Webcam for surveillance. The design and principle of operation of a webcam Modern webcams, their characteristics and design

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Using a webcam, they set up video surveillance in their own home or office. To do this, we select the right equipment, install special software and configure the system. Let's look at how to choose a webcam for surveillance and organize IP video surveillance, what you should consider and what problems arise in the process.

How does a surveillance webcam work?

It works on the same principle as digital video cameras and cameras. The basis is a built-in analog-to-digital converter (ADC), which transforms analog signals coming from a digital sensor into digital code and performs further color formatting.

A compression circuit connected to the USB interface controller allows you to quickly transfer the received data to a computer. The last stage is responsible for the speed and quality of digital code transmission.

Today, IP video surveillance has become widespread, which involves transferring image data from video cameras to a PC via a Wi-Fi signal.

Video equipment has functional differences from web cameras with HD image resolution, but the base remains the same:

transfer data directly to a computer without recording on a web-cam matrix;
work in real time;
HD image resolution;
recording data using special software if desired;
Monitoring images from a computer device that has public access to the data.

In the case of special devices for IP tracking, an additional recorder-router with Wi-Fi function is installed, through which data is exchanged between the camera and the computer.

But the result is the same: the image from the device (or devices) is transferred to the PC online, allowing you to monitor the room. Tracking via a standard web-cam connected via a USB port or Wi-Fi works on the same principle.

In both cases, they use a cloud data storage system to have access to viewing recordings or broadcasts from different IP addresses and devices. This is a web storage, access to which is based on the principle of a personal account; the volume of data is traditionally limited and depends on the status: paid or free registration.

Manufacturers of software and equipment for IP tracking offer the use of specialized cloud video storage, but in the case of self-configuration, the choice is not limited to them.

Base for creating video surveillance:

computer;
Webcam;
special software;
uninterruptable power source;
access to the Internet.

The general scheme for organizing surveillance: a web-cam is connected to a computer, a special data recording program is installed, cloud storage is connected, and everything is protected with a password.

It is important to consider: select and configure the tracking device according to the rules so that the picture maintains image clarity and covers a wide viewing angle, for which it is important to correctly place the camera in the room.

Tip: Connect an uninterruptible power supply to prevent crisis situations.

You can turn a standard webcam into an IP video surveillance tool using special programs and additional device properties. Let's look at an example of how to choose the right webcam for surveillance.

Advantages and disadvantages

The basis for organizing tracking is the competent choice of device. We recommend giving preference to cameras with high image resolution and paying attention to the speed and type of data transfer.
There are two types of devices:

digital code transmission via USB module;
wireless connection using Wi-Fi technology.

USB camera. These are standard devices in a low price range, connected via a cable to the port of a computer device. Among the models there are basic ones with SD and HD image quality, with advanced functionality (backlight, shooting in a dark room, motion indicator, etc.).

Cameras with a resolution of 640x528 pixels, but not less, are suitable for surveillance. To get a bright, contrasting and detailed picture, you must use an HD camera.

This is a priority for surveillance, since the recognition of offenders in the recording depends on the detail of the image.

Peculiarities: With HD resolution, problems may arise at the stage of setting up video surveillance in a free program where there are restrictions on picture quality.
Advantage: the price range for USB models is significantly lower than for wireless ones;
Flaws: restriction of the freedom of location of the camera literally tied by a cable to the computer.

Wi-Fi web-cam. The price range of the cameras is above average. On the other hand, you can place it in an apartment or office, within reach of Wi-Fi waves. The model range is divided into two categories: for standard use and for IP tracking.

The second option has additional functions: built-in motion sensors, infrared vision mode for night tracking, and use of the camera without additional programs.

The second name of the subtype is network camera, due to the personal IP address of the device, which can be accessed using encryption keys. A network webcam is connected via a local network, similar to peripheral ones. Windows and iOS automatically recognize the camera; only for Linux a driver is installed separately.

The image resolution traditionally corresponds to HD parameters. Specialized models are produced for installation outdoors: they are protected from impacts, water penetration and ultraviolet radiation.

Peculiarities: Connection requires Wi-Fi technology in your computer;
Advantages: the location of the camera is not tied to the location of the computer, IP models do not require additional programs and drivers;
Flaws: Cost is higher than wired models.

Let's look at an example of what camera functionality is needed to organize surveillance via a PC.

Webcam Specifications for Surveillance

Sensor resolution. Affects image quality, which is so important when recording visual data. The dependence is as follows: the more, the higher the detail of the image, the more clearly visible are small details, faces and text. The minimum for our case is 680x480 VGA, with it the image is clear, and the load on the computer’s RAM does not slow down the work. As the load increases, the PC's central processor slows down; if the data transfer speed over the Internet is not higher than 20 Mb/s, you should limit yourself to this resolution. PCs with 2GB of RAM, two processor cores and are more suitable for connecting web-cams with High Definition resolution of 1280x720 (abbreviation HD 720p) and higher. You can choose a higher one, but the requirements for the system parameters of the computer will increase. This video quality is detailed, contrasty, and allows you to see small text and details of a person’s appearance on the recording.
Wi-Fi connection. Cameras with remote installation are suitable for covert surveillance: they are mounted at a point in the room with a wide viewing angle, are not conspicuous and traditionally operate in resolutions starting from 720p.
Personal IP address. Facilitates camera installation and room monitoring.
Night vision mode. All standard models operate in the traditional ISO (light sensitivity) range and do not recognize images in the dark. The camera's built-in infrared sensor recognizes objects without additional lighting and is suitable for surveillance at night. Alternative: purchase a regular webcam with built-in backlight or arrange additional LED lighting in the room.
Number of frames per second. The indicator is designated as FPS; the higher its numerical value, the higher the video quality. The minimum indicator for our case is 40.
Motion Sensor. Present in special IP models for tracking. Allows you to turn your PC into not only a DVR, but also an alarm system complete with installed software.
Matrix sensitivity. The higher it is, the less light the camera will remain active and useful while continuing to shoot. Pay attention to the LUX indicator when choosing, give preference to models with the highest indicators.
Universal mount. Choose models with convenient and durable fasteners that will allow you to attach the device to a computer, furniture, wall or ceiling, or place it on a flat surface.
Fisheye function. Coverage of the viewing area is 3600, allowing you to capture all corners of the room.
Uninterruptible power supply device. When using a standard webcam, it is necessary to ensure that the PC operates around the clock without interruption. If the premises are broken into, communications may be cut off, including electricity. The UPS will allow you to register a hack and send data from the camera to a cloud storage server.

How to use

For proper setup, use the installation algorithm:

Determine the monitoring area in the room. Select control points: safe, cash register, workspace and the like. Position the camera so that all areas are viewed simultaneously.
Connect the camera to a computer or recorder, depending on its type.
If you connect the device via a cable, its length should not be more than 300 m, otherwise data loss and noise are inevitable.
Perform initial setup of drivers and software, if necessary.
Set up the power supply, in our case, connect an uninterruptible power supply to the PC.
Check your internet connection.
Using a standard webcam, install a specialized video surveillance program on your PC.
Set up light sensitivity, number of frames per second, color profile, resolution and additional functionality (motion sensor, infrared radiation).
Connect to a cloud video recording service.
Check the image quality and data transfer speed.

Pay attention to the viewing angle and lighting in the room. If there is a shortage, provide additional light sources; we recommend using LED lamps to save energy consumption.

Standard web-cam with connection via USB port are presented in a low price range. They consume less electricity and do not depend on additional power sources like a battery. The disadvantage is the location limitation.
Models with wi-fi module are mobile, operate within a network coverage radius, and do not require additional software for connection. Presented in a resolution of over 720p: the picture is detailed, contrasty and bright. The disadvantage is the need for additional equipment such as a router and a recorder.
IP-cam designed for tracking, they feature additional functionality such as night vision, motion sensor and direct connection to the cloud storage server. Control of order in the room at night: when connected to specialized alarm system software, a home alarm is obtained.

Problems

A typical problem with video surveillance via a standard webcam is the power supply. When you turn off your computer, your work session ends.

The difficulty can be resolved by connecting an uninterruptible power supply to the PC.

Second problem: poor image quality. The difficulty lies in the manufacturer’s parameters and computer data. For smooth operation, a PC with 2 GB of RAM and two processor cores is suitable. The higher the data, the less interference there is in the work.

The third problem: data hacking. Create accounts in certified programs; IP models are produced with built-in information encoding.

A digital webcam is a network device that consists of a video camera (CCD), a compression processor and a built-in web server. As a rule, a webcam is used as a device for organizing video recording, video conferencing or video surveillance and transmitting video images over a LAN/WAN/Internet network. To operate a webcam on a network, no special devices or a personal computer are required. Depending on the settings, access to the video image received by the webcam can be open to all network users or only authorized users.

The design and principle of operation of a webcam

A modern webcam is a digital device that records video, converts an analog video signal into a digital one, compresses a digital video signal and transmits video images over a computer network. Therefore, the webcam includes the following components:

CCD matrix,

lens,

optical filter,

video capture card,

video compression unit,

central processor and built-in web server,

flash memory,

network interface

serial ports,

alarm inputs/outputs.

It is used as a photodetector in most web cameras. CCD matrix ( CCD, CCD - charge-coupled device) is a rectangular photosensitive semiconductor plate with an aspect ratio of 3: 4, which converts the light incident on it into an electrical signal. The CCD matrix consists of a large number of photosensitive cells. In order to increase the light sensitivity of a CCD matrix, a structure is often formed that creates a microlens in front of each of the cells. The technical parameters of a webcam usually indicate the format of the CCD matrix (diagonal length of the matrix in inches), the number of effective pixels, scan type (interlaced or interlaced) and sensitivity.

Lens is a lens system designed to project an image of an observation object onto the light-sensitive element of a web camera. The lens is an integral part of the webcam, so the quality of the video image received by the webcam depends on its correct selection and installation. Quite often, a webcam comes with a lens. Lenses are characterized by a number of important parameters, such as focal length, relative aperture (F), depth of field, type of mount (C, CS), format.

Optical infrared cut filters , which are installed in webcams, are optically precise plane-parallel plates mounted on top of the CCD matrix. They operate as optical low-pass filters with a cutoff frequency of about 700 nm, near red. They cut off the infrared component of light waves, providing the webcam with correct color reproduction. However, many black-and-white webcams do not have such filters installed, which is why monochrome webcams have higher sensitivity.

Video capture card The web camera (digitization unit) converts the analog electrical signal generated by the CCD matrix into a digital format. The signal conversion process consists of three stages:

Sampling,

Quantization

Coding.

Sampling- reading the amplitude of the electrical signal at regular intervals (period). This stage of signal conversion is characterized by the sampling frequency.

Quantization is the process of presenting sampling results in digital form. The change in the level of the electrical signal over the sampling period is represented as a code word of 8, 10 or 12 bits, which give 256, 1024 and 4096 quantization levels, respectively. The accuracy of the signal representation in digital form depends on the number of quantization levels.

Coding. In addition to the information about changes in signal level obtained at the previous stage, the encoding process generates bits indicating the end of the clock pulse and the beginning of a new frame, as well as additional error protection bits.

Compression block webcams compress the digitized video signal into one of the compression formats (JPEG, MJPEG, MPEG-1/2/4, Wavelet). Thanks to compression, the size of the video frame is reduced. This is necessary for storing and transmitting video over the network. If the local network to which the webcam is connected has limited bandwidth, then in order to avoid overflowing the network traffic, it is advisable to reduce the amount of transmitted information by reducing either the frequency of frame transmission over the network or the frame resolution. Most compression formats that webcams use provide a reasonable compromise between these two ways of solving the problem of transmitting video over a network. Compression formats known today make it possible to obtain a digitized stream with a bandwidth of 64 KB - 2 MB (with this bandwidth, video data streams can work in parallel with other data streams in networks).

Video compression in a webcam can be done either in hardware or in software. Software implementation of compression is cheaper, but due to the high computational capacity of compression algorithms, it is ineffective, especially when you need to view video from a webcam online. Therefore, most leading manufacturers produce webcams with hardware compression. For example, each AXIS Communications network camera is equipped with an ARTPEC compression processor, which performs high-speed video compression into the JPEG/MJPEG format.

CPU is the computing core of the webcam. It carries out operations for outputting digitized and compressed video images, and is also responsible for performing the functions of a built-in web server and a control program for web cameras.

Interface for Ethernet serves to connect the webcam to a 10/100 Mbit/s Ethernet network.

To work on the network, the webcam can have serial port for connecting a modem and working in dial-up mode in the absence of a local network. You can also connect peripheral equipment to the webcam through the serial port.

Flash memory card allows you to update webcam control programs and store custom HTML pages.

RAM serves to store temporary data that is generated during the execution of control programs and user scripts. Many Internet cameras have a so-called video buffer. This is a part of RAM reserved for recording and temporary storage of video frames captured by the webcam. The information in the video buffer is updated cyclically, i.e. the new frame is recorded instead of the oldest one. This function is necessary if the webcam performs security video surveillance, since it allows you to restore events preceding and following the alarm from security sensors connected to the webcam.

Alarm inputs/outputs are used to connect alarm sensors to the webcam. When one of the sensors is triggered, an alarm signal is generated, as a result of which the webcam processor composes a set of frames recorded in the video buffer before, after and at the time of the alarm. This set of frames can be sent to a specified e-mail address or via FTP.

Connecting and installing a webcam

Typically, a webcam is connected to the Internet via a 10BaseT/100BaseTX/1000BaseTX Ethernet port or using a modem via a serial port. Once the webcam is physically connected to the network, it is assigned an IP address. Most often, the webcam does not have a default IP address; it is installed either using the appropriate function of a standard web browser, or by a DOS command that uses the serial number of the webcam assigned to it by the manufacturer for identification. In addition, manufacturers are developing special programs for webcams that greatly simplify the procedure for assigning an IP address to a webcam (for example, IP Installer from AXIS Communications). Thanks to the built-in software for a web server, FTP server, FTP client, e-mail client, etc., the webcam connects directly to the LAN/WAN/Internet network and works in it as an independent network device. This distinguishes webcams from other digital cameras, which require that they be connected to a personal computer via a USB or LPT port. In addition, webcams can support working with user scripts and JAVA applets.

To install a webcam outdoors or indoors, many manufacturers include special fasteners in the design of the camera body designed for installation on walls, ceilings, brackets and rotating devices. Some webcams have built-in rotating devices designed to be mounted on a horizontal or vertical surface.

Additional features and functions of the webcam

Motion Detector is a software module whose main task is to detect web cameras moving in the field of view at a video surveillance site. The motion detector not only detects movement in the image field, but also determines the dimensions of the object and the speed of its movement. Depending on the video surveillance tasks, the webcam motion detector is configured to detect the movement of objects with the utmost minimization of false alarms (interference filtering), and flexible alarm processing logic is set (alarm recording, integration with other security equipment).

Audio transmission over the network in most cases is carried out by connecting an additional audio module to the webcam. For example, AXIS Communications, to expand the functionality of webcams, produces a special audio module AXIS 2191, compatible with most AXIS webcams.

Password protection serves to restrict access to the webcam by persons who do not have access rights.

By default, webcam video can be viewed from any network computer that has a standard web browser installed, such as Internet Explorer or Netscape Navigator. However, you can limit the number of people who have access to the webcam by entering a user-level password. Many webcams support multi-level password protection to differentiate access and administration rights.

Webcam programs

Typically, the webcam image can be viewed using a standard web browser, such as Internet Explorer or Netscape Navigator. However, many manufacturing companies develop exclusive programs for webcams.

They combine the functions of a web browser and management software to manage, configure and view webcam images (eg AXIS Camera Explorer or JVC Professional's V.networks network device management software). There is also software for distributed network video surveillance systems that supports equipment from various manufacturers, such as Sphinx-DV from Digicore Systems.

Connecting the webcam to the network

Currently, a webcam can connect to the network in several ways, which are based on different data transfer standards.

10/100 MbitEthernet. This is the most popular way to transfer data from a webcam to the network. There are two standards for 10 Mbit Ethernet networks: 10Base2 (using coaxial cable) and 10BaseT (using twisted pair). 10Base2 is used extremely rarely due to the sensitivity of coaxial cable to external noise. The 100BaseTX standard uses twisted pair cable and provides data transfer rates of 100 Mbps.

1000 Mbit Ethernet, Gigabit Ethernet. The 1000BaseTX standard used here is an improved version of 100BaseTX. This standard is used mainly for building local network backbones.

Standard telephone modems. This is a cheap and fairly common way to connect a webcam to the global network. The main disadvantage of this connection method is the low data transfer speed (maximum data download speed is 56 kbit/s, maximum upload speed is 33.6 kbit/s). The webcam is connected to the modem via a serial port.

ISDN modems. The ISDN (Integrated services Digital Network) standard is used to transmit digitized graphics, audio and video information and other digital data over private or public digital telephone networks. The ISDN standard provides data transmission from a web camera at speeds of up to 128 kbit/s over two channels.

xDSL modems. DSL (Digital Subscriber Line) is a technology that provides high bandwidth over simple copper telephone wires. The webcam data transfer speed may vary depending on the company providing the service. On average, it is 1 Mbit/s for downloading data and 250 kbit/s for uploading.

Cable modems. A cable modem is a modem that provides access to the Internet over cable television networks. Cable modems use asymmetric technology, which is best suited for user access to the Internet. At the same time, the maximum possible speed of receiving data from a webcam with such a modem can reach about 40 Mbit/s (although it usually does not exceed 1 Mbit/s), and the data transmission speed is about 10 Mbit/s.

Cellular modems. Using a cellular modem, you can connect your webcam to the Internet using cellular communication lines. Data transfer rates are typically between 5 and 20 kbps.

More detailed technical information on specific models of webcams from Axis Communications and JVC Professional is presented on the same website in the video cameras section. Brief technical specifications and prices for webcams are given in the ARMO-Systems online store.

How to access a webcam over the Internet

How to access a webcam over the Internet.

Example: After you already receive the image from the webcam on your computer, you decide that it would be nice to be able to access the camera wherever there is Internet. For example, as a store owner, you want to control the activities in the store from your home, instead of having to be present every minute at the workplace

Step 1: System Requirements

Scenario A)

If your building (where the camera should be located) is already connected via Ethernet to an ISP (Internet Service Provider), simply set up an account, plug the network camera into the switch via the network output, and you should get a dynamically assigned public IP for the network camera -address. Follow the installation commands for the network camera. Special software or utility for the webcam will be useful in identifying the IP address.

Since the assigned IP address may be changed by your ISP (due to the limited supply of IP addresses shared among its clients), see Step 4 below to find out how you can assign cameras to a specific IP address.

Scenario B)

If your building is not equipped with Ethernet access, then in most cases you may need the following devices:

broadband modem for connecting an asymmetrical digital subscriber line (usually supplied by your Internet service provider) or cable television

broadband router, which can also be called an Internet Gateway, (A broadband router allows local network users to share a single Internet connection. It also serves as an interface between the Internet, the ISP and the Local Network)

a switch that allows different devices from the network to communicate directly with each other and allows devices from the local network to have separate IP addresses),

NOTE: Most broadband routers have a built-in switch function, so no separate hardware is required.

network camera

local computer

computer for remote monitoring

Step 2: Assign an IP address to your camera

Since a broadband router typically assigns automatic, local IP addresses to devices on the local network, such IP addresses are subject to change. A static (permanent) IP address is recommended for the network camera. To assign a static IP address, find out the router's IP address range, which, for example, could be from 192.168.0.2 to 192.168.0.35. If you choose to use an out-of-range IP address, such as 192.168.0.100, as a static IP address for the camera, it is likely that you will not risk your device conflicting with other devices that receive automatic addresses.

Setting the IP address for your camera can be done in three different ways, as indicated in the camera manual. Once the IP address is assigned, set the subnet, and gateway (this information can be obtained from the router), and configure the camera settings: password, registered users to ensure access restrictions to the camera.

Step 3: Port Forwarding

The broadband router, as mentioned earlier, provides the interface between the Internet, the ISP and the Local Network. The router obtains an external IP address from the Internet service provider and supplies internal (local) IP addresses to devices on the local network.

To access a network camera that resides on a local network, you must identify the external IP address of your router (see your router's manual), and configure your router so that the external IP address is directed to the static, local IP address of the network camera . This process is called opening a port; that is, when you type the router's external IP address from any network computer, the Internet locates your router, in turn forwarding your request to the local IP address that is assigned to the network camera.

Launch your Web browser and log into the router's built-in Web pages through Login to Router Configuration Pages.

Find the menu item “port forwarding” (or similar), with a table approximately as shown below:

Since the camera sends its video over HTTP, you must configure the HTTP service like this:

Save the configuration to the router and exit the configuration pages. The configuration is complete. Any requests reaching the router's external IP address on port 80 will now be sent to the camera's IP address: 192.168.0.100.

If you want to make more than one network camera accessible via the Internet, then you must use additional (unofficial) router ports, such as 80xx, and associate them with the network address of the IP camera.

Step 4: What can you do if your ISP frequently changes Dfi external IP address

Create an account in the DNS service that serves and registers domain names (for example www.nic.ru, etc.) and bind it to an external IP address. A domain name, such as www.web-kamera.ru, is clear to the user, easy to remember, and you can assign each domain its own network device, i.e. its IP address. Whenever the router's IP address changes, it will be automatically registered by the DNS service to update your IP address so that you can access your network camera using the same address.

Most broadband routers have native DNS support, such as www.dyndns.org.

Another alternative: You can buy or rent a static external IP address from your Internet service provider.

Found a typo? Select and press CTRL+Enter

11 Jun 2011

The design and principle of operation of a webcam

CCD matrix,

lens,

optical filter,

video capture card,

video compression unit,

central processor and built-in web server,

flash memory,

network interface

serial ports,

alarm inputs/outputs.

Sampling,

Quantization

Coding.

Sampling- reading the amplitude of the electrical signal at regular intervals (period). This stage of signal conversion is characterized by the sampling frequency.

Interface for Ethernet serves to connect the webcam to a 10/100 Mbit/s Ethernet network.

Flash memory card allows you to update webcam control programs and store custom HTML pages.

Connecting and installing a webcam

Additional features and functions of the webcam

Password protection serves to restrict access to the webcam by persons who do not have access rights.

Webcam programs

Typically, the webcam image can be viewed using a standard web browser, such as Internet Explorer or Netscape Navigator. However, many manufacturing companies develop exclusive programs for webcams.

Connecting the webcam to the network

Currently, a webcam can connect to the network in several ways, which are based on different data transfer standards.

1000 Mbit Ethernet, Gigabit Ethernet. The 1000BaseTX standard used here is an improved version of 100BaseTX. This standard is used mainly for building local network backbones.

Cellular modems. Using a cellular modem, you can connect your webcam to the Internet using cellular communication lines. Data transfer rates are typically between 5 and 20 kbps.

How to access a webcam over the Internet

How to access a webcam over the Internet.

Step 1: System Requirements

Scenario A)

Scenario B)

If your building is not equipped with Ethernet access, then in most cases you may need the following devices:

broadband modem for connecting an asymmetrical digital subscriber line (usually supplied by your Internet service provider) or cable television

a switch that allows different devices from the network to communicate directly with each other and allows devices from the local network to have separate IP addresses),

NOTE: Most broadband routers have a built-in switch function, so no separate hardware is required.

network camera

local computer

computer for remote monitoring

Step 2: Assign an IP address to your camera

Step 3: Port Forwarding

Launch your Web browser and log into the router's built-in Web pages through Login to Router Configuration Pages.

Find the menu item "port forwarding" (or similar), with a table approximately as shown below:

Service name	Start port	End port	Server IP address
			Not configured
			Not configured
			Not configured

Since the camera sends its video over HTTP, you must configure the HTTP service like this:

Service name	Start port	End port	Server IP address
			Not configured

Unofficial port

Step 4: What can you do if your ISP frequently changes Dfi external IP address

Most broadband routers have native DNS support, such as www.dyndns.org.

Another alternative: You can buy or rent a static external IP address from your Internet service provider.

Webcams. Purpose, principle of operation and main characteristics.

in the discipline (specialization) “Computer Hardware”

I checked

Nikolskaya K.Yu.

student of group PS-170

Badalova A.A.

Abstract protected

with assessment

Chelyabinsk 2014

Badalova A.A. Webcams. Purpose, principle of operation and main characteristics. – Chelyabinsk: SUSU, PS-170, 20 p., 4 ill., bibliogr. list – 5 names.

The purpose of the essay is to learn about the purpose, operating principles and main characteristics of web cameras.

The objectives of the essay are to study the design and operating principle of web cameras, learn how to install web cameras and connect them to the network, learn about the importance of web cameras in the modern world.

The main characteristics of web cameras and methods of connecting to the network are considered. Describes programs for webcams and how to connect a webcam to the network.

1. Introduction (page 4)

2. Definition (page 5)

3. History of the creation of the webcam (page 6)

4. Design and principle of operation of the webcam (page 7-11)

5. Additional features and functions of webcams (p. 12)

6. Connecting the webcam to the network (pages 13-15)

7. Methods of using webcams (pages 16-17)

8. Programs for webcams (page 18)

9. Conclusion (page 19)

10. Bibliography (page 20).

Introduction.

Webcams are increasingly becoming a part of our lives. They are used to build video systems for both geographically large and small objects. They become especially indispensable for control and monitoring of remote points where there is a need to use maintenance-free equipment. When you urgently need to install “temporary” cameras, webcams are indispensable, because their installation does not require pulling separate wires, and therefore installation will be quick and easy.

The purpose of my work is to learn about the purpose, operating principles and main characteristics of web cameras.

To do this, I will study the history, design and main characteristics, as well as the scope of application of webcams, learn how to install them and connect them to the network.

Webcam concept.

The history of the creation of the webcam.

It all started in one of the computer laboratories in Cambridge back in the early 90s of the last century, when the Global Wide Web was just beginning its victorious march across the planet. A group of scientists, about 15-20 people, worked on a project in the field of network technologies. The working conditions were spartan - there was only one coffee maker for the entire team, which could not meet the needs of the entire team. The main work was carried out in the laboratory; the staff lived in the same building, but in a different part of it. To spur their thinking process with a cup of invigorating drink, participants in the scientific project were forced to frequently visit the corridor located on the floor above, where the coffee maker was located. Often such trips failed, since some colleagues had already managed to empty the coveted container. The situation required a non-standard solution, and it was found.
One of the computers in the laboratory had a video surveillance device (frame grabber). A camera was connected to it, which was aimed at the object of observation. The same computer played the role of a web server using specially written software. Those who wanted to know whether there was coffee had to run client software on their computer that connected to the server. As a result, a black and white image was displayed on the remote computer in a small window, updated three times a minute. A note about this interesting complex was published in Comm-Week magazine on January 27, 1992. Not much time has passed since the appearance of the first prototypes of IP cameras, but they have already turned into a fully formed, separate class of devices that make everyday life easier, more convenient and more fun.

Figure 1. Image from the first webcam

The design and principle of operation of a webcam.

A modern webcam is a digital device that records video, converts an analog video signal to a digital signal, compresses a digital video signal, and transmits video images over a computer network. Therefore, the webcam includes the following components:

CCD matrix,

lens,

optical filter,

video capture card,

video compression unit,

central processor and built-in web server,

flash memory,

network interface

serial ports,

alarm inputs/outputs.

·
It is used as a photodetector in most web cameras. CCD matrix ( CCD, CCD - charge-coupled device) is a rectangular photosensitive semiconductor plate with an aspect ratio of 3: 4, which converts the light incident on it into an electrical signal. The CCD matrix consists of a large number of photosensitive cells. In order to increase the light sensitivity of a CCD matrix, a structure is often formed that creates a microlens in front of each of the cells. The technical parameters of a webcam usually indicate the format of the CCD matrix (diagonal length of the matrix in inches), the number of effective pixels, scan type (interlaced or interlaced) and sensitivity.

· Lens is a lens system designed to project an image of an observation object onto the light-sensitive element of a web camera. The lens is an integral part of the webcam, so the quality of the video image received by the webcam depends on its correct selection and installation. Quite often, a webcam comes with a lens. Lenses are characterized by a number of important parameters, such as focal length, relative aperture (F), depth of field, type of mount (C, CS), format.

· Optical infrared cut filters , which are installed in webcams, are optically precise plane-parallel plates mounted on top of the CCD matrix. They operate as optical low-pass filters with a cutoff frequency of about 700 nm, near red. They cut off the infrared component of light waves, providing the webcam with correct color reproduction. However, many black-and-white webcams do not have such filters installed, which is why monochrome webcams have higher sensitivity.

· Video capture card The web camera (digitization unit) converts the analog electrical signal generated by the CCD matrix into a digital format. The signal conversion process consists of three stages:

Sampling, quantization, coding.

Sampling- reading the amplitude of the electrical signal at regular intervals (period). This stage of signal conversion is characterized by the sampling frequency.

· Compression block webcams compress the digitized video signal into one of the compression formats (JPEG, MJPEG, MPEG-1/2/4, Wavelet). Thanks to compression, the size of the video frame is reduced. This is necessary for storing and transmitting video over the network. If the local network to which the webcam is connected has limited bandwidth, then in order to avoid overflowing the network traffic, it is advisable to reduce the amount of transmitted information by reducing either the frequency of frame transmission over the network or the frame resolution. Most compression formats that webcams use provide a reasonable compromise between these two ways of solving the problem of transmitting video over a network.

Compression formats known today make it possible to obtain a digitized stream with a bandwidth of 64 KB - 2 MB (with this bandwidth, video data streams can work in parallel with other data streams in networks).

· CPU is the computing core of the webcam. It carries out operations for outputting digitized and compressed video images, and is also responsible for performing the functions of a built-in web server and a control program for web cameras.

· Interface for Ethernet serves to connect the webcam to a 10/100 Mbit/s Ethernet network.

· To work on the network, the webcam can have serial port for connecting a modem and working in dial-up mode in the absence of a local network. You can also connect peripheral equipment to the webcam through the serial port.

· Flash memory card allows you to update webcam control programs and store custom HTML pages.

· RAM serves to store temporary data that is generated during the execution of control programs and user scripts. Many Internet cameras have a so-called video buffer. This is a part of RAM reserved for recording and temporary storage of video frames captured by the webcam. The information in the video buffer is updated cyclically, i.e. the new frame is recorded instead of the oldest one. This function is necessary if the webcam performs security video surveillance, since it allows you to restore events preceding and following the alarm from security sensors connected to the webcam.

· Alarm inputs/outputs are used to connect alarm sensors to the webcam. When one of the sensors is triggered, an alarm signal is generated, as a result of which the webcam processor composes a set of frames recorded in the video buffer before, after and at the time of the alarm. This set of frames can be sent to a specified e-mail address or via FTP.

Figure 2. Webcam device.

5. Additional features and functions of the webcam

· Motion Detector is a software module whose main task is to detect web cameras moving in the field of view at a video surveillance site. The motion detector not only detects movement in the image field, but also determines the dimensions of the object and the speed of its movement. Depending on the video surveillance tasks, the webcam motion detector is configured to detect the movement of objects with the utmost minimization of false alarms (interference filtering), and flexible alarm processing logic is set (alarm recording, integration with other security equipment).

· Audio transmission over the network in most cases is carried out by connecting an additional audio module to the webcam. For example, AXIS Communications, to expand the functionality of webcams, produces a special audio module AXIS 2191, compatible with most AXIS webcams.

· Password protection serves to restrict access to the webcam to persons who do not have access rights.

Typically needed in four cases: for work video conferences, video calls to family and friends, as well as for streaming and recording video blogs. Depending on the purpose of your camera, you need to choose a specific model - for conversations with loved ones, a not very advanced camera is enough, but for recording videos for your blog, higher-level cameras are recommended.

As is the case with many other electronic devices, a webcam can be purchased for a couple of tens of dollars or several hundred - it all depends on your wishes and budget.

In the next section, we will talk about the most important characteristics of webcams, then we will give some useful tips, and then we will present to your attention ten interesting models that can be found and purchased in our catalog.

Key Features You Should Pay Attention to

Sensor resolution, MP

Characterizes the number of photosensitive elements of the camera matrix that capture light during the process of taking video or photos. The higher the resolution, the better. To record HD video, models with a 1-megapixel sensor are sufficient; for FullHD, a 2-megapixel model is required. In most cases, a higher resolution is not needed.

Video resolution, pixels

Even the cheapest modern webcams can record video in FullHD resolution. Their main difference is the maximum frame rate and the quality of the video itself. Before bribing a specific model, be sure to check out the examples of videos that were shot with its help - they are easy to find on YouTube.

Photo resolution, pixels

In general, webcams are not designed for taking photos - except for social networks. But no one bothers you to take a few pictures with them if you don’t have another device with a camera at hand. The quality will most likely be mediocre at most - even top webcams use interpolation to increase the resolution of images.

Frame rate per second

Not all models can record FullHD video at a frequency of 30 frames per second - usually only expensive cameras can do this. But in many cases this is not necessary - it is unlikely that the smooth movements of your face are important for video conferencing and communication with friends. But if you are choosing a camera for streaming or blogging, then a high frequency is extremely necessary - on a full-size video, less than 30 frames per second looks disgusting.

It is worth noting that manufacturers often lie about the maximum frame rate of the video their cameras shoot - cheap models are characterized by characteristic “brakes” and jerks in the stream.

Focusing

The presence of an automatic focusing system in the camera significantly improves the final image quality and allows the user to move freely in the frame without losing focus.

Manual focusing allows you to fine-tune the focus of the lens for specific conditions - for example, making video calls from a chair in front of the monitor.

The cheapest cameras do without focusing systems at all and have a fixed focus.

Viewing and rotation angles

A very important parameter of a webcam is the viewing angle of its lens, which determines the amount of space that fits into the frame. It is best to choose a model with a viewing angle of 70 degrees or more.

For a comfortable installation of the camera, the ability to rotate it, both horizontally and vertically, is also important. Many models can rotate 360 degrees horizontally, but this is not needed too often - generally 180 degrees is enough.

Connection

The vast majority of modern webcams are connected to a PC using USB ports (USB 2.0). Very few models use Bluetooth or Wi-Fi - it's simply not necessary when the user usually has a smartphone with an equally, if not more capable camera at hand.

Microphone

Almost all webcams you can buy now have a built-in microphone. Most of these microphones, however, do a rather poor job of recording sound - if you plan to vlog or stream, it is better to use a microphone on the headset or a separate microphone. However, expensive webcams handle audio quite well - again, examples of audio recording from them can be found on YouTube.

For almost every webcam model, you can find an example of video and audio recording on YouTube. If you are satisfied with the quality of the video found, pay attention to the conditions of its shooting, in particular the lighting. As long as the quality doesn't suffer too much in the dark, the camera is worth considering.

Be sure to make sure that the camera connection cable will reach the USB port of your PC. Monitors with USB ports are very convenient in this regard - the camera in most cases is located either on the monitor or next to it.

Many good professional cameras have a thread on the bottom for tripod mounting. If you are going to use it, check for the presence of such threads.

If you are going to use software from a camera manufacturer, read reviews about it online. Very often this software is old, unfinished and simply buggy.

Webcam for surveillance. The design and principle of operation of a webcam Modern webcams, their characteristics and design

How does a surveillance webcam work?

Advantages and disadvantages

Webcam Specifications for Surveillance

How to use

Problems

The design and principle of operation of a webcam

Connecting and installing a webcam

Additional features and functions of the webcam

Webcam programs

Connecting the webcam to the network

How to access a webcam over the Internet

The design and principle of operation of a webcam

Connecting and installing a webcam

Additional features and functions of the webcam

Webcam programs

Connecting the webcam to the network

How to access a webcam over the Internet

Key Features You Should Pay Attention to

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