Analysis on Common Terms of Security Monitoring

ASF

It is an abbreviation for Advanced Streaming format. It is a file compression format that can directly watch video programs on the Internet. Because it uses the MPEG4 compression algorithm, the compression rate and image quality are very good. Because the ASF exists in a video "stream" format that can be watched instantly on the Internet, it is not surprising that its image quality is a little bit worse than that of the VCD, but it is better than the RAM format which is the same as the video "stream" format.

AVI

AVI is an abbreviation of AudioVideoInterleave. The old video format released by Microsoft in the WIN3.1 era has the advantages of good compatibility, convenient calling, and good image quality. The disadvantage is that the data volume is large.

<br> <br> standard video signal having a standard video input standard video input (RCA). The standard video signal is encoded at the time of output, the signal is compressed and output, and it is decoded when received. This will lose some signal.

The CCD size CCD size refers to the diagonal dimension of the photosensitive surface of the CCD image sensor. The early CCD size is relatively large, which is linch, 2/3 inch, and 1/2 inch, and thus the CCD size used for the television monitoring camera in recent years. Take 1/3 inch as the mainstream.

<br> <br> lens image size generally can be divided 25.4mm (linch), 16.9mm (2 / 3inch), 12.7mm (1 / 2inch), 8.47mm (1 / 3inch) and 6.35mm (1 / 4inch) There are several specifications, which correspond to different imaging dimensions. When selecting the lens, the imaging size of the lens should match the size of the target surface of the camera.

Magnetic focusing

A method of using a magnetic field to converge electron beams.

DIVX

DIVX video encoding technology can be said to be a new video compression format that poses a threat to DVD (some say it is a DVD killer). It was modified by Microsoft MPEG4v3 and uses MPEG4 compression algorithm. At the same time, it can also be said that it was developed to break ASF's various agreements. The use of this encoding technology that is said to be the United States banned exports - MPEG4 compressed a DVD requires only 2 CDROM! This means that you don't need to buy a DVDROM to get video quality that is comparable to it, and all this just requires you to have a CDROM! Moreover, playing this code, the requirements of the machine is not high, CPU as long as it is more than 300MHZ (whether you are PII, CELERON, PIII, AMDK6/2, AMDK6III, AMDATHALON, CYRIXx86) is equipped with 64 MB of memory and an 8 MB Memory card can be played smoothly. This is definitely an amazing technology. The future is limitless!

Low-frequency distortion

Distortion occurs at low frequencies. TV systems generally refer to frequencies below 15.75 kHz.

Low-light camera, (Lowlightlevel/LLLcamera)

CCTV cameras that can work in extremely low light.

Distortionelectrical

When a signal is compared with the original signal, undesired waveform changes occur.

Dotted signal generator (Dotbargenerator)

Equipment that generates special spot signals. It is commonly used to measure the scanning linearity and geometric distortion of television cameras and video monitors.

Electromagnetic focusing

Using one or more deflection coils in an electronic lens system, a process of converging the cathode ray bundles into one point by the action of an electromagnetic field.

Dynamic range

In the television system, the practical illumination range of the camera. In this case, there are both strong and shadowed areas in the field of view, and all details can be seen. The quantity is generally measured by the voltage difference or power difference between the maximum allowable level of illumination and the minimum level of illumination.

Jitter

Due to mechanical disturbances or signal instability caused by variations in power supply voltage, component characteristics, etc., the signal instability may be amplitude or phase, or both.

EIA interface

A set of standard signal characteristics specified by the Electronic Industries Association (EIA), including duration, waveform, voltage, and current.

EIA sync signal (EIAsyncsignal)

RS-170 (monochrome image) standard, RS-170A (color image) standard, RS-312, RS330, RS-420 and subsequent documents in the Electronics Industry Association, for synchronizing the scan signals.

F-number (f-number)

The F value is the ratio of the objective focal length (FL) to the entrance pupil perimeter (D), ie F=FL/D. The F value is proportional to the focal length and inversely proportional to the lens perimeter. The smaller the F value, the better the light transmission performance of the lens.

Load

Parts that receive the energy output by the device.

Magnification

The number indicating the difference in size between the subject and the image. It is usually based on a 1 inch focal length lens and a 1 inch target size (magnification = M=1). The lens with a focal length of 2 inches has a magnification of M=2.

Interference:

It tends to disturb the alien spurious signals of the signals that are expected to be obtained.

Isolation amplifier

The input and output circuits are specially designed to avoid the amplifiers that affect each other.

Interlacing, 2:1~(Interlace, 2to1):

A scanning technique used in closed-circuit television systems. Among them, each frame consists of two fields, two fields are synchronously scanned at a rate of 2 to 1, and the time or phase relationship between adjacent scanning lines in the connected field is fixed.

Light:

Electromagnetic rays, which can be seen by the eye, range in wavelength from 400 nm (blue) to 750 nm (red).

Luminous flux:

The rate of passage of light.

Aperture (Iris)

The adjustable optical mechanical bore inside the camera lens can be used to control how much light passes through the lens.

Aperture Value Lens Transmittance Optical Distortion (optical):

The term used to describe the image is not an exact reproduction of the object. There are many different types of distortion.

Infrared radiation:

Wavelengths greater than 750 nm (the red end of the visible spectrum), less than the microwave wavelength invisible light.

Echo:

Signal reflected from one or more points during signal transmission. Compared with the original signal, there is a significant difference in amplitude and time. Echo can lead or trail behind the original signal, causing reflected waves or "ghosting".

IP protection rating is an indicator of dust and water resistance of equipment. This indicator is often used in European and British products and consists of two figures. The former is the defensive index for solids, and the latter is the defensive index for liquids. The IP rate related to the protective cover: IP55: Dustproof, but it will enter a limited amount of dust. Prevent low-pressure water from all directions, but it will enter a limited amount of water. IP65: Dustproof, will not enter the dust. Prevent low-pressure water from all directions, but it will enter a limited amount of water. IP66: Dustproof, will not enter the dust. Prevent high-pressure water from all directions, but it will enter a limited amount of water.

Laser:

Abbreviation for Lightamplificationbystimulatedemissionofradiation. The laser is an optical resonant cavity, equipped with flat mirrors or spherical mirrors at both ends and optical amplification materials in the middle. It uses optical or electrical methods to excite the material, causing the atoms of the material to be excited to produce a beam of light that is emitted through the mirror at one end. The output beam is highly monochromatic (solid) and non-diffusing.

Focal length (FL)

The distance from the lens center or its second principal plane to the image's focus point. FL units are generally millimeters or inches.

Focal length In practical applications, users often ask questions about how far the camera can see the object or how wide the camera can see the scene. This is actually determined by the focal length of the selected lens because the focal length determines When the size of the captured image is used to record an object at the same position with a lens having a different focal length, the size of a scene taken by a camera with a long focal length lens is large, whereas the size of a scene taken by a camera with a short focal length lens is small. Of course, the sharpness of the imaged subject is also related to the resolution of the selected CCD camera and the resolution of the monitor.

Theoretically, any kind of lens can take very distant objects and form a very small image on the CCD target surface, but is limited by the physical size of the CCD unit (pixel), when the image is small enough to be smaller than one pixel of the CCD sensor. Hours, it is no longer possible to form an image of the subject, even if the image is a few pixels in size, the image is difficult to identify what.

When you know the size of the object you are shooting and the distance from the object to the lens, you can use the following two formulas to estimate the focal length of the selected lens:

f=hD/H

f=vD/V

In the formula, D is the distance from the center of the lens to the subject; H and V are the horizontal and vertical dimensions of the subject, respectively; v is the height of the target surface; and h is the horizontal width of the target surface.

The size of the imaging scene is inconsistent with the size of the imaged object. For example, the same car park can be used to monitor the same car park. Short shots can be used to monitor the panorama of the entire car park and see the entrances and exits. The vehicle outside enters and exits, but can not see the license plate number of the car (the car only occupies a very small area on the monitor screen); while the long-focus lens can be used to see the license number of the car (which The car occupies most of the screen area, but it cannot monitor the entire parking lot. Therefore, when it is necessary to monitor the panoramic view to see a part, it is generally considered to use an electric two variable or electric three variable lens. Of course, under the premise of selecting the lens, the use of high-resolution cameras and monitors can also see the local details when the monitored object has a small imaging size.

Focal length, back ~ (Focallength, back):

The distance between the posterior vertex of the lens and the focal plane of the lens.

Focalplane:

It is at right angles to the principal axis of the lens or mirror and passes through the plane of the focus point; the image produced on this plane works best.

The lens lens is an indispensable component in the television monitoring system. The lens and the CCD camera cooperate to image the long distance target on the CCD target surface of the camera.

Lens:

A transparent optical component consisting of one or more curved (usually spherical) optical glasses. It can be used to gather or disperse the light emitted by the subject to generate a real or virtual image of the subject.

Lensspeed/f-number

Transparency of the lens.

Electrostatic focusing:

A method of focusing a cathode ray beam into small dots by applying electrostatic potential to one or more elements in an electronic lens system.

Variable iris (Irisdiaphragm)

The mechanism inside the lens to control the size of the bore. Or refers to a device used to open or close the lens bore to adjust the f-stop of the lens.

Lux:

The unit of illumination in the International System of Units, which relates to the unit of length in meters. 1 lux equals 1 lumen per square meter.

Luminance signal:

The portion of the NTSC color television signal that involves scene illumination or brightness.

Lumen/Im:

The unit of luminous flux. The flux of a uniform point radiation equivalent to one candle light passes through a solid angle (spherical) flux, which is also equivalent to the luminous flux on the surface where all points of a candle light's uniform point radiation source are equally spaced.

MPEG

MPEG is an abbreviation of Motion Picture Experts Group and it includes MPEG-1, MPEG-2 and MPEG-4 (note that there is no MPEG-3, and the familiar MP3 is just MPEG Layer 3). MPEG-1 is believed to be the most accessible to all because it is widely used in the production of VCDs and web applications for downloading some video clips. It can be said that 99% of VCDs are compressed in MPEG1 format (note VCD2. 0 does not mean that VCD is compressed with MPEG-2.) Using MPEG-1 compression algorithm, a 120-minute movie (without video file) can be compressed to about 1.2GB. MPEG-2 is used in the production (compression) of DVDs, and it also has a considerable application area in some HDTVs (High Definition Television Broadcasting) and some high-demand video editing and processing. Using a MPEG-2 compression algorithm to compress a 120-minute movie (without a video file) can be compressed to a size of 4 to 8GB (of course, the performance metrics such as image quality are not comparable to MPEG-1). . MPEG-4 is a new compression algorithm. The ASF format using this algorithm can compress a 120-minute-long movie (without video file) to a video stream of about 300M, which can be viewed on the Internet. Other DIVX formats can also be compressed to about 600M, but their image quality is much better than ASF.

The MPEG-4 standard for modern mobile communication and personal communication services requires expansion from ordinary voice to multimedia services, that is, providing information media such as voice, text, data, graphics, and video, enabling users to carry out vivid, rich, and effective multimedia information in mobile communication networks. Communication, the key technology to achieve it is even low-speed audio and video compression.

The MPEG-4 target is specifically designed for audiovisual coding at frequencies below 64Kbps and is suitable for applications such as mobile communications, personal communications, fixed public communications networks and videotelephony for a wide range of applications such as narrow-band multimedia communications to achieve content-based compression coding, with good compatibility, Scalability and reliability MPEG-4 main functions:

Content-based multimedia data access tools Content-based management and digital stream editing Natural and synthetic scenes mixed coding Time-domain random access Improved coding efficiency Multiplexed digital stream encoding Universal storage Resilience in fault-taking environments Content-based scalability nAVI

nAVI is the abbreviation for newAVI. It is a modification of the Microsoft ASF compression algorithm (not an imaginary AVI). NAVI improves some of the deficiencies of the original ASF format, allowing NAVI to have a higher frame rate. Of course, this is at the expense of ASF's video streaming features.

NTSC

NationalTelevisionSystemsCommittee (National Television System Committee). It is a television standard in some countries in North America, Japan, and South America. NTSC has a resolution of 525 lines and a refresh rate of 60 Hz. NTSC refers to a video or television signal.

PAL

PAL is a video standard. PhaseAlternateLine (PAL phase alternating line), PAL format is a color television broadcasting standard established by West Germany in 1962, PAL has a resolution of 625 lines and a refresh rate of 50Hz, he overcomes the shortcomings of NTSC system due to phase-sensitivity color distortion , West Germany, Britain, Singapore, China, Hong Kong, Australia, New Zealand and other countries have adopted this standard.

QuickTime

QuickTime (MOV) is a video format created by Apple (Apple). For a long time, it was only on Apple's MAC. Later it developed to support the WINDOWS platform, but in fairness, it is an excellent video encoding format whether it is broadcast locally or as a video stream format on the Internet. So far, it has 4 versions, of which the 4.0 version has the best compression ratio!

QCIF

QCIF is a commonly used standardized image format. In the H.323 protocol suite, the standard acquisition resolution of a video capture device is specified. QCIF=176×144 pixels.

QSIF

Quarter-sizeStandardImageFormat, about 25% of the image size of the standard SIF size, NTSC is 176*112 pixels, and PAL is 176*144 pixels. The MPEG-1 compression standard supports QSIF image size.

Leading edge:

The main part of the pulse riser is generally located at 10-90% of the total amplitude.

Diopter:

The term describing the optical power of the lens. Its value is the reciprocal of the focal length in meters. For example, a lens with a focal length of 25 cm (0.25 cm) has an optical power of 4 diopters.

Drive Pulses:

Refers to sync pulses and blanking pulses.

REALVIDEO

The REALVIDEO (RA, RAM) format has been positioned from the beginning to the video streaming application, and is also the original creator of video streaming technology. It can achieve uninterrupted video playback with 56K MODEM dial-up Internet access. Of course, its image quality and MPEG2, DIVX ratio is not flattered. After all, to achieve continuous video transmission over the Internet requires a lot of bandwidth, ASF's powerful contenders in this regard!

Incident light:

Light that shines directly on the object.

Softening

The inevitable process of image appearance can be achieved by using a softening filter in the image acquisition process. The blockiness of the edge of the object in the image can be removed, thereby increasing the quality of the image at a low rate of compression and compression of the compressed image.

SourcevideoSourcevideo (source image)

Original images accessed by digital image editing and compression applications. Non-digital lake images are first collected in digital format. The source image can be a videotape, a laser disk, or a dynamic script, or it can be an existing digital image file.

Sourcevideodevice

Sourcevideodevice A device used to play non-digital images. Source video devices include VCRs, compact disc players, and video camcorders for VCD players.

SQCIF

SQCIF is a commonly used standardized image format. SQCIF = 128 x 96 pixels.

The S video input has an S video input interface (SVideo). Since the S video signal does not need to be encoded or decoded, there is no signal loss, so the S video signal is of better quality than the standard video signal.

SIF

StandardImageFormat, NTSC system is 350 * 240 pixels, PAL system is 352 * 288 pixels. The MPEG-1 compression standard supports SIF image size.

The camera of the camera is a front-end device that acquires the image of the surveillance site. It uses a CCD image sensor as a core component, and a synchronization signal generation circuit, a video signal processing circuit, and a power supply. In recent years, new low-cost CMOS image sensors have developed rapidly. Cameras based on CMOS image sensors have begun to be applied to videophones or conference television systems that do not require high image quality. Since the resolution and low illumination of the CMOS image sensor are temporarily inferior to those of the CCD image sensor, the use of the camera in the television monitoring system is still a CCD camera.

The camera is divided into black and white and color, because the black and white camera has the advantages of high resolution, low illumination, and especially it can be imaged under infrared light, so in the television monitoring system, the black and white CCD camera still has a high market share. Incidentally, the cameras in the list of CCTV surveillance equipment listed by each merchant are usually without a lens (except for the integrated camera). Therefore, in practical applications, the cameras should be based on the actual environment of the surveillance site and user requirements. With the appropriate lens (see Section 2-2 of this chapter for details).

Camera Image Signal to Noise Ratio The camera image signal to noise ratio refers to the ratio of the size of the video signal to the size of the noise signal multiplied by 20 log, both of which are generated simultaneously and inseparable. The noise signal is a useless signal, and its presence It has an effect on useful signals, but it cannot be separated from the video signal. Therefore, when selecting a camera, some useful signals should be chosen to be relatively larger than the noise signal to a certain extent, so the ratio of the two is used as a measure of the standard. If the signal-to-noise ratio of the image is large, the picture of the image will be clean and there will not be any noise interference (snowflake shape in the main picture). People will look very comfortable; if the signal to noise ratio of the image is small, then the picture The meeting will be full of snowflakes, which will affect the normal viewing effect. The signal-to-noise ratio given by the general camera is the value when the AGC (automatic gain control) is turned off, because when the AGC is turned on, the small signal is boosted, so that the noise level is also increased accordingly. The SNR of a CCD camera is typically 45 to 55 dB. When measuring SNR parameters, a video clutter measuring instrument should be used to connect directly to the video output terminal of the camera.

The field of view lens has a defined field of view, and the angle of view of the height and width of the field of view of the field of view is called the field of view angle. The angle of view is related to the focal length f of the lens and the size of the target surface of the camera (horizontal dimension h and vertical dimension v). The horizontal field angle ah and the vertical field angle av of the lens can be respectively calculated by the following equation, ie, ah= 2arctg(h/2f)

Av=2arctg(v/2f)

As can be seen from the above two equations, the shorter the focal length f of the lens is, the larger the viewing angle is, or the larger the camera target surface size h or v is, the larger the viewing angle is. If the angle of view of the selected lens is too small, it may be due to the monitoring of the blind corners. If the angle of view of the selected lens is too large, the size of the monitored subject may be too small to be identified. And the screen edge distortion. Therefore, only by selecting a lens with a proper angle of view according to a specific application environment can it be ensured that neither the monitoring of blind spots nor the subject picture to be monitored can be as large and clear as possible.

Video visual or image information. Convert a moving or stationary image into an electrical signal. In computer video, the red, green, blue, and sync signals are separate electrical signals. In VHS video, the red, green, blue, and sync signals are a single electrical signal. In S-VHS video, the red, green, blue, and sync signals are separated.

Video Driver (VD)

Video driver (VideoDriver, VD for short) refers to the camera output video signal level to the internal of the auto iris lens, and then by its internal drive circuit output control voltage, so that the lens aperture adjustment motor rotation;

The video capture card video capture card occupies an expansion slot in the computer through which the video signal is captured by the playback device. In general, video capture cards come with a docking station that provides various jacks for connecting playback devices. Digital video signals occupy very large hard disk space, so many capture cards compress the signals while capturing video signals to avoid possible bottlenecks in the CPU, data bridge (connecting capture cards and computers), and writing to hard disks. . When the video stream is captured on a computer, it will be stored as a video file. You can specify a frame rate, such as 15 frames, with your video capture software. The video capture software will use the capture card to save the input video signal to the buffer at a rate of 15 frames per second, and then write the video file. Into the hard disk.

Video overlay video overlay is the ability to overlay computer graphics on real-time or video signals and store the overlayed video images on a hard disk.

Loss:

The reduction in signal level or intensity, usually expressed in decibels. Also refers to power dissipation without practical use.

Interlace, random:

A scanning technique used in closed-circuit television systems. Among them, the two fields that make up the frame are not synchronized, and the time or phase relationship of adjacent lines of the connected field is not fixed.

Lens, Fresnel ~ (Lens, fresnel):

A lens that is cut into narrow rings and flattened. There is a circle of narrow concentric circles or steps on the lens that can converge the light (in each direction) into an image.

Image plane:

At the imaging point, a plane perpendicular to the optical axis.

Visualcomponent (screen component)

The picture part of an image (the part you can see). It is kept separately from the sound components so that the two components can be used separately. When talking about audio and picture components, picture components are often called image components.

Differentialgain:

When the image signal carrying a 3.58-MHz color subcarrier changes from a blanking level to a white level, the amplitude of the color subcarriers in the entire circuit changes. Derivative gain is usually measured in dB or percentage.

Differential phase:

When a picture signal carrying a 3.58-Mhz color subcarrier changes from a blanking level to a white level, the phase of the color subcarrier in the entire circuit changes. The differential phase is usually measured in degrees.

Relative aperture In order to control the amount of light flux through the lens, a diaphragm (commonly known as the aperture) is provided at the rear of the lens. Assuming that the effective aperture of the diaphragm is d, due to the relationship of light refraction, the actual effective aperture of the lens is D, and the ratio of D to the focal length f is defined as the relative aperture A, ie, A=D/f

The relative aperture of the lens is determined by the illuminance of the captured image. The illuminance E of the image is proportional to the square of the relative aperture of the lens. Generally, the inverse of the relative aperture is used to represent the size of the lens aperture, that is, F=f/D.

In the formula, F is generally called the F-number of the light field and is marked on the adjustment circle of the lens diaphragm. The value of the F is the sequence value of 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, etc. In the neighboring values, the latter value is a multiple of the previous value. Since the illumination of the image plane is proportional to the square of the diaphragm, the brightness of the image surface changes twice for each position of the diaphragm. The smaller the value of F, the larger the field of light and the greater the luminous flux reaching the target surface of the camera.

Number of pixels The number of pixels refers to the maximum number of pixels of the camera CCD sensor, some give the number of pixels in the horizontal and vertical directions, such as 500H*582V, and some groups the value of the first two products, such as 300,000 pixels. For a certain size of the CCD chip, the larger the number of pixels, the smaller the area of ​​each pixel unit, and the higher the resolution of the camera formed by the chip. For example, some of the pixels of a CCD sensor used in a television security camera have reached 480,000 pixels.

Signal-to-noise ratio The ratio of the signal's maximum fidelity output to the unavoidable electronic noise in dB. The bigger the value, the better. Below the 75 dB indicator, noise may be found in silence.

Line amplifier:

An audio or video signal amplifier that drives a transmission line. Installed in the middle of the main cable, amplifiers for loss reduction (usually wideband type).

Linearity:

The output signal changes directly or proportionally as the input signal changes.

Linepairs:

The term used to define the definition of television. A television line consists of a black line and a white line. 525-line NTSC screen = 485 pairs.

Limited resolution:

The resolution measurement method is usually expressed by the number of distinguishable TV lines on the test pattern in each television image.

Intensified CCD/ICCD:

A CCD camera connected to an electron tube or microchannel plate image intensifier through an optical fiber.

Intensified siliconintensified target/ISIT:

A SIT tube that connects the fiber to additional booster devices to increase sensitivity. The use of two booster stages can provide a sensitivity of 2000 times that of a standard camera tube.

Luminance

The illuminance refers to a luminosity value of a scene when the illuminance of the subject to be shot is low to a certain degree and the level of the video signal output by the camera is as low as a predetermined value. When measuring this parameter, the maximum relative aperture of the lens should also be specified. For example, with the F1.2 lens, when the brightness value of the subject is as low as 0.04lx, the amplitude of the video signal output by the camera is 50% of the maximum amplitude, ie, 350mV (the maximum width of the standard video signal is 700mV). The minimum illumination of this camera is called 0.04lx/F1.2. The brightness value of the subject is low, and the amplitude of the video signal to be output by the camera cannot reach 350mV. Reflected on the screen of the monitor, it will be a gray image with a difficulty in distinguishing the levels.

Frame frame A video image in a series of video images. The film is composed of a series of continuous pictures. Each picture is a frame, PAL is 25 frames per second, and NTSC is 30 frames per second.

Frame Rate The number of frames per second that is used to measure the speed of video signal transmission in frames per second (fps). When capturing dynamic video content, the higher this number, the better.

DC Driver (DD Driver)

The DC driver (DD) method means that the camera has a lens drive motor with a lens iris motor. It can directly output the DC control voltage to the iris motor in the lens and turn it. Therefore, the cost of a camera with a DC drive interface It is slightly higher (because part of the circuit is added).

Lag:

In a TV pick-up tube, the charge map of two or more frames of images is briefly paused after excitation is removed.

Progressive scan draws the entire frame impedance (Impedance) on the screen:

The input/output characteristics of a circuit or an electronic device. For optimal signal transmission, the characteristic impedance of the cable used to connect two circuits or devices must be the same as the characteristic impedance of the circuit or device. The unit of impedance is ohms.

Fall Protection include Full Body Harness, half body harness(waist safety belt) and Energy Absorbing Lanyard.

It for provide safety protection for high-altitude operators,this equipment use in construction worker and electrician work,when someone fall down, this Safety Fall Protection can be protected people from dangerious.

The use period of seat belt is usually 3-5 years.

Fall Protection

Fall Protection,Safety Fall Protection,Full Body Safety Harness For Fall Protection,Fashion Fall Protection

Greateagle Safety Products Co., Ltd. , https://www.greateaglesafety.com