This article is designed to deal with the main terminology in video surveillance systems. In the descriptions of video surveillance cameras, registrars you often see incomprehensible names for you and diguristic designations. This article describes the description of these designations and terms to figure out what and how it works.
Video surveillance standards:
- Analog video surveillance - video signal is transmitted in analog form.
- Digital IP video surveillance - video signal is transmitted in digital form.
- AHD Video Surveillance - Analog Video Surveillance HD Quality. Advantage this standard It is the ability to transmit a signal to a distance of up to 500 m without amplification by the usual coaxial cable. On the same cable can be sent to the control signals of PTZ cameras, as well as sound. AHD standards:
- AHD-L - 960H resolution - the ability of AHD cameras to work to a conventional analog video recorder;
- AHD-M - resolution 720p - 960p (1 - 1.3 Mp, respectively);
- AHD-H is 1080p resolution (Full HD - 2 MP).
- HD-TVI.
- HD-CVI.
Functions and technology of video surveillance cameras:
AGC AUTOMATIC GAIN CONTROL - automatic gain adjustment. With AGC mode on, the camera automatically enhances the video signal when the illumination decreases. The technology allows you to get a high-quality picture on the monitor at low light illumination. As a rule, the gain adjustment range is limited to a range of 12-20 dB (i.e. 4-10 times), as a greater increase in the enhancement of the video signal leads to high noise and impairment of the image.
Alc (Automatic Light Control) is an automatic light adjustment technology. It is used for the optimal operation of the autodiaphragm on scenes with increased contrast. The ALC managed processor forcibly reveals the aperture holes in order to highlight a dark object, even with very high overall illumination. This method Arises due to the "dimming in the white" of the most illuminated areas. The setting occurs at the most contrast scene.
ATW. (AUTO TRACKING WHITE) - automatic adjustment of the white balance with adaptation for changing conditions of illumination. If the color temperature in the range from 1,800 ° K to 10,500 ° K (for example, a fluorescent lamp or open air), then this mode is used when setting up the camcorder.
AWB. (Automatic White Balance) - Automatic White Balance. This feature allows you to compensate for color distortions caused by different sources of lighting (sunlight, incandescent lamp or fluorescent light).
ATR (Adaptive Tone Play) is a function that provides selective compensation to improve the contrast of objects, as well as playback of colors in the case when there are areas in the image as the presence of very bright and highly darkened areas. The ATR function improves the quality of the video surveillance camera, performing an optimization of the color component of the image taking into account the bright component in this area.
AE (Automatic Exposition) - an electronic shutter that allows you to maintain a constant image brightness regardless of the illumination of the observed scene. Lens gate control with a large number of values \u200b\u200bis possible in manual and automatic modes (shutter in the menu).
Blc (Back Light Compensation) - Rear light compensation or compensation of the oncoming illumination is the function of the camcorder that allows you to control the automatic adjustment of the amplification and the electronic shutter not throughout the area of \u200b\u200bthe screen, but by its central part, which allows you to compensate for the surplus of lighting. The function allows you to avoid switching from the "night" mode to the "Day" mode with a short-lasting illumination of the photo sensor as a result of a sharp drop of illumination and get a high-quality image even if the chamber is sent a bright light source or object on the background of a bright illuminated area. If the light behind the object is bright and directed directly to the lens, the diaphragm is narrowed, and the foreground object looks dark and blurred in the image. Thanks to the BLC function, the aperture hole is still widely open, so objects in the foreground are obtained by light and clear even on the background of bright light. In most cases, BLC provides normal illumination of the central part of the frame, but on some models of the CCT cameras, the BLC can select the aperture value by several frame zones, ensuring that best quality Images.
WDR (Wide Dynamic Range) - Wide dynamic range - The ratio of the maximum value of the image brightness and its minimum value. The function allows you to organize high-quality viewing both bright and dark sections of the frame. Double frame scanning with quick modern processors Share the frame into two parts consisting of dark and bright sections of the frame. Each component is processed separately (the dark part becomes brighter, light remains the same or slightly decreases in brightness), then these two parts are combined into a frame. It turns out a picture of equally highly treated dark and bright areas. In addition to brightness, the image contrast is automatically adjusted.
D-WDR (Digital Wide Dynamic Range) is an extended dynamic range with digital signal processing. To get a high-quality image at the same time bright and dark sections of the frame. The amount of grayscale grades (halftone), which can transmit the camcorder only a part of the full spectrum from pure white to pure black. And if the frame is simultaneously present and bright and dark areas (for example, a bright sky on a sunny day and an object in the shade), the camcorder is forced to calculate the exposure, trying to cover the maximum gradation of brightness. As a result, bright objects are darker (closer to gray) and dark - lighter (closer to gray). Thus, the contrast of the image is lost. The technology of expansion of the dynamic range just allows you to transfer all gradations of gray in all sections of the frame with maximum accuracy, keeping the contrast, but the detail loss occurs. But to save the detail (definition) and uses digital processing this process and represents the D-WDR technology.
DIS. (Digital Image Stabilization) - digital image stabilization system. The function allows you to compensate for small chamber shakes.
DNR. (Digital Noise Reduction) is a noise reduction system in a color image at low light. The names of this feature a lot depends on the chip or cameras manufacturer: the most common: 3D-DNR (3 demension Signal Noise Reduction), SSNR (Samsung Signal Noise Reduction), 2DNR. It should be noted that 2DNR and 3DNR are distinguished by the signal processing method and according to the quality of the resulting result. When the DNR is turned off, the image is "covered" with multi-colored noise, which dramatically increases the recording volume.
2dnr. - Noise suppression technology, 2DNR algorithm involves the processing of individual video frames, analyzing and correcting pixels that are likely to be noise. 2DNR demonstrates a good result in relation to moving objects, this algorithm is used in the frames of the frame where the movement is present. In 2D-NR mode, the image is smoothed, which makes it more readable and significantly reduces the amount of data recorded by the recorder. The degree of smoothing is regulated by the video processor.
3dnr. - Noise suppression technology, 3DNR analyzes differences between frames to correct the pixels and improve quality. As a rule, 3DNR better gives noise than 2DNR, but at the same time moving objects may look blurred. 3DNR technology is used in static areas of the review area.
3DNR + 2DNR. - Simultaneous use of two functions (the chambers allow you to specify the necessary degree of processing separately for each function) allows you to make an image to better and significantly reduce the level of noise.
HLI (High Light Inverter) - the darkening function of re-plain pixels allows you to level the effect of the illumination from the directional light source to the entire image, the light will be localized in the sites in which its source is located. Thanks to this feature, the video surveillance camera is able to work effectively during the oncoming illumination, for example, from the light of automotive headlights.
IR-Cut. (Infraredcut) - infrared filter. Does not allow an excess infrared image that does not see the human eye to fall on the matrix, which allows you to get a clear undischarged image, avoid the illumination caused by infrared radiation. Under conditions of poor illumination, the IR filter is turned off, the sensitivity of the chamber increases, the matrix registers the message emitted spectrum. In order for the human eye to see the image of undistorted, a black and white image is applied when the IR filter is disabled.
ICR, "Day-Night" (Infrased Cut Filter Mechanically Removable) - a mechanically shifted IR filter located in front of the matrix of the camcorder. Often it is called the "Day-Night" function. In nighttime infrared radiation Used by a video camera to achieve a detailed image in the dark or low light conditions. In the daytime, an IR filter with a mechanical drive is shifted, closing the free-sensitive matrix of the camcorder in order to avoid unwanted side effects caused by infrared radiation.
MD. (Motion Detect) - Motion detection, tuned by sensitivity and location in the frame. The entire image is divided, for example, by 720 zones (48x15) and each zones can be configured to detect movement with a task of a common sensitivity. In the event of a motion detection, the processor highlights a short-circuing edging zone and a slight increase in the brightness that, in addition to the recorder detector, it may increase the likelihood of the occurred event.
OSD. (On-screen display) - OSD menu or display on the screen. If necessary, it may be displayed on top of the main image. This menu is applied to additional settings Video surveillance cameras, cause such a menu when there is a special joystick control on the camera cable.
PM. (Privacy Mask) - The masking function of private zones allows the user to hide parts of the image that should not be displayed in the frame. You can configure several private zones.
SENS-UP. (or DSS. - Digital Slow Shutter) - Video signal processing function, allowing the user to select the speed of the electronic shutter of the camcorder. At the same time, the time of charge accumulation on the matrix (exposure time) increases, which leads to an increase in the sensitivity of the camcorder in conditions of insufficient lighting. The negative side of the technology is to increase the degree of blurring of the picture in proportion to the increase in exposure time.
Smart-Ir. - control of the brightness of the glow of IR diodes. Incorrect selection of IR illumination significantly worsens the image quality in night observation. At the same time, one part of the scene is flooded with white light, and the second remains dark with indistinguishable items. The reason for this may be the incorrect design of the IR spotlight or excessive power of IR LEDs. To eliminate the last disadvantage, the processor other than the D-DWR mode provides dynamic power control of the IR searchlight based on the illumination level analysis. In this case, the illumination power increases as the brightness of the image is reduced, i.e. compensates for the lack of light, and does not turn on or off across the sensor signal as in ordinary camerasoh. Thus, the function in question allows you to not evode the image area when the object observation object is approached. For example, when a person approaches, Smart-IR will reduce the illumination intensity, and its face will not turn into a light spot.
IR illumination - Used in constructing video surveillance systems operating under low light conditions, as well as in the absence of any light. The principle of operation is based on radiation this type Lights in the IR range (720-940 nm), invisible to the human eye, but perceived by the CCD matrix of the camcorder (only in black and white). The IR illumination is a set of IR diodes or collimators placed near the camera lens and emitting the IR-range light in the chamber viewing area, individual IR spokes can also be applied. It is characterized by a range of backlight from 5 to 100 or more than meters.
Backlight Compensation, BLC) - The function of video and photo devices, which makes it possible to exclude the situation when an image of an object on the background of a bright light source is darkened. If we talk about the BLC function in order, then first need to touch the reasons why the object in a bright background may turn out to be darkened in the image. The fact is that when the camera lens is sent to a bright source of lighting, then in a portion of the pixel of the photosensitive matrix, the saturation and those pixels are coming to which the image of the object should be projected, do not have time to accumulate. Hence the effect of dimming with which many, for sure, came across.
Compensation of counterclosure Designed just to solve such a problem. Now we will deal with how BLC works. To do this, automatic amplification adjustment, electronic shutter and auto-diaphragm are specially adjusted.
- Automatic gain adjustment (ARU) - if express simple languageThis is a process in which we have at the output (the level of lighting in the picture) differs from what was at the entrance (the level of lighting is in reality). That is, when the external level of lighting is too bright and it can "overload" the matrix of the camcorder or the camera, ARU allows you to limit the load level on the matrix in some way.
- The electronic shutter is a device that adjusts the time during which the light flux is projected onto a photomatrice. Roughly speaking, the longer the shutter is open, the more light falls on the matrix. So we can prevent the image to illuminate using automatic setting The shutter so that the chamber "herself" removes so much time as it is necessary so that there is no excess lighting.
- AUTODIAFRAGMA - a device in a camera lens that allows you to change the size of the hole through which the light penetrates on the matrix. There is something like this in nature: when we look at the bright light, our pupils narrow. The same autodiaphragm does the same when we use the BLC function.
So, to compensate for counterclosure digital photo (Video-) The camera sets up all three parameters above so that information about the light level is projected on the matrix is \u200b\u200bonly partially. That is, the BLC feature does that the level of brightness remains approximately the same on the resulting image. Of course, the easiest way for this is to adjust the level of "incoming" lighting. Fortunately, digital technology has advanced in this regard very far - the electronic shutters of digital cameras allow you to even establish different exposure time for different sections of the image being removed.
To improve the quality of video phixation and increasing the informative of the video, in video surveillance, special technologies of dynamic image improvement are used. Various video camera manufacturers use various video quality improvement algorithms in video cameras that are based on general principles Processing.
To improve image quality, uses:
- Digital noise reduction (noise filtering)
- Automatic fence compensation
- Expansion of dynamic range
- Autofocus (automatic lens focus)
- Automatic white balance
- Switching day / night mode (automatic or manual)
Digital Noise Cancellation (DNR, Digital Noise REDUCTION)
Visually noise is manifested in the form of "snow" in the image from the camera.
High signal / noise surveillance calibration, and, consequently, high-quality video surveillance is achieved, including digital filtering noise.
There are methods for suppressing digital noise at the sensor level and digital camera paths, as well as noise reduction can be carried out with further digital processing Video signal software Video surveillance.
Suppression of digital stochastic noise with post-converting is carried out by averaging the brightness of the pixel according to some group of pixels, which algorithm considers "similar". At the same time, the details of the image slightly decreases. Algorithms of deferred noise cancellation are most effective for filtering fine-grained and medium-trimmed noise.
The greater the value of the signal-to-noise ratio for the video signal, the less interference and distortion has an image on the monitor screen. Relationship values \u200b\u200bfrom 45 to 60 dB correspond to the acceptable video signal quality, value less than 40 dB means high level Noise in the video signal and, as a result, the low quality of the video image.
Automatic Illumination Compensation (BLC, Back Light Compassion)
Compensation of illumination - This is a function that allows you to avoid excessive darkening of objects during the oncoming light, that is, at the time when the observation object is between the camcorder and the light source.
The principle of compensation of the illumination is based on a combination automatic gain adjustment, adjusting aperture and electronic shutter.
Automatic gain adjustment (ARU)
Automatic gain adjustment - This, in fact, adjust the sensitivity of the matrix of the camcorder. In case the level of illumination exceeds a certain threshold, the ARU allows you to limit the load on the matrix by changing the gain coefficient.
Electronic shutter
Electronic shutter adjusts the process of projection of frame on the matrix of the camcorder, or rather - the accumulation time electric charge. The longer the shutter is open (the longer the exposure), the greater the light falls on the matrix, the greater its illumination. With overpressure, the exposure is automatically reduced. The electronic shutter of some modern video cameras ensures the frame of fixation of the frame to 1/100000 seconds. 
AVTODIAFRAGMA
Diaphragm - This is a device in the lens of the camcorder, which is responsible for the sizes of the hole through which the light penetrates on the matrix. It performs the same functions as the pupil of a human eye, which is narrowed with excess light by limiting light access to the retina. The diaphragm of the camcorder during the illumination is also narrows, thereby reducing the light load on the matrix of the camcorder.
To compensate for the oncoming illumination, the three parameter described above are automatically configured in the digital video camera so that the brightness level remains approximately the same on the entire area of \u200b\u200bthe image, which avoids the dimming of objects in the counter.
Dynamic Range Extension (WDR, Wide Dynamic Range)
WDR (Wide Dynamic Range) - The function of expanding the dynamic range of the camcorder, which provides balancing of chromaticity and brightness, while maintaining the overall contrast of the image when video surveillance. WDR technology simultaneously maintains the quality of the video in highly illuminated areas, in areas with low light levels and with intensively changing, including color, lighting.
The effect is achieved due to the double opening of the shutter for the formation of each frame of the video recording. The first discovery of the shutter takes place at high speed, the second is smaller. With digital post-processing of the video cameras obtained by frames, the image obtained by means of their association does not contain an illuminated and darkened areas.
Compared to illumination compensation technology (BLC), the extension of the dynamic range (WDR) is a more modern and more advanced image improvement technology. In some camcorders, these technologies can be used in combination to achieve maximum result.
Automatic White Balance (AWB, Auto White Balance)
White Balance (AWB) for video surveillance systems - this is a function setting in automatic mode The so-called "image temperature" and eliminating color transmission distortion.
White automatic balance is most relevant video surveillance in roomswhere light sources change during the day: daylight flowing through window and doorways in the evening replace incandescent lamps and fluorescent lamps. 
When setting the White Balance function (AWB), installed check color temperature, And in the process of operation, the camcorder is adjusted in such a way as to minimize the color temperature deviation of the image from the specified, cutting off the light spectrum.
The application of the White Balance (AWB) function allows you to significantly improve color reproduction when video surveillance in facilities with artificial lighting and decorative illumination.
By installing video surveillance at the object, the master necessarily takes into account how lit by the site to which the camera will be directed. If the lens "looks" to the side, where the light is poured most of the day, the illumination of a number of objects will occur. That is, the operator will not be able to consider the details of the whole occurring in the protected area. This is one of the reasons why such a large role is paid to the planning points of installation of tracking devices.
The owners of ordinary cameras and phones are also collided with the illumination. BLC feature - This is an option allowing compensate illumination. With it, all objects in the frame look equally illuminated, although it does not always correspond to reality.
Why there is an illumination
The camcorder is often compared with human vision organs - it also has its clarity, light sensitivity, perceives a certain number of frames per second. When we look at the subject between us and a bright source of lighting, it does not always come out to consider its details.
The cause of the illumination lies in the fact that the individual pixels from which the matrix consists are capable of perceiving a certain maximum light. If it is more, in the image displayed on the screen, simply light spot will appear. However, before the maximum achieved, a kind of saturation occurs. For example, the sun behind his back "loads" the matrix is \u200b\u200bso much that its capacity becomes not enough to clearly perceive other elements.
The pixels do not have time to accumulate a sufficient charge, so at best, the photo of the object is less illuminated than in fact. This creates certain problems and in a security video surveillance:
It is not always possible to recognize the car number if the latter has the headlights;
Bright light prevents from considering the person of a person who penetrates the territory;
It is difficult to consider small details (inscriptions on boxes with a commodity).
Appearance technology BLC allowed to partially get rid of these problems. It is possible to meet it in video cameras for custom shooting, and even in mobile phones.
Floor compensation blc.
If a simple words Explain that this (BLC) managed, we will tell about how this compensation works in practice. There are 3 options:
- The use of the shutter, which would be periodically closed, cutting off the light source from the sensitive matrix. If it has been open a short time, then the likelihood of dropping is reduced.
Using a diaphragm, which would in the event of an increase in the flow of light beyond some limit, was narrowed. Similar and occurs in the world of living beings - with insufficient illumination, the diaphragm is revealed as much as possible, and with excessive - it is narrowed to the limit;
Automatic gain adjustment - pre-processing of an image based on the settings of the maximum level of lighting. If they are exceeded in a separate area, it is artificially underestimated. At the output (TV screen, monitor), the operator will see already processed data;