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four frames per second. In one second, the camera scene can change dramatically. A person for example can have walked a distance of 1 meter, and therefore if the distance is divided into four parts, i.e. four frames or "snapshots" in time, then each frame invariably looks like a blur, unless the subject keeps relatively still.
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resolution of the image chips in most of these devices is 320,000 pixels (analogue quality is measured in TV lines but the results are the same); they generally capture horizontal and vertical fields of lines and blend them together to make a single frame; the maximum frame rate is normally 30 frames
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quality can be achieved with more compression (MPEG-2 is standard for DVD-video, and has a higher compression ratio than 5:1, with a slightly lower video quality than 5:1 at best, and is adjustable for the amount of space to be taken up versus the quality of picture needed or desired). The highest
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which can record analogue signals as pictures. If the analogue signals are recorded to tape, then the tape must run at a very slow speed in order to operate continuously. This is because to allow a three-hour tape to run for 24 hours, it must be set to run on a slow time-lapse basis, usually about
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Multi-megapixel IP-CCTV cameras can capture video images at resolutions of several megapixels. Unlike with analogue cameras, details such as number plates are easily readable. At 11 megapixels, forensic quality images are made where each hand on a person can be distinguished. Because of the much
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in the computer, and the card then converts the analogue signal to digital. These cards are relatively cheap, but inevitably the resulting digital signals are compressed 5:1 (MPEG compression) for the video recordings to be saved on a continuous basis.
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Because network cameras are embedded devices, and do not need to output an analogue signal, resolutions higher than closed-circuit television 'CCTV' analogue cameras are possible. A typical analogue CCTV camera has a
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Some DVRs also allow digital broadcasting of the video signal, thus acting like a network camera. If a device does allow broadcasting of the video, but does not record it, then it's called a
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An analogue or digital camera connected to a video server acts as a network camera, but the image size is restricted to that of the video standard of the camera. However, optics (lenses and
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These cameras do not require a video capture card because they work using a digital signal which can be saved directly to a computer. The signal is compressed 5:1, but
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higher resolutions available with these types of cameras, they can be set up to cover a wide area where normally several analogue cameras would have been needed.
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camera that transmits video signals to a specific set of monitors or video recording devices, rather than broadcasting the video over public airwaves. The term "
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screens and specialised software. Digital video manufacturers claim that turning CCTV installations into digital video installations is inherently better).
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could quickly fill up a hard drive. Uncompressed recordings may look fine but one could not run uncompressed quality recordings on a continuous basis.
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are embedded devices that require less maintenance and simpler setup than a PC-based solution, for a medium to a large number of analogue cameras.
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However, in any situation where standard-definition video cameras are used, the quality is going to be poor because the maximum
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cabling, and one PC), or to replace entire CCTV installations (cameras become network cameras, tape recorders become
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Saving uncompressed digital recordings takes up an enormous amount of hard drive space, and a few hours of
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Network cameras can be used for very cheap surveillance solutions (requiring one network camera, some
523:. National Urban Security Technology Laboratory, U.S. Department of Homeland Security. October 2020.
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picture quality of DVD is only slightly lower than the quality of basic 5:1-compression DV.
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Vandal dome style camera, MN State
Capitol, St. Paul, Minnesota
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or network cameras are digital video cameras, plus an embedded
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signals to a storage device such as a video tape recorder or
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PTZ camera, Gabut lighthouse, Charente
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PTZ camera, United States
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472:Bullet style camera, Bank of Spain, Madrid, Spain
255:to enable the recordings to be stored on a PC as
205:1. Pan-Tilt-Zoom (PTZ); 2. Vandal Dome; 3. Bullet
399:Gallery of security cameras in use at landmarks
460:Bullet style camera, Al-Khazneh, Petra, Jordan
448:Bullet style camera, la Sainte Trinité, France
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127:Learn how and when to remove this message
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30:For broader coverage of this topic, see
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243:These cameras can record straight to a
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163:was the inventor of the CCTV camera.
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535:"CCTV Cameras Explained"
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537:. 5 September 2017.
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