This work is based on a study of contemporary research in the field of vision science, particularly computational models of bottom-up visual attention. The use of computational models of visual attention to detect salient by design regions of interest in images is investigated. The method is then refined to detect objects of interest in broad image databases that are not necessarily salient by design. An interface for image retrieval, organization, and annotation that is compatible with the attention-based retrieval method has also been implemented.
It incorporates the ability to simultaneously execute querying by image content, keyword, and collaborative filtering.
ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP)
The user is central to the design and evaluation of the system. A game was developed to evaluate the entire system, which includes the user, the user interface, and retrieval methods. Since its foundation in , the laboratory's continuous mission has been to produce a valuable research in the fields of multimedia processing and multimedia communications. In particular, research has been focused in the areas of image and video analysis, video coding, and multimedia security.
Distributed media streaming employs multiple senders to cooperatively and simultaneously transmit a media stream to a receiver over the Internet, exploiting both sender diversity and path diversity to improve robustness in the system. This new model for media streaming has raised many challenging and interesting research issues. Previous research have studied many of the application-level issues, such as sender selection and packet scheduling. In this dissertation, we continue on the same line of research, but focuses on the fundamental issues of error control, congestion control, and transport protocol design.
We first study how streaming quality can be improved through distributed retransmission -- retransmission from alternate senders other than the origin of the lost packet. We explore the question of whether distributed retransmission recovers more packet losses than non-distributed retransmission by comparing two naive distributed retransmission schemes with the traditional non-distributed scheme. Through analysis, simulations, and PlanetLab experiments, we found that distributed retransmission leads to fewer lost packets and shorter loss burst length.
To address the practical issue of who to retransmit from, we propose a distributed retransmission scheme that selects a sender with the lowest packet loss rate to retransmit from. Results show that our proposed scheme effectively recovers packet losses and improves playback quality. Second, we investigate the issue of TCP friendliness in distributed media streaming. The traditional notion of TCP friendliness is not suitable for multi-flow applications, such as distributed media streaming, as it is unfair to other single-flow applications.
We therefore introduce the notion of task-level TCP friendliness for distributed media streaming, where we require the total throughput for a set of flows belonging to the same task to be friendly to a TCP flow. To this end, we design a congestion control protocol to regulate the throughput of the flows in an aggregated manner. The regulation is done in two steps.
First, we identify the bottlenecks and the subset of flows on the bottlenecks. Then, we adjust the congestion control parameter such that the total throughput of the subset is no more than that of a TCP flow on each bottleneck. Network simulation using multiple congestion scenarios shows the efficacy of our approach.
ACM Transactions on Multimedia Computing, Communications and Applications
The combine requirements of flexible retransmission and TCP-friendliness above lead to the need for a unreliable, congestion controlled transport protocol. An option is to use DCCP. In this dissertation, however, we proposed an alterative to DCCP which is much simpler to implement. TCP Urel is simple to implement.
ACM SIGMM - the Special Interest Group on Multimedia
Our interest spans distributed systems, operating systems, embedded systems, and programming systems. In particular, we are studying how to provide systems support for multimedia data types video, audio, graphics in the context of applications such as video on demand, tele-conferencing, webcast productions, computer games, video surveillance, running on personal computers and mobile devices.
Resource limitations lead to a number of challenges in all communication systems. This is also the case for video communication over networks based on the Internet Protocol IP , where limited rates are shared among competing, heterogeneous users. Packet losses, delays and connectivity losses will be experienced to a varying degree depending on network loads, physical properties and mobility-related issues. These factors, as well as source coding characteristics, in source the visual quality experienced by the users.
One of the main contributions of the work presented in this thesis is that performance gains can be attained when considering characteristics of source coding, networks and congestion control jointly. Throughout the presented work, optimization of visual quality is at the centre of attention. The thesis is divided into three main parts, with contributions as follows. Part A deals with rate-distortion optimized packet loss protection when communicating video over multiple channels simultaneously.
Source coder characteristics and characteristics of the logically or physically different channels are taken into account in order to yield an optimized packet loss protection of the video. This part presents different optimization algorithms, which are in turncompared in terms of both performance and complexity. Part B uses the algorithms of part A in the context of congestion control.
Specifically, the potential problem of misbehaving receivers is considered. In current systems, there exists an incentive for non-conformant congestion control by video receivers in that an improved video quality can be achieved through obtaining an unfairly high bandwidth share. Since this has unfortunate effects on the connection characteristics of competing users, it poses a potential problem for mass deployment of UDP User Datagram Protocol based video services.
Specifically, the framework attempts to reverse the situation and provide an incentive in terms of visual quality for adhering to congestion control guidelines for fair bandwidth sharing.
Download Acm Transactions On Multimedia Computing Communications And Applications May 2000
The framework is developed for both unicast and multicast cases, and is presented along with optimization algorithms and simulation results. Part C considers real-time video delivery in mobile ad-hoc networks. As this type of networks exhibit rather harsh characteristics in terms of throughput, packet losses and mobility-induced route losses, new solutions are required. The approach taken in this work is based on a distributed rate-distortion optimization framework, where multiple sources are used concurrently.
The system uses scalable video coding and rateless channel codes in order to allow for uncoordinated sources and distributed optimization. The complete system is implemented in a network simulator, and is shown to exhibit considerable performance gains compared to previous proposed systems. The main focus of the research being conducted at the Centre is, as the name implies, quantifiable aspects of Quality of Service QoS.
Here the term QoS should be understood as having a perhaps unusually broad scope. Indeed, much of the research conducted at the Centre is based on the insight that QoS must involve as diverse factors as user experience, perception, expectation, dependability and security - in addition to the more classical packet forwarding statistics.
In terms of expertise, the Centre is comprised of experts within the fields of information security, dependability, networking, performance, and audiovisual signal processing. While these topics traditionally are treated separately, research at the Centre is inherently cross-disciplinary. Certainly, when QoS is defined as above, the integration of these relatively diverse fields of competence is a necessity. An important part in ongoing research within the assessment of QoS is case studies, measurements and tests.
Whereas the mentioned lab facilities are of prime importance in the assessment of QoS, basic research is being conducted along more theoretical strands as well.
Within the development of QoS, mechanisms for dynamic networks, resource allocation, dependability and security are major research topics. Considering security, important subtasks include the modelling of human behavior, risk assessment and cryptographic services. Research into dependability primarily concentrates on the development of technologies that allow for service differentiation, as well as accompanying methods of tailoring the QoS parameters of each service to its requirements. Work within resource allocation considers technologies for multipath environments, including monitoring, estimation and path selection.
An important prerequisite for being able to quantify and provide QoS is found in the processing done at endpoints and in gateways. Within network media handling, the provisioning of functionality within media representation is of prime interest. Research is being conducted within media compression and representation, transcoding and transmoding, loss resilience and monitoring of perceptual quality.
Interactivity is an important keyword here, both between user and system and between the different technical components in the media delivery chain. It offers an Intel's OpenCV-like programming interface for easily porting existing OpenCV applications, while taking advantage of the high level of parallelism and computing power available from recent graphics processing units GPUs.
The FAU Salient image database consist of images organized into 14 categories. Each image is designed to have one or more salient objects in it. The photos were taken in a variety of locations both indoors and outdoors around the Boca Raton campus of Florida Atlantic University. Examples of salient object categories include stop signs, warning signs, tennis balls, basketballs.
NOSSDAV will continue the workshop's long tradition of focusing on emerging topics, controvesial ideas, and future research directions in the area of multimedia systems research. The workshop will be held in a setting that stimulates lively discussions among the senior and junior participants. Further, public availability of source code and data sets is highly encouraged. The aim of IMMERSCOM is to promote multi- and cross-disciplinary research on capturing, processing, analyzing, coding, communication and rendering of rich audio-visual content in order to enable remote immersive experiences of people, objects and environments.
The body of technologies that enable such immersive experiences is collectively referred to as Immersive Telecommunications Technologies. Applications of these technologies are varied, and include tele-presence, industrial automation, health care, education, and entertainment. Many of these are beginning to be viewed as green technologies. ACM HotMobile , the Tenth Workshop on Mobile Computing Systems and Applications continues the series of highly selective, interactive workshops focused on mobile applications, systems, and environments, as well as their underlying state-of-the-art technologies.
HotMobile's small workshop format makes it ideal for presenting and discussing new directions or controversial approaches. The International MultiMedia Modeling MMM Conference is a leading international conference for researchers and industry practitioners to share their new ideas, original research results and practical development experiences from all MMM related areas. The MMM Conference is inviting enterprises from different sectors to present their latest products and demos in the areas of multimedia and signal processing.
The goal of this Special Issue is to inspire and gather new, refreshing ideas in the field of content-based multimedia information indexing, search and retrieval that would make the solutions in the field mature enough to get adopted in practical systems and realistic application scenarios.
Related ACM Transactions on Multimedia Computing, Communications and Applications (May)
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