DIGITAL CCTV A Security Professional’s Guide phần 1 pptx

[...]... and a viewer sees a good reproduction of the camera’s image We 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... 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... 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. .. essential for the security professional to know how the Internet works and how LANs and WANs function in relation to the World Wide Web WHY SWITCH TO DIGITAL? There are many reasons to make the switch to digital for security surveillance and recording applications Probably the strongest reason is that digital information can be stored and retrieved with virtually no degradation, meaning that with digital. .. 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... There are many levels of 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. .. 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... closely match the non-linearity of color picture tubes 12 Digital CCTV Figure 1- 8 Gamma Correction COMPONENTS OF A VIDEO SIGNAL—LUMINANCE, HUE, AND SATURATION Analog video is an electrical signal that represents luminance, hue, saturation, and synchronizing pulses For simplicity we have considered video as a black-and-white image up to this point Luminance is the term that describes dark and light values... this reason, sync generators are seldom used in CCTV systems Since almost all of the cameras in a CCTV system use either primary Alternating Current (AC) power or low voltage AC power, and since both primary AC and low voltage AC have a 60-cycle alternating current, the AC itself can be used as a cheap synchronizing source As the AC power crosses zero on its excursion from plus to minus and back, as seen... new advancements in the technology of video surveillance Software that intelligently monitors images and automatically detects potential security threats changes the dynamics of video monitoring for security Today’s digital video surveillance systems are much more than camera eyes that view and record the scenes around them Surveillance systems now analyze and make decisions about the images they are . 17 9 12 More Digital Video Applications 18 9 13 From VTRs to VCRs, DVRs, and NVRs 19 7 14 Central Station Monitoring and Video 205 15 More Digital Video Applications 211 16 New Roles of Digital Video. 7 Guided Video Transmission 11 1 8 Wireless Video Transmission 12 9 9 Examples of Digital Video for Security 14 7 10 Pieces and Parts 16 3 11 Integrating Digital Video with Other Technologies 17 9 12 . strongest reason is that digital information can be stored and retrieved with virtually no degradation, meaning that with digital images, copies are as good as the originals. When a digital recording