Correction to: Transmission of correct gaze direction in video conferencing using screen-embedded cameras

Multimedia Tools and Applications -     

Real-time panorama video system using networked multiple cameras

Although panorama creation has been studied extensively, previous works still have limitations because they depend on customized hardware or post processing, resulting in high production cost and complexity. We propose and implement real-time panorama video system by using off-the-shelf embedded boards and camera modules. For real-time, we developed the performance improving methods such as reducing the homography computation load and employing multi thread structure. We conducted a series of experiments to investigate how different blending combinations and the number of threads affect the performance and image quality. We also analyzed the time consumption of threads and stitching steps.     

Personnel tracking on construction sites using video cameras

This paper discusses the possibility of- and need for-tracking workforce on construction jobsites using video cameras. An evaluation of algorithms and their associated results is presented. The principal objective of this paper is to test and demonstrate the feasibility of tracking workers from statically placed and dynamically moving cameras. This paper also reviews existing techniques to monitor workforce and describes areas where this work might be useful in engineering applications. The main difficulties associated with tracking on a construction site is the significant amount of visual clutter, the changing photometric visual content throughout the course of a day, and the presence of occluding and moving obstacles. The tracking of workers within the field of view of the camera will involve four tracking techniques, density mean-shift, Bayesian segmentation, active contours, and graph-cuts. Typical construction site video will be processed using the proposed algorithms and analyzed to determine the most appropriate tracking method for the video presented.     

TriMedia1300在视频会议中的应用

介绍和分析了Philips公司的TriMedia微处理器及其升级产品TriMedia1300的系统组成和特点。针对视频会议中存在的实时性问题,提出了一种基于TriMedia1300视频会议的简单、快速开发方案,并对TriMedia1300在视频和图像处理方面的性能与个人计算机进行了比较,给出了它们运算速度比较的结果。     

A novel approach to 3-D gaze tracking using stereo cameras

A novel approach to three-dimensional (3-D) gaze tracking using 3-D computer vision techniques is proposed in this paper. This method employs multiple cameras and multiple point light sources to estimate the optical axis of user's eye without using any user-dependent parameters. Thus, it renders the inconvenient system calibration process which may produce possible calibration errors unnecessary. A real-time 3-D gaze tracking system has been developed which can provide 30 gaze measurements per second. Moreover, a simple and accurate calibration method is proposed to calibrate the gaze tracking system. Before using the system, each user only has to stare at a target point for a few (2-3) seconds so that the constant angle between the 3-D line of sight and the optical axis can be estimated. The test results of six subjects showed that the gaze tracking system is very promising achieving an average estimation error of under 1 degrees.     

视频会议中视频分割合成的研究

视频会议系统正在吸引越来越多在地域上分散的人们的注意。随着多媒体信息处理和通信技术的飞速发展,虚拟视频会议系统越来越成为可能。和传统的基于二维图像表述的视频会议系统比较,三维虚拟会议系统能为人们提供更好的以人为中心的交流。在这两种情况下,高效精确的视频分割和视图合成都是关键问题。就以下3方面的主要技术进行了研究：背景分离、视差估计以及视图合成。     

Desktop video conferencing in the organisation

While the potential advantages of video conferencing are appealing, the technology has not been implemented in more than a handful of organisations. This is likely to change in the future as video conferencing moves to the desktop. This paper examines the issues surrounding the area and, in particular, attempts to determine the impact of video conferencing on organisations. A framework is provided for understanding desktop video conferencing in the organisational context, and the relative benefits of and problems in the use of desktop video conferencing are discussed. Finally, a number of suggestions are made on how organisations may reconcile the implications of utilising desktop video conferencing technology.     

视频会议系统身份认证的一种解决方案

视频会议系统的安全问题日趋重要。身份认证是视频会议系统安全体制中最为重要的环节。文章总结了当前视频会议系统中对用户身份进行认证的方法,指出了它们存在的缺陷。提出了一种基于智能IC卡和改进的kerberos协议的视频会议系统身份认证的解决方案,并对其安全性进行了分析     

视频会议双机热备的应用

本文针对电子政务视频会议中的双机热备问题,提出了．MCU双机热备和终端双机热备的技术应用分析,探讨其征视频会议中主工作设备出现故障时,能够在规定的时间内自动切换、信号平滑,充分保证会议的高可靠性。     

Vision-based estimation of the number of occupants using video cameras

Although occupancy information is critical to energy consumption of existing buildings, it still remains to be a major source of uncertainty. For reliable and accurate occupant modeling with minimal uncertainties, capturing precise occupant information on occupants is essential. This paper proposes a computer vision-based approach that utilizes deep learning architectures to estimate of the number of people in large, crowded spaces using multiple cameras. Various vision techniques (head detection, background elimination, head tracking) are implemented in three methods: (i) a method that instantaneously counts people in a scene, (ii) a method that incrementally counts people entering/exiting a room and (iii) a combination of the first two methods. These methods were applied in a classroom with heavy occlusions, and resulted in a high prediction capacity when compared to ground truth measurements. Future work in video-analytical approaches can address problems regarding lowering the computational cost of analysis, capturing occupancy data in complex room geometries and addressing concerns in privacy preservation.     

Contour-based object tracking with occlusion handling in video acquired using mobile cameras

We propose a tracking method which tracks the complete object regions, adapts to changing visual features, and handles occlusions. Tracking is achieved by evolving the contour from frame to frame by minimizing some energy functional evaluated in the contour vicinity defined by a band. Our approach has two major components related to the visual features and the object shape. Visual features (color, texture) are modeled by semiparametric models and are fused using independent opinion polling. Shape priors consist of shape level sets and are used to recover the missing object regions during occlusion. We demonstrate the performance of our method in real sequences with and without object occlusions.     

视线追踪系统眼部特征检测及视线方向计算方法研究

基于单视觉主动红外光源系统,提出了一种视线检测方法．在眼部特征检测阶段,采用投影法定位人脸;根据人脸对称性和五官分布的先验知识,确定瞳孔潜在区域;最后进行人眼特征的精确分割．在视线方向建模阶段,首先在头部静止的情况下采用非线性多项式建立从平面视线参数到视线落点的映射模型;然后采用广义回归神经网络对不同头部位置造成的视线偏差进行补偿,使非线性映射函数扩展到任何头部位置．实验结果及在交互式图形界面系统中的应用验证了该方法的有效性．     

基于IE浏览器的IP组播视频会议系统

实现了一种基于IE浏览器的组播视频会议：以Microsoft TAPI3.0（telephony application program interface）COM组件为核心,结合Windows 2000 Active Directory,采用IP组播技术实现多方通信,大大减少了网络带宽的开销.客户端用户无需安装其它的软件,直接利用WEB浏览器来进行多方的语音和视频聊天.介绍了微软TAPI3.0的体系结构、IP组播会议服务体系和主要模块的实现方法,讨论了会议系统的实际部署问题.     

Data generation and representation method for 3D video conferencing using programming by demonstration

Video conferencing provides an environment for multiple users linked on a network to have meetings. Since a large quantity of audio and video data are transferred to multiple users in real time, research into reducing the quantity of data to be transferred has been drawing attention. Such methods extract and transfer only the features of a user from video data and then reconstruct a video conference using virtual humans. The disadvantage of such an approach is that only the positions and features of hands and heads are extracted and reconstructed, whilst the other virtual body parts do not follow the user. In order to enable a virtual human to accurately mimic the entire body of the user in a 3D virtual conference, we examined what features should be extracted to express a user more clearly and how they can be reproduced by a virtual human. This 3D video conferencing estimates the user’s pose by comparing predefined images with a photographed user’s image and generates a virtual human that takes the estimated pose. However, this requires predefining a diverse set of images for pose estimation and, moreover, it is difficult to define behaviors that can express poses correctly. This paper proposes a framework to automatically generate the pose-images used to estimate a user’s pose and the behaviors required to present a user using a virtual human in a 3D video conference. The method for applying this framework to a 3D video conference on the basis of the automatically generated data is also described. In the experiment, the framework proposed in this paper was implemented in a mobile device. The generation process of poses and behaviors of virtual human was verified. Finally, by applying programming by demonstration, we developed a system that can automatically collect the various data necessary for a video conference directly without any prior knowledge of the video conference system.     

云视频会议平台研究

为解决云计算环境下视频会议的开发与应用,提出了包括基础设施即服务IaaS、平台即服务PaaS和软件即服务SaaS的云视频会议平台框架,分析了云视频会议的服务功能和会议流程,并建立了云视频会议平台系统。平台的应用能够促进信息的实时沟通,在降低企业开发、维护成本的同时,提升企业的决策能力。     

A performance analysis of personal computers in a video conferencing environment

New intelligent adapters, advanced bus architectures, and powerful microprocessors have resulted in a new generation of personal computers with true multimedia capabilities. Collaborative applications are the most demanding applications of multimedia technologies today. We present a performance analysis of how effective video conferencing applications can be supported with personal computers connected through a local area network (LAN). We also evaluate the performance impact of an advanced, peer-to-peer I/O protocol. The key factor in the performance of a video conferencing system over a LAN is the video compression and decompression algorithms. At high video frame rates, the peer-to-peer I/O protocol performs better than the traditional, bus-master, interrupt-driven I/O protocol.     

基于分布式代理的自适应视频会议系统的设计

如何克服服务器负载过重造成的瓶颈效应,及如何适应网络的动态变化,是视频会议系统一直面临的问题.提出了一种基于分布式代理的自适应视频会议系统.该系统充分利用当前的网络条件,采用分布式代理,使用应用层组播和IP层组播相结合的混合组播方式,解决了服务器瓶颈问题;采用基于MPEG-4FGS速率修整技术,使系统具有极好的网络自适应性.     

The instructor's gaze guidance in video lectures improves learning

Instructor behaviour is known to affect learning performance, but it is unclear which specific instructor behaviours can optimize learning. We used eye‐tracking technology and questionnaires to test whether the instructor's gaze guidance affected learners' visual attention, social presence, and learning performance, using four video lectures: declarative knowledge with and without the instructor's gaze guidance and procedural knowledge with and without the instructor's gaze guidance. The results showed that the instructor's gaze guidance not only guided learners to allocate more visual attention to corresponding learning content but also increased learners' sense of social presence and learning. Furthermore, the link between the instructor's gaze guidance and better learning was especially strong for participants with a high sense of social connection with the instructor when they learned procedural knowledge. The findings lead to a strong recommendation for educational practitioners: Instructors should provide gaze guidance in video lectures for better learning performance.     

Frame-level temporal calibration of video sequences from unsynchronized cameras

This paper describes a method for temporally calibrating video sequences from unsynchronized cameras by image processing operations, and presents two search algorithms to match and align trajectories across different camera views. Existing multi-camera systems assume that input video sequences are synchronized either by genlock or by time stamp information and a centralized server. Yet, hardware-based synchronization increases installation cost. Hence, using image information is necessary to align frames from the cameras whose clocks are not synchronized. The system built for temporal calibration is composed of three modules: object tracking module, calibration data extraction module, and the search module. A robust and efficient search algorithm is introduced that recovers the frame offset by matching the trajectories in different views, and finding the most reliable match. Thanks to information obtained from multiple trajectories, this algorithm is robust to possible errors in background subtraction and location extraction. Moreover, the algorithm can handle very large frame offsets. A RANdom SAmple Consensus (RANSAC) based version of this search algorithm is also introduced. Results obtained with different video sequences are presented, which show the robustness of the algorithms in recovering various range of frame offsets for video sequences with varying levels of object activity.