Compress-then-analyze vs. analyze-then-compress: Two paradigms for image analysis in visual sensor networks

We compare two paradigms for image analysis in vi- sual sensor networks (VSN). In the compress-then-analyze (CTA) paradigm, images acquired from camera nodes are compressed and sent to a central controller for further analysis. Conversely, in the analyze-then-compress (ATC) approach, camera nodes perform visual feature extraction and transmit a compressed version of these features to a central controller. We focus on state-of-the-art binary features which are particularly suitable for resource-constrained VSNs, and we show that the ”winning” paradigm depends primarily on the network conditions. Indeed, while the ATC approach might be the only possible way to perform analysis at low available bitrates, the CTA approach reaches the best results when the available bandwidth enables the transmission of high-quality images

Adjusting WiMAX for a Dedicated Surveillance Network

WiMAX (Worldwide Interoperability for Microwave Access) devices have been used widely in the market. WiMAX-based video surveillance products have also been available. The acceptance of WiMAX in the market, as well as the availability of WiMAX products, contributes to the possibility of implementing it for dedicated video surveillance application. However, since WiMAX is designed to accommodate various applications with different quality of service (QoS) requirements, WiMAX–based dedicated surveillance network may not achieve optimum performance, as all SSs generate the same QoS requirements. The scheduler cannot implement traffic type priority; therefore, service classification does not work as expected. This paper proposes WiMAX adjustment to transform a multi-purpose WiMAX network into a network dedicated to video surveillance. NS-2 simulations show that the proposed adjustment is able to deliver low delay and high quality video surveillance.DOI:http://dx.doi.org/10.11591/ijece.v3i4.318

A Rate-Distortion Optimized Coding Method for Region of Interest in Scalable Video Coding

The support for region of interest (ROI) browsing, which allows dropping background part of video bitstreams, is a desirable feature for video applications. With the help of the slice group technique provided by H.264/SVC, rectangular ROI areas can be encoded into separate ROI slices. Additionally, by imposing certain constraints on motion estimation, ROI part of the bitstream can be decoded without background slices of the same layer. However, due to the additional spatial and temporal constraints applied to the encoder, overall coding efficiency would be significantly decreased. In this paper, a rate-distortion optimized (RDO) encoding scheme is proposed to improve the coding efficiency of ROI slices. When background slices are discarded, the proposed method uses base layer information to generate the prediction signal of the enhancement layer. Thus, the temporal constraints can be loosened during the encoding process. To do it in this way, the possible mismatch between generated reference frames and original ones is also considered during rate-distortion optimization so that a reasonable trade-off between coding efficiency and decoding drift can be made. Besides, a new Lagrange multiplier derivation method is developed for further coding performance improvement. Experimental results demonstrate that the proposed method achieves significant bitrate saving compared to existing methods

SegUA: um sistema móvel para apoio à rotina de vigilância

Mestrado em Engenharia de Computadores e TelemáticaOs serviços de vigilância e segurança têm a obrigação de documentar um conjunto de incidentes observados no decorrer das rondas, e esta documentação é, sobretudo, produzida em papel, o que dificulta a sua consolidação e processamento subsequentes. Para além disso, a vigilância é uma actividade inerentemente móvel, havendo, assim, espaço para estudar a aplicação de novos dispositivos computacionais no acompanhamento do profissional para facilitar a aquisição de dados, e organização e comunicação destes. Partindo da realidade do campus da Universidade de Aveiro e procedimentos associados, este trabalho procurou introduzir melhorias processuais nas actividades de vigilância e sua gestão. No novo processo de trabalho, os vigilantes utilizam um módulo móvel para navegar nos mapas de uma organização e registar, no ponto de observação, os incidentes, podendo extender o relato com elementos multimédia. Durante a execução das rondas, é possível, centralmente, observar o posicionamento dos Vigilantes e obter, de forma quase imediata, os resultados das rondas. Os incidentes são imediatamente encaminhados para os pontos de serviço da instituição, que têm a responsabilidade de tomar acções subsequentes, eliminando a necessidade de execução de um processo moroso de triagem actual. O sistema desenvolvido incorpora vistas orientadas por mapas, e integra-se com o Sistema de Informação Geográfica central para obter mapas e informações das entidades espaciais. ABSTRACT: Surveillance personnel need to report a wide range of incidents during their watches, which are mostly recorded on paper. This seriously hinders processing and archiving of such incidents for future analysis. The mobile nature of surveillance tasks presents an opportunity to study the introduction of mobile devices to assist in data acquisition, communication and organization, thus improving the quality of the data produced by the surveillance service. Using the Universidade de Aveiro and its associated surveillance procedures as a source of requirements, this project aims at improving the existing workflow and providing an incident handling system, thus enabling easy access to data. In the proposed workflow process, watchmen use a mobile device to report incidents, instead of paper. This mobile device allows the user to view maps and previously reported incidents, and to extend the incident facts with multimedia data. While watchmen carry out their watches, it is possible to centrally supervise their progress and current location in near real-time. In addition, reported incidents are immediately routed to their designated service points, where these incidents will be handled. The designed system supports map visualization, and integrates with the organization’s Geographic Information System to obtain spatial data and maps