DIGITAL CCTV A Security Professional’s Guide docx

[...]... being translated into a digital language, so to speak In fact, a very good way to understand analog and digital video technologies is to consider them as two different languages Everyone must learn a language as a child and some people even grow up learning more than one language We may later choose to learn more languages, which require a certain amount of time and concentration because it is not what... carrying the same video information as an analog system Digital video is a series or string of numbers that represent the voltage levels of an analog video signal An ideal digital system has the same characteristics as an ideal analog system; both are completely transparent and reproduce the original applied waveform without error 19 20 Digital CCTV Remember the waves from chapter one? That information is... between cameras Figure 1-12 illustrates video signals that are synchronized vertically 2 What Exactly is Digital Video? There are several technologies behind the growth of digital video for security surveillance applications Once the personal computer gained popularity and became affordable, companies began creating security and surveillance applications for it—developing frame grabbers that convert analog... a record With all of the advancements available in digital technology, it is not as “perfect” as analog video and does present a variety of new problems in transmission and storage Because digital video consists of large amounts of data, it must be compressed, in most cases, to be useful Compression discards a significant amount of the original information and results in a new kind of degradation called... gray within the overall grayscale, ranging from slightly gray and almost white to very dark charcoal colors that are nearly black The level of gray, white, or black in a video signal is derived from the luminance portion of the signal Inside the camera there are various support circuitries and an imager that converts light to an electronic signal On the front 6 Digital CCTV of the camera, a lens causes... Live in an Analog World Figure 1-7 11 Composite Video Signal GAMMA Gamma is basically explained as the relationship between the brightness of a pixel as it appears on the screen and the numerical value of that pixel Gamma correction controls the overall brightness of an image Images that are not properly corrected can look either bleached out or too dark Cathode-ray tubes have a peculiar relationship... explain various concepts in enhanced detail For a number of readers, it will be a primer of video concepts HOW AN ANALOG VIDEO IMAGE IS GENERATED We live in an analog world, and vision is an analog function Waves and electromagnetic fields are analog, meaning they are continuous signals capable of smooth fluctuation Electric current, characterized by its flowing current, is also analog Electricity is a. .. either a direct flow or current called DC or an alternating flow or current called AC In an analog CCTV system, an analog camera “sees” an event, which it turns into an electronic signal It then transmits the signal over some type of medium and the signal terminates at a display or recording mechanism In the United States, a video image is made up of 525 horizontal lines, according to the NTSC standard... into digital images When Ethernet and TCP/IP standards were developed, network-based applications became viable Next, advances in wireless communications provided unprecedented mobility to surveillance applications All of these advances in technology are possible because of video digitalization One of the important things to grasp about digital video is that it is simply an alternative way of carrying... called “artifacts” This discarding of information by compression techniques has raised questions about whether digital video or compressed digital video can be used as evidence in a court case WHAT ELSE CAN DIGITAL DO FOR VIDEO? As an added bonus, most digital video systems permit the manipulation of devices from a location off-site Pan/tilt/zoom features on cameras can be controlled allowing an enhanced . image rates. vii This book provides practical information about how digital video works, how digital video is stored and transmitted, what digital systems can and cannot accomplish, and what. loud) than analog music from x Introduction a tape or a record. With all of the advancements available in digital technology, it is not as “perfect” as analog video and does present a variety. readers, it will be a primer of video concepts. HOW AN ANALOG VIDEO IMAGE IS GENERATED We live in an analog world, and vision is an analog function. Waves and electromagnetic fi elds are analog,