Fully synchronized full lock is the best way to fully synchronize between two cameras for precision applications such as broadcast studios. It will synchronize: horizontal, vertical, even/odd areas, color trigger frequency and phase.
Vertical synchronization is the easiest way to synchronize two cameras, with vertical drive frequency to ensure that the video can be used to display several image sources on the same monitor using an old-fashioned switching period or quad-split machine. The vertical drive signal is typically composed of pulses with a repetition rate of 20/16.7 milliseconds (50/60 Hz) and a pulse width of 1 to 3 milliseconds.
Color Video Composite Signal Synchronous color video composite signals represent video and color trigger signals, meaning that the camera can be synchronized with an external composite color video signal. However, although it is called color video composite signal synchronization, only horizontal sync and vertical sync are actually performed, and no color trigger sync.
External synchronization is very similar to color video composite signal synchronization. One camera can synchronize to the video signal of another camera, and an external synchronization camera can use the input color video composite signal to extract horizontal and vertical sync signals for synchronization.
DC line locking is an ancient technology that uses DC 50/60 Hz power line current to synchronize cameras. Because DC 24 volt power supplies are widely used in most building fire alarm systems, they are very easy to obtain. Since the old model of the switcher and the splitter system does not have a digital memory function, it is necessary to maintain a stable image, and the synchronization between the cameras is necessary. The DC line lock is the camera's synchronization with the AC 50/60 Hz, and the time correlation and level between the color channels. The absence of a constraint in the vertical signal results in poor color conversion (color stage design), so all users who use AC line lock inevitably lose good color conversion. Fortunately, today's splitters and 16-channel composite processors and hard disk recorders have internal memory to overcome this problem, eliminating the need for synchronization signals, so the AC line lock may be phased out in a few years.
Colorless scrolling digital signal processor When using a fluorescent camera, the video camera can only produce images with severe color scrolling. The image will change from white to blue, pink to white, and so on. This is due to problems caused by AC power running at 50/60 Hz. The incandescent bulb provides a steady light, while the light from the fluorescent lamp fluctuates at a rate of 8.3 ms due to the intensity and color of the alternating current. The traditional camera calculates the white balance by 100~150ms (0.1~0.15), which is 8.5ms slower than the AC, so it can never catch up. Color scrolling can be clearly produced by the current image through 8 cycles.
Backlight compensation provides the ideal exposure of the target in front of very strong background light, regardless of whether the primary target moves to the middle, up, down, left or right or anywhere on the screen. An ordinary camera that does not have super dynamic characteristics has only a shutter speed of 1/60 second and an aperture of F2.0. However, a very bright background behind a main target or a point source is inevitable, and the camera will acquire The average of all recent light and the level of exposure is not a good method, because as the shutter speed increases, the aperture is closed and the main target becomes too dark to be seen. To overcome this problem, a method called backlight compensation is widely used on most cameras by weighted region theory. The image is first divided into 7 or 6 regions (the two regions are repeated), and each region can be independently weighted to calculate the exposure level. For example, the middle portion can be added to the remaining blocks 9 times, so one is in the middle of the picture. The target of the position can be seen very clearly, since the exposure is mainly calculated with reference to the light level of the middle area. However, there is a very big drawback. If the main target moves from idle to the top, bottom, left and right positions of the picture, the target will become very dark, because now it is not distinguished and has not been weighted.
F indicates the aperture of the lens, F stops 2:1 and f3.4 mm indicates that the focal length of the lens is 3.4 mm. Lens F2.0 and f3.4~4 are very economical. They should be used at low prices. They are widely used in single-board cameras. The aperture of F2.0 lens can collect half of the human eye, f3.4 mm lens. It has a 60 degree viewing angle on a 1/4 inch CCD and a 90 degree viewing angle on a 1/3 inch CCD, very close to the human eye. The eyes of the human eye can contain a larger angle of view, ranging from 150 to 180 degrees from person to person, but keep in mind that F-stop and f-focus are just basic parameters of a shot and do not represent quality. Ultra-wide dynamics are the features that make the camera see the image in very strong contrast. Wide dynamic cameras are dozens of times larger than traditional cameras with only a 3:1 dynamic range. Natural light is arranged from 120,000 Lux to 0.00035 Lux at Starlight Night. When the camera looks out of the window from the inside, the indoor illumination is 100 Lux, and the illumination of the outside scenery may be 10,000 Lux, compared to 10,000/100 = 100:1. This contrast can be easily seen by the human eye, because the human eye can handle a contrast ratio of 1000:1. However, the traditional closed-circuit surveillance camera has a big problem in handling it. The traditional camera has only 3:1 contrast performance, it can only Choose to use the 1/60 second electronic shutter to get the correct exposure of the indoor target, but the outdoor image will be cleared (all white); or the camera can choose 1/6000 second to get the perfect exposure of the outdoor image, but the indoor The image will be erased (all black).
The peak sensing mode uses the average of the image highlights instead of the entire image to determine the exposure index. Users who use the rule system can cope with the most demanding requirements, such as capturing a white point image in the night, and also seeing this small bright White dots of detail and color.
CMOS is called Complementary tal-OxideSemiconductor, which is translated into a complementary oxidized metal semiconductor. CMOS manufacturing technology is no different from general computer chips, mainly using semiconductors made of two elements, silicon and germanium, to coexist with N (band-to-electric) and P (with +-electric) levels in CMOS. The semiconductor, the current generated by these two complementary effects can be recorded and interpreted by the processing chip into an image.
CCD is called ChargeCoupledDevice, Chinese translation is charge coupled device. It is made of a high-sensitivity semiconductor material that converts light into electric charge, and then converts the electrical signal into a digital signal through an analog-to-digital converter chip. The digital signal is compressed and transmitted to the computer via the USB interface. The captured image.
The concept of depth of field: When an object is clearly focused, all scenes from a certain distance in front of the object to a certain distance behind it are also clear. The distance from front to back with a fairly clear focus is called depth of field. The depth of field is divided into deep foreground and deep depth of field, and the depth of the back is deeper than the foreground. The deeper the depth of field, the more distant the scene can be clear, and the depth of field is shallow, the scene far from the focus is blurred.
The focal length is an uncompromising optical parameter of any optical instrument. From the optical principle, the focal length is the distance from the focus to the center of the lens. For the lens, the focal length has a very important meaning. The length of the focal length is proportional to the size of the image. The longer the focal length, the larger the image, and the shorter the focal length, the smaller the image. The focal length of the lens is inversely proportional to the size of the viewing angle. The longer the focal length, the smaller the viewing angle, and the shorter the focal length, the larger the viewing angle. The focal length is inversely proportional to the depth of field. The longer the focal length, the smaller the depth of field, and the shorter the focal length, the greater the depth of field. The length of the focal length is inversely proportional to the intensity of the perspective. The longer the focal length, the weaker the perspective, and the shorter the focal length, the stronger the perspective. The focal length is inversely proportional to the contrast. The longer the focal length, the smaller the contrast, and the shorter the focal length, the greater the contrast. The farther the focus distance is, the deeper the depth of field is, and the closer the focus distance is, the shallower the depth of field. Therefore, you should select a lens with a large focusing distance when shooting a distant view, and a product with a smaller focusing distance when shooting a close-up. The lens focusing distance is expressed in cm (cm), which is clear at a glance.
The switch has two modes of manual switching and automatic switching. The manual mode is to switch which way to switch which way to see; the automatic mode is to let the preset video switch in sequence, and the switching time can be adjusted by a knob. Usually between 1 second and 35 seconds. If it is not required to monitor at all times, a switch can be added in the monitoring room to connect the camera output signal to the input of the switch. The output of the switch is connected to the monitor. The input of the switch is divided into 2, 4, 6, 8, 12, 16 channels, the output is divided into single and dual, and can also switch audio (depending on the model).
The video server is a special computer device for compressing, storing and processing video and audio data. It is widely used in video surveillance, network teaching, Ip video conferencing, commercial insertion and video program on demand. The video server adopts M-JPEG, H.261, H.263, MPEG-2, MPEG-4 and other compression formats, and compresses and encodes the video data in accordance with the technical specifications to meet the requirements of storage and transmission. With multi-channel input and output, a variety of video and audio format interfaces. It can be equipped with network interfaces such as SCSI and FC for networking and video data transmission and sharing. It consists of video and audio compression encoder, large-capacity storage device, input/output channel, network interface, video and audio interface, RS422 serial interface, protocol interface, software interface, video and audio interface matrix, etc. Phase and video processing capabilities.
A network camera is a new generation camera that combines traditional camera and network technology. It can transmit images to the other end of the network connection port through the network, and the remote browser does not need any professional software, as long as the standard A web browser (such as "MicrosoftIE or Netscape" can monitor its image. The network camera has an embedded chip embedded in the real-time operating system. The video signal transmitted by the camera is digitized and compressed by a high-efficiency compression chip and transmitted to the network bus. Web server: Users on the network can directly view the camera image on the web server by using a browser, and the authorized user can also control the action of the camera pan/tilt lens or operate the system configuration.
Dynamic detection The entire monitoring screen is divided into multiple small areas. The user can arbitrarily select the area of ​​the area, and can set the sensitivity of the selected monitoring area by 1-20 levels. This will be detected by the camera server when something moves, and video recording will be performed at the same time.
The communication interface of the communication interface in the security monitoring system is mainly for the input and output of video and audio. Therefore, the communication interface generally has the following types: RS-232, RS-485, general network interface, can support PSTN, ISDN and LAN various networking environments, with USB2.0 ultra-high-speed data interface, connect the computer to backup important image data Optional with progressive scan VGA output interface.
The monitor is the standard output of the monitoring system, and with the monitor we can view the images sent from the front end. The monitor is divided into two colors, black and white, and the size is 9, 10, 12, 14, 15, 17, 21 inches, etc., commonly used is 14 inches. The monitor also has a resolution, which is represented by the number of lines as the camera. In actual use, the number of monitor lines is generally required to match the camera. In addition, some monitors also have audio input, S-video input, RGB component input, etc., except for the audio input monitoring system, most of the other functions are used for image processing, and will not be introduced here.
Video amplifier When the video transmission distance is relatively long, it is better to use a video line with a thicker line diameter, and at the same time, the video amplifier can be added to enhance the signal strength in the line to achieve long-distance transmission. The video amplifier can enhance the brightness, chrominance, and sync of the video, but the inter-line interference signals are also amplified. In addition, too many video amplifiers cannot be connected in series in the loop, otherwise saturation will occur, resulting in image distortion.
The gimbal is a mounting platform consisting of two alternating currents that can move horizontally and vertically. According to the use environment, it is divided into indoor type and outdoor type. The main difference is that the outdoor type sealing performance is good, waterproof, dustproof and load-bearing. The mounting method is divided into side loading and lifting, which is whether the gimbal is installed on the ceiling or mounted on the wall. The shape is divided into ordinary type and spherical type. The spherical head is placed in a hemispherical and spherical protective cover. In addition to preventing dust from interfering with images, it is also concealed, beautiful and fast.
Embedded systems refer to the integration of operating systems and functional software into computer hardware systems. Simply put, the application software of the system is integrated with the hardware of the system, similar to the way the BIOS works. It has the characteristics of small software code, high automation and fast response. Particularly suitable for systems that require real-time and multitasking.
Full duplex can be sent and received at the same time. Full-duplex requirements: Receive and transmit each have separate channels, can be used to achieve communication between two stations and star network, ring network, not available for bus network.
Half-duplex can't be sent and received at the same time, and sending and receiving is time-divided. Half-duplex requirements: Transceivers can share the same channel. Local area networks that can be used in various topologies are most commonly used in bus networks. Half-duplex data rates are theoretically half of full-duplex.
The direction curtain infrared detector generally adopts the bidirectional pulse counting operation mode, that is, the A direction to the B direction alarm, and the B direction to the A direction does not alarm. With intrusion direction recognition capability, the user enters the warning zone from inside to outside, and does not trigger an alarm. Returning within a certain period of time will not cause an alarm. Only an illegal intruder will invade the alarm from the outside, which greatly facilitates the user to fortify. The activity in the alert area does not trigger the alarm system.
The automatic high-speed tracking fastball is a combination of optical, electronic, mechanical, information processing and network. It consists of camera, power transmission, motion control device, image analysis, recognition, compression and communication based on high-speed parallel processing. Features video capture, position control, orientation and lens presets, moving target detection, recognition and tracking, flame and smoke detection alarms. When the moving target enters the field of view of the spherical camera, the high-speed DSP chip is used to perform differential calculation on the image of the previous frame and the current image. When a certain value is reached, it is determined that a certain part of a frame is a moving object, and then The ball machine automatically issues instructions to the dome of the dome camera, so that the spherical camera can control the continuous tracking of the moving object without human operation or the support of the computer system. Line Lock Synchronization (LINELOCK) is a type of synchronization that uses AC power to lock the camera's sync pulse. When the image has network interference caused by AC power, turn this switch to the line lock synchronization (LL) position to eliminate the interference from the AC power supply.
The video signal output by the automatic gain control camera must reach the standard level specified by the TV transmission. That is, in order to output the standard video signal under different illumination conditions, the gain of the amplifier must be made within a large range. adjust. This gain adjustment is usually done automatically by detecting the average level of the video signal. The circuit that implements this function is called an automatic gain control circuit, or AGC for short. Cameras with AGC function will have higher sensitivity in low illumination, but the noise will be more obvious at this time. This is because the signal and noise are simultaneously amplified.
The sound source is the source of the sound. There is no sound source. It is impossible to restore the sound with the sound system. The sound source has two meanings. One is the carrier that records the sound. Only when the sound is recorded on a certain carrier, can the sound of the carrier be restored by the audio device, which is the source of the sound in the sound system. So called the sound source. Another meaning of the sound source refers to the device that plays the sound source carrier. Signals that are continuous in time and whose amplitude changes continuously with time are called analog signals (for example, sound waves are analog signals, currents transmitted in audio systems, voltage signals are analog signals), and the source of recording and processing analog signals is analog sound sources, such as magnetic tape. / deck, LP / LP record player. The signal recorded and processed by the analog sound source is the original color of the sound (accurately, the electrical signal converted from the sound). It can be directly amplified by a conventional amplifier, which is convenient and straightforward to process; the digital sound source records and processes all 0. The abstract binary data stream formed by combining with 1 arrangement is very unintuitive. Sound waves are analog and cannot be used directly for digital sound sources. They must be converted to digital signals by conversion equipment to be recorded on the digital sound source carrier. During playback, the data read by the digital source device cannot be directly amplified by a conventional amplifier and must be converted to an analog signal. It can be seen that the digital audio signal processing process is much more complicated. However, the advantages of digital audio sources are outstanding: the signal-to-noise ratio and dynamic range are far better than analog audio sources. The quality of the signal does not decrease after multiple copies and multiple transmissions. This analog audio source can't be done anyway.
AVS is China's self-developed audio and video coding technology standard. The AVS Working Group was established in June 2002 and the first working meeting began in August of that year. After 7 AVS formal working sessions and 3 additional video group additional meetings, after a year and a half, 182 proposals were reviewed and 41 proposals were adopted. The AVS video part was finalized on December 19, 2003. The core technologies featured in AVS-Video include: 8x8 integer transform, quantization, intra prediction, quarter-precision pixel interpolation, special inter-frame motion compensation, two-dimensional entropy coding, and deblocking in-loop filtering. Current AVS-Video technology enables compression of video in different formats, such as standard definition (CCIR601 or equivalent), low definition (CIF, SIF).
The real-time editing technology means that the hard disk recorder can process the collected raw data in real time and convert it into a standard MPEG-1 or MPEG-2 format image file, and directly store it to the hard disk without any backlog and loss of data in the middle; Mainly compared with computer burning, when the computer is burned, the original data is collected first, and then the data is processed into a standard MPEG-1 or MPEG-2 format image file. Real-time codec technology requires that the speed of the entire system be fast enough, otherwise it can only be achieved by reducing the quality of the image and reducing the amount of data.
The super HAD image sensor has a built-in CCD image sensor using the "SuperHoleAccumulatio nDiode (HAD)" electronic image quality enhancement technology to improve the sensing performance of the CCD and enhance the digital signal processing function, effectively reducing noise and reducing unnecessary interference when shooting images. It makes the picture clearer and clearer, and the color layer is more distinct. It is especially effective when the spot light source is insufficient or shooting night scenes.
The white balance is WhiteBalance. The color of the object will change due to the color of the projected light. Images taken in different light situations will have different color temperatures. For example, a photo taken in an environment illuminated by a tungsten lamp (light bulb) may be yellowish. In general, the CCD has no way to automatically correct the change of light like the human eye. Therefore, through the correction of the white balance, it will adjust the intensity of the red, green and blue colors of the entire image according to the image characteristics in the current image to correct the error caused by the external light. Some cameras offer manual white balance adjustment in addition to automatic white balance or specific color temperature white balance.
The variable code stream encoding and decoding technology means that the codec can automatically adjust the bandwidth according to the size of the data amount, and the image changes faster, the bandwidth allocated when the color is richer is larger; the image changes slowly, and the color is less rich when allocated. The bandwidth is smaller, which saves the space of the hard disk while ensuring the quality of image recording.
The bandwidth provided by the fixed code stream codec is fixed. Regardless of the amount of data, when the image color is rich and the change is fast, the bandwidth is not enough to reduce the quality of the video. It seems that the image is a little paused or the color is changed; When it is not large, it provides more bandwidth and wastes storage space.
Pixels are one of the important indicators for measuring cameras. Some products are labeled with 300,000 pixels or 350,000 pixels in the box. In general, products with higher pixels have better image quality. On the other hand, the higher the pixel, the better. For the same picture, the higher the pixel, the stronger the ability to parse the image. In order to obtain a high-resolution image or picture, the amount of data recorded is also large. Much more, the requirements for storage devices are much higher, so you should pay attention to the relevant storage devices when choosing.
The access control system is a new way of access management: allowing authorized people to enter a designated area while rejecting unauthorized people. The protagonist of the system is a card reader or PIN pad mounted on the door side. They transfer the read data to the local controller and confirm whether it can pass according to the database compiled in advance.
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