土豆网：“全土豆计划”提升用户体验

土豆网无线及终端业务副总裁吴铮表示，土豆网持续致力于消除视频用户在创造、分享视频时所遭遇的终端、网络等困扰，未来将与运营商、终端厂商以及其他合作伙伴进行广泛合作，通过创造理想的网络视频合作环境，为中国网络视频用户提供更好的服务与体验。     

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.     

基于丢包率统计的无线流媒体码率动态适配技术的研究

随着移动通信技术的不断发展,流媒体视频在无线环境下的应用得到普及。然而,移动网络环境所存在的不稳定性可能导致误码率高以及阻塞丢失严重的情况,从而严重影响用户的观看体验。因此,如何在现有移动网络环境发生频繁切换或网络较不稳定的情况下,仍使用户获得较好的流媒体视频播放体验,成了迫切需要解决的课题。本文研究提出了一种基于丢包率统计的无线环境下流媒体码率动态适配的方法,能够根据网络环境条件为用户重新选择适合用户的播放体验的视频码率,从而保证视频的传输质量和流畅度,优化用户的视频体验。     

自适应流媒体技术在CDN中的应用研究

内容分发网络(CDN)面临多终端、多业务融合所带来的各种技术挑战,自适应流媒体技术是一种结合了流控和HTTP渐进式下载的分发技术,它能够自动适应网络带宽,为用户提供良好的视频播放体验。论述CDN平台承载自适应流媒体业务所面临的技术挑战,并提出相应的应用解决方案,提高用户的视频服务体验,满足不断发展的视频服务需求。     

三网融合下H.264/SVC应用简析

形态不同、解码和显示能力不同、接入方式不同、网络环境不同的终端分享同一视频,要想使用户感觉和体验一致,需要采用自适应编码技术。文章分析H.264/SVC(可伸缩视频编解码)自适应编解码技术在三网融合视频业务中应用的必要性,探讨其在三屏互动和移动视频业务中的应用,讨论H.264/SVC的两项关键技术:视频转码技术和宽带检测技术,指出现有的终端数量庞大,很难升级改造使其支持H.264/SVC解码,因此必须逐步引入。     

5G高低频组网协同机制与策略

提出一种综合考虑业务需求、用户体验、终端能力、空口能力、网络状态的协同机制。该机制利用智能化手段预测多层目标网络的用户体验预期,实现用户与网络的最优匹配。该机制按照用户体验最优、网络效能最高的策略编排网络,避免了传统的单一协同机制带来的诸多问题。用户体验与网络效能双优的高低频协同机制与策略对于未来高低频多层网络的有机融合有着重要的理论意义。     

融合视频通信中提升视频服务质量的终端关键技术研究

为应对移动互联网下视频通信的变化,本文对不同终端的屏幕及不同网络环境下视频通信的最佳分辨率格式进行了研究,并提出了一种屏幕适配的视频协商技术,对其进行了分析和探讨.以期利用现有条件,通过技术方案的优化,提升视频通信的用户体验.     

智慧家庭的VR全景视频业务实现

全景视频作为一种新的视频格式极大程度地改变了用户观看视频的方式,可以提升智慧家庭在视频领域的用户体验。IPTV良好的解码能力以及优异的网络支撑等优势对全景视频的应用推广具有积极作用。结合VR全景视频的特点,分析了超高分辨率全景视频在IPTV平台中的技术挑战,同时基于FOV视点自适应框架,结合MCTS编码、多分辨率和多tile视频分发和终端根据视点部分解码tile技术,给出一种IPTV超高分辨率全景业务实现方案。     

基于Q学习的异构无线网络动态切换策略

提出了一种基于Q学习的动态切换策略,用于最大化用户体验(QoE).基于Q学习的动态切换策略选择最佳网络,不仅利用当前网络状态还利用了未来网络状态和用户终端状态.不同于其他动态规划算法,该算法不需要获取无线网络环境的信息,而是通过利用用户终端过去经验来学习最优策略.仿真结果显示,该动态切换策略能以较少网络间切换次数来接近甲骨文优化算法性能,从而使用户体验得到更优质的网络音频服务.     

5G业务无线承载方案探讨

由于5G业务的多样性和网络的复杂性,传统的单独基于信道质量或基于负荷的无线承载策略并不能满足用户差异化的网络需求.因此5G网络需要智能无线承载策略,即以感知提升为目标,综合考虑业务需求、网络负荷、信道质量、终端能力等各种因素,将用户引导到最优目标频点,以实现网络资源与业务需求精确匹配,实现业务体验最优.     

Optical microwave source

A novel device for tunable optical microwave generation is presented. The capability to tune the microwave frequency as well as the locking characteristics of the developed device are experimentally investigated     

Markovian source separation

A maximum likelihood (ML) approach is used to separate the instantaneous mixtures of temporally correlated, independent sources with neither preliminary transformation nor a priori assumption about the probability distribution of the sources. A Markov model is used to represent the joint probability density of successive samples of each source. The joint probability density functions are estimated from the observations using a kernel method. For the special case of autoregressive models, the theoretical performance of the algorithm is computed and compared with the performance of second-order algorithms and i.i.d.-based separation algorithms.     

Lossy source coding

Lossy coding of speech, high-quality audio, still images, and video is commonplace today. However, in 1948, few lossy compression systems were in service. Shannon introduced and developed the theory of source coding with a fidelity criterion, also called rate-distortion theory. For the first 25 years of its existence, rate-distortion theory had relatively little impact on the methods and systems actually used to compress real sources. Today, however, rate-distortion theoretic concepts are an important component of many lossy compression techniques and standards. We chronicle the development of rate-distortion theory and provide an overview of its influence on the practice of lossy source coding     

Nanoplasmonic-gold-cylinder-array-enhanced terahertz source

Photoconductive antennas (PCAs) based on nanoplasmonic gratings contact electrodes have been proposed to satisfy the demand for high power, efficiency and responsivity terahertz (THz) sources. Reducing the average photo-generated carrier transport path to the photoconductor contact electrodes was previously considered the dominant mechanism to improve PCAs'' power. However, considering the bias in a real device, the electric field between gratings is limited and the role of surface plasmonic resonance (SPR) field enhancement is more important in improving THz radiation. This paper, based on SPR, analyzes the interaction between incident light and substrate in nano cylinder array PCAs and clearly shows that the SPR can enhance the light absorption in the substrate. After the optimization of the structure size, the proposed structure can offer 87% optical transmission into GaAs substrate. Compared with conventional PCAs, the optical transmission into the substrate will increase 5.8 times and the enhancement factor of substrate absorption will reach 13.7 respectively.     

Causal source codes

Causal source codes are defined. These include quantizers, delta modulators, differential pulse code modulators, and adaptive versions of these. Several types of causal codes are identified. For memoryless sources it is shown that the optimum performance attainable by causal codes can be achieved by memoryless codes or by time-sharing memoryless codes. This optimal performance can be evaluated straightforwardly.     

Depolarised broadband source

A depolarised broadband source is demonstrated by depolarising the output of a superluminescent diode with a short length of Hitachi single polarisation fibre. A degree of polarisation of less than 10?3 is achieved.     

可自矫正程控电压源

基于程控电压源的设计，为使其转换结果更为精确，利用A/D、D/A的组合电路进行自动矫正，系统由单片机进行控制，并附有键盘、显示等外围设备，使整个系统趋于实用，同时具有很好的扩展和改进余地、以满足不同要求。