Browsing by Author "Correia, Pedro"
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- Multiple Description Coding for Multipath Video StreamingPublication . Correia, Pedro; Assunção, Pedro; Silva, VítorThis Chapter addresses robust video coding and adaptation of compressed streams in multipath communications environments, using Multiple Description Coding (MDC). A review of Multiple Description (MD) video coding is presented, covering different video coding approaches. Different path diversity topologies and MDC networking applications are described, including MD video adaptation schemes to operate at network edges, for robust video streaming. A multi-loop architecture for Advanced Video Coding (AVC) to prevent drift distortion accumulation is also described. A simulation study of MDC for AVC is presented to evaluate the coding efficiency, the effects of distortion propagation and streaming performance in lossy networks. These research findings extend the current state-of-the-art MDC methods by developing new networking capabilities in different application scenarios maintaining coding efficiency, and increasing error robustness, when subject to transmission losses.
- Multiple Description of Coded Video for Path Diversity Streaming AdaptationPublication . Correia, Pedro; Assunção, Pedro A.; Silva, VitorThis paper extends the current concept ofmultiple description coding (MDC) to the compressed domain, by proposing efficient splitting of standard single description coded (SDC) video into a multi-stream representation. A novel multiple description video splitting (MDVS) scheme is proposed to operate at network edges, for increased robustness in path diversity video streaming across heterogeneous communications chains. It is shown that poor performance of existing methods is mainly due to distortion accumulation, i.e., drift, when decoding is carried out with missing descriptions. The proposed scheme is able to effectively control drift distortion in both intra and inter predictive coding, evenwhen only one description reaches the decoder. This is achieved by generating a controlled amount of relevant side information to compensate for drift accumulation, whenever any description is lost in its path. The simulation results show that any individual description can be decoded on its own without producing drift, achieving significant quality improvement at reduced redundancy cost. The overall performance evaluation, carried out by simulating video streaming over lossy networks with path diversity, also demonstrates that MDVS enables higher quality video in such heterogeneous networking environments, for a wide range of packet loss rates.
- Multiple description video transcoding with temporal drift controlPublication . Correia, Pedro; Assunção, Pedro; Silva, VitorThis paper proposes a multiple description (MD) transcoding scheme capable of preventing drift by distortion accumulation in temporally predicted motion compensated slices. Drift compensation is achieved by generating a controlled amount of side information to be used for decoding whenever a description fails to reach the end user terminal. The side information is generated by re-encoding the transcoding residue with an independent quantisation parameter which also controls redundancy. A simplified architecture is devised to reduce transcoding complexity in regard to the number of processing functions and buffer requirements. The experimental results show that temporally predicted frames do not suffer from drift and their quality is significantly improved at reduced redundancy cost in comparison with a classic MD transcoding scheme.
- Optimal priority MDC video streaming for networks with path diversityPublication . Correia, Pedro; Ferreira, Lino; Assunção, Pedro; Cruz, Luis; Silva, VitorThis paper proposes a robust video streaming scheme for priority networks with path diversity, based on a combined approach of multiple description coding (MDC) with optimal picture classification into two priorities. A binary classification algorithm is proposed to define high (HP) and low (LP) priority network abstraction layer units (NALU), which in turn define the packet priorities. An optimisation algorithm is used to find HP pictures, based on dynamic programming and relying on minimisation of the packet loss concealment distortion. The paper shows that the proposed algorithm is able to effectively improve the decoded video without increasing the MDC stream redundancy. The overall performance evaluation, carried out by simulating MDC video streaming over lossy networks with path diversity, demonstrates that the proposed algorithm yields higher video quality for a wide range of packet loss rates (PLR). Comparing with no-priority MDC video streaming schemes, the simulation results show that the proposed algorithm can improve the average PSNR results in 0.7-3.2dB for packet loss rates between 3% and 15%.
- Recognition of human activity based on sparse data collected from smartphone sensorsPublication . Gordalina, Goncalo; Correia, Pedro; Pires, Gabriel; Oliveira, Luis; Figueiredo, Maria João; Martinho, Ricardo; Rijo, Rui, Rui Pedro Charters Lopes; Assunção, Pedro; Seco, Maria Alexandra Abreu Henriques; Fonseca-Pinto, RuiThis paper proposes a method of human activity monitoring based on the regular use of sparse acceleration data and GPS positioning collected during smartphone daily utilization. The application addresses, in particular, the elderly population with regular activity patterns associated with daily routines. The approach is based on the clustering of acceleration and GPS data to characterize the user’s pattern activity and localization for a given period. The current activity pattern is compared to the one obtained by the learned data patterns, generating alarms of abnormal activity and unusual location. The obtained results allow to consider that the usage of the proposed method in real environments can be beneficial for activity monitoring without using complex sensor networks.
- 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.