图文电视播出系统

图文电视播出系统是图文电视广播系统中重要组成部分之一。其主要功能是把数据文件按CCST图文电视广播规范形成数据行,根据不同用户的需求,准确地插到正常电视信号中循环播出。     

图文电视的种类及节目策划

1　图文电视的种类及基本构成图文电视即文字电视广播 (ＴＥＬＥＴＥＸＴ) ,是一种以图片 (图形 )与文字相结合的形式向观众传输信息的电视节目 ,根据播出和接收方式的不同 ,可分为下列 3种形式的图文电视。1.1　逆程图文电视由计算机将需要发送的图片、文字等信息以数字、数据的形式存储、处理后 ,叠加在正常电视信号的场消隐期 (ＶＢＩ)中的某几行上传送 ,既不占用专门的电视频道 ,也不影响正常电视节目的播出。用户必须使用加装了图文电视解读卡的个人计算机 ,或采用具有图文电视接收功能的电视机进行收看。1.2　正程图文电视正程图文电…     

图文电视解码器

我国图文电视标准于1993年4月由国家技术监督局正式颁布,迄今已有不少电视台按此标准开通了图文电视节目,如中央1台、中央2台及山东、浙江、四川、河南等省级卫视台等。图文电视接收解码器的任务是从电视信号中,拾取图文电视数据行,经过数据处理和解码,然后显示在电视机的屏幕上。     

正程图文电视伴音播出解决方案

1　问题的提出一般而言 ,逆程图文电视是指在电视信号场逆程中插入数据进行数据广播 ,用户通过带有图文电视接收功能的电视机或计算机接收图文数据。而正程图文电视则是利用计算机直接播出电视信号 ,其节目能被普通电视机接收。目前 ,许多电视台利用电视空闲时段或有线频道循环播出正程图文电视节目 ,内容有新闻和各种经济、文体信息等等。作为普通电视节目的有效补充 ,图文电视取得了良好的社会效益和经济效益。在正程图文电视播出过程中 ,图文电视伴音 (背景音乐 )通常用一单独的ＣＤ机或计算机光驱播放。在实际应用中 ,由于正程图文电视…     

图文电视与可视图文

图文电视始创于英国,在1976年初开始应用。我国从80年代初期开始研制图文电视,并制定了有利于汉字扩充及具有完美再现图形能力的CPCPS制式。图文电视是利用电视信号的场消隐期传送图文数据的广播系统。因为图文电视是一种以文字为主,插图为辅的信息传送,所以图文电视也称为电视文字广播。图文电视的文字及图形经过数字技术加工处理,转换成数字脉冲信号,然后将信号压缩在场消隐期的空闲电视行上发送出来。由于图文电视     

CCST制图文电视

ＣＣＳＴ制图文电视徐宁，刘维献１图文电视的意义及发展概况图文电视是目前世界各国争先发展的一项电视多工广播方式，它是利用时分复用的原理，在全电视信号的场消隐期内的特定行的正程传送图文信息，诸如商品广告、股票信息、市场行情、交通信息等有价值的信息。在正常...     

正程图文电视伴音播出解决方案

一般而言,逆程图文电视是指在电视信号场逆程中插入数据进行数据广播,用户通过带有图文电视接收功能的电视机或计算机接收图文数据广播。而正程图文电视则是利用计算机直接播出电视信号,其节目能被普通电视机接收。目前,许多电视台利用电视空闲时段或有线频道循环播出正程图文电视节目,内容有新闻和各种经济、文体信息等等。作为普通电视节目的有效补充,图文电视取得了良好的社会效益和经济效益。     

浅谈电视机加装图文电视解码器

1引言图文电视信号是以数字信号的形式叠加在电视场逆程行中传输的，也就是说图文电视是利用电视的空闲行，不需占用新的频谱资源，利用原电视信号的发射、传输、覆盖系统，以电视信号做为载体的。有了以上基本概念，我们给出一个图文电视系统的框图，如图1所示。图1图文电视的系统框图普通的接收机收到含有图文电视信号的电视节目时，仅能收看电视节目（并对收看电视节目无任何影响）。但增加了图文电视解码器的图文电视接收机不仅可以收看电视节目还可收看大量图文电视信息。我国图文电视标准于1993年4月由国家技术监督局正式颁布执行，迄…     

几种图文电视播出系统的测试与比较

1 引言 图文电视(Teletext)是一种利用电视信号场逆程进行的数据广播技术。近两年,随着人们对信息需求的增加和技术的进步,图文电视作为一种方便、经济的信息传输手段,日益受到人们青睐。除广电系统外,社会上的公司、科研单位等也意识到其潜在的市场价值,开发出了多种图文电视播出和接收设备,对图文电视技术的普及应用和发展起到     

为长虹2588型彩电增加图文电视功能

图文电视是利用场消隐期间有数十条黑扫描行不传送电视图像信号,而将文字和图形以数字信号的形式插入到电视信号的场逆程的空余行中,利用现有的电视发射系统发送,经带有图文电视解码器的电视机接收后,显示出文字或图形等信息的一种公共电视。目前,收看图文电视的方法主要有三种:一是用专门生产的带有图文电视接收功能的电视机,这类电视机国产的不多见,部分进口彩电虽有此项功能,但因接收图文电视制式不符合我国标准,因此无使用价值;二是采用图文接收机与普通电视机配合使用,但这种机外型接收机价格     

Steady-state electron transport in the III–V nitride semiconductors: A sensitivity analysis

We studied the sensitivity of the steady-state electron transport in GaN to variations in the important material parameters related to the band structure. We found (a) that an increase in the lowest conduction-band-valley effective mass leads to a lowering and broadening of the peak in the velocity-field characteristic, as well as to an increase in the field at which the peak occurs; (b) that increases in the upper conduction-band-valley effective masses dramatically decrease the saturation drift velocity, with very little other effect; (c) that increased nonparabolicity of the lowest conduction-band valley leads to a broadening and shifting to higher electric fields of the peak in the velocity-field characteristic; (d) that increases in the intervalley energy separation lead to moderate increases in the peak drift velocity; and (e) that increases in the degeneracy of the upper conduction-band valleys leads to a moderate decrease in the saturation drift velocity.     

基于混沌序列的视频隐私保护系统设计与实现

视频监控的设计目的是维护社会稳定,对于违法犯罪行为能够及时发现并且采取有效措施。然而这类系统在设计之初却忽略了对于个人隐私的保护问题。视频在传递过程中的泄露或者不法分子非法获取视频很容易侵犯个人隐私,造成不良后果。文章研究了基于混沌序列的图像加密解密算法对视频监控中的人脸进行加密,从而保护个人隐私。本系统有两点功能,一是可以对摄像头前的人脸信息进行实时加密,保证了视频录入过程中已经实现了人脸加密;二是对现有的视频中的人脸信息进行加密,保证了视频在传递期间人脸信息的安全性。     

Analysis of lateral-mode behavior in broad-area InGaN quantum-welllasers

A wave-optical model that is coupled to a microscopic gain theory is used to investigate lateral mode behavior in group-III nitride quantum-well lasers. Beam filamentation due to self-focusing in the gain medium is found to limit fundamental-mode output to narrow stripe lasers or to operation close to lasing threshold. Differences between nitride and conventional near-infrared semiconductor lasers arise because of band structure differences, in particular, the presence of a strong quantum-confined Stark effect in the former. Increasing mirror reflectivities in plane-plane resonators to reduce lasing threshold current tends to exacerbate the filamentation problem. On the other hand, a negative-branch unstable resonator is found to mitigate filament effects, enabling fundamental-mode operation far above threshold in broad-area lasers     

Near field in the vicinity of wireless base-station antennas: anexposure compliance approach

Great social concern has risen about the potential health hazard of living near a cellular telephony base-station antenna, and certain technical questions have been posed on the appropriate way to measure exposure in its vicinity. In this paper, a standard spherical near-near field transformation is proposed to obtain the electromagnetic field close to the antenna in free space conditions. The field obtained in this way allows us to define an exclusion zone from the exposure compliance point of view, but also makes it possible to bound the error committed by standard field measurement procedures. Furthermore, the visualization of the electromagnetic field in the proximity of the antenna in free space conditions, allows us to define clearance templates that have to be met in the siting of the antenna in complex environments in order not to obstruct its main beam     

A multi-faceted approach to forecasting broadband demand andtraffic

When forecasting the development of new services, it is advisable to look closely at user demand and the way it is developing, to understand what is driving the changes in demand. Because of the varied nature of these new services, a number of different approaches to forecasting their demand can be applied. The growth in new services, as modeled in this optimistic scenario, leads to a massive increase in the volume of traffic carried by the network. This is not due solely to the growth in the number of terminals, but also to the availability of bandwidth at reasonable prices. The services would still exist if they had to operate over ISDN, but once ATM starts to be used, the available bandwidth allows application designers to incorporate the features and offer the response times needed to provide truly usable applications. This, in turn, reinforces the growth in demand     

Bispectrum estimation: A digital signal processing framework

It is the purpose of this tutorial paper to place bispectrum estimation in a digital signal processing framework in order to aid engineers in grasping the utility of the available bispectrum estimation techniques, to discuss application problems that can directly benefit from the use of the bispectrum, and to motivate research in this area. Three general reasons are behind the use of bispectrum in signal processing and are addressed in the paper: to extract information due to deviations from normality, to estimate the phase of parametric signals, and to detect and characterize the properties of nonlinear mechanisms that generate time series.     

Information transmission with time-continuous random processes

Shannon's definition for the information content of a Gaussian, time-continuous process in Gaussian noise is extended to the case where the observation interval is finite, and where the processes may be nonstationary, in a straightforward way. The extension is based on a generalization of the Karhunen-Loeve Expansion, which allows both the signal and noise processes to be expanded in the same set of functions, with uncorrelated coefficients. The resultant definition is consistent with that of Gel'fand and Yaglom, and avoids the difficulties posed by Good and Doog to Shannon's original definition. This definition is shown to be useful by applying it to the calculation of the information content of some cases of stationary signals in stationary noise, with different spectra, and to one case where both are nonstationary. Limiting relations are derived, to show that this reduces to previously established results in some cases, and to enable one to obtain rule-of-thumb estimates in others. In addition, both the matched filter and the Wiener filter are related to the information; the matched filter in a very direct way, in that it converts a time-continuous process to a set of random variables while conserving the information.     

Power requirements for deep-space telecommunication links

The signal-to-noise ratio in a given equivalent bandwidth must be maintained above a minimum value during a deep-space mission in order to provide predictable performance, and in order to maintain effective telemetry communications with spacecraft at interplanetary distances it is necessary for earth stations to use maximum antenna gain. One solution is to extend telecommand range by reducing system noise temperature in the spacecraft receiver and reducing the bandwidth of the receiver's phase-lock loop. Low-noise preamplifiers have not yet been applied in planetary spacecraft in order to maintain simplicity and reliability. An answer to the problem seems to be high-power transmitters (earth-based) with outputs in the 1000-GW range.     

Finite element models of thoracic conductive anatomy: sensitivityto changes in inhomogeneity and anisotropy

A moderately detailed 3-D finite element model of the conductive anatomy of a canine thorax was used to examine the sensitivity of the results obtained during simulated transthoracic defibrillation to variations in skeletal muscle anisotropy and differing degrees of model inhomogeneity. The authors results suggest that the myocardial current density distribution is not particularly sensitive to the method used to model skeletal muscle anisotropy. However, anisotropy variations caused defibrillation parameters such as paddle to paddle impedance and threshold current to change by as much as 50%. The authors found a greater sensitivity in the myocardial current density and the defibrillation parameters to variations in model inhomogeneity. The changes observed in both depended substantially on paddle placement. This sensitivity to paddle placement highlights the difficulty in predicting how a reduction in anatomical detail will affect the myocardial current density distribution. In general, the authors found the defibrillation parameters to be more sensitive than the myocardial current density distribution to the variations in anatomical detail they examined     

Influence of the gate internal impedance on losses in a power MOStransistor switching at a high frequency in the ZVS mode

In order to use a power metal oxide semiconductor (MOS) transistor switching in the zero voltage mode at high frequencies, the output capacitance has to be maximal and the input capacitance minimal. These characteristics are available in the datasheets. Nevertheless, to choose a transistor ideal for such an application, having minimal losses, additional characterizations have to be done in order to complete the datasheets. In particular, it is necessary to make sure that all the cells of the MOS transistor can be opened in a time shortly before the voltage rise time at turn-off, in order to reduce as low as possible the turn-off losses. The present paper points out that the gate to source impedance characterizes the ability of the device to turn-off very quickly and the knowledge of that parameter is useful to choose a MOS transistor having minimal losses in very high frequency zero voltage switching (ZVS) applications