Data compression for full motion video transmission

Clearly transmission of visual information will be a major, if not dominant, factor in determining the requirements for, and assessing the performance of the Space Exploration Initiative (SEI) communications systems. Projected image/video requirements which are currently anticipated for SEI mission scenarios are presented. Based on this information and projected link performance figures, the image/video data compression requirements which would allow link closure are identified. Finally several approaches which could satisfy some of the compression requirements are presented and possible future approaches which show promise for more substantial compression performance improvement are discussed

Issues in designing transport layer multicast facilities

Multicasting denotes a facility in a communications system for providing efficient delivery from a message's source to some well-defined set of locations using a single logical address. While modem network hardware supports multidestination delivery, first generation Transport Layer protocols (e.g., the DoD Transmission Control Protocol (TCP) (15) and ISO TP-4 (41)) did not anticipate the changes over the past decade in underlying network hardware, transmission speeds, and communication patterns that have enabled and driven the interest in reliable multicast. Much recent research has focused on integrating the underlying hardware multicast capability with the reliable services of Transport Layer protocols. Here, we explore the communication issues surrounding the design of such a reliable multicast mechanism. Approaches and solutions from the literature are discussed, and four experimental Transport Layer protocols that incorporate reliable multicast are examined

Vergence control system for stereo depth recovery

This paper describes a vergence control algorithm for a 3D stereo recovery system. This work has been developed within framework of the project ROBTET. This project has the purpose of designing a Teleoperated Robotic System for live power lines maintenance. The tasks involved suppose the automatic calculation of path for standard tasks, collision detection to avoid electrical shocks, force feedback and accurate visual data, and the generation of collision free real paths. To accomplish these tasks the system needs an exact model of the environment that is acquired through an active stereoscopic head. A cooperative algorithm using vergence and stereo correlation is shown. The proposed system is carried out through an algorithm based on the phase correlation, trying to keep the vergence on the interest object. The sharp vergence changes produced by the variation of the interest objects are controlled through an estimation of the depth distance generated by a stereo correspondence system. In some elements of the scene, those aligned with the epipolar plane, large errors in the depth estimation as well as in the phase correlation, are produced. To minimize these errors a laser lighting system is used to help fixation, assuring an adequate vergence and depth extraction .The work presented in this paper has been supported by electric utility IBERDROLA, S.A. under project PIE No. 132.198

Spread spectrum-based video watermarking algorithms for copyright protection

Merged with duplicate record 10026.1/2263 on 14.03.2017 by CS (TIS)Digital technologies know an unprecedented expansion in the last years. The consumer can now benefit from hardware and software which was considered state-of-the-art several years ago. The advantages offered by the digital technologies are major but the same digital technology opens the door for unlimited piracy. Copying an analogue VCR tape was certainly possible and relatively easy, in spite of various forms of protection, but due to the analogue environment, the subsequent copies had an inherent loss in quality. This was a natural way of limiting the multiple copying of a video material. With digital technology, this barrier disappears, being possible to make as many copies as desired, without any loss in quality whatsoever. Digital watermarking is one of the best available tools for fighting this threat. The aim of the present work was to develop a digital watermarking system compliant with the recommendations drawn by the EBU, for video broadcast monitoring. Since the watermark can be inserted in either spatial domain or transform domain, this aspect was investigated and led to the conclusion that wavelet transform is one of the best solutions available. Since watermarking is not an easy task, especially considering the robustness under various attacks several techniques were employed in order to increase the capacity/robustness of the system: spread-spectrum and modulation techniques to cast the watermark, powerful error correction to protect the mark, human visual models to insert a robust mark and to ensure its invisibility. The combination of these methods led to a major improvement, but yet the system wasn't robust to several important geometrical attacks. In order to achieve this last milestone, the system uses two distinct watermarks: a spatial domain reference watermark and the main watermark embedded in the wavelet domain. By using this reference watermark and techniques specific to image registration, the system is able to determine the parameters of the attack and revert it. Once the attack was reverted, the main watermark is recovered. The final result is a high capacity, blind DWr-based video watermarking system, robust to a wide range of attacks.BBC Research & Developmen

Solutions and Tools for Secure Communication in Wireless Sensor Networks

Secure communication is considered a vital requirement in Wireless Sensor Network (WSN) applications. Such a requirement embraces different aspects, including confidentiality, integrity and authenticity of exchanged information, proper management of security material, and effective prevention and reaction against security threats and attacks. However, WSNs are mainly composed of resource-constrained devices. That is, network nodes feature reduced capabilities, especially in terms of memory storage, computing power, transmission rate, and energy availability. As a consequence, assuring secure communication in WSNs results to be more difficult than in other kinds of network. In fact, trading effectiveness of adopted solutions with their efficiency becomes far more important. In addition, specific device classes or technologies may require to design ad hoc security solutions. Also, it is necessary to efficiently manage security material, and dynamically cope with changes of security requirements. Finally, security threats and countermeasures have to be carefully considered since from the network design phase. This Ph.D. dissertion considers secure communication in WSNs, and provides the following contributions. First, we provide a performance evaluation of IEEE 802.15.4 security services. Then, we focus on the ZigBee technology and its security services, and propose possible solutions to some deficiencies and inefficiencies. Second, we present HISS, a highly scalable and efficient key management scheme, able to contrast collusion attacks while displaying a graceful degradation of performance. Third, we present STaR, a software component for WSNs that secures multiple traffic flows at the same time. It is transparent to the application, and provides runtime reconfigurability, thus coping with dynamic changes of security requirements. Finally, we describe ASF, our attack simulation framework for WSNs. Such a tool helps network designers to quantitatively evaluate effects of security attacks, produce an attack ranking based on their severity, and thus select the most appropriate countermeasures

Optomechanical and Crystallization Phenomena Visualized with 4D Electron Microscopy: Interfacial Carbon Nanotubes on Silicon Nitride

With ultrafast electron microscopy (UEM), we report observation of the nanoscopic crystallization of amorphous silicon nitride, and the ultrashort optomechanical motion of the crystalline silicon nitride at the interface of an adhering carbon nanotube network. The in situ static crystallization of the silicon nitride occurs only in the presence of an adhering nanotube network, thus indicating their mediating role in reaching temperatures close to 1000 °C when exposed to a train of laser pulses. Under such condition, 4D visualization of the optomechanical motion of the specimen was followed by quantifying the change in diffraction contrast of crystalline silicon nitride, to which the nanotube network is bonded. The direction of the motion was established from a tilt series correlating the change in displacement with both the tilt angle and the response time. Correlation of nanoscopic motion with the picosecond atomic-scale dynamics suggests that electronic processes initiated in the nanotubes are responsible for the initial ultrafast optomechanical motion. The time scales accessible to UEM are 12 orders of magnitude shorter than those traditionally used to study the optomechanical motion of carbon nanotube networks, thus allowing for distinctions between the different electronic and thermal mechanisms to be made

Spatiotemporal oriented energies for spacetime stereo

This paper presents a novel approach to recovering tem-porally coherent estimates of 3D structure of a dynamic scene from a sequence of binocular stereo images. The approach is based on matching spatiotemporal orientation distributions between left and right temporal image streams, which encapsulates both local spatial and temporal struc-ture for disparity estimation. By capturing spatial and tem-poral structure in this unified fashion, both sources of in-formation combine to yield disparity estimates that are nat-urally temporal coherent, while helping to resolve matches that might be ambiguous when either source is considered alone. Further, by allowing subsets of the orientation mea-surements to support different disparity estimates, an ap-proach to recovering multilayer disparity from spacetime stereo is realized. The approach has been implemented with real-time performance on commodity GPUs. Empir-ical evaluation shows that the approach yields qualitatively and quantitatively superior disparity estimates in compari-son to various alternative approaches, including the ability to provide accurate multilayer estimates in the presence of (semi)transparent and specular surfaces. 1

Image Understanding and Robotics Research at Columbia University

The research investigations of the Vision/Robotics Laboratory at Columbia University reflect the diversity of interests of its four faculty members, two staff programmers and 15 Ph.D. students. Several of the projects involve either a visiting computer science post-doc, other faculty members in the department or the university, or researchers at AT&T Bell Laboratories or Philips laboratories. We list below a summary of our interest and results, together with the principal researchers associated with them. Since it is difficult to separate those aspects of robotic research that are purely visual from those that are vision-like (for example, tactile sensing) or vision-related (for example, integrated vision-robotic systems), we have listed all robotic research that is not purely manipulative