are just some of the additional layers of disadvantage and confusion already suffered by non- English-speaking defendants. These factors make it less likely that justice will be done.

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We investigate the problem of obtaining a dense reconstruction in real-time, from a live video stream. In recent years, multi-view stereo (MVS) has received considerable attention and a number of methods have been proposed. However, most methods operate under the assumption of a relatively sparse set of still images as input and unlimited computation time. Video based MVS has received less attention despite the fact that video sequences offer significant benefits in terms of usability of MVS systems. In this paper we propose a novel video based MVS algorithm that is suitable for real-time, interactive 3d modeling with a hand-held camera. The key idea is a per-pixel, probabilistic depth estimation scheme that updates posterior depth distributions with every new frame. The current implementation is capable of updating 15 million distributions/s. We evaluate the proposed method against the state-of-the-art real-time MVS method and show improvement in terms of accuracy. © 2011 Elsevier B.V. All rights reserved.

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DUE TO COPYRIGHT RESTRICTIONS ONLY AVAILABLE FOR CONSULTATION AT ASTON UNIVERSITY LIBRARY AND INFORMATION SERVICES WITH PRIOR ARRANGEMENT

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To guarantee QoS for multicast transmission, admission control for multicast sessions is expected. Probe-based multicast admission control (PBMAC) scheme is a scalable and simple approach. However, PBMAC suffers from the subsequent request problem which can significantly reduce the maximum number of multicast sessions that a network can admit. In this letter, we describe the subsequent request problem and propose an enhanced PBMAC scheme to solve this problem. The enhanced scheme makes use of complementary probing and remarking which require only minor modification to the original scheme. By using a fluid-based analytical model, we are able to prove that the enhanced scheme can always admit a higher number of multicast sessions. Furthermore, we present validation of the analytical model using packet based simulation. Copyright © 2005 The Institute of Electronics, Information and Communication Engineers.

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The concern over the quality of delivering video streaming services in mobile wireless networks is addressed in this work. A framework that enhances the Quality of Experience (QoE) of end users through a quality driven resource allocation scheme is proposed. To play a key role, an objective no-reference quality metric, Pause Intensity (PI), is adopted to derive a resource allocation algorithm for video streaming. The framework is examined in the context of 3GPP Long Term Evolution (LTE) systems. The requirements and structure of the proposed PI-based framework are discussed, and results are compared with existing scheduling methods on fairness, efficiency and correlation (between the required and allocated data rates). Furthermore, it is shown that the proposed framework can produce a trade-off between the three parameters through the QoE-aware resource allocation process.

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Witnesses often experience lengthy delays prior to being interviewed, during which their memories inevitably decay. Video-communication technology - favored by intergovernmental organizations for playing larger roles in judicial processes - might circumvent some of the resourcing problems that can exacerbate such delays. However, whereas video-mediation might facilitate expeditious interviewing, it might also harm rapport-building, make witnesses uncomfortable, and thereby undermine the quality and detail of their reports. Participants viewed a crime film and were interviewed either one day later via video-link, one day later face-to-face, or 1-2 weeks later face-to-face. Video-mediation neither influenced the detail or the accuracy of participants' reports, nor their ratings of the quality of the interviews. However, participants who underwent video-mediated interviews after a short delay gave more accurate, detailed reports than participants who waited longer to be interviewed face-to-face. This study provides initial empirical evidence that video-mediated communication (VMC) could facilitate the expeditious conduct of high-quality investigative interviews. © 2013 © 2013 Taylor & Francis.

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More powerful computers and affordable digital-video equipment means that desktop-video editing is now accessible and popular. In two experiments, we investigated whether seeing fake-video evidence, or simply being told that video evidence exists, could lead people to believe they committed an act they never did. Subjects completed a computerized gambling task, and when they returned later the same day, we falsely accused them of cheating on the task. All of the subjects were told that incriminating video evidence existed, and half were also exposed to a fake video. See-video subjects were more likely to confess without resistance, and to internalize the act than told-video subjects, and see-video subjects tended to confabulate details more often than told-video subjects. We offer a metacognitive-based account of our results. Copyright © 2008 John Wiley & Sons, Ltd.

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The use of hMSCs for allogeneic therapies requiring lot sizes of billions of cells will necessitate large-scale culture techniques such as the expansion of cells on microcarriers in bioreactors. Whilst much research investigating hMSC culture on microcarriers has focused on growth, much less involves their harvesting for passaging or as a step towards cryopreservation and storage. A successful new harvesting method has recently been outlined for cells grown on SoloHill microcarriers in a 5L bioreactor [1]. Here, this new method is set out in detail, harvesting being defined as a two-step process involving cell 'detachment' from the microcarriers' surface followed by the 'separation' of the two entities. The new detachment method is based on theoretical concepts originally developed for secondary nucleation due to agitation. Based on this theory, it is suggested that a short period (here 7min) of intense agitation in the presence of a suitable enzyme should detach the cells from the relatively large microcarriers. In addition, once detached, the cells should not be damaged because they are smaller than the Kolmogorov microscale. Detachment was then successfully achieved for hMSCs from two different donors using microcarrier/cell suspensions up to 100mL in a spinner flask. In both cases, harvesting was completed by separating cells from microcarriers using a Steriflip® vacuum filter. The overall harvesting efficiency was >95% and after harvesting, the cells maintained all the attributes expected of hMSC cells. The underlying theoretical concepts suggest that the method is scalable and this aspect is discussed too. © 2014 The Authors.

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Various digital watermarking (WM) techniques for still imaging have been studied in the last several years. Recently, many new WM schemes have been proposed for other types of digital multimedia data, such as text, audio and video. This paper presents a brief overview of existing digital video WM. We classify WM techniques and discuss the properties of video WM. Since each WM application has its own specific requirements, WM design must take the intended application into consideration. Video WM applications are also discussed in the paper. The features of video WM implementations in software and hardware and their differences are presented through the description of four examples of existing work.

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Video analysis provides an educational, motivating, and cost-effective alternative to traditional course- related activities in physics education. Our paper presents results from video analysis of experiments “Collision of balls” and “Motion of a ball rolled on inclined plane” as examples to illustrate the laws of conservation of impulse and mechanical energy.

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AMS Subj. Classification: H.3.7 Digital Libraries, K.6.5 Security and Protection

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This research is focused on the optimisation of resource utilisation in wireless mobile networks with the consideration of the users’ experienced quality of video streaming services. The study specifically considers the new generation of mobile communication networks, i.e. 4G-LTE, as the main research context. The background study provides an overview of the main properties of the relevant technologies investigated. These include video streaming protocols and networks, video service quality assessment methods, the infrastructure and related functionalities of LTE, and resource allocation algorithms in mobile communication systems. A mathematical model based on an objective and no-reference quality assessment metric for video streaming, namely Pause Intensity, is developed in this work for the evaluation of the continuity of streaming services. The analytical model is verified by extensive simulation and subjective testing on the joint impairment effects of the pause duration and pause frequency. Various types of the video contents and different levels of the impairments have been used in the process of validation tests. It has been shown that Pause Intensity is closely correlated with the subjective quality measurement in terms of the Mean Opinion Score and this correlation property is content independent. Based on the Pause Intensity metric, an optimised resource allocation approach is proposed for the given user requirements, communication system specifications and network performances. This approach concerns both system efficiency and fairness when establishing appropriate resource allocation algorithms, together with the consideration of the correlation between the required and allocated data rates per user. Pause Intensity plays a key role here, representing the required level of Quality of Experience (QoE) to ensure the best balance between system efficiency and fairness. The 3GPP Long Term Evolution (LTE) system is used as the main application environment where the proposed research framework is examined and the results are compared with existing scheduling methods on the achievable fairness, efficiency and correlation. Adaptive video streaming technologies are also investigated and combined with our initiatives on determining the distribution of QoE performance across the network. The resulting scheduling process is controlled through the prioritization of users by considering their perceived quality for the services received. Meanwhile, a trade-off between fairness and efficiency is maintained through an online adjustment of the scheduler’s parameters. Furthermore, Pause Intensity is applied to act as a regulator to realise the rate adaptation function during the end user’s playback of the adaptive streaming service. The adaptive rates under various channel conditions and the shape of the QoE distribution amongst the users for different scheduling policies have been demonstrated in the context of LTE. Finally, the work for interworking between mobile communication system at the macro-cell level and the different deployments of WiFi technologies throughout the macro-cell is presented. A QoEdriven approach is proposed to analyse the offloading mechanism of the user’s data (e.g. video traffic) while the new rate distribution algorithm reshapes the network capacity across the macrocell. The scheduling policy derived is used to regulate the performance of the resource allocation across the fair-efficient spectrum. The associated offloading mechanism can properly control the number of the users within the coverages of the macro-cell base station and each of the WiFi access points involved. The performance of the non-seamless and user-controlled mobile traffic offloading (through the mobile WiFi devices) has been evaluated and compared with that of the standard operator-controlled WiFi hotspots.