一种适用于数字视频传输的实时传输协议

网络数字视频监控系统的关键技术之一是视频传输.本文针对网络数字视频监控系统中视频传输的特点,对适用于数字视频传输的实时传输协议进行了研究.在对实时传输协议（RTP）和实时传输控制协议（RTCP）规范进行深入研究的基础上,根据网络数字视频监控系统具体应用的要求,设计了一种称之为“SRTP/SRTCP”的实时数据传输协议,并对该协议进行了具体实现.     

数字视频广播卫星传送标准中的RS码

在数字卫星电视信号传送中的ＦＥＣ中,常采用ＲＳ码,讨论了ＲＳ码的三个问题;１）伽罗华域ＧＦ（２＾８）;２）ＲＳ的码的编码;３）ＲＳ码的检错和纠错。     

数字视频网络传输层协议的选择

随着视频压缩技术的日益成熟，数字视频监控产品逐渐成为了市场的主流。人们迫切希望网络技术能够成功地应用于数字视频监控领域，以使人们能够通过网络实现异地监控。正是在这种背景下，“基于网络的数字视频传输”课题研究日显重要。本文围绕网络视频传输的实时性和传输质量两大重要指标，从“解决传输层协议问题”入手，通过对TCP和RTP的比较，提出了“基于UDP协议的RTP实时视频传输”的设计思想，较好地保证了数字视频传输的实时性和服务质量。     

PDM: A versatile digital transmission system for video

This report discusses a pulse density modulation (PDM) video transmission system. PDM is a one-bit digital coding scheme with advantages of transparency due to an inherently extended signal bandwidth and relatively simple decoding; these make it ideal for a variety of applications. The system outlined is designed to carry a single analogue video channel, together with several sound channels, over a 140 or 280 Mbit/s digital transmission-link. An alternative option to the sound channels will be to carry a 2.048 Mbit/s data channel. Since the analogue video input will be PDM coded, this will enable the system to carry video formats which have a flat base-band frequency response requirement of in excess of 20 MHz (such as HDTV), allowing a large degree of flexibility in use.     

LVDS技术在数字视频传输系统中的应用

提出一种基于LVDS技术的视频传输系统,该系统是以APA150和DS92LV18为核心,考虑到长距离图像传输的需要,增加了LVDS差分信号预加重和均衡功能.实践证明,该系统能够满足视频图像的远距离实时传输要求,结构简单且扩展性强.     

数字图像传输中的误差控制与掩蔽技术

讨论信道噪声和网络拥塞对数字图像传输造成的影响及其相应的解决方法。在不考虑网络自身因素的情况下，重点从编解码的角度出发探讨误码控制和掩蔽技术。     

卫星地球站数字视频系统的测量

随着视频处理和传送技术的发展，当今卫星地球站数字广播传输系统与经典的模拟微波广播电视传输系统及电视发射机在视频信号处理和调制方面有着本质的区别。若仍用模拟视频测量技术去测量卫星数字视频广播系统，用测量静止的模拟视频技术指标去衡量数字视频传输系统的性能是非常不恰当的。如何监测地球站数字传输系统设备，如何通过测量地球站数字视频的技术指标去衡量数字系统性能，是下文讨论的问题。１两种传送系统的本质区别卫星地球站数字视频传输系统与经典的模拟视频微波传送系统框图如图１所示。１．１模拟系统从图１a可知：模拟微…     

数字电视地面广播COFDM传输中的软判决技术

深入研究了数字电视地面广播COFDM解调方案中的解映射软判决技术,提出了适用于该系统的信道状态信息CSI提取方法。在此基础上通过算法仿真分析,进一步提出一种新的克服单频和PAL模拟电视同频干扰的消除法并给出计算公式。本设计基于国家数字高清晰度电视总体组的多载波BDB-T传输方案,方案样机采用FPGA实现其相应的硬件电路,经过在实际无线环境中传输测试,证明了所提方法的易实现性和其良好性能。     

A 20-channel optical communication system using subcarriermultiplexing for the transmission of digital video signals

Microwave subcarriers have been used to demonstrate an optical communication system suitable for the distribution of digital video channels. The design, performance, and optical link requirements are discussed for a 2-Gb/s subcarrier-multiplexed (SCM) system with 20 microwave subcarriers modulated at 100 Mb/s and using a frequency-shift-keyed format. The system uses the 2-6-GHz bandwidth and represents the first example of an SCM system using more than one octave of bandwidth. The bit error rate was measured for all 20 channels; results for five typical channels are shown and discussed. The performance results show that a digital SCM approach is attractive in an optical link for a multichannel wide bandwidth video distribution system made from standard microwave components     

Bidirectional WDM passive optical network for simultaneous transmission of data and digital broadcast video service

We have demonstrated an easily upgradable bidirectional passive optical network for the simultaneous transmission of wavelength-division-multiplexing channels and digital broadcast video signals. The proposed network could transmit 15 2.5-Gb/s downstream channels, 15 155-Mb/s upstream channels, and one broadcast signal consisting of more than 70 digital video channels.     

Content-based resynchronization for robust video transmission

Recent advances in technology have resulted in a significant growth in wireless communications, which have resulted in a strong demand for reliable transmission of video data. The challenge of robust video transmission is to protect the compressed data against hostile channel conditions while bringing little impact on bandwidth efficiency. Here, using macroblock (MB)-based segmentation results, we propose a framework for the positioning of resynchronization markers such that the image quality of foreground can be improved at the expense of sacrificing the unimportant background. Experimental results demonstrate that this scheme significantly improves the subjective quality of video sequence for robust video transmission.     

Digital video transmission for broadband networks

The information society to come is characterized by a large information flow in the integrated broadband network. Today it is the distribution of TV programmes that requires high transmission capacity. This leaves the cable operator with a problem. How should the CATV network of today be constructed? It must fulfil the need for distribution now and it must be prepared for new services to come. Some aspects of the above problem are discussed in this paper. It is emphasized that digital techniques as well as optical fibre transmission should be included in a modern cable network. The Danish DOCAT network concept is presented as one way to accomplish this. DOCAT combines optical fibre transmission in the trunk network with conventional coaxial techniques in the subscriber network.     

视频传输中的码率控制技术

码率控制是视频通信系统中的一个天键环节，主要用于调摔编码视频的输出质量。设计码率摔制系统时一般需要涉及目标码率计算、信源与信道模型建立、视频编码方法、率失真估计、码率分配、跳帧、实时性、传输环境和系统性能评估等诸多方面。新出现的网络视频流媒体传输、无线信道传输、MPEG-4的对象编码传输、信噪比精细可分级编码传输等实际应用要求鲁棒高效的码率控制算法来满足视频实时传输的需要。相应的码率摔制算法已成为近几年的研究热点。本文给出了视频码率控制技术的系统框架和基本要求，介绍了现有的各种恒定码率(CBR)与可变码率(VBR)摔制算法，综合比较了各自的优缺点，概括论述了视频码率控制技术的发展现状，并给出了下一步的研究方向。     

New codes for digital transmission

Two new pseudoternary codes suitable for digital line transmission are proposed. Each is of 10B7T format. They have digital-sum variation, intersymbol interference, timing content and framing information comparable with 4B3T and MS43, respectively, but offer a higher information capacity for a given symbol rate.     

Codes for digital line transmission

Some ternary line codes using alternative codeword sets are described; it is shown that, compared with the currently accepted 4B3T codes, some reduction in redundancy can be achieved without increasing the digital-sum variation.     

Multimode-fiber technology for digital transmission

Multimode-fiber systems are presently being installed to meet some of the burgeoning demands for digital transmission in the telecommunications industry. These first-generation systems operate near 0.85-µm wavelength with laser transmitters and avalanche-photodiode receivers. Second-generation multimode systems may use simpler and more reliable LED's and p-i-n photodiodes operating near 1.3 µm, where fibers exhibit much lower loss and dispersion. This paper summarizes the state of the art of multimode-fiber digital transmission with special emphasis on emerging technologies for operation in the 1.1-1.7- µm wavelength region. Graded-index multimode fibers, lasers, LED's, photodetectors, receiver sensitivities, and noise penalties are considered. Finally, some of the requirements and challenges in applying these technologies are discussed.     

Design tools for analog and digital ICs

The era of the system on a chip is well under way, bringing in its train new headaches for the IC design engineer. One reason for the difficulties is that such systems are increasingly being built up from an assembly of pre-designed components-so-called intellectual property (IP) or virtual components-which sometimes come from diverse sources. Further, a decision is often demanded very early in the design process as to which functions will be executed in hardware and which in software, after which concurrent design of both components is necessary to ensure they work together. Then, too, the shrinking dimensions of the structures that make up the chip are compelling consideration of their physical and electrical properties in much more detail than ever before. All the while, market pressures are forcing companies to design and verify application-specific ICs with millions of logic gates in less and less time     

Lightweight digital video stabilization for small-size robot

Though constrained by payload and processing, small robots have gained applications in collecting visual information from the scene. Typically these small-size robots do not carry data loggers and send the video information to a hand-held device at a remote location for visual observations. Due to sophisticated processing and control limitations from mechatronics resources, the video captured by the robot is subjected to the effects of unintended motion, which requires digital methods for video stabilization. For a lightweight solution for video stabilization, we avoid use of any external hardware and develop a Singular Value Decomposition (SVD) based digital algorithm that avoids explicit feature tracking and motion estimation during stabilization. The process involves identifying a subspace with minimal dimensions that contains information of intentional motion alone. This work identifies the minimal subspace for video stabilization using the sliding window geometry method for practical implementation. Further, a shape-preserving filter is utilized to remove perturbations induced by the unintended motions, thereby resulting in the reconstruction of the stabilized video sequence. Experimental results on two different small-size robots viz spherical robot and Unmanned Aerial Vehicle (UAV) in indoor and outdoor settings, respectively, show quality outcomes without any change in parameters of the proposed filter design. Performance comparison with existing methods on the quality of stabilized video shows that the proposed stabilization method overcomes the non-availability of features for tracking due to large amplitudes and limited onboard resources. With the proposed video stabilization method, there is a potential for wider applicability of small-size robots in remote visual observations.     

Long transition analysis for digital video sequences

Video indexing is a technique used to extract objects within a video sequence and index them so that they can be used for future retrieval. In many video sequences, special effects such as fade and wipe are incorporated, and in some cases, it is desirable to be able to include objects within such effects for indexing. In this paper, we introduce an automatic process that determines the type of transition and extracts information from it, so that this information can be used in object extraction. Such a process consists of four stages: shot boundary refinement, shot type determination, frame reconstruction for soft transitions, and shot classification for hard transitions. In this paper, we will give the implementation, timing, and performance analysis for each stage. Long transition analysis bridges the gap between shot boundary detection and object tracking and smoothes the process of automatic video indexing for video databases.