AI function in security video surveillance

AI is everywhere. Artificial Intelligence AI–>Machine Learning ML–>Deep Learning DL–>Computer Vision CV, and the realization of AI intelligence functions in security mainly rely on computer vision to realize the understanding and recognition of images, speech and text. The AI ​​function is mainly affected by the three factors of algorithm, computing power, and big data.AI function
AI functions in security include smart functions based on front-end cameras, smart functions based on back-end central platforms, or cloud-side integration.
Among them, based on the AI ​​intelligent function of the front-end camera, there is a new concept, software-defined camera, that is, whether the intelligent function of the camera is mainly determined by software (SDC) or hardware, which has caused heated discussions and debates in the industry. My point of view: The market demand is determined, not by technology.

Common AI functions in the security field are divided into the following 4 categories:

Human body analysis: face recognition, posture recognition, human body feature extraction, etc.;
Vehicle analysis: license plate recognition, vehicle recognition, vehicle feature extraction, etc.;
Behavior analysis: target tracking and monitoring, abnormal behavior analysis, etc.;
Image analysis: video quality diagnosis, video summary analysis, etc.
If it is further subdivided, there are currently these smart functions:

Humanoid, animal detection
Face detection
Snapshots, attributes, glasses, hairstyle, gender, facial expressions, etc.
People and traffic statistics
Vehicle, pedestrian road violation
Multi-dimensional perception (human expression, car, behavior analysis)
Video structured
General smart function
Behavior analysis: cross-border detection, area intrusion detection, entry/exit area detection, wandering detection, people gathering detection, fast motion detection, parking detection, item left/take detection
Anomaly detection: scene change detection, audio anomaly (audio steep rise / steep fall detection, audio presence or absence detection), virtual focus detection
Statistics: over-line counting function
Vehicle inspection
Support license plate capture, color, model, main brand, sub-brand, year model, etc. identification, machine non-human recognition, detection of forward or reverse driving vehicles, pedestrians and non-motor vehicles, automatic identification of vehicle license plates, you can capture no license plate Pictures of vehicles.
Computing power
The computing power is the computing power of the processor. The general unit is TOPs, which is the abbreviation of Tera Operations Per Second. 1TOPs means that the processor can perform one trillion operations (10^12) per second.

Corresponding to GOPs (Giga Operations Per Second), MOPs (Million Operation Per Second). 1GOPs means that the processor can perform one billion times per second (10^9)
Operation, 1MOPs means that the processor can perform one million operations (10^6) per second.

In some cases, the power consumption of the processor is also an important factor to consider. Therefore, TOPs/W is also used as a performance index to evaluate the computing power of the processor. TOPs/W is used to measure how many trillion operations the processor can perform under the condition of 1W power consumption.

The computing power and power consumption of some common processors can refer to this statistic: Neural Network Accelerator Comparison

Lightspeeur2803 has an energy efficiency ratio of 24Tops/W, which is currently the AI ​​chip with the highest energy efficiency ratio. Google’s TPU3.0 computing speed has reached 420TOPs.

In the security chip, Hi3516CV500 reached 0.5TOPs, Hi3516DV300/Hi3516AV300 reached 1.0TOPs, Hi3519AV100 reached 2.0Tops, and Hi3559AV100 reached 4.0TOPs (Huawei used this chip to make a 20TOPs police bayonet camera).

Rockchip’s RV1109 supports 1.2Tops, and RV1126 supports 2.0Tops.

The computing power is mainly determined by the performance of the AI ​​chip. AI chips are mainly divided into four types: traditional CPU, GPU, semi-customized chips, and fully customized chips.

AI chip classification

Name Main Manufacturer Features
CPU Intel, AMD cannot process calculations in parallel
GPU NVIDIA, AMD have powerful parallel computing capabilities and floating-point computing capabilities. The GPU platform is very efficient in algorithm training. However, when processing a single input in inference, the advantages of parallel computing cannot be fully utilized.
FPGA Xilinx, Altera programmable array, semi-customized
ASIC TPU Google ASIC Tensor Processing Unit, Tensor Processor
NPU Cambrian, Apple NPU (Neural Network Processing Unit), Neural Network Processor
VPU Intel Vector Processing Unit vector processor
BPU Horizon Brain Processing Unit, brain processor
BM1680 Bitmain
DPU Wave Computing Deep Learning Processing Unit, the deep learning processor
HPU Microsoft Holographics Processing Unit Holographic Image Processor
IPU Graphcore Intelligence Processing Unit
Algorithm (algorithm) is a series of well-defined specific calculation steps in mathematics and computer science. It is often used in calculations, data processing and automatic reasoning. As an effective method, an algorithm is used to calculate a function. It contains a series of clearly defined instructions and can be clearly expressed in a limited time and space.

Mathematicians and logicians in the early 20th century encountered difficulties in defining algorithms, until British mathematician Turing put forward the famous Turing thesis and proposed an abstract model of a hypothetical computer. This model is called a Turing machine. . The emergence of Turing machine solved the problem of algorithm definition, and Turing’s thought played an important role in the development of algorithm.

The core of the algorithm is to create an abstract model of the problem and a clear solution goal. After that, different modes and methods can be selected according to the specific problem to complete the design of the algorithm.

Common algorithms in machine learning include decision tree, random forest algorithm, logistic regression, SVM, naive Bayes, K nearest neighbor algorithm, K mean algorithm, Adaboost algorithm, neural network, Markov and so on.

Different algorithms may be used to solve different problems, or the same algorithm may be used. No certain algorithm is omnipotent, only the scope of application is different. It is important to choose the right algorithm for different scenarios.

There is no distinction between advanced and low-level algorithms. Quick and easy problem-solving is the foundation. Blindly pursuing complex algorithms is sometimes equivalent to “smashing mosquitoes with anti-aircraft guns.”

Big data
According to incomplete statistics, there are currently about 225 million surveillance cameras used in all walks of life across the country, and the amount of data generated in a medium-sized city in 90 days is about 36PB. How to use these isolated, disorderly, unstructured data, centralized management, and orderly and selective structured processing will be of extraordinary significance.

At present, a series of projects such as Xueliang Project, Safe City and Smart City have realized video surveillance networking in a certain area and centralized management of video data. These video big data can be used to help establish and train various algorithm models and improve algorithms. At the same time, the improved and optimized algorithm can be quickly added to the project practice and be tested in actual combat.

In the future, we can further cultivate and mine video big data to maximize its value.

Thurder Protection in Security Video Surveillance System

Thunder protection is a systematic project. In addition to various devices themselves, they need to have certain thunder protection and surge protection capabilities. In the engineering design and installation of security systems, attention should also be paid to the thunder protection of equipment and systems.

Thunder hazard
Thunder and lightning is a very spectacular sound, light and electrical phenomenon in nature. At the same time, a thunder disaster is also a very serious natural disaster. The thunder damage to the weak current security system and electronic information system is mainly through the following types of thunder:

Direct thunder
Direct thunder refers to thunder strikes directly on buildings or thunder protection devices, causing electromagnetic, thermal and mechanical effects. About 3.1 billion thunder strikes occur on the earth every year, and direct thunder strikes account for 1/5–1/6.

The peak voltage of direct thunder can reach tens of thousands of volts or even millions of volts, and the peak current can reach tens of KA or even hundreds of KA, but its duration is usually only a few μs to hundreds of μs, which is huge in terms of instantaneous power. Yes, so it is very destructive.

Inductive thunder
Inductive thunder refers to all objects on the ground when a thundercloud comes, especially conductors, due to electrostatic induction, will gather a large amount of thunder with the opposite polarity of the bound charge. After the thundercloud strikes the ground or discharges another thundercloud, The charge in the cloud becomes a free charge, which generates a very high electrostatic voltage (induced voltage), and its overvoltage amplitude can reach tens of thousands to hundreds of thousands of volts. This overvoltage often causes damage in buildings. Wires, poorly grounded metal conductors and large metal equipment discharge and cause electric sparks, which can cause fires, explosions, endanger personal safety or cause harm to various electronic information systems such as security. This is an electrostatic induction mine.

In another case, when a thunder strike occurs, a strong induced electromagnetic field is formed near the passage due to the large rate of change of the thunder current, which causes interference and damage to the electronic equipment in the building. It may also cause the surrounding metal components to generate induced current, generate a lot of heat and cause a fire. This is an electromagnetic induction mine.

Conductive thunder
When the outdoor overhead line is directly struck by thunder or induced thunder, the high potential will invade along various cable lines and be transmitted into equipment or buildings. This kind of thunder intrusion will cause harm to electronic information equipment or cause damage in the building. Metal equipment discharges, causing damage.

Thunder protection standard
The main organizations for the formulation of thunder protection standards are the Thunder and thunder Protection Technical Committee (TC81) under the International Electrotechnical Commission (IEC), and the corresponding National thunder Protection Standardization Technical Committee (SAC/TC258) under the Chinese Association for Standardization (CAS), and International Telecommunications Union (ITU).

The main thunder protection standards of IEC/TC81 are:

IEC-61024 (thunder protection of buildings)
IEC-62305 (thunder Protection)
IEC-61643 (low-voltage surge protection device)
IEC-1312 (protection of thunder electromagnetic pulse)
IEC 61000-4-2 (Electromagnetic compatibility test and measurement technology, electrostatic discharge immunity test). Corresponding to GB/T-17626.2
IEC61000-4-5 (Electromagnetic compatibility test and measurement technology, surge immunity test)
ITU-T (International Telecommunication Union Telecommunications Part) K series (anti-interference protection):

ITU-T K.21 (the ability of terminal telecommunication equipment to withstand overvoltage and overcurrent). Corresponding to GB/T-17626.5
ITU-T K.20 (Electromagnetic Compatibility Technical Standard for Telecommunications Switches)
IUT-T K.27 (connection structure and grounding in the telecommunication building)

Chinese standards:

GB/T-17626 (Electromagnetic compatibility test and measurement technology)
GB50057-2016 (Code for thunder protection design of buildings)
GB500174-2017 (Data Center Design Specification)
GA173-2002 (thunder Protection Device for Computer Information System)
GB50343-2012 (Technical Specification for thunder Protection of Building Electronic Information System)
GA267-2018 (Computer Information System Thunder and thunder Electromagnetic Pulse Safety Protection Specification)
GB50311-2016 (Code for Design of Generic Cabling System Engineering)
YD5078-98 (Technical Regulations for thunder Protection of Communication Engineering Power System)
GB/T-9361-2011 (Safety Requirements for Computer Sites)
DL/T621-1997 (Grounding of AC electrical equipment)
GB/T-19856-2005 (thunder Protection Communication Line). Corresponding to IEC 61663:2001
GB50689 (Code for thunder Protection Grounding and Engineering Design of Communication Bureau (Station))

thunder protection
Security cameras, data transmission equipment, back-end management equipment, etc. generally have a certain degree of anti-thunder and anti-surge and anti-surge capabilities.

For example, a certain model of Hikvision camera indicates the protection level: TVS 6000V thunder protection, anti-surge, and anti-surge, in line with GB/T17626.5 level four standards. A certain PTZ dome camera of Dahua indicates that it supports TVS 8000V thunder protection, anti-surge and anti-surge protection. A certain PTZ dome camera of Univision is marked with a 6KV anti-surge design for the network port.

thunder protection for buildings and computer rooms
According to the requirements of GB50057-2016 (Code for thunder Protection Design of Buildings), buildings should meet thunder protection requirements.

For the newly-built security management computer room, it should be placed within the protection range of thunder rods, or be installed with thunder rods to reduce the probability of being struck by thunder. At the same time, it should be grounded and grounded.

There are many calculation methods for the protection range of thunder rods. For details, please refer to the article on the protection range of thunder rods. It should be noted that the protection range of the thunder rod and its height do not increase proportionally. For security cameras installed outdoors, we can calculate the range of thunder rod protection according to the 45° broken line method, that is, the radius of the protection range is the height of the thunder rod.

Grounding is an important method of thunder protection for buildings and various electrical equipment, especially grounding resistance. The larger the grounding resistance, the more unfavorable the discharge of overvoltage and overcurrent, so the grounding resistance should be strictly controlled within the required range.

Ground resistance
GB50174 (Code for Design of Electronic Computer Room) stipulates: AC grounding should be less than 4 ohms, and safety grounding should be less than 4 ohms.

GB50057 (Code for Design of thunder Protection for Buildings) stipulates that the grounding resistance for thunder protection should be less than 10 ohms.

YD2011 (Code for Design of thunder Protection and Grounding for Microwave Stations) pointed out: It is strictly forbidden to make zero protection. The power frequency grounding resistance should not be greater than 10 ohms.

YDJ 26-89 (Interim Technical Regulations on Grounding Design of Communication Bureau (Station)): It is strictly forbidden to use the neutral wire as the AC protective ground wire. The grounding resistance value of the comprehensive communication building should not be greater than 1 ohm.

The thunder protection design in YD5003 (Code for Design of Special Telecommunication Buildings): The impulse grounding resistance of the thunder protection grounding device of the telecommunications building should not be greater than 10 ohms, and the three-in-one grounding (joint grounding) should meet the working grounding resistance requirements.

According to the requirements of the above national regulations, the grounding resistance of general buildings should be less than 10 ohms, and the grounding resistance of computer rooms should be less than 4 ohms. Switches, small computers and other equipment generally require DC working grounding resistances of less than 1 ohm.

Grounding resistance measurement method

The arrangement of the electrodes is shown in the figure below. The distance d1 between the current electrode and the edge of the grounding grid is generally 4 to 5 times the maximum diagonal length D of the grounding grid, so that the potential distribution between them appears in a flat section. In general, the distance d2 between the voltage electrode and the edge of the grounding grid is about 50% to 60% of the distance d1 from the current electrode to the grounding grid.

Ground resistance measurement
When measuring, move the voltage electrode along the connection line between the grounding grid and the current electrode three times, each time the moving distance is about 5% of d1, if the resistance value measured three times is close.

For example, it is difficult to take d1 from 4D to 5D. In areas with relatively uniform soil resistivity, d1 can be 2D and d2 is D; in areas or regions with uneven soil resistivity, d1 can be 3D and d2 is 1.7D.

The voltage pole and current pole can also be arranged in a triangle as shown in the figure below. Generally take d2=d1≥2D, and the included angle is about 30 degrees.
Ground resistance triangulation

The current pole and voltage pole should be arranged in a direction perpendicular to the line or underground metal pipeline. Avoid measuring grounding resistance immediately after rain.

When the AC ammeter-voltmeter method is adopted, the arrangement of the electrodes should adopt a triangular arrangement.

Selection of protective grounding wire diameter
According to the selection method of the wire diameter of the equipment protective grounding wire in IEC60950 “Safety of Information Technology Equipment”, the wire diameter of the protective grounding wire is selected as follows:

Rated current of the equipment A Nominal cross-sectional area MM2
6 0.75
6~10 1
10~13 1.25
13~16 1.5
16~25 2.5
25~32 4
32~40 6
40~63 10
63~80 16
80~100 25
100~125 35
125~160 50
160~190 70
190~230 95
230~260 120
260~300 150
Equipment installation thunder protection
Cameras and other equipment installed outdoors should be placed within the effective protection range of thunder rods.
The camera should be equipped with corresponding thunder protection devices such as power cables, video cables, control signal cables and communication cables.
The grounding wire of the camera protective cover, the equipment grounding wire, the thunder arrester grounding wire, the general grounding wire, etc. must be equipotentially connected to form an equipotential body.
The camera is installed outdoors with a pole with a thunder rod. The thunder rod is likely to cause induced thunder. One is the introduction of large current, but electromagnetic induction. Be sure to pay attention to the equipment grounding and equipotential connection, otherwise the thunder rod will be counterproductive and bring destructive effects.
When the camera is installed outdoors, when the existing poles (such as street light poles, traffic light poles, and telephone poles) are used for installation, if there is no grounding body, a new grounding body needs to be built.

Use angle steel or steel pipe with a length of not less than 2.5m and drive directly into the ground. The distance between the upper end and the ground should not be less than 0.7m. The section of the angle steel should be no less than L×W×H = 50×50×5mm, the wall thickness of the steel pipe should be no less than 3.5mm, and the material should be galvanized steel.

The protective grounding cables of cameras and other equipment should be connected to the angle steel by electric welding, and the surface of the welding points should be coated with anti-rust paint for anti-rust treatment. The cross-sectional area of the protective grounding cable shall not be less than 16 square meters, and the cable shall be as short as possible during construction and cannot be coiled.

Schematic diagram of a typical outdoor pole-mounted camera thunder protection
Transmission line thunder protection
Transmission equipment (such as switches, fiber optic transceivers, etc.) should be installed with the same thunder protection measures as cameras.
It is recommended to lay the cable through the metal pipe and bury it in the ground. At the same time, ensure effective grounding at both ends of the metal pipe.
If the metal pipe cannot be worn all the way, the metal pipe must be buried in the ground before the cable is connected to the monitoring room and the network camera. The buried length should not be less than 15m. The metal sheath of the cable and the metal pipe should be effectively connected to the thunder protection ground at the access end. . Finally, corresponding thunder protection devices should be installed at both ends of all transmission cables.
Use shielded transmission cables, and use thunder protection devices at both ends of each cable.
Optical fiber cables will not conduct electricity and are not susceptible to electromagnetic interference. The use of optical fibers to transmit signals can better prevent thunder hazards.
Reference materials:

Comprehensive thunder protection scheme for security video surveillance system
The main points of thunder protection design in security video surveillance system
Univision: Installation Guide of Network Camera
Tags: safety, surge, thunder protection