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Technical Document

 

Q:- What is CCTV ?
Ans:- CCTV means Closed Circuit Television. It is the system of security camera connected to Television.

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Q:- What is H-264 ?
Ans : - H-264 is the first Version commonly used for the Recording, Compression and Distribution. Is also called AVC (Advance Video Coding)

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Q:- What is SVC ?
Ans :- SVC (Scalable Video Coding) it is the second version used for Recording, Compression and Distribution.

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Q:- What type of Security Camera Available ?

 

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Q:- What is DVR ?
Ans :- Digital Video Recorder (DVR) is the CPU of the Security System which record the Video in to Hard Disk from Camera.

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Q:- What is NVR ?
Ans:- Network Video Recorder is the CPU of Network Security System which record the Video in to Hard Disk from IP Camera.

 

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Q:- What is the IR Camera ?
Ans :- IR camera is the Infrared camera. Which can work in the dark also it work in electromagnetic radiation with a wavelength longer than that of visible light.

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Q:- What are the resolution available in Security Camera ?
Ans:- Camera Resolution is measured in TV Lines (TVL). The Vertical TV lines is not Variable. But Horzontal TV Lines, which is used as the parameter of camera, lens, transmission and monitor.

 

Black & white 510 (H) * 492 (V) Medium Resolution 380TVL
Black & White 768 (H) * 492 (V) High Resolution 570 TVL
Color 510 (H) * 490 (V) Low Resolution 420 TVL
Color 768 (H) * 494 (V) Low Resolution 480 TVL
Color 811 (H) * 508 (V) Medium Resolution 520 TVL
Color 768 (H) * 494 (V) Medium Resolution 580 TVL
Color 768 (H) * 494 (V) High Resolution 600 TVL
Color 976 (H) * 494 (V) High Resolution 700 TVL

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Q:- What is CCD Format Size ?
Q:- Early CCTV cameras had a circular tube as the sensor. The format size was determined by the diameter of the tube, which is the diagonal measurement of the picture. Even though today CCD sensors are flat, rectangular silicon chips, this method of measurement is still used today.

Larger CCDs gather more light, and therefore tend to be more sensitive than smaller-format CCDs. Camera price increases with sensor size, so the selection of sensor size must be balanced against both your budget and application.

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Q:- What is the meaning of lens ?
A:- Lenses are the “eyes” of a CCTV system. They are essential for creating video functions. Lenses perform two main functions: First, it determines the scene that will be shown on the monitor – this is a function of the focal length. Second, it controls the amount of light reaching the sensor – this is a function of the iris. Focal length can be fixed or variable (e.g., a zoom lens). The iris may be manually adjusted or automatically controlled by the camera.

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Q:- How to calculate the right lens ?

  • W = width of object
  • H = height of object
  • L =  Distance of the object
  • w (small) = width of image sensor format
    • ½ format = 6.4mm
    • 1/3 format = 4.8mm
    • ¼ format = 3.6 mm
  • f (small) = focal length


Example:
You would like the full image of a 6-foot (1.8m) tall person to appear on a CCTV monitor. The person is approximately 20 feet (6m) away from the security camera. The camera uses a 1/3-inch format CCD sensor.
h = 3.6mm
H = 1.8m = 1800 mm
L = 6m = 6000 mm

You need 12 mm lens for the best result of the application.

 

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Q:- What is IRIS ? Why image is washed-out ?
A :- The iris controls the amount, or quantity, of light striking the face of the image sensor. To provide optimum performance, it’s critical that neither too much nor too little light fall on the camera sensor. If too much light hits the image sensor, the image is “washed-out” (the image is all white or portions of the image are “too hot,” where light-colored surfaces lose all detail). Closing the iris corrects this. At the other extreme, too little light hitting the image sensor results in a black image or one in which only the brightest objects are visible. Opening up the iris corrects this situation. Irises may be fixed, operate manually, or operate automatically.
Fixed Iris
A fixed iris lens offers no adjustment for different lighting conditions,
Manual Iris
Manual iris lenses are best suited to indoor applications, where the lighting level is controllable and consistent. For external use (where conditions generally vary the most),
Electronic Iris
In cameras with automatic (electronic) iris control, the circuitry continuously samples the amount of light hitting the image sensor and opens or closes the iris accordingly. Auto iris is especially valuable in settings where light levels are constantly changing - exterior locations, for example.

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Q- What is Backlight Compensation (BLC)
A:- Backlight is the light behind the object of interest in a scene. This can be a major problem, especially in cameras with automatic iris control, because the camera will often adjust to keep the bright background within acceptable levels.
Think about a camera aimed at a door at the end of a dark hallway. When someone opens the door and steps into the hallway, the camera will try to compensate for the sudden bright exterior background. The result will be that the person in the doorway appears silhouetted and detail is lost in “shadow.” In extreme cases, there may be no discernible detail at all. Cameras must have backlight compensation to overcome this situation.

 

 

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Q:- Wide Dynamic Range
A:- Loosely defined, a camera’s dynamic range is the difference between the maximum and minimum acceptable signal levels. If part of a scene is illuminated too low, chances are there are not enough photons coming from that area to be converted to a meaningful electronic signal. The detail in the dark won’t be “seen” by the camera. Conversely, if part of a scene is very strongly illuminated (e.g. sunlight streaming through a window), the image from that area of the scene could be washed out. In the worst-case scenario, the scene could, and often does, contain areas of extremely low and high levels of illumination.

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Q:- What is Dynamic Noise Reduction
A:- Noisy recorded scenes can dramatically increase the size of the digital files (which are usually archived over time on a remote hard disk). In extreme cases, noisy scenes can reduce the archive period – for example, from a month of video to no more than a week. Electronic noise is caused by a number of sources, including cable attenuation, thermal effects, and over-amplification. The camera itself can also be a source of noise, which is seen as snow or graininess in the displayed image.
Some cameras include Dynamic Noise Reduction (DNR) to enhance image quality by reducing or canceling electronic noise, especially in low-light conditions. The DNR system in the camera cancels out noise by comparing images produced over time. A powerful algorithm developed for the camera then performs a pixel-by-pixel audit of the pictures – and any small, random changes that are symptomatic of noise are automatically eliminated from the scene (see the example below).

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Q:- What is Signal-to-Noise Ratio ?
A :-

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