Adaptive packet scheduling for scalable video streaming with network coding

Over the last decade, the emergence of new multimedia devices has motivated the research on efficient media streaming mechanisms that adapt to dynamic network conditions and heterogeneous devices’ capabilities. Network coding as a rateless code has been applied to collaborative media streaming applications and brings substantial improvements regarding throughput and delay. However, little attention has been given to the recoverability of encoded data, especially for the streaming with a strict deadline. This in turn leads to severe quality of experience. In this paper, we solve the unrecoverable transmission by proposing a multi-generation packet scheduling problem, which is treated as a video quality maximization problem and solved using dynamic programming algorithm. Experimental results confirm that the proposed algorithm brings better data recoverability and better quality of service in terms of video quality, delivery ratio, lower redundancy rate under different network sizes.     

用水发电的那些事*

水不仅是生命之源,而且还作为介质为人类提供了极其丰富的绿色能源。选取了几种利用水驱动发电的技术,包括传统水力发电、潮汐能发电、海洋温差发电,也详细探讨了近年新兴的盐差发电和“水伏”发电,力求以通俗的语言将水发电技术进行科普介绍。     

荧光/化学发光探针成像检测超氧阴离子自由基的研究进展

超氧阴离子自由基(O·-2)是细胞内氧气单电子还原后最先产生的一类含氧的高活性物种(活性氧,ROS),与生命过程息息相关.正常稳态浓度的O·-2起重要的信号调控作用,包括细胞的增殖、分化、自噬等.但O·-2浓度的异常,又与癌症、神经退行性疾病、糖尿病等多种疾病的发生发展密切相关.因此,监测O·-2浓度的变化对揭示相关疾病的机理具有至关重要作用.由于荧光成像检测方法具有诸多优势,发展高灵敏、高选择性检测O·-2的荧光探针成为揭示相关疾病发生发展分子机制的关键切入点.近年来,随着荧光显微技术的发展,研究者开发了多种荧光/化学发光探针,实现了对细胞及活体内O·-2水平的可视化监测.本文综述了近五年用于检测O·-2的分子探针、纳米探针、蛋白探针以及化学发光探针的研究进展,并对其发展前景进行了展望.     

小型无人机快速最优化稳像方法研究

小型无人机电子稳像可以纠正视频影像中存在的晃动、震动、畸变等不稳定因素,有利于视频影像目标跟踪、精确打击,同时还能缓解观察者的视觉疲劳。电子稳像有3个主要的步骤:全局运动估计、主运动估计和运动补偿。本文主要对主运动估计的方法进行研究,并提出了一种快速最优化的稳像方法,该方法能够快速准确的估计小型无人机视频影像的主运动。该方法结合了L1最优化方法的精确性和Kalman滤波方法处理速度快的优点,并克服Kalman滤波法预测精度不高和L1最优化方法只能事后处理的问题,从而获到更好的稳像效果。最后采用实际飞行数据对本文提出算法进行了验证,结果表明,本文所提出的方法在保证稳像处理精度的前提下,也保证了处理效率。     

图像和视频的快速去雾算法研究

雾、霾等恶劣天气会导致室外图像能见度和对比度降低。虽然可以通过增强有雾图像的对比度得到清晰的图像,但对比度的过度增强可能会截断像素值,造成信息丢失。因此,本文基于信息丢失问题提出了一种快速、优化的去雾算法。通过最小化信息丢失,使输出图像不仅能保留较多的细节,且具有较高的对比度。此外,通过将RGB颜色空间转换为YUV颜色空间,仅对亮度分量Y进行处理,提高了算法的运算速度。算法的对比实验结果表明,本文的算法不仅去雾效果明显,而且运算速度快,完全能满足视频去雾的实时性要求。     

Online traffic smoothing for delivery of variable bit rate media streams

Traffic smoothing for delivery of online variable bit rate (VBR) media streams is one of the most important problems in designingmultimedia systems. Given an available client buffer, a window size, and a window-sliding size, previous window-based online smoothing methods have tried to reduce the peak bandwidth allocated in each window. However, as bandwidths allocated in different windows are minimized independently, these methods require a large peak bandwidth for transmitting an entire stream. In this paper, a new window-based method is proposed. It introduces two new ideas, the dynamic windowsliding size and the aggressive workahead, for delivery of online VBR media streams. Our aggressive and dynamic window sliding (ADWS) method can automatically decide on the suitable window-sliding sizes for different windows. Thus, the allocated peak bandwidth can be further reduced. By examining various media streams, ADWS is shown to be effective and efficient. Considering the online transmission of the movieStar Wars with a 90-kB client buffer, ADWS yields 13% less in peak bandwidth, compared with the bestknown window-based online smoothing algorthm SLWIN(1). Its computation cost (the window-sliding number) is 75% of that required by SLWIN(1).This work was partially supported by NSC, Taiwan, under grants. NSC88-2213-E-001-011, NSC88-2213-E-001-012, and NSC88-2213-E-001-025. A primitive version of this work appeared in IEEE INFOCOM'99 [7].     

Real-time moving object segmentation in H.264 compressed domain based on approximate reasoning

This paper presents a real-time segmentation algorithm to obtain moving objects from the H.264 compressed domain. The proposed segmentation works with very little information and is based on two features of the H.264 compressed video: motion vectors associated to the macroblocks and decision modes. The algorithm uses fuzzy logic and allows to describe position, velocity and size of the detected regions in a comprehensive way, so the proposed approach works with low level information but manages highly comprehensive linguistic concepts. The performance of the algorithm is improved using dynamic design of fuzzy sets that avoids merge and split problems. Experimental results for several traffic scenes demonstrate the real-time performance and the encouraging results in diverse situations.     

Segmentation of Moving Objects Using Mathematical Morphology

1IntroductionInthelastfewyears,n'ovelandverydemandingapplications,suchasdesktopvideoconferencing,videophone,multimediacommunicationsandmobilecommunications,havegivenarenewedimpetustoresearchintheareaofverylowbit-ratevideocoding.Establishedvideocodingstandards,suchasH.261andMPEG-2,performratherpoorlywhenusedforhighcompressionratios.Themaininherentdeficiencywiththeseblock-basedapproachesisthatthevideosceneandmotionaremodeledasbeingcomprisedofsquareblocks.Thus,atverylowbitrates,thereconstructed…     

应变测量的光栅法

本文提出一种新的应变测量方法。用模压全息光栅作为应变传感器，测量光栅衍射点空间位置的变化量，直接获得应变或应力分量。全息光栅的模压制作，可以大幅度地降低成本。视频技术与微机技术的运用可以自动地获得应变和应力的数值。     

广角镜头图像畸变校正系统的研究

介绍了一种广角镜头图像畸变的实时校正系统。通过对光学系统畸变原理的分析,采用一定的算法对像素空间的位置进行几何变换,减少了由镜头大视场带来的几何畸变。整个系统以FPGA为核心控制器件,结合数字图像编码解码芯片和SDRAM存储器,可实现视频图像的实时校正。时钟倍频器在系统中可以为SDRAM及其控制模块提供与其它时钟同相位的高频时钟。