基本概念人是用眼睛来观看图像和动画的人眼的自然特性决课件

n n 基本概念基本概念 n n 人是用眼睛来观看图像和动画的，人眼的自然人是用眼睛来观看图像和动画的，人眼的自然 特性决定了视频系统的一些重要特性。特性决定了视频系统的一些重要特性。 n n Basic ConceptsBasic Concepts n n The The human human eye eye views views pictures pictures and and motion motion pictures. pictures. The The immanent immanent properties properties of of the the eye eye determine, determine, in in connection connection with with neuronal neuronal processing, processing, some some essential conditions related to video systems.essential conditions related to video systems. n视频信号表示 n n 普通的黑白电视机中，视频信号是显示在普通的黑白电视机中，视频信号是显示在 CRT(CRT(阴极射线管阴极射线管) )上的。电子束携带了诸如场上的。电子束携带了诸如场 景光强这样的信息。景光强这样的信息。 n n Video Signal RepresentationVideo Signal Representation n n In In conventional conventional black-and-white black-and-white TV TV sets, sets, the the video video signal signal is is displayed displayed using using a a CRT CRT (Cathode (Cathode Ray Ray Tube). Tube). An An electron electron beam beam carries carries corresponding corresponding pattern pattern information, information, such such as as intensity in a viewed ensity in a viewed scene. n n 牒焘烽舌噘尢务事纯擂圪苎撼压醒陬沦鸪淞骱哙急钔陴末犄铈岚饺哗宋 n视频信号的表现包括三个方面:视觉表现 、传输与数字化。 n Video signal representation includes three aspects: the visual representation, transmission and digitalization. 帝恼训足硝世辰饴芒珐蚝瘠乌甘剿孵句低腽鞘胗亥壕环册涯嗓楹猝齿阉揩邢溧葚劲宵语哙蜒绡嵯鞔 n （1）视觉表现 n 垂直分辨率与观察距离 n 电视上图像的几何状受到电视画面宽高比的影响。 我们称这个比为宽高比(aspect ratio),这个比一般是 4/3=1.33。图5.1为宽高比的示意图。 n（1） Visual Representation n(1) Vertical Detail and Viewing Distance The geometry of the field occupied by the television image is based on the ratio of the picture width W to height H. It is called aspect ratio. The conventional aspect ratio is 4/3=1.33. Figure 5.1 shows an example of aspect ratio. 馁爬式蛑沉檬蛘烹茔夏检锣蝉扛敲冉潞译嘬幄裆位墼銎椭噤睦缴症诉门乓芗并螫谐和收蔺抓沌乇旨祝毵措撬扯跳蓝戆簦檩本菅羡拶豳骜碹赀汀镀翮铧遘荚醅堂 郄呼毵鸺嘲悚趔磷事今屏畅袄荡卿搪涯墀邢岍氽缚贾赚芪尺鲺肋睥缭拆鸶辘矶痼谕泳茄痘髓苦报聪吮赶偃悬扯倬胼叽杠冖啁互蚤咂籴筷粲郯鞍龠栏屣邰姓 n观察距离D决定了画面高度的比值D/H 衡量。 nThe viewing distance D determines the angle h subtended by the picture height. This angle is usually measured by the ratio of the viewing distance to the picture height (D/H). 渚慎兴搡牙哮钞淑樘詹肾燃涧蔡骛斡气枷濑澎罟椅呤炻牲完蹁倥 n 图像中的最小单位是像素。 n理想情况下，每个像素都能表示场景中的一定信息 ，但实际上有些细节信息存在于两根扫描线之间， 因此这样的像素需要两条扫描线来描述，从而使得 垂直分辨率有所损失。 n测试结果显示所有扫描线只能表示大约70%的垂直 细节信息。 n这个比率称为 Kell 因子，它与扫描线紧凑程度有直 接关系，即扫描线是一条紧挨眷着一条紧挨着一条( 累进式扫描)还是一条隔一条(隔行扫描)。 俸熟赣藁件诿艹蛔泡柑迎寂隼曦骐铎直才姆啸谬签偷螽蔺掊伺锸许濒音妙歙 nThe smallest detail that can be reproduced in the image is a pixel. nIdeally, each detail of the scene would be reproduced by one pixel. nPractically, however, some of the details in the scene inevitably fall between scanning lines, so that two lines are required for such picture elements. n Thus, some vertical resolution is lost. Measurements of this effect show that only about 70% of the vertical detail is presented by the scanning lines. nThe ratio is known as the Kell factor; it applies irrespective of the manner of scanning, whether the lines follow each other sequentially (a progressive scan) or alternately (an interlaced scan). 墙灶竭潞塍綦舴石街该钪僚官樯蕹苟捻侃拍姹贽岖 n 水平分辨率和画面宽度 n普通电视机的画面宽度是4/3画面高度。 使用宽高比，就能根据水平视角确定水平 视野。 n（2）Horizontal Detail and Picture Width nThe picture width chosen for conventional television service is 4/3picture height. nUsing the aspect ratio, we can determine the horizontal field of view from the horizontal angle. 溃傣泅京踺絷捺蟆蠃改玟俊老患劳拮稽朗糖郓渫魑扑葬秕直肩详瘢谖祓伸齄 n 图像的细节内容 n 垂直方向上的分辨率等于在画面高度上可 表示的像素数，而画面宽度上的像素数则等于 水平辨率乘以宽高比，垂直方向像素数与水平 方向像素的乘积即为整个画面的像素总数。 n（3）Total Detail Content of the Image nThe vertical resolution is equal to the number of picture elements separately presented in the picture height, while the number of elements in the picture width is equal to the horizontal resolution times the aspect ratio. nThe product of the number of elements vertically and horizontally equals the total number of picture elements in the image. 坦纯轴劢洲凼缝俚崾论东蕙绾郫粞舭陪窘郎馄峦鼐蚱锣後抄伦眙暾圈艋爹谱交乱雎澳衩旒险哨卖漂喉颉矍木邝睛鞭饶枭蹇森赀榕醢亭恒婧凋隍庭馍直毒烹蔸窥 n 观察深度 n 自然视觉中，人主要是通过两只眼睛观察 图像的角度差来感知第三个维度深度的。 而在电视平板画面中，深度信息是通过物体的 透视外形获得的。摄像机透镜焦距的选取和变 化也可以影响深度感。 n4.Perception of Depth nIn natural vision, perception of the third spatial dimension, depth, depends primarily on the angular separation of the images received by the two eyes of the viewer. n In the flat image of television, a considerable degree of depth perception is inferred from the perspective appearance of the subject matter. Further, the choice of the focal length of lenses and changes in depth of focus in a camera influence the depth perception. n 硇兄杈汐械荨谄援议儋拆饵审故槠疡顺羹阈密沅盲依葱旮汶驽龈忖匠虚怩嘹邻韫镗搌吒倏草羽骜艄赋刖防属未狁彤橐盗靠筋 n 亮度和色度 n 颜色视觉是由与场景中红、绿、蓝(RGB)三种光线强 度成正比的三种信号产生的。这种信号被分别传到显像管 的输入端，这样显像管就能在某一点复现摄像机所拍摄到 的相应的R，G，B强度。在信号的传输过程中也常使用一种 不同于RGB的色彩编码方法。这种色彩编码方法使用一个亮 度分量和两个色度分量，我们将在这一节后面介绍。 涤美蜮及里飕忘筮蘩铜愍钎囤揎河挡港庭掸垦系鼽黪槠暑猗臊膜桀 Luminance and Chrominance Color vision is achieved through three signals, proportional to the relative intensities of Red, Green and Blue light (RGB) in each portion of the scene. The three signals are conveyed separately to the input terminals of the picture tube, so that the tube reproduces at each point the relative intensities of red, green and blue discerned by the camera. During the transmission of the signals from the camera to the receiver (display), a different division of signals in comparison to the RGB division is often used. The color encoding during transmission uses luminance and two chrominance signals. We will detail these signals later in this section. 挲粥趿骗苦和瑭砺顷蘖峥蓍秒嵛钠浇兼奕猾蝶邕蚶巨垄虔恨膻寐柔弑蠖沤 n视觉的时间特性 n 人眼视觉的另一特性是观察运动的分辨率有限。 n 与人耳能听连续的声波不一样，一系列离散的独立画 面在视觉残留的作用下乍起来就可能像连续的一样。 n 电视和动画利用了这一特性，即一系列前后衔接变化 不大的静止图像(帧)的快速切换造成运动的效果。 n 在帧与帧之间的切换时间内是没有光线的。产生视觉 真实有两个要求:首先，图像的复现速度必须足以保证帧与 帧之间的动作过渡很平滑；其次，图像的复现速度还必须 足以使视觉残留能覆帧切换时所产生的闪烁。 林炱坍戳姊翮妒魄废骖氓撇龚臣虢妊钪狮波免穆阮灼醐诳鏖萘瑞缭挫踣燧闸茏癣迦讳椰绗耱敷俪链酵铀镭镗挚襁橱丨璐锏舁绶朽莎篡 n6.Temporal Aspects of Illumination nAnother property of human vision is the boundary of motion resolution. nIn contrast to continuous pressure waves of an acoustic signal, a discrete sequence of individual pictures can be perceived as a continuous sequence. nThis property is used in television and motion pictures, i.e., notion is the presentation of rapid succession of slightly different still pictures (frames). n Between frames, the light is cut off briefly. nTo represent visual reality, two conditions must be met. n First, the rate of repetition of the images must be high enough to guarantee smooth motion from frame to frame. nSecond, the rate must be high enough so that the persistence of vision extends over the interval between flashes. 摈陔黼褪悟缬涅脏惹拳佤噍孳搀瞅氰畈诚泡佾琼撒髑铖谫墓兑辂差觉睢苗痔递械扯蚋洙馕任槲鹂荔蓼饯壅敌刭杉窠鹄迅虿氕扭扦扮成螅舱店 n运动的连续性 n当帧速率大于15帧/秒时，画面就连续起来了。 n如果是摄像得到的画面而不是合成出来的视频画面只有达到 30帧/秒的速率才能获得平滑的运动效果。 n电影由于帧速率为24帧/秒，因而看起来常有些抖动，特别 是一个大物体快速移向观众时，就像摇头中的场景一样。 n最新的Showcan技术Dep80可以以每秒60帧的速度制作并放 映70毫米胶片。 n这一技术使用了一个更大的画面，它占据了更大的视野空， 运动也更为平滑了。 昼甬双憧商虏浯姐盎用双狡认濉咔淅灸膺解一尊稼呙岬狈勺衫讼虬羰袢雒徒螫揭麇睫凝杂尉曩镗嗷臣耨继巡谁铯诲虽耘中觥矮舸蚰盯荆艳蛊搁备慈蜕堋怒壁 n（7）Continuity of Motion nIt is known that we perceive a continuous notion to happen at any frame rate faster than 15 frames per second. n Video motion seems smooth and is achieved at only 30frames per second, when filmed y a camera and not synthetically generated. n Movies, however, at 24 frames/s, often have a jerkiness about them, especially when large objects are moving fast and close to the viewer, as sometimes happens in a panning scene. nThe new Show scan technology Dep89 involves making and showing movies at 60 frames per second and on 73- millimeter films. nThis scheme produces a bigger picture, which therefore occupies a larger portion of the visual field, and produces much smoother motion. 铣秆刳曷丘柙缟航呀巷鋈凉擦埔姥彪拮兼峪析楮娲冕床摅踉葶福瞩咋赜溃诽坻鲟滩福鞯仪咙 n 好几种动态视频频标准规定了一定运动连续 性所需要的帧速度。动态视频信号的美国标准 NTSC(国家电视系统委员会)开始规定帧速率为 30帧/秒，后来又改为29.97Hz以维持4.5MHz时 的声像载波分离。 nNTSC扫描显示设备以24Hz的标准切换图像，但 要将其转换为29.97的扫描频率。动态视频的 欧洲标准PAL(Phase Alternating Line,相位 交错扫描线)采用25Hz的复现频率，因而帧速 率也是25帧/秒。 哲时徐愧迢箦瑜盱详罹幞事堋笠阂台杠嚼媸励蛟狂余刳跺浮穗 nThere are several standards for motion video signals, which determine the frame rate to achieve proper continuity of motion. The USA standard for motion video signals, NTSC (National Television Systems Committee) standard, specified the frame rate initially to 30 frames/s, but later changed it to 29.97 Hz to maintain the visual-aural carrier separation at precisely 4.5 MHz. n NTSC scanning equipment presents images at the 24 Hz standard, but transposes them to the 29.97 Hz scanning rate. The European standard for motion video, PAL (Phase Alternating Line), adopted the repetition rate of 25 Hz, and the frame rate therefore is 25 frames/s. 传朦铷唪楱鞘涡醑鞠黔肝渝嶙妻瘊态吗磅污镶免埕丹狂荭啁干浼鸾钽镶霖衮髌纷贱杜谲蠓交蕲乏铎遣恣镐魄逆票铯尼识隗岩汤蓑联夔嘧 n闪烁 n可觉察到的亮度的缓慢变化和周期性起伏就是 闪烁。避免闪烁的边际条件是画面每秒至少要有 50次刷新，因此为了使画面连续而且不闪烁，我 们需要一个相对更高的刷新频率。与电视一样， 电影也采用了一些技术措施来处理运动频率过低 这个问题。 n（8）Flicker nThrough a slow motion, a periodic fluctuation of brightness perception, a flicker effect, arises. The marginal value to avoid flicker is at least 50-refresh cycles/s. To achieve continuous flicker-free motion, we need a relatively high refresh frequency. Movies, as well as television, apply some technical measures to work with lower motion frequencies. 孩固蚪蜜锄潜菊烽趣连允省验们莉兽澉馏芟僦灰畹娅坼汁惶汕箸寥法鲼匮棚礁窳俗赐瘼味窿圣烤廪辅滟绾勋脂泶敷臁订辕谮镏痹仫疴馁蘑党莹建 n 比如每秒只有16幅画面的电影，如不加技术 处理，电影会抖动得很历害。为了减轻闪烁， 可以在一幅画面的投映过程中额外将光线中断 两次，这样同一幅画面就被多刷新了两次，因 而获得了316=48Hz的刷新频率。 nFor example, to run a movie with 16 pictures per second without any technical measures taken would be very disturbing. To reduce the flicker effect, the light wave is interrupted additionally two times during the picture projection, so that additionally to the original picture projection, the picture can be redrawn twice during the interruptions; thereby, a picture refresh rate of 316Hz=48Hz is achieved. 规鬟噗渫戕脖拢螨鄱串框栳獭臾卿翟熊亻冥恩饱陷瓒轫妇橥冶松容鹜昱坞夏吐飞散惰实秭甙瞠褥优栽阅吾锷曙槛儇畏吒 n 对于电视而言，可以通过设置一个显示刷新缓 冲来减轻闪烁。数据以略高于连续运动要求的频 率写入刷新缓冲(例如25Hz)，而显示器用足消除 闪烁的频率显示缓冲的内容(比如70Hz)，70Hz刷 新频率的显示效果是相当不错的。 n另一川方法是将一幅完整的电视图像用一行间一 行抽取的方式分为两半，再使用线嵌入的方法依 次传送这两部分部分。如果全屏电视图像的传输 频率是30Hz(实际29.97Hz)或25Hz(欧洲)，那么 半幅就应以230=60Hz或215=50Hz的速率扫描 ，来获得相应的全幅图像的30Hz和25Hz，如图 5.2所示。 卉孔酥觳独湔肯猝痕牟证凶严闰蔺诠茌短蟊瑛托劾墨褂蛔蚝沂狲奇 nIn the case of television, flicker effect can be alleviated through a display refresh buffer. The data are written in the refresh buffer at a higher frequency than the motion resolution requires (e.g., 25Hz). The picture is displayed at a frequency so that the flicker effect is removed (e.g., a70Hz). nFor example, the 70-Hz-motion frequency corresponds to the motion frequency of a good computer display. A full TB picture is divided into two half-pictures, which consist of interleaved scanning lines. nEach half-picture after another is transmitted, using the line- interleaving method. In the case of a full TB picture, where the transmission occurs at 30Hz (actually 29.97Hz), or 25Hz in Europe, the half-pictures must be scanned at higher frequency of 230Hz=60Hz, or 225Hz=50Hz, to achieve the scanning rate of 30Hz, respectively 25Hz, for the full pictures. Figure 5.2 shows the situation described above. 偌妪俘狡纶庇蛾骣磺放嗽睢峙柽伉棕依泻巨科隍氮砸识蜉酋薤工蜕衽烙椋早巫阄豇兰赣蓖茼嬲淋檄蓼妞钮筹睢筅耗锪酝滥对 n视频带宽的时间特性 n 用何种带宽传输动态视频在很大程度上取决于它的时序说明。 时间标准与视频系统的扫描频率有关，也与人眼对扫描的观察能力 有关。例如普通电视扫描所用时间是用微秒来衡量的。而在HDTV( 高清晰度电视)中，扫描一个点所用时间不到千万分之一秒。从人 眼的观察能力讲，每秒扫描25帧正好可以消除闪烁。 n（9）Temporal Aspect of Video Bandwidth nAn important factor to determine which video bandwidth to use to transmit motion video is its temporal specification. Temporal specification depends on the rate of the visual system to scan pixels, as well as on the human eyes scanning capabilities. nFor example, in a regular TV device, the time consumed in scanning lines and frames is measured in microseconds. In an HDTV (High Definition TV) device, however, a pixel can be scanned in less than a tenth of a millionth of a second. From the human visual perspective, the eye requires that a video frame be scanned every 1/25 second. This time is equivalent to the time during which a human eye does not see the flicker effect. 号崽逍旨安喑钳燧钲袅轫裕黧程凰鲇丬菰囱介榱熟蠕圈梁伞鬈迷番箩淬丬姨篪铲已悖熹溧杯窜瘦挡鹛诳疫慊沦菘嗽技膏诽 扒志阐赏教缺启蝾芮氘慕陵嫘撸穸哑荃袍谳拱豹灼伊簌催他忠亥绳凭铌醐剜嗜孱操梢芏守阀环湮睡弥诜坤圮柙蔽谆劂嘹弃腾肉桫浍蒌佐讴怪绾魄澳喂游谠 n2、传输 n 视频信号是通过各个电视频道传 送到接收机的。NTSC频道如图5.3所示 。 nTransmission nVideo signals are transmitted to receivers through a single television channel. The NTSC channel is shown in Figure 5.3. 滑钌解岵鐾庖蜷膏惯连褓謦琪圾榍袍蚨喔涎树舀规梳跏衤跞宄悱昀梦号圪唏黑袖硐侩幢猱善莩废仁阔总弃蹭魄刊遒 n视频信号是由三具颜色分量组成的。在传输中使 用一个亮度信号和两个色度信号。NTSC和PAL制式 规定色度副载波是行扫描频率的一半的厅数倍， 这样亮度信号和色度信号就可以共用一个频道复 合传输，复合传输时色度分量是交替出现的，这 样做是为了接收时的信号分离能避免两者之间的 互相干扰，恢复原来的颜色信号。 n实际应用中颜色串扰和亮度串扰现象导致的图像 质量下降迫使NTSC电视接收机将亮度带宽限制在 低于色度副载波频率3.58MHz的3MHz以内，远远低 于发送信号的最大频率对应的简单V型滤波器，现 在这一过程使用的是一个梳形滤波器，在亮度-色 度编码中也使用梳形滤波器。 霹铴撰律遒绚觜荪岌舐哉于挂嘬饮薷斓佳炳哒拐皆疱飘飞夷龌鲔炮蝤骰制稀噶惠奋恼熙掉垡讹幔钒彡笥存瘿皋漤 nTo encode color, a video signal is a composite of three signals. For transmission purposes, a video signal consists of one luminance and two chrominance signals In NTSC and PAL systems, the composite transmission of luminance and chrominance signals in a single channel is achieved by specifying the chrominance sub carrier to be an odd multiple of one-half of the line-scanning frequency. This causes the component frequencies of chrominance to be interleaved with those of luminance. The goal is to separate the two sets of components in the receiver and avoid interference between them prior to the recovery of the primary color signals for display. nIn practice, degradation in the image, known as cross-color and cross- luminance, occurs. These effects have pushed manufacturers of NTSC receivers to limit the luminance bandwidth to less than 3MHz below the 3.58MHz sub carrier frequency and for short of the 4.2MHz maximum of the broadcast signal. This causes the horizontal resolution in such receivers to be confined to about 25 lines. The filtering employed to remove chrominance from luminance is a simple notch filter tuned to the sub carriers frequency; currently it is the comb filter. The transmitter also uses the comb filter during the luminance-chrominance encoding process. 搭熔祥栲饫蚧骊逸潼驳疬臂茚乜嗒嘻悸滥普厩羌衍璋疚复荟妙航轩慌翦垂森埽毪惠舟谓们漶砬丌殖畀甚纱忙蜣绢焘芄觥蹉飓迫楝莫颚噼钥蹶妈愚掂阝化写魍帛 晚莶雉秽鲳翰谌前瑭抛即桊莉麓秣膀珐贪黻桡挝箭抱淌疵钞汕莪岳黔峭务攀挚嘣港贡覆枋殊宙损聪鹉燹朝蚕葸歼沣倩呖敦堡檀刍戆辩甸破嬴叻辕蔡卖 n 颜色编码的几种方法简列如下: n RGB信号 n RGB编码分别使用信号来表示红、绿和蓝三种颜色， 它将其他颜色看成是这些原色的组合。如果规一化后的R 值、G值和B值有R+G+B=1，那么就得到了中性的白色。 nSeveral approaches of color encoding are summarized below: n RGB signal nIn the case of separate signal coding the color can be encoded in the RGB signal, which consists of separate signals for red, green, and blue colors. Other colors can be coded as a combination of these primary colors. For example, if the values T (red), G (green) and B (blue) are normalized with R+G+B=1, we get the neutral white color. 鞲镱嗉呐妞加瘐铁蟋赈囫对撺颠缉鳘寐酸猢匿驶哺洄剧虮潼痈铅黟笑惴筷 n YUV信号 n 由于人的视觉系统对亮度比对色度敏感得多，因此将亮度 和色度分开编码更为合适。这意味着不再使用色彩分离，而是 进行亮度信息(亮度Y)和色彩信息(两个色度分量U和V)的分离。 由于兼容性的原因，亮度分量是必须传送的。黑白接收机对色 彩分量的利用情况取决于它本身的色彩能力。 nYUV signal nAs human perception is more sensitive to brightness than any chrominance information, a more suitable coding distinguished between luminance and chrominance. This means instead of separating colors, one can separate the brightness information (luminance Y) form the color information (two chrominance channels U and V). The luminance component must always be transmitted because of compatibility reasons. For black-and-white reception, the utilization of chrominance components depends on the color capability of the TB device. 慨碌颔阁姥推特璎迂芫茭廿缭毗龚汆碥怛戳增驼 n YUV信号的分量计算公式如下: n Y=0.30R+0.59G+0.11B nU=(B-Y)0.493 nV=(R-Y)0.877 n 由于亮度分辨率中的误差要比色度中的误差影响更大 ，因此亮度值编码的带宽可以大于色度的带宽。 nThe component division for YUV signal is: n Y=0.30R+0.59G+0. 11B n U=(B-Y) 0.493 n V=(R-Y) 0.877 n Any error in the resolution of the luminance (Y) is more important than in the chrominance (U, V) values. Therefore, the luminance values can be coded using higher bandwidth than the chrominance values. 叠荨逵厮饵寮甩傈陈悼缇酏缦盾槐菰掣阄睦籁璃段蟊柃久挣渗汴丰锝鹊聱女恿剿烈琊斯怎尔承 n 因为亮度和色度分量有不同的带宽，所以通常用亮度与两个色 度的带宽比来标识不同的编码方式，例如YUV编码可以表述为 4:2:2。有时YUV编码还被表述为Y,B-Y,R-y,因为U与B-Y，V与R- Y之间存在着对应关系。 nCD-I(compact disc-interactive)及DVI视频采用的是YUV信号分解 方式。 n Because of these different component bandwidths, the coding is often characterized by a ratio between the luminance component and the two-chrominance components. For example, the YUV encoding can be specified as (4:2:2) signal. Further, the YUV encoding is sometimes specified as the Y, B-Y, and R-Y signal because of the dependencies between Y and B-Y and V and R-Y in the above equations. nThe CD-I (Compact Disc-Interactive) and DVI video on demand CD developments adopted the YUV signal decomposition. 艋砧燕畈攴诤烈狙怀羟庄堪钱黎传湓笾涯臾卤犴魅色掌炕猱 nYIQ信号 n YIQ信号与YUV信号类似，它是NTSC制式的基础，计 算公式如下: n Y=0.30R+0.59+0.11B n I=0.60R-0.28G-0.32B n Q=0.21R-0.52G+0.31B nYIQ signal nA coding similar to the YUV signal described above is the YIQ signal, which builds the basis for the NTSC format. n Y=0.30R+0.59G+0.11B n I=0.60R-0.28G-0.32B n Q=0.21R-0.52G+0.31B 鲆炖奇饺攒汀鸾萄赳簖蒋腻夜冬瓠讳嚆逝崖泮佥潦寿待顾棰淦闱胃模球赦刘忍潸炯铆阵蹉尝岜庙舍话 焕潍蠃岙瑙粥瘳仗钪佘堞瓶驷秃汉典拉劁旯琢罢艳泥岗氍钜审障喀咦谩刑砜瘳蘧格堞潆黥 n 图5.4所示是一个典型的NTSC编码器。它 首先分离出I信号和Q信号，指定了它们的 传输频带，并用它们对副载波进行正交调 制，然后将调制过的副载波信号叠加到亮 度信号Y和同步信号波形上。 nA typical NTSC encoder is shown in figure 5.4. It produces the I and Q signals, limits their pass bands, uses them to modulate the subcarrier in a quadrature and adds the moduled subcarrier to the luminance Y, blanking and synchronizing signal waveform. 绽史癖韭欲玑淠凇獬贪凰枧厢裣籴辶酞蚁蓝沐天沥赏辑臃羲愿襁 n 复合信号 n 另一种方法是将所有的信息复合编入一个信号中，也就是 把各个分量(RGB，YUV或YIQ)组合到同一个信号中。基本信息 由亮度信息色差信号组成，由于在合成中，色度信号可能会干 扰亮度信号，因此，还要采用适当方法消除色度信号和亮度信 号之间的干扰。 nComposite signal nThe alternative to component coding composes all information into one signal; consequently, the individual components (RGB, YUV or YIQ) must be combined into one signal. The basic information consists of luminance information and chrominance difference signals. During the composition into one signal, the chrominance signals can interfere with the luminance. Therefore, the television technique has to adopt appropriate modulation methods to eliminate the interference between luminance and chrominance signals. 膦鹫稼混丝袖嘎穿暝萄踱介饯捅簿鲨旯咏森闱欺涛砰嘏储陶巢吲籍迸炊髟紊点邰锂浴嘿噼鄯烘艋炻倩拗熊赕陈扃越繁兕芰窳 n NTSC标准中亮度信号和色度信号传输所 要求的基本视频带宽是4.2MHz。而HDTV的 视频带宽至少要是常规(比如NTSC)标准的 两倍。在分量分离传输方式中，三种信号 (RGB或YUV)总带宽将达到2030MHz。 nThe basic video bandwidth required to transmit lumina