Side information creation for efficient Wyner-Ziv video coding: Classifying and reviewing

Video coding technologies have played a major role in the explosion of large market digital video applications and services. In this context, the very popular MPEG-x and H-26x video coding standards adopted a predictive coding paradigm, where complex encoders exploit the data redundancy and irrelevancy to 'control' much simpler decoders. This codec paradigm fits well applications and services such as digital television and video storage where the decoder complexity is critical, but does not match well the requirements of emerging applications such as visual sensor networks where the encoder complexity is more critical. The Slepian Wolf and Wyner-Ziv theorems brought the possibility to develop the so-called Wyner-Ziv video codecs, following a different coding paradigm where it is the task of the decoder, and not anymore of the encoder, to (fully or partly) exploit the video redundancy. Theoretically, Wyner-Ziv video coding does not incur in any compression performance penalty regarding the more traditional predictive coding paradigm (at least for certain conditions). In the context of Wyner-Ziv video codecs, the so-called side information, which is a decoder estimate of the original frame to code, plays a critical role in the overall compression performance. For this reason, much research effort has been invested in the past decade to develop increasingly more efficient side information creation methods. This paper has the main objective to review and evaluate the available side information methods after proposing a classification taxonomy to guide this review, allowing to achieve more solid conclusions and better identify the next relevant research challenges. After classifying the side information creation methods into four classes, notably guess, try, hint and learn, the review of the most important techniques in each class and the evaluation of some of them leads to the important conclusion that the side information creation methods provide better rate-distortion (RD) performance depending on the amount of temporal correlation in each video sequence. It became also clear that the best available Wyner-Ziv video coding solutions are almost systematically based on the learn approach. The best solutions are already able to systematically outperform the H.264/AVC Intra, and also the H.264/AVC zero-motion standard solutions for specific types of content. (C) 2013 Elsevier B.V. All rights reserved.

A denoising approach for iterative side information creation in distributed video coding

In distributed video coding, motion estimation is typically performed at the decoder to generate the side information, increasing the decoder complexity while providing low complexity encoding in comparison with predictive video coding. Motion estimation can be performed once to create the side information or several times to refine the side information quality along the decoding process. In this paper, motion estimation is performed at the decoder side to generate multiple side information hypotheses which are adaptively and dynamically combined, whenever additional decoded information is available. The proposed iterative side information creation algorithm is inspired in video denoising filters and requires some statistics of the virtual channel between each side information hypothesis and the original data. With the proposed denoising algorithm for side information creation, a RD performance gain up to 1.2 dB is obtained for the same bitrate.

Design and performance of a novel low-density parity-check code for distributed video coding

Low-density parity-check (LDPC) codes are nowadays one of the hottest topics in coding theory, notably due to their advantages in terms of bit error rate performance and low complexity. In order to exploit the potential of the Wyner-Ziv coding paradigm, practical distributed video coding (DVC) schemes should use powerful error correcting codes with near-capacity performance. In this paper, new ways to design LDPC codes for the DVC paradigm are proposed and studied. The new LDPC solutions rely on merging parity-check nodes, which corresponds to reduce the number of rows in the parity-check matrix. This allows to change gracefully the compression ratio of the source (DCT coefficient bitplane) according to the correlation between the original and the side information. The proposed LDPC codes reach a good performance for a wide range of source correlations and achieve a better RD performance when compared to the popular turbo codes.

Determinantes do comportamento de compra verde em Portugal

Apesar do avanço tecnológico, uma grande maioria dos consumidores contínua a utilizar excessivamente os recursos naturais não renováveis do planeta, resultado de um consumo exagerado e inconsciente. Atualmente, os consumidores possuem mais informação sobre as questões ambientais e, alguns, refletem esse conhecimento nas suas decisões de compra. Com a crescente preocupação e atenção, quer por parte da população, quer por parte das organizações governamentais e empresas, para com o meio ambiente e a sua preservação, as questões ecológicas têm cada vez mais importância nas estratégias das empresas. Na presente investigação é analisado o comportamento de compra verde com a utilização das variáveis sociodemográficas (género, idade, número de filhos, rendimento e habilitações literárias) e psicográficas (conhecimento ecológico, coletivismo e individualismo), indo ao encontro do objetivo geral de investigação que visa compreender qual a relevância destas variáveis face ao comportamento de compra verde. O estudo desenvolvido é operacionalizado por via de um método quantitativo, através da utilização de um inquérito por questionário com base nas escalas do conhecimento ecológico (Laroche et al., 2001), coletivismo e individualismo (Singelis et al., 1995 e Triandis & Gelfand (1998)) e do comportamento de compra verde (Jain & Kaur, 2004). O questionário foi aplicado a uma amostra de conveniência (N=350), dando origem a uma análise quantitativa face aos dados obtidos. Os resultados indicam que as variáveis psicográficas exercem maior influência no comportamento de compra verde do que as variáveis sociodemográficas. As variáveis psicográficas, conhecimento ecológico e coletivismo, têm uma grande influência no comportamento de compra verde, ao contrário do individualismo. Por seu lado, do conjunto das variáveis sociodemográficas, apenas a idade e o número de filhos influenciam significativamente o comportamento de compra verde.

Racionalidade de emissão de obrigações subordinadas: Estudo de caso do Banco Comercial do Atlântico (BCA) Cabo Verde

Mestrado em Contabilidade e Gestão de Instituições Financeiras

Avaliação da aptidão física funcional de idosos hipertensos da Cidade da Praia, Cabo Verde: estudo piloto

Introdução – A avaliação da aptidão física permite a identificação de níveis de incapacidade e risco de perda funcional, pelo que é extremamente útil na estruturação de programas de atividade física específicos, que constituem a primeira intervenção no que toca à intervenção não-farmacológica na Hipertensão Arterial Sistémica (HAS). Objetivo – Avaliar a aptidão física funcional e os níveis de atividade física de idosos hipertensos da Cidade da Praia – Cabo Verde. Metodologia – A flexibilidade, força e resistência muscular, resistência aeróbia e composição corporal foram avaliadas através da bateria de Fullerton e dinamometria isométrica manual. O nível de atividade física foi avaliado pelo questionário Seven Day Physical Activity Recall (7D-PAR). Resultados – Participaram 75 idosos, com idades compreendidas entre os 60 e os 99 anos, 68% dos quais eram mulheres, com índice de massa corporal (IMC) de 25,2±5,4, com diagnóstico clínico de HAS. O tempo despendido em atividades de intensidade moderada encontrava-se dentro dos valores recomendados, embora a atividade intensa se encontrasse muito abaixo do recomendado e não efetuassem qualquer exercício de força e flexibilidade. A resistência aeróbia expressa pelo Teste 6 Minutos de Marcha (T6MM) apresentou valores médios baixos (293,5±112,2m), bem como a flexibilidade e a força de preensão. Esta associação é um indicador de baixa capacidade funcional. Conclusão – Os baixos níveis de aptidão física apresentados, associados a baixos níveis de atividade física indiciam baixa capacidade funcional e justificam a necessidade urgente da inserção de programas de atividade física nesta população.

Joining the online video conversation? Discourse and practices of European political institutions and politicians on YouTube

To mimic the online practices of citizens has been declared an imperative to improve communication and extend participation. This paper seeks to contribute to the understanding of how European discourses praising online video as a communication tool have been translated into actual practices by politicians, governments and organisations. By contrasting official documents with YouTube activity, it is argued that new opportunities for European political communication are far from being fully embraced, much akin to the early years of websites. The main choice has been to use YouTube channels fundamentally for distribution and archiving, thus neglecting its social media features. The disabling of comments by many heads of state and prime ministers - and, in 2010, the European Commission - indicates such an attitude. The few attempts made to foster citizen engagement, in particular during elections, have had limited success, given low participation numbers and lack of argument exchange.

Via verde coronária e enfarte agudo do miocárdio: tempo médio entre a admissão no serviço de urgência central e a reperfusão por angioplastia primária

Mestrado em Tecnologia de Diagnóstico e Intervenção Cardiovascular - Ramo de especialização: Intervenção Cardiovascular

O empreendedorismo como uma alternativa profissional atual : estudo comparativo entre Cabo Verde e Portugal

Mestrado em Gestão e Empreendedorismo

Correlation modeling for a distributed scalable video codec based on the HEVC standard

The growing heterogeneity of networks, devices and consumption conditions asks for flexible and adaptive video coding solutions. The compression power of the HEVC standard and the benefits of the distributed video coding paradigm allow designing novel scalable coding solutions with improved error robustness and low encoding complexity while still achieving competitive compression efficiency. In this context, this paper proposes a novel scalable video coding scheme using a HEVC Intra compliant base layer and a distributed coding approach in the enhancement layers (EL). This design inherits the HEVC compression efficiency while providing low encoding complexity at the enhancement layers. The temporal correlation is exploited at the decoder to create the EL side information (SI) residue, an estimation of the original residue. The EL encoder sends only the data that cannot be inferred at the decoder, thus exploiting the correlation between the original and SI residues; however, this correlation must be characterized with an accurate correlation model to obtain coding efficiency improvements. Therefore, this paper proposes a correlation modeling solution to be used at both encoder and decoder, without requiring a feedback channel. Experiments results confirm that the proposed scalable coding scheme has lower encoding complexity and provides BD-Rate savings up to 3.43% in comparison with the HEVC Intra scalable extension under development. © 2014 IEEE.

H.264/AVC backward compatible Bit-Depth scalable video coding

As high dynamic range video is gaining popularity, video coding solutions able to efficiently provide both low and high dynamic range video, notably with a single bitstream, are increasingly important. While simulcasting can provide both dynamic range videos at the cost of some compression efficiency penalty, bit-depth scalable video coding can provide a better trade-off between compression efficiency, adaptation flexibility and computational complexity. Considering the widespread use of H.264/AVC video, this paper proposes a H.264/AVC backward compatible bit-depth scalable video coding solution offering a low dynamic range base layer and two high dynamic range enhancement layers with different qualities, at low complexity. Experimental results show that the proposed solution has an acceptable rate-distortion performance penalty regarding the HDR H.264/AVC single-layer coding solution.

Perceptually driven video error protection using a distributed source coding approach

In video communication systems, the video signals are typically compressed and sent to the decoder through an error-prone transmission channel that may corrupt the compressed signal, causing the degradation of the final decoded video quality. In this context, it is possible to enhance the error resilience of typical predictive video coding schemes using as inspiration principles and tools from an alternative video coding approach, the so-called Distributed Video Coding (DVC), based on the Distributed Source Coding (DSC) theory. Further improvements in the decoded video quality after error-prone transmission may also be obtained by considering the perceptual relevance of the video content, as distortions occurring in different regions of a picture have a different impact on the user's final experience. In this context, this paper proposes a Perceptually Driven Error Protection (PDEP) video coding solution that enhances the error resilience of a state-of-the-art H.264/AVC predictive video codec using DSC principles and perceptual considerations. To increase the H.264/AVC error resilience performance, the main technical novelties brought by the proposed video coding solution are: (i) design of an improved compressed domain perceptual classification mechanism; (ii) design of an improved transcoding tool for the DSC-based protection mechanism; and (iii) integration of a perceptual classification mechanism in an H.264/AVC compliant codec with a DSC-based error protection mechanism. The performance results obtained show that the proposed PDEP video codec provides a better performing alternative to traditional error protection video coding schemes, notably Forward Error Correction (FEC)-based schemes. (C) 2013 Elsevier B.V. All rights reserved.

Intraplate seismicity across the Cape Verde swell: a contribution from a temporary seismic network

We present an analysis and characterization of the regional seismicity recorded by a temporary broadband seismic network deployed in the Cape Verde archipelago between November 2007 and September 2008. The detection of earthquakes was based on spectrograms, allowing the discrimination from low-frequency volcanic signals, resulting in 358 events of which 265 were located, the magnitudes usually being smaller than 3. For the location, a new 1-D P-velocity model was derived for the region showing a crust consistent with an oceanic crustal structure. The seismicity is located mostly offshore the westernmost and geologically youngest areas of the archipelago, near the islands of Santo Antao and Sao Vicente in the NW and Brava and Fogo in the SW. The SW cluster has a lower occurrence rate and corresponds to seismicity concentrated mainly along an alignment between Brava and the Cadamosto seamount presenting normal faulting mechanisms. The existence of the NW cluster, located offshore SW of Santo Antao, was so far unknown and concentrates around a recently recognized submarine cone field; this cluster presents focal depths extending from the crust to the upper mantle and suggests volcanic unrest No evident temporal behaviour could be perceived, although the events tend to occur in bursts of activity lasting a few days. In this recording period, no significant activity was detected at Fogo volcano, the most active volcanic edifice in Cape Verde. The seismicity characteristics point mainly to a volcanic origin. The correlation of the recorded seismicity with active volcanic structures agrees with the tendency for a westward migration of volcanic activity in the archipelago as indicated by the geologic record. (C) 2014 Elsevier B.V. All rights reserved.

Constrains on the structure of Maio Island (Cape Verde) by a three-dimensional gravity model: Imaging partially exhumed magma chambers

We propose a 3-D gravity model for the volcanic structure of the island of Maio (Cape Verde archipelago) with the objective of solving some open questions concerning the geometry and depth of the intrusive Central Igneous Complex. A gravity survey was made covering almost the entire surface of the island. The gravity data was inverted through a non-linear 3-D approach which provided a model constructed in a random growth process. The residual Bouguer gravity field shows a single positive anomaly presenting an elliptic shape with a NWSE trending long axis. This Bouguer gravity anomaly is slightly off-centred with the island but its outline is concordant with the surface exposure of the Central Igneous Complex. The gravimetric modelling shows a high-density volume whose centre of mass is about 4500 m deep. With increasing depth, and despite the restricted gravimetric resolution, the horizontal sections of the model suggest the presence of two distinct bodies, whose relative position accounts for the elongated shape of the high positive Bouguer gravity anomaly. These bodies are interpreted as magma chambers whose coeval volcanic counterparts are no longer preserved. The orientation defined by the two bodies is similar to that of other structures known in the southern group of the Cape Verde islands, thus suggesting a possible structural control constraining the location of the plutonic intrusions.

Projecto de execução do centro comercial Mercado da Praia: Cidade da Praia: Cabo Verde

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil