P2P网络流媒体关键技术

P2P网络流媒体技术一直是学术界和产业界的研究热点.本文围绕覆盖网络拓扑结构,对现有的P2P流媒体系统作了全面的归类总结,深入介绍和分析了覆盖网络构建、数据块调度策略等P2P流媒体核心技术,并概要讨论视频编码、网络编码、覆盖网络拓扑优化、安全与激励机制等P2P流媒体相关增强技术.对典型P2P流媒体系统的性能进行了比较,...     

一种基于P2P流媒体的网络教学系统设计

随着互联网的迅速发展,远程网络教育已经逐渐普及。然而已有的网络技术不支持动态多媒体数据和实时流数据,且存在着流媒体技术中服务器的承载问题。针对这些问题设计基于P2P流媒体技术的网络教育系统,其中每个网络节点既是服务的消费者又是服务的提供者,针对Web服务模式,有效地解决了流媒体系统中存在的问题,同时具有对网络带宽和服务器处理能力要求低、易部署和易扩展的特点。     

流媒体文件多码率自适应处理系统研究

为了应付流媒体系统应用网络带宽不足问题,设计了基于多码率文件传输技术和可变编解码参数Filters播放链路动态重连机制的自适应流媒体传输系统。该系统在网络带宽发生波动的条件下,能够自适应地选择与可用带宽相匹配码率的视频数据进行动态传输,进而减少视频数据缓冲等待次数和等待时间,有效提高网络带宽利用率和媒体内容服务质量,同时采用"最短"的链路进行媒体内容的动态重连,避免Filters动态重连中出现"卡塞感",有效提高流媒体系统的服务质量。     

移动网络中HTTP视频流终端数据分析及应用

伴随移动通信技术的发展,越来越多的用户选择通过移动网络随时随地观看网络视频,移动视频业务迅速增长.在现有的无线视频传输方式中,由于TCP的可靠性以及易穿透防火墙和网络地址转化等优点,基于TCP的HTTP流逐渐成为网络视频的主流传榆方式.另一方面,用户对业务体验需求的上升,也给移动数据的传输带来巨大挑战.该文通过采集和分析HTTP流的终端数据,获到了HTTP流在HSPA+中传输特性及关键参数的特征,分析结果表明其视频块传输速率变化与自回归模型近似,并在此基础上,提出一种视频等级自适应控制算法,能够有效地改善用户体验.     

A distributed utility‐based scheduling for peer‐to‐peer video streaming over wireless networks

Interactive multimedia applications such as peer‐to‐peer (P2P) video services over the Internet have gained increasing popularity during the past few years. However, the adopted Internet‐based P2P overlay network architecture hides the underlying network topology, assuming that channel quality is always in perfect condition. Because of the time‐varying nature of wireless channels, this hardly meets the user‐perceived video quality requirement when used in wireless environments. Considering the tightly coupled relationship between P2P overlay networks and the underlying networks, we propose a distributed utility‐based scheduling algorithm on the basis of a quality‐driven cross‐layer design framework to jointly optimize the parameters of different network layers to achieve highly improved video quality for P2P video streaming services in wireless networks. In this paper, the quality‐driven P2P scheduling algorithm is formulated into a distributed utility‐based distortion‐delay optimization problem, where the expected video distortion is minimized under the constraint of a given packet playback deadline to select the optimal combination of system parameters residing in different network layers. Specifically, encoding behaviors, network congestion, Automatic Repeat Request/Query (ARQ), and modulation and coding are jointly considered. Then, we provide the algorithmic solution to the formulated problem. The distributed optimization running on each peer node adopted in the proposed scheduling algorithm greatly reduces the computational intensity. Extensive experimental results also demonstrate 4–14 dB quality enhancement in terms of peak signal‐to‐noise ratio by using the proposed scheduling algorithm. Copyright © 2015 John Wiley & Sons, Ltd.     

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。     

P2P流媒体中的多发送端选择算法

 在多对单P2P流模式下,如何选择多个发送端,并为其最优地分配发送速率和数据是一个难题.为此,提出了一种新的多发送端选择和最优速率及数据分配算法(MSRDA).首先把待解决的问题模型化为线性最优化问题,然后给出了求解最优化问题的算法.不同于已有的算法只按链路的丢包率来选择发送端,MSRDA根据到各发送端链路的丢包率与链路的可用带宽比升序排序来选择多发送端,并最优地分配发送速率和数据.理论分析和仿真实验结果表明:在不同的网络条件下MSRDA能有效地减少聚合带宽的丢包率,并具有自适应性,优于现有同类算法.     

Design and Implementation of a Network‐Adaptive Mechanism for HTTP Video Streaming

This paper proposes a network‐adaptive mechanism for HTTP‐based video streaming over wireless/mobile networks. To provide adaptive video streaming over wireless/mobile networks, the proposed mechanism consists of a throughput estimation scheme in the time‐variant wireless network environment and a video rate selection algorithm used to increase the streaming quality. The adaptive video streaming system with proposed modules is implemented using an open source multimedia framework and is validated over emulated wireless/mobile networks. The emulator helps to model and emulate network conditions based on data collected from actual experiments. The experiment results show that the proposed mechanism provides higher video quality than the existing system provides and a rate of video streaming almost void of freezing.     

城域网承载流媒体业务统计特征及承载建议

新一代基于SDH的城域网采用了GFP,VC,LCAS等技术以有效地传送数据业务,目前仍然是城域骨干网络的主流部署方案,但是新兴的以视频业务为代表的流媒体业务给整个城域网络系统带来了严峻的带宽和服务考验,通过对流媒体业务的分析提出了适当的流媒体业务模型,依据该流媒体业务模型分析了在不同的传输速率及数据源的条件下流媒体业务的流量特征,并以该分析为基础参考SDH的特点提出了一种城域网承载流媒体业务方案,最后分析了该方案的实用性.     

P2P流媒体技术原理及应用

基于P2P的流媒体技术是一项非常有前途的技术,该技术有两方面的优点:不需要互联网路由器和网络基础设施的支持,因此性价比高且易于部署;流媒体用户不只是下载媒体流,而且还把媒体流上载给其他用户,因此,这种方法可以扩大用户组的规模,且由更多的需求带来更多的资源。由于P2P流媒体系统中节点存在不稳定性,因此P2P流媒体系统需要在文件定位技术、节点选择技术、容错以及安全机制方面有所突破。此外在如何管理节点并建立发布树、如何应付不可预知的节点失效、如何适应网络状态变化方面也面临着一些挑战。     

基于Directshow的H.264流媒体播放器设计

基于目前最新的视频压缩编解码标准H.264,采用Directshow应用框架,设计了网络流媒体播放器系统;Directshow是微软提供的基于windows平台的优秀的流媒体应用架构,H.264标准具有高压缩比和优良的网络亲和性,基于Directshow和H.264设计的网络流媒体播放器不仅具有优良的系统架构,同时具有更好的灵活性和可扩展性,可以很方便地应用于视频点播系统（Video On Demand System）中和移植到嵌入式WINCE平台。基于Directshow分析和设计了网络源Filter和H.264解码Filter,同时阐述了网络流媒体播放器系统的整体框架。     

Reducing Channel Capacity for Scalable Video Coding in a Distributed Network

In recent years, the development of multimedia devices has meant that a wider multimedia streaming service can be supported, and there are now many ways in which TV channels can communicate with different terminals. Generally, scalable video streaming is known to provide more efficient channel capacity than simulcast video streaming. Simulcast video streaming requires a large network bandwidth for all resolutions, but scalable video streaming needs only one flow for all resolutions. In previous research, scalable video streaming has been compared with simulcast video streaming for network channel capacity, in two user simulation environments. The simulation results show that the channel capacity of SVC is 16% to 20% smaller than AVC, but scalable video streaming is not efficient because of the limit of the present network framework. In this paper, we propose a new network framework with an SVC extractor. The proposed network framework shows a channel capacity 50% (maximum) lower than that found in previous research studies.     

无线网络中的快速自适应实时流媒体控制算法

在流媒体网络传输中,如何降低媒体流的误码率和提供更好的媒体质量一直是流媒体研究所关注的焦点问题.本文在分析比较各类算法后,提出了一种适用于无线网络中的快速自适应实时流媒体控制算法,该算法能快速获取当前网络情况,并在保证媒体流质量稳定的前提下,非常快速、准确地调整发送端的媒体流速率.实验表明,该算法能够在不稳定的网络环境...     

具负载平衡之IPTV影音串流系统

影音媒体具高带宽及实时特性,因此影音串流系统的服务质量的提升端赖影音服务器的有效管理。在此提出一套Video replication及Access request distribution的算法,藉由将热门影音分散到各影音服务器以及影音存取的分散,以达到各影音服务器系统负载平衡的效果。在此比较了3个不同的算法的负载平衡的状况,经实例验证,提出的算法确能达到影音服务器负载平衡的效果,承载更多的系统服务要求。该系统构建在Smart-i TV的IPTV系统台,并讨论了实作的相关技术。     

Scalable 3D video streaming over P2P networks with playback length changeable chunk segmentation

3D video distribution over P2P networks has been thought as a promising way for 3D video entering home. The convergence of scalable 3D video coding and P2P streaming can provide diverse 3D experiences for heterogeneous clients with high distribution efficiencies. However, the conventional chunk segmentation and scheduling algorithms originally aiming at the non-scalable 2D video streaming are not very efficient for scalable 3D video streaming over P2P networks due to the particular data characteristics of scalable 3D video. Based on this motivation, this paper first presents a playback length changeable 3D video chunk segmentation (PLC3DCS) algorithm to provide different error resilience strengths to video and depth as well as layers with different importance levels in the 3D video transmission. Then, a hybrid-priority based chunk scheduling (HPS) algorithm is proposed to be tied in with the proposed chunk segmentation algorithm to further promote the overall 3D video P2P streaming performance. The simulation results show that the proposed PLC3DCS algorithm with the corresponding HPS can increase the success delivery rates of chunks with more important levels, and further improve the user’s quality of 3D experience.     

P2P流媒体技术及其在网络教育中的应用研究

P2P(peer to peer)网络是互联网资源共享的理想途径,为了解决流媒体与带宽之间的矛盾,提出将P2P技术应用于流媒体传输。在流媒体中融入P2P技术,用户可以突破当前网络带宽瓶颈并提高节目播放质量。在此基础上,给出了一个具体的P2P流媒体直播系统的实例。构建了满足现代网络教育的P2P流媒体实现平台,重点叙述基于此平台的网络教育系统基本结构和解决方案,使系统可以满足高质量的教学视频直播。     

基于信息中心5G车联网中社会感知的流媒体缓存与转发策略

5G 通信技术的到来为车载自组网（VANET）提供高质量的视频流服务奠定了基础。然而,现有的VANET 仍然采用以主机通信而非内容分发的 IP 网络来分发视频数据,造成了网络功能与设计目标之间的不匹配,为提供高质量的视频服务带来了巨大挑战。基于上述问题,提出了一种以信息为中心的社会感知流媒体缓存和转发策略（SACF）,其时间复杂度为O(m²)。首先,通过分析用户节点的行为构建社会感知的虚拟社区;然后,提出了一种视频快速转发机制来支持用户就近获取视频内容;最后,提出了一种基于社区的缓存策略来优化视频的缓存分布。仿真实验结果表明,与最新的解决方案相比,该算法的缓存命中率提高了18%,查找时延降低了33%,平均网络开销减少了14.6%。     

ARMOR – A system for adjusting repair and media scaling for video streaming

To optimize scarce network resources and present the highest quality video, streaming video systems need adapt to the video content as well as the network conditions. This paper presents ARMOR, a video streaming system that dynamically adjusts repair and media scaling to meet current video and network conditions. In order to adapt effectively, ARMOR, and any dynamic video adaptation system, needs to predict the video quality as perceived by end users over the range of scaling and repair choices. Thus, this paper first proposes a novel video quality metric called distorted playable frame rate that provides estimation of user perceptual quality considering temporal and quality degradations. Comprehensive user studies show distorted playable frame rate is more accurate than other video quality metrics. Analytic experiments with distorted playable frame rate and the ARMOR optimization algorithm illustrate the predictive power of the metric in a dynamic, streaming video system. Lastly, implementation and experiments of a complete, fully-functioning ARMOR system show the effective practicality of the proposed approach.     

A brief survey on adaptive video streaming quality assessment

Quality of experience (QoE) assessment for adaptive video streaming plays a significant role in advanced network management systems. It is especially challenging in case of dynamic adaptive streaming schemes over HTTP (DASH) which has increasingly complex characteristics including additional playback issues. In this paper, we provide a brief overview of adaptive video streaming quality assessment. Upon our review of related works, we analyze and compare different variations of objective QoE assessment models with or without using machine learning techniques for adaptive video streaming. Through the performance analysis, we observe that hybrid models perform better than both quality-of-service (QoS) driven QoE approaches and signal fidelity measurement. Moreover, the machine learning-based model slightly outperforms the model without using machine learning for the same setting. In addition, we find that existing video streaming QoE assessment models still have limited performance, which makes it difficult to be applied in practical communication systems. Therefore, based on the success of deep learned feature representations for traditional video quality prediction, we also apply the off-the-shelf deep convolutional neural network (DCNN) to evaluate the perceptual quality of streaming videos, where the spatio-temporal properties of streaming videos are taken into consideration. Experiments demonstrate its superiority, which sheds light on the future development of specifically designed deep learning frameworks for adaptive video streaming quality assessment. We believe this survey can serve as a guideline for QoE assessment of adaptive video streaming.     

P2P网络流媒体播放系统研究

介绍了一种基于P2P网络平台上新的流媒体播放技术,它将P2P网络技术和流媒体技术结合起来,充分利用网络闲置的带宽资源和存储资源,突破了传统的流媒体播放系统带宽瓶颈.它采用多点下载和文件分块重组方法,一边下载一边播放,能够保持节目流完整而流畅地播放.