QoE-aware video cooperative caching and transmission mechanism based on TWDM-PON and C-RAN

The quality of user experience suffers from performance deterioration dramatically due to the explosively growing data traffic.To improve the poor performance of cell-edge users and heavy-load cell users,which caused by dense network and load imbalance respectively,an QoE-aware video cooperative caching and transmission mechanism in cloud radio access network was proposed.Cooperative gain-aware virtual passive optical network was established to provide cooperative caching and transmission for video streaming by adopting collaborative approach in optical domain and wireless domain.Furthermore,user experience for video streaming,bandwidth provisioning and caching strategy were jointly optimized to improve QoE,which utilized the methods of dynamic caching in optical domain and buffer level-aware bandwidth configuration in wireless domain.The results show that the proposed mechanism enhances the quality of user experience and effectively improves the cache hit rate.     

可伸缩视频流的安全网络编码方案

为了使可伸缩视频流在异构网络中达到分层安全等级的目的,运用随机函数来随机化视频流各层中的部分数据流,并结合网络编码来抵御已知的明文攻击。此外,对网络编码器进行了研究,设计有序随机线性网络编码器用于可伸缩视频的传输,可以用很少的随机化操作来达到可扩展的安全等级,并降低通信开销。分析表明,所提方案可有效增加网络的吞吐率。     

面向移动内容分发网络环境的移动视频预取技术研究进展

随着移动互联网的发展和视频应用的普及,移动内容分发网络(MCDN)应运而生。预取技术是内容分发的关键技术之一,它通过预测用户未来的请求,提前将预测的内容预取至网络边缘,从而减少数据的获取时延、提升用户体验质量(QoE)。为深入阐述移动视频预取技术的发展现状,从用户移动行为感知、内容属性感知、网络资源感知等角度分析梳理了移动视频预取技术的最新研究成果,同时分析了各类预取方案的性能及其主要优缺点,最后指出未来可以进一步研究的方向。     

适用于实时交通监控的时空可伸缩视频编码方法

提出了一种适用于视频监控的时空可伸缩编码方法。首先提出一种适用于可伸缩视频编码特点的监控算法,利用该算法将运动区域从背景中提取出来,并用模式和方向快速判别算法去掉对编码增益很小的冗余模式,基本层利用该算法进行编码,增强层利用基本层的信息预测可能的模式集合,然后进行零块预先判决,最后对最高时间级的高速运动块通过视觉门限来降低其空间冗余度。实验证明,该方法能够较大地提高编码速度和一定程度上提高压缩率,并且视觉质量损失很小。     

Performance of the color set partitioning in hierarchical tree scheme (CSPIHT) in video coding

This paper describes the implementation of the recently introducedcolor set partitioning in hierarchical tree (CSPIHT)-based scheme for video coding. The intra- and interframe coding performance of a CSPIHT-based video coder (CVC) is compared against that of the H.263 at bit rates lower than 64 kbit/s. The CVC performs comparably or better than the H.263 at lower bit rates, whereas the H.263 performs better than the CVC at higher bit rates. We identify areas that hamper the performance of the CVC and propose an improved scheme that yields better performance in image and video coding in low bit-rate environments.     

视频用户体验理论与实践

随着视频服务逐渐成为人们获取信息的主要途径之一,消费者对观看体验的要求不断提高,视频用户体验质量已经成为视频服务的主要竞争因素.首先对用户体验质量理论进行了系统的阐述,指出了用户体验质量与服务质量之间的差别和联系,同时给出了用户体验评价方法的主要步骤和视频质量评价的具体方法.进一步地,对我国现阶段视频用户体验评价研究及标准化的进展进行详细介绍,概括了目前我国视频服务的用户体验现状并给出了相关的改进方向意见.     

Reliable transmission mechanism with differentiated protection in virtualized fiber-wireless access network

In view of the different reliability requirements of network service,a reliable transmission mechanism with differentiated protection was proposed in virtualized fiber-wireless access network.The quality of protection required by users and the fees that can be paid were used as a prerequisite.The backup protection resources were flexibly allocated by quantifying the multi-level protection quality with the probability of recovery.Then,for reducing traffic congestion and the unprotected services,the level service differentiation algorithm was used to choose protection link which was satisfied with the level of protection quality.The results show the proposed mechanism has more advantages in terms of long-term benefit-to-cost ratio and underlying network resource overhead,and provides users with a more flexible virtual network transmission while satisfying users’ reliability requirements.     

基于OpenFlow的SVC流媒体时延自适应分级传输方法

针对当前互联网流媒体传输的时延敏感性问题,提出一种基于OpenFlow的SVC（scalable video coding,可分级视频编码）流媒体时延自适应分级传输方法,该方法有效结合SVC流媒体可分级和OpenFlow灵活可编程的特性,在网络带宽受限和链路拥塞的复杂网络环境下,通过构建基础层和增强层2个独立路由,实现了动态网络下SVC流媒体分级自适应高效传输。仿真结果表明,该方法在提升SVC流媒体传输效率和质量,改善用户体验方面有重要作用。     

MPEG-4视频标准及其关键算法

MPEG-4引入了视频对象的概念,有效地支持基于内容的图像编码,对不同的视频源标准格式和不同的视频码率提供有效的编码,以满足众多多媒体的应用需求。本文系统地分析了MPEG-4视频编码算法,对MPEG-4视频标准的关键概念进行了详细的解释。     

一种低编码复杂度可分级的视频编码系统

在可分级视频编码（SVC,scalable video coding）的框架下,利用分布式视频编码（DVC,distributed video coding）技术,设计了一种低编码复杂度的SVC方案。该系统具有空间可分级的特性,各分层中仅用到了传统的帧内编码技术和DVC技术,最大限度的减小了SVC系统的编码复杂度。在该...     

质量可伸缩视频编码原理分析及测试

在分析可伸缩视频一些关键技术原理的基础上,对中等粒度的质量可伸缩算法进行了测试,分析了实验结果。结果证明质量可伸缩编码的不同质量层可满足不同应用环境和终端设备的需求,具有误码鲁棒性和网络适应能力。     

Efficient handoff based on link quality prediction for video streaming in urban transport systems

The continuously increasing interest in developing efficient vehicle‐roadside communication networks to provide on‐board connectivity has recently brought to the definition of several solutions based on different wireless technologies. Among them, wireless local area network‐based solutions emerged as an attracting alternative to guarantee high‐quality connectivity enabling services, like video streaming, that require stringent quality of service guarantees. In this work, we propose a handoff procedure based on a forecasting model of the link quality for mobile routers operating in vehicle‐roadside wireless local area network‐based networks. First, a preliminary set of experiments is performed in a realistic environment to study the behavior of the wireless channel when mobility in urban environment is considered. Then, considering the hands‐on experience gained from the initial set of experiments, a novel handoff procedure is designed, which exploits a forecasting technique to predict link channel quality. The proposed procedure is then exploited in a cross‐layer manner to proactively reduce the number of transmitted layers during handoff in the case of real‐time video traffic based on H.264/SVC encoding. The proposal is assessed by means of simulation and compared with existing solutions. Results demonstrate that our proposal guarantees performance comparable with other algorithms. The advantage of predicting the handoff point is demonstrated by means of simulations employing a realistic video streaming traffic model, showing how the quality of experience perceived by end‐users can be improved through the adaptation of the traffic load. Copyright © 2016 John Wiley & Sons, Ltd.     

Joint resource optimization for nonorthogonal multiple access-enhanced scalable video coding multicast in unmanned aerial vehicle-assisted radio-access networks

A joint resource-optimization scheme is investigated for nonorthogonal multiple access (NOMA)-enhanced scalable video coding (SVC) multicast in unmanned aerial vehicle (UAV)-assisted radio-access networks (RANs). This scheme allows a ground base station and UAVs to simultaneously multicast successive video layers in SVC with successive interference cancellation in NOMA. A video quality-maximization problem is formulated as a mixed-integer nonlinear programming problem to determine the UAV deployment and association, RAN spectrum allocation for multicast groups, and UAV transmit power. The optimization problem is decoupled into the UAV deployment–association, spectrum-partition, and UAV transmit-power–control subproblems. A heuristic strategy is designed to determine the UAV deployment and association patterns. An upgraded knapsack algorithm is developed to solve spectrum partition, followed by fast UAV power fine-tuning to further boost the performance. The simulation results confirm that the proposed scheme improves the average peak signal-to-noise ratio, aggregate video-reception rate, and spectrum utilization over various baselines.     

多描述视频编码方法研究

稳健的视频编码压缩方法是实时网络视频传输的关键，多描述视频编码可为解决不可靠信道视频传输的丢包、误码和延时等所带来的视频质量严重降质问题提供一种新途径。本文介绍了面向网络传输的多描述视频编码的研究现状和一些典型的多描述视频编码器，并对其中的关键技术进行了分析、讨论。     

无线异构网络中的低复杂度分级视频传输技术

针对无线异构网络中进行视频无线传输遇到的网络拥塞、传输丢失等问题,提出了低编码复杂度分级编解码传输方案,基于逐级优化理论和可分级编码理论,设计了视频分级编码策略:利用小波变换后的不同分解层不同子带构成基本层(Base Layer,BL)和三个增强层,获得了码率分级和质量分级的特性.实验结果证明,随着不同层的更新,视频分级系统的解码质量和整体率失真性能都逐级改善.该传输方案实现了在信道条件动态变化的无线网络环境下仍能流畅传输并接收到有用信息,适用于信道条件不稳定的无线异构网络.     

Multiple Region‐of‐Interest Support in Scalable Video Coding

In this letter, we propose a new functionality to scalable video coding (SVC), that is, the support of multiple region of interests (ROIs) for heterogeneous display resolution. The main objective of SVC is to provide temporal, spatial, and quality scalability of an encoded bitstream. The ROI is an area that is semantically important to a particular user, especially users with heterogeneous display resolutions. Less transmission bandwidth is needed compared to when the entire region is transmitted/decoded and then sub‐sampled or cropped. To support multiple ROIs in SVC, we adopt flexible macroblock ordering (FMO), a tool defined in H.264, and based on it, we propose a way to encode and, independently, decode ROIs. The proposed method is implemented on the joint scalable video model (JSVM) and its functionality verified.     

MDVQM: A novel multidimensional no-reference video quality metric for video transcoding

In this paper, we study the impact of quantization, frame dropping and spatial down-sampling on the perceived quality of compressed video streams. Based on the analysis of quality ratings obtained from extensive subjective tests, we propose a no-reference metric (named MDVQM) for video quality estimation in the presence of both spatial and temporal quality impairments. The proposed metric is based on the per-pixel bitrate of the encoded stream and selected spatial and temporal activity measures extracted from the video content. All the values required to compute the proposed video quality metric can be obtained without using the original reference video which makes the metric for instance useful for making transcoding decisions in a wireless video transmission scenario. Different from comparable metrics in the literature, we have also considered the case when both frame rate and frame size are changed simultaneously. The validation results show that the proposed metric provides more accurate estimation of the video quality than the state of the art metrics.     

基于感兴趣区域的自适应帧内更新编码算法

针对视频压缩码流对信道差错异常敏感的问题,提出了一种基于感兴趣区域的自适应帧内更新编码算法。该算法利用人眼的视觉感知特性设计感兴趣区域提取模型,根据信道差错累积情况自适应调整帧内更新编码策略,将更少的失真分配给人眼感兴趣区域,提高差错信道下传输视频图像的主客观质量。实验结果表明,与基于端到端失真的帧内更新算法相比,在不同的信道丢包条件下,所提算法可以获得更好的主客观质量,感兴趣区域的峰值信噪比(PSNR)平均提高0.87 dB左右,提高了差错信道下视频通信的鲁棒性。     

Flexible three-band motion-compensated temporal filtering for scalable video coding

A novel scheme for scalable video coding using three-band lifting-based motion-compensated transform is presented in this article. A series of flexible three-band motion-compensated lifting steps are used to implement the temporal wavelet transform, which provide improved compression performance by selecting specific motion model according to real video sequences, and offer higher temporal scalability flexibility by using three-band lifting steps. The experimental results compared with motion picture expert group (MPEG)-4 codec concerning standard video sequences demonstrate the effectiveness of the method.     

Evaluation of objective quality metrics for multidimensional video scalability

Multidimensional video scalability refers to the possibility that a video sequence can be adapted according to given conditions of video consumption by adjusting one or more of its features such as frame size, frame rate, and spatial quality. An important issue in implementing an adaptive video distribution scheme using scalability is how to maximize the quality of experience for the delivered contents, which raises a more fundamental issue, that is, how to estimate perceived quality of scalable video contents. This paper evaluates existing state-of-the-art objective quality metrics, including both generic image/video metrics and ones particularly developed for scalable videos, on the problem of quality assessment of multidimensional video scalability. It is shown that, on the whole, some recently developed metrics targeting scalability perform best. The results are thoroughly discussed in relation to the nature of the problem in comparison to what has been reported in existing studies for other problems.