En-Route Transcoding缓存的优化放置和替换

对en-route transcoding缓存中的缓存路由和协同放置及替换问题进行了研究.提出了CCRA(cost-aware cache routing algorithm)缓存路由算法,能以可控的探测开销来发现潜在的、具有最小访问开销的缓存对象.在此基础上,建立了en-route transcoding缓存的分析模型,将缓存放置和替换问题形式化为一个最优化问题,并利用一种基于动态规划的方法来求解最佳缓存放置策略.仿真结果表明,与已有的元算法放置策略相比,该协同放置和替换策略可以获得更好的CSR性能.

一种有资源适应性的transcoding代理缓存机制

在基于transcoding代理的流媒体服务系统中,CPU和网络是两种潜在的瓶颈资源.本文提出了一种有资源适应性的transcoding代理缓存机制,统一考虑CPU和网络的资源需求,以提高系统的服务能力.首先推导了多版本缓存策略下网络收益和CPU收益的计算方法.通过引入一个时变的影响因子α(t),给出了缓存系统聚合资源收益的表达.在此基础上给出了单个对象的缓存价值函数,并设计了RAC替换算法.实验表明RAC具有较好的资源适应性和系统吞吐率.

Energy-Efficient Joint Caching and Transcoding for HTTP Adaptive Streaming in 5G Networks with Mobile Edge Computing

With the new promising technique of mobile edge computing (MEC) emerging, by utilizing the edge computing and cloud computing capabilities to realize the HTTP adaptive video streaming transmission in MEC-based 5G networks has been widely studied. Although many works have been done, most of the existing works focus on the issues of network resource utilization or the quality of experience (QoE) promotion, while the energy efficiency is largely ignored. In this paper, different from previous works, in order to realize the energy efficiency for video transmission in MEC-enhanced 5G networks, we propose a joint caching and transcoding schedule strategy for HTTP adaptive video streaming transmission by taking the caching and transcoding into consideration. We formulate the problem of energy-efficient joint caching and transcoding as an integer programming problem to minimize the system energy consumption. Due to solving the optimization problem brings huge computation complexity, therefore, to make the optimization problem tractable, a heuristic algorithm based on simulated annealing algorithm is proposed to iteratively reach the global optimum solution with a lower complexity and higher accuracy. Finally, numerical simulation results are illustrated to demonstrated that our proposed scheme brings an excellent performance.

MPEG-2到H.263 Transcoding的若干关键问题

该文在前人的工作基础上提出了在压缩域MPEG-2到H.263码流transcoding的通用框架,并进行了深入的分析和优化。这种优化的目标是,在实现视频流格式转换和瘦化的同时能够最大程度地利用源视频流的计算信息。该文对transcoding过程进行了形式化推导和分析,使transcoding的计算复杂性和存储消耗大大降低,同时理论上能实现在transcoding级上的更好视频质量(与传统方法相比)。这种通用框架能够以标准附件的形式加入高级应用功能,如数据隐藏模块、误码掩藏模块、链路适应模块。这种工作的意义在于,通过把transcoding复杂性推向网络边缘设备transcoder,降低了用户的硬件更新成本和视频服务器存储成本,使不同类型终端和不同链路环境的用户能够高效地透明地访问高质量视频流域。同时,计算复杂性和存储消耗的降低有利于服务器端以较低成本实现更多用户接入能力。

Fast mode decision algorithm for spatial resolutions down-scaling transcoding to H.264

A fast mode decision algorithm is proposed in this paper to accelerate the process of transcoding videos into H.264with arbitrary rate spatial resolution down-scaling. The proposed algorithm consists of three steps. First, an early-stop technique is introduced to determine the 16× 16-mode blocks, which take up about 70% of all the macroblocks; then, a bottom-up merging process is performed to determine the mode of rest non-early-stopped blocks; and then, we adopt half-pixel motion estimation to further refine the acquired predictive motion vectors. In order to obtain the predictive motion vectors for early-stop and merging processes, we propose a motion vector composition scheme, which can reuse the information in the input pre-encoded videos to handle the spatial resolution down-scaling. Experimental results showed that our algorithm is about four times faster than the Cascaded-Decoder-Encoder method and has negligible PSNR drop and little bit rate increase.

Resynchronization and remultiplexing for transcoding to H.264/AVC

H.264/MPEG-4 AVC standard appears highly competitive due to its high efficiency, flexibility and error resilience. In order to maintain universal multimedia access, statistical multiplexing, or adaptive video content delivery, etc., it induces an immense demand for converting a large volume of existing multimedia content from other formats into the H.264/AVC format and vice versa. In this work, we study the remultiplexing and resynchronization issue within system coding after transcoding, aiming to sustain the management and time information destroyed in transcoding and enable synchronized decoding of decoder buffers over a wide range of retrieval or receipt conditions. Given the common intention of multiplexing and synchronization mechanism in system coding of different standards, this paper takes the most widely used MPEG-2 transport stream (TS) as an example, and presents a software system and the key technologies to solve the time stamp mapping and relevant buffer management. The solution reuses previous information contained in the input streams to remultiplex and resynchronize the output information with the regulatory coding and composition structure. Experimental results showed that our solutions efficiently preserve the performance in multimedia presentation.

MEC-Assisted Flexible Transcoding Strategy for Adaptive Bitrate Video Streaming in Small Cell Networks

Adaptive bitrate video streaming(ABR)has become a critical technique for mobile video streaming to cope with time-varying network conditions and different user preferences.However,there are still many problems in achieving high-quality ABR video streaming over cellular networks.Mobile Edge Computing(MEC)is a promising paradigm to overcome the above problems by providing video transcoding capability and caching the ABR video streaming within the radio access network(RAN).In this paper,we propose a flexible transcoding strategy to provide viewers with low-latency video streaming services in the MEC networks under the limited storage,computing,and spectrum resources.According to the information collected from users,the MEC server acts as a controlling component to adjust the transcoding strategy flexibly based on optimizing the video caching placement strategy.Specifically,we cache the proper bitrate version of the video segments at the edge servers and select the appropriate bitrate version of the video segments to perform transcoding under jointly considering access control,resource allocation,and user preferences.We formulate this problem as a nonconvex optimization and mixed combinatorial problem.Moreover,the simulation results indicate that our proposed algorithm can ensure a low-latency viewing experience for users.

Video transcoding for adaptive bitrate streaming over edge-cloud continuum

Video transcoding is to create multiple representations of a video for content adaptation.It is deemed as a core technique in Adaptive BitRate(ABR)streaming.How to manage video transcoding affects the performance of ABR streaming in various aspects,including operational cost,streaming delays,Quality of Experience(QoE),etc.Therefore,the problems of implementing video transcoding in ABR streaming must be systematically studied to improve the overall performance of the streaming services.These problems become more worthy of investigation with the emergence of the edge-cloud continuum,which makes the resource allocation for video transcoding more complicated.To this end,this paper provides an investigation of the main technical problems related to video transcoding in ABR streaming,including designing a rate profile for video transcoding,providing resources for video transcoding in clouds,and caching multi-bitrate video contents in networks,etc.We analyze these problems from the perspective of resource allocation in the edge-cloud continuum and cast them into resource and Quality of Service(QoS)optimization problems.The goal is to minimize resource consumption while guaranteeing the QoS for ABR streaming.We also discuss some promising research directions for the ABR streaming services.

Fast Intra Downsizing Based on Direction for H.264/AVC Transcoding

A fast algorithm based on direction in intra frame downsizing in H.264 is proposed,which used modes information of macroblocks before transcoding and the direction relation of modes between decoding and re-encoding in transcoding.This algorithm also made use of statistics between decoded modes and re-encoded modes,which came from a lot of sequences data experiments.Without full modes encoding,it can improve the speed of reducing intra-prediction frame resolution obviously.Comparing to traditional transcoding,it only needs to compute one of thirteen modes in re-encoding.The experiments show that this algorithm can significantly speed up 92 percent transcoding time in intra-prediction frame of H.264 with slight PSNR degradation.It also can support an improvement in real-time for transcoding and ability of bandwidths changing.

Scheduling Heuristics for Live Video Transcoding on Cloud Edges

Efficient video delivery involves the transcoding of the original sequence into various resolutions,bitrates and standards,in order to match viewers’capabilities.Since video coding and transcoding are computationally demanding,performing a portion of these tasks at the network edges promises to decrease both the workload and network traffic towards the data centers of media providers.Motivated by the increasing popularity of live casting on social media platforms,in this paper we focus on the case of live video transcoding.Specifically,we investigate scheduling heuristics that decide on which jobs should be assigned to an edge minidatacenter and which to a backend datacenter.Through simulation experiments with different Qo S requirements we conclude on the best alternative.

ZTE IPTV Low Bit Rate High Definition Transcoding Solution Nominated for Global IPTV Industry Award

ZTE Corporation announced on 1 March that its innovative IPTVlowbitrate highdefinition transcoding solution has been nominated for the World＇s Best Component or Enabler Award by the IPTV World Forum. The ZTE solution is on display at the Mobile World Congress 2012 （MWC 2012） in Barcelona.

拼音转码对汉语二语听力理解水平的影响——来自路径效应分析的证据

汉字不直接表音,汉语拼音转码水平对汉语二语听力理解的认知作用是汉语国际教育中的重要理论问题。本研究采用路径分析方法考察138名初、中、高汉语水平在华留学生拼音转码、汉字产出及汉语听力理解水平之间的关系,其中拼音转码测查包含了听觉、视觉两个通道的任务。结果发现:(1)听觉通道的语音-拼音转码(听写拼音)比视觉通道的汉字-拼音转码(看汉字写拼音)容易些,两种转码成绩间有着深层关联;(2)两种拼音转码成绩均对汉语听力理解水平有显著影响,影响力受学习者汉语水平和母语背景的调节,其中听觉转码在初、中级阶段均有显著影响,视觉转码的影响在中级阶段开始显著,两种转码影响在高级阶段开始收敛但仍对汉字产出成绩有显著影响。在母语背景差异方面,汉字圈学生拼音转码对听力理解的影响更多受到汉字水平的调节,非汉字圈学生则主要是直接的听觉转码路径;(3)影响源分析发现,拼音转码对听力理解的影响主要来源于难点声韵母和声调成绩。结果表明,拼音转码对汉语二语听力理解具有多路径的重要影响,作为二语的汉语拼音教学要保证一定的质量及持续性。

基于5G的演播室信号直播与制作

传统演播室信号直播依赖4G或更早期的技术,在速度和稳定性方面有所限制。5G提供了更高的数据传输速度和更低的延迟,为高质量、实时的视频直播创造了条件。从电视技术专业的视角,分析基于5G的信号回传系统设计,包括前端系统和自动转码系统;分析4G技术在演播室信号直播中的优势,阐述5G在演播室信号直播及制作中的应用,重点关注LIVE模式和S&F模式,为未来演播室技术的发展提供新的视角和实践指导。

Close-Loop Bell-Bloom Magnetometer with Amplitude Modulation

A high sensitive optical amplitude modulation magnetometer is investigated and demonstrated experimentally. We build an experimental platform for the atomic magnetometer and configure it as a Bell-Bloom magnetometer with amplitude modulation of 50% duty cycle square waveform. The open-loop input-output model is deduced from the Bloch equation and is verified experimentally. Instead of locking the frequency by using a voltage control oscillator, we realize a closed loop using the coils to generate a feedback field which avoids the stringent require- ment of a high resolution frequency meter and markedly expands the dynamic range as well as the bandwidth. We realize an open loop sensitivity of 0.8pT/Hz1/2 at 20 Hz using a single light beam, which exceeds that of the state-of-the-art Bell-Bloom magnetometers, and the corresponding closed loop sensitivity is 1.2 pT/Hz1/2.

Adaptive rate control on wireless transcoder

To guarantee the real-time transmission of a video stream, based on the stochastic optimal control method, a frame layer adaptive rate control algorithm for the wireless transcoder is proposed, which is capable of dynamically determining the transcoder＇s objective bit rate, according to the bandwidth variation of the wireless channel and the buffer occupancy. Then the transient performance, steady performance, and computational complexity of the algorithm are analyzed. Finally, the experiment results demonstrate that the algorithm can improve the synthetic performance of rate control through the compromise between the end-to-end delay and the playout quality.

Close-Loop System Identification Using Over-sampling Scheme and Its Estimate Accuracy Analysis

A new identification method for a linear discrete-time closed-loop system is proposed based on an output over-sampling scheme. When the system outputs are over-sampled the new output sequences would contain more information about the plant structure. Using general least squares method （GLS） the plant over-sampled model should be recognized. Then the original plant model should be obtained by its relationship with the over-sampled model. Compared with conventional approaches the advantage of the new method is that even if the ordinary identifiability conditions are not satisfied, a close-loop system can be identified by using the oversampled output without utilizing any external test signal. Accuracy analysis shows the relationship between the estimation error and the over-sampling rate. Numerical simulation illnstrates its effectiveness.

Subsystem model-based close-loop grey-box identification method for hydraulic stewart platform

In order to solve the problem of difficult modeling and identification caused by time-variable parameters,multiple inputs and outputs and unstable open loop,a subsystem model-based close-loop grey-box identification method was put forward when consider the main coupling effects of hydraulic Stewart platform.Firstly,the whole system is divided into three TITO(Two Input Two Output) subsystems according to the characteristics of the pseudo-mass matrix,hence transfer function matrix model of the subsystem can also be found.Secondly,since the Stewart platform is unstable,the close-loop transfer model of the subsystem is derived under the proportional controllers.The inverse M serial is adopted as the identification signal to get the experimental data.All parameters of the subsystem are determined in close-loop indirect identification by PEM(Prediction Error Method).Finally,a case study validates the correctness and effectiveness of the subsystem model-based close-loop grey-box identification method for hydraulic Stewart platform.

Efficient video downscaling transcoder from MPEG-2 to H.264

The new H.264 video coding standard achieves significantly higher compression performance than MPEG-2. As the MPEG-2 is popular in digital TV, DVD, etc., bandwidth or memory space can be saved by transcoding those streams into H.264 in these applications. Unfortunately, the huge complexity keeps transcoding from being widely used in practical applications. This paper proposes an efficient transcoding architecture with a smart downscaling decoder and a fast mode decision algorithm. Using the proposed architecture, huge buffering memory space is saved and the transcoding complexity is reduced. Performance of the proposed fast mode decision algorithm is validated by experiments.

轨道交通工程设计元数据应用研究

目前轨道交通各专业设计过程及最终的设计成果交付大部分使用的是平面图纸的形式,而数据的彼此交付多采用表格来完成。若没有标准化的分类描述处理方式,会给不同专业、不同部门之间协同合作带来极大不便。为解决该问题,通过对轨道交通工程设计数据资源进行整合梳理,根据元数据标准规范设计数据的语义、格式、结构、描述,建立一个轨道交通行业统一的元数据分类及描述结构标准;按此标准建立一个设计者习惯填报的数据格式,并通过对各专业填报的元数据文件按照统一格式进行结构化格式转换、IFD编码、校验,形成一个标准化数据文件,既可以达到铁路各专业人员协同设计交互文件的目的,又可以达到直接交付工管中心的要求。该研究实现轨道交通工程设计元数据准确、便捷的填报、维护、交付和利用,使轨道交通设计成果元数据贯穿设计、施工、运营、维护整个铁路生命周期,提升设计精细化管理能力,同时实现设计成果的无纸化交付和管理。