London, United Kingdom
London, United Kingdom

Time filter

Source Type

Knijnenburg B.P.,University of California at Irvine | Knijnenburg B.P.,TU Eindhoven | Willemsen M.C.,TU Eindhoven | Gantner Z.,University of Hildesheim | And 2 more authors.
User Modeling and User-Adapted Interaction | Year: 2012

Research on recommender systems typically focuses on the accuracy of prediction algorithms. Because accuracy only partially constitutes the user experience of a recommender system, this paper proposes a framework that takes a user-centric approach to recommender system evaluation. The framework links objective system aspects to objective user behavior through a series of perceptual and evaluative constructs (called subjective system aspects and experience, respectively). Furthermore, it incorporates the influence of personal and situational characteristics on the user experience. This paper reviews how current literature maps to the framework and identifies several gaps in existing work. Consequently, the framework is validated with four field trials and two controlled experiments and analyzed using Structural Equation Modeling. The results of these studies show that subjective system aspects and experience variables are invaluable in explaining why and how the user experience of recommender systems comes about. In all studies we observe that perceptions of recommendation quality and/or variety are important mediators in predicting the effects of objective system aspects on the three components of user experience: process (e.g. perceived effort, difficulty), system (e.g. perceived system effectiveness) and outcome (e.g. choice satisfaction). Furthermore, we find that these subjective aspects have strong and sometimes interesting behavioral correlates (e.g. reduced browsing indicates higher system effectiveness). They also show several tradeoffs between system aspects and personal and situational characteristics (e.g. the amount of preference feedback users provide is a tradeoff between perceived system usefulness and privacy concerns). These results, as well as the validated framework itself, provide a platform for future research on the user-centric evaluation of recommender systems. © Springer Science+Business Media B.V. 2012.


Aroyo L.,VU University Amsterdam | Nixon L.,STI International | Miller L.,Center House
Digest of Technical Papers - IEEE International Conference on Consumer Electronics | Year: 2011

The NoTube European project1 puts the TV user back in the driver's seat by generating user profiles from data the user creates on the Social Web, and in this way facilitating a personalised TV experience without an intrusive user profiling process. © 2011 IEEE.


Grau O.,Center House
Proceedings of the IEEE International Conference on Computer Vision | Year: 2011

Silhouette-based reconstruction techniques using multiple wide-baseline camera set-ups are popular building blocks to generate models of temporal human action. This contribution reviews visual hull computation algorithms. In particular we focus on the class of volumetric-based algorithms. We identify different processing strategies based on hierarchical, octree-based processing and suggest a new dynamic strategy that can significantly minimise the computational effort. The techniques discussed are evaluated with synthetic and real data sets. The savings demonstrated in computations on the real test sequences are in the order of a factor six on a 512512512 volumetric resolution. © 2011 IEEE.


Borer T.,Center House
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

Low complexity video coding addresses different applications, and is complementary to, video coding for delivery to the end user. Delivery codecs, such as the MPEG/ITU standards, provide very high compression ratios, but require high complexity and high latency. Some applications, by contrast, need the opposite characteristics of low complexity and low latency at low compression ratios. This paper discusses the applications and requirements of low complexity coding and, after discussing the prior art, describes the standard VC-2 (SMPTE 2042) codec, which is a wavelet codec designed for low complexity and ultra-low latency. VC-2 provides a wide range of coding parameters and compression ratios, allowing it to address applications such as texture coding, lossless and high dynamic range coding. In particular this paper describes the results for the low complexity coding parameters of 2 and 3 level Haar and LeGall wavelet kernels, for image regions of 4x4 and 8x8 pixels with both luma/color difference signals and RGB. The paper indicates the quality that may be achieved at various compression ratios and also clearly shows the benefit of coding luma and color components rather than RGB. © 2013 SPIE.


Vinayagamoorthy V.,Center House | Allen P.,R and D North Laboratory | Hammond M.,Center House | Evans M.,R and D North Laboratory
Conference on Human Factors in Computing Systems - Proceedings | Year: 2012

This paper presents a Case Study of the BBC's recent research and development work into the user experience of Internet-Connected Television. User expectations and aspirations around their TV experiences are changing radically as the platform increasingly supplements broadcast network connectivity with IP connectivity. Despite the relative youth of the platform, it is clear that Connected TV and its users support and seek user experiences which are quite distinctive from web browsing on personal computers, or earlier forms of interactive TV platforms. We describe a number of the BBC's recent research projects developing knowledge and tools to support future user experiences for TV, ranging from typography to alternative input interfaces. In each case, we describe the motivation, the development approach and the empirical assessment of impact of the technology and experiences embodied by our prototypes. © 2012 ACM.


Noland K.C.,Center House
IEEE International Symposium on Broadband Multimedia Systems and Broadcasting, BMSB | Year: 2013

In this paper we design the first interlacing filter derived from scientific measurements of the human sensitivity to interlacing artefacts across the vertical-temporal video spectrum. We then test it against a range of existing linear, time-invariant interlacing filters using standard subjective test methodology. We show that although there is some overlapping of the confidence intervals, on average the optimised filter is preferred to the other filters tested. © 2013 IEEE.


Marston D.,Center House
130th Audio Engineering Society Convention 2011 | Year: 2011

Broadcasters are now transmitting 5.1-channel surround sound as part of their HD TV services. However, since much of the audio content in original programme material is 2-channel stereo, broadcasters are required to switch between the two formats. Switching between 2 and 5.1-channel formats can cause problems in decoding the content, including switching artefacts and loudness changes. In general it is preferable to transmit all programme audio in 5.1 surround, and this can be achieved by automatically up-mixing any 2-channel stereo content to 5.1 format prior to broadcasting. This paper reports on tests designed to assess the subjective performance of a selection of upmixers for use in the broadcast chain.


Datta A.K.,Center House | Eapen A.,Center House | Birch H.,Center House | Kurinchi-Selvan A.,Center House | Lockwood G.,Center House
Reproductive BioMedicine Online | Year: 2014

All IVF-ICSI cycles carried out between October 2009 and October 2012 using GnRH agonist (GnRHa) ovulation trigger (n = 62) followed by a single dose of HCG plus progesterone and oestradiol in the luteal phase because of anticipated ovarian hypertsimulation were retrospectively compared with historic control cycles using HCG trigger (n = 29) and standard luteal phase support. Women's mean age, body mass index, anti-Müllerian hormone, FSH, LH, starting and total stimulation dose, number of follicles, oocytes, embryos, fertilization, implantation, polycystic ovary syndrome, ICSI, live birth and ongoing pregnancy rates per embryo transfer were similar (GnRHa 40.7% versus HCG 35.0%). For each started cycle, GnRHa resulted in 11.4% higher (statistically non-significant) live birth and ongoing pregnancy rate (OR 1.73, CI 0.64 to 4.69), with a similar difference for double-embryo transfers (OR 1.62, CI 0.44 to 6.38) and less need for freezing all embryos (9.7% versus 27.6%; P = 0.04). Incidence of mild-to-moderate OHSS was 16.2% with GnRHa trigger and 31.0% with HCG trigger) and no severe OHSS in the former. The addition of single low-dose HCG in the luteal phase after GnRHa trigger for suspected high-responders reduced the incidence of OHSS with good clinical outcomes, compared with HCG trigger. © 2014 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.


Fingerhut C.,Center House
IEEE International Symposium on Broadband Multimedia Systems and Broadcasting, BMSB | Year: 2013

In this paper we introduce the concept for a coding and multiplexing platform for on air broadcasting services based on virtual machines and describe the implementation of a prototype. The system that we present is based on open source software components running on commodity IT hardware. The system allows real-time encoding and transcoding of standard and high definition source material, and the generation and playout of a multi-program transport stream. © 2013 IEEE.


Karpuk D.A.,Aalto University | Moss P.,Center House
2015 IEEE International Conference on Communication Workshop, ICCW 2015 | Year: 2015

In this paper we consider strategies for MIMO interference channels which combine the notions of interference alignment and channel pre-inversion. Users collaborate to form data-sharing groups, enabling them to clear interference within a group, while interference alignment is employed to clear interference between groups. To improve the capacity of our schemes at finite SNR, we propose that the groups of users invert their subchannel using a regularized Tikhonov inverse. We provide a new sleeker derivation of the optimal Tikhonov parameter, and use random matrix theory to provide an explicit formula for the SINR as the size of the system increases, which we believe is a new result. For every possible grouping of K = 4 users each with N = 5 antennas, we completely classify the degrees of freedom available to each user when using such hybrid schemes, and construct explicit interference alignment strategies which maximize the sum DoF. Lastly, we provide simulation results which compute the ergodic capacity of such schemes. © 2015 IEEE.

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