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- Tracking human routines towards adaptive monitoring: the MOVIDA.domus platformPublication . Gordalina, Gonçalo; Figueiredo, João; Martinho, Ricardo; Rijo, Rui; Correia, Pedro; Assunção, Pedro A. Amado; Seco, Alexandra; Pires, Gabriel; Oliveira, Luís; Fonseca-Pinto, RuiAccording to estimates by the World Health Organization, the average life expectancy will continue to rise. This indicator, being a measure of success in terms of healthcare, is not synonymous with quality of life and will increase healthcare costs. Associated with this problem are also the changes in terms of the organization of society, which has not been able to solve these constraints of functional limitations, dementia, social isolation, and loneliness. This paper presents the concept of adaptive surveillance based on mobile technology and artificial intelligence, presented in the context of a global physical activity monitoring program (MOVIDA), in his domus dimension designed to the elderly people with some functional limitation or dementia. The proposed solution for an adaptive surveillance is thus to conduct direct supervision programs, to enroll persons who live alone or in nursing homes who need supervision without limiting their individual autonomy. The preliminary results show that it is possible to use the data obtained from a mobile smartphone to identify routines and use this information to identify daily patterns. Changes to these routine patterns can be used to generate alarms for caregivers.
- User-Experience with Haptic Feedback Technologies and Text Input in Interactive Multimedia DevicesPublication . Silva, Bruno; Costelha, Hugo; C. Bento, Luis; Barata, Marcio; Assuncao, PedroRemote control devices are commonly used for interaction with multimedia equipment and applications (e.g., smart TVs, gaming, etc.). To improve conventional keypad-based technologies, haptic feedback and user input capabilities are being developed for enhancing the UX and providing advanced functionalities in remote control devices. Although the sensation provided by haptic feedback is similar to mechanical push buttons, the former offers much greater flexibility, due to the possibility of dynamically choosing different mechanical effects and associating different functions to each of them. However, selecting the best haptic feedback effects among the wide variety that is currently enabled by recent technologies, remains a challenge for design engineers aiming to optimise the UX. Rich interaction further requires text input capability, which greatly influences the UX. This work is a contribution towards UX evaluation of remote control devices with haptic feedback and text input. A user evaluation study of a wide variety of haptic feedback effects and text input methods is presented, considering different technologies and different number of actuators on a device. The user preferences, given by subjective evaluation scores, demonstrate that haptic feedback has undoubtedly a positive impact on the UX. Moreover, it is also shown that different levels of UX are obtained, according to the technological characteristics of the haptic actuators and how many of them are used on the device.
- Retargeting UHD 4k Video for SmartphonesPublication . Kumar, Rohit; Navarro, António; Assunção, Pedro; Ferreira, LinoThis paper evaluates a new video-retargeting algorithm jointly with two others previously published in the literature. Four Ultra High Definition (UHD) 4K resolution video sequences were used for subjective assessment. Subjective testing results show that the proposed algorithm yields the best performance when UHD 4K video is retargeted to 1920 × 1080 resolution. The main application of these retargeting algorithms is to increase the quality of experience (QoE) provided to consumers when playing UHD videos on small screen devices like smartphones.
- Video transcoding from H.264/AVC to MPEG-2 with reduced computational complexityPublication . Moiron, Sandro; Faria, Sergio; Navarro, António; Silva, Vitor; Assunção, PedroThis paper addresses video transcoding from H.264/AVC into MPEG-2 with reduced complexity and high rate-distortion efficiency. While the overall concept is based on a cascaded decoder-encoder, the novel adaptation methods developed in this work have the advantage of providing very good performance in H.264/AVC to MPEG-2 transcoding. The proposed approach exploits the similarities between the coding tools used in both standards, with the objective of obtaining a computationally efficient transcoder without penalising the signal quality. Fast and efficient methods are devised for conversion of macroblock coding modes and translation of motion information in order to compute the MPEG-2 coding format with a reduced number of operations, by reusing the corresponding data embedded in the incoming H.264/AVC coded stream. In comparison with a cascaded decoder-encoder, the fast transcoder achieves computational complexity savings up to 60% with slightly better peak signal-to-noise ratio (PSNR) at the same bitrate.
- Pareto-Based Method for High Efficiency Video Coding With Limited Encoding TimePublication . Correa, Guilherme; Assunção, Pedro; Agostini, Luciano Volcan; Cruz, Luis A. da SilvaSeveral different methods have been investigated in recent years, aiming at computational complexity reduction and scaling of High Efficiency Video Coding (HEVC) software implementations. However, maintaining the encoding time per frame or group of pictures (GOPs) below an adjustable upper bound is still an open research issue. A solution for this problem is devised in this paper based on a set of Pareto-efficient encoding configurations, identified through rate-distortion-complexity analysis. The proposed method combines a medium-granularity encoding time control with a fine-granularity encoding time control to accurately limit the HEVC encoding time below a predefined target for each GOP. It is shown that the encoding time can be kept below a desired target for a wide range of encoding time reductions, e.g., up to 90% in comparison with the original encoder. The results also show that compression efficiency loss (Bjøntegaard delta-rate) varies from negligible (0.16%) to moderate (9.83%) in the extreme case of 90% computational complexity reduction.
- Accuracy versus complexity of MARG-based filters for remote control pointing devicesPublication . Rasteiro, Miguel ; Costelha, Hugo; Conde Bento, Luis; Assunção, PedroAlthough most current pointing devices rely on relative rotation increments, absolute orientation allows for a more intuitive interaction. However, this is difficult to implement in low-energy consumption devices since accurate fusion filters are computationally intensive. This work presents a comparative study of low-complexity filters and state-of-the-art orientation tracking systems, enabling to access complexity versus portability. A relevant set of different MARG units currently available on the market were studied under systematic tests and human subjective user analysis. Experimental results show that it is possible to obtain similar accuracy using low-complexity filters to the ones observed with state-of-the-art orientation tracking systems. © 2015 IEEE.
- Reconstruction of lost depth data in multiview video-plus-depth communications using geometric transformsPublication . Marcelino, Sylvain; Soares, Salviano; Faria, Sergio; Assunção, PedroThis paper addresses depth data recovery in multiview video-plus-depth communications affected by transmission errors and/or packet loss. The novel aspects of the proposed method rely on the use of geometric transforms and warping vectors, capable of capturing complex motion and view-dependent deformations, which are not efficiently handled by traditional motion and/or disparity compensation methods. By exploiting the geometric nature of depth information, a region matching approach combined with depth contour reconstruction is devised to achieve accurate interpolation of arbitrary shapes within lost regions of depth maps. The simulation results show that, for different packet loss rates, up to 20%, the depth maps recovered by the proposed method produce virtual views with better quality than existing methods based on motion information and spatial interpolation. An average PSNR gain of 1.48 dB is obtained in virtual views synthesised from depth maps using the proposed method.
- Towards key-frame extraction methods for 3D video: a reviewPublication . Ferreira, Lino; Luis A. da Silva Cruz; Assunção, PedroThe increasing rate of creation and use of 3D video content leads to a pressing need for methods capable of lowering the cost of 3D video searching, browsing and indexing operations, with improved content selection performance. Video summarisation methods specifically tailored for 3D video content fulfil these requirements. This paper presents a review of the state-of-the-art of a crucial component of 3D video summarisation algorithms: the key-frame extraction methods. The methods reviewed cover 3D video key-frame extraction as well as shot boundary detection methods specific for use in 3D video. The performance metrics used to evaluate the key-frame extraction methods and the summaries derived from those key-frames are presented and discussed. The applications of these methods are also presented and discussed, followed by an exposition about current research challenges on 3D video summarisation methods.
- Video summary generation and coding using temporal scalabilityPublication . Ferreira, Lino; Cruz, Luís; Assunção, Pedro A. AmadoIn this paper two algorithms for video summary generation and coding are proposed. Two distortion metrics used in the video summary generation algorithm are compared and an algorithm with reduced computational complexity is presented. The paper also proposes two frame structures in the temporal domain suitable for coding using temporal scalability of the H.264/SVC.
- Subjective Evaluation of Haptic Feedback Technologies for Interactive MultimediaPublication . Silva, Bruno; Costelha, Hugo; Bento, Luís Conde; Barata, Márcio; Assunção, Pedro A. AmadoCurrent trends in the development of remote control devices for user interaction with multimedia equipment and applications are increasingly advancing the traditional keypad-based technologies, in order to improve the functionality of remote control devices and also to enhance the user experience. Haptic feedback allows the user to have a similar sensation to that provided by conventional buttons, with the advantage of a much greater flexibility, including dynamic choice of mechanical effects capable of discriminating between different functions. However, selection of haptic feedback effects that are capable of enhancing the user experience remains a great challenge for engineers and product designers. This work is a contribution towards this goal by presenting a usability study of two technologies (eccentric rotating mass and linear resonant actuator) capable of providing different haptic feedback effects in remote control devices. A subjective evaluation study was carried out to obtain subjective scores for a significant number of haptic feedback effects. The number of preferred actuators of each type and whether haptic feedback is suitable in remote control devices for interactive multimedia, were also evaluated. The results of this study show that most users prefer an interface with haptic feedback and different scores were obtained for different haptic feedback effects, according to the characteristics and number of the actuators.