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Webcam device description. Webcam - technical specifications, how to choose, rules of use. Connecting and installing a webcam

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INTRODUCTION

The first ever webcam was launched in 1991 and showed a coffee machine in the Trojan Room of the University of Cambridge. It does not work now because it was disabled on August 22, 2001. The latest photo taken with this camera can still be seen on its Internet home page. The global web has just begun its victorious march across the planet. A group of scientists, 15-20 people, worked on a project in the field of network technologies. The working conditions were spartan for the whole team there was only one coffee maker, 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 whip up the thought process with a cup of invigorating drink, the participants in the scientific project were forced to frequent the corridor, which was located on the floor above, where the coffee maker was located. Often, such trips failed, as some colleagues had already managed to empty the coveted container. The situation demanded a non-standard solution, and it was found.

One of the computers in the lab 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 if there was coffee had to run the client software on their computer that connects to the server / 3 /. As a result, a black and white image was displayed on the remote computer in a small window, which was updated three times a minute. A note about this interesting complex was published in Comm-Week on January 27, 1992. Not so much time has passed since the first prototypes of IP cameras appeared, but they have already become a fully formed, separate class of devices that make everyday life easier, more convenient and more fun.

Like many networking technologies, webcams and video chats have become massively popular. The need for "live" video images has given rise to webcams capable of broadcasting over the Internet in a video stream format that does not require the viewer to manually update the image; and soon, special plugins became unnecessary in modern browsers.

1. TYPES OF WEB-CAMERAS

A webcam is a small-sized digital video or photo camera capable of capturing images in real time for further transmission over the Internet (in programs such as Skype, Instant Messenger or any other video application). It has a built-in web server, network interface and connects directly to LAN / WAN / Internet. Many network cameras have such additional tools as: motion detectors, sending messages by e-mail, working with a modem, connecting external sensors, etc. / 1 /. Users can access the camera through a standard web browser. Depending on the settings, access to the video image received by the web-camera can be open to all network users or only authorized users.

Webcams that deliver images over the Internet upload images to a web server either on demand, continuously, or at regular intervals. This is achieved by connecting the camera to a computer or by using the capabilities of the camera itself. Some modern models have hardware and software that allows the camera to independently act as a web server, FTP server, FTP client, and / or send images by e-mail.

Webcams designed for video conferencing are usually simple camera models that connect to a computer running a program like Instant Messenger. Camera models used for security purposes can be equipped with additional devices and functions (such as motion detectors, connecting external sensors, etc.) video chat interface detector camera

There are three types of webcam groups: desktop, portable and universal. Desktop webcams are most often used for a desktop personal computer, portable for laptops, and universal ones, respectively, for laptops and computers. Also, webcams are divided into wireless and wired.

A wireless camcorder is a recording device that transmits audio and video signals to a receiver without a cable connection. Such cameras are used at facilities where, for various reasons, it is inconvenient to lay a cable network. The main advantages of wireless cameras are the absence of the need for long and labor-intensive cable laying, high noise immunity, and reliability.

Wireless cameras are convenient to use as cameras for covert surveillance, because there are no bulky cable networks. Such a hidden mini camera allows you to create the appearance of lack of surveillance at the facility / 2 /. Also, a portable video camera is available with a micro-camera, with its help you can record video in various difficult conditions. In turn, wireless cameras are divided into two types - analog and digital, due to the different technology (method) of signal transmission.

Analog wireless camcorders are prone to interference and most often distort the transmitted image, but are much cheaper. True, in most cases, analog video cameras are prohibited by law.

Digital wireless video cameras (IP cameras) transmit a signal in digital format, and the digital signal is not susceptible to the influence of waves and interference, including from other cameras. Such a signal is absolutely not distorted during transmission. These devices do not need to be connected to a computer, they themselves are network nodes with their own IP-address (hence the name "IP-camera"). In fact, these are a kind of servers that transmit a signal to the network independently using the TCP or even UDP protocol.

There are two types of wireless digital cameras - with a video signal transmission over a radio channel (WiFi wireless cameras, USB, Wi-Max) and cameras that transmit a signal over a cellular connection (GSM wireless cameras, 3G cameras, CDMA wireless cameras).

The most popular are WiFi cameras, as the most affordable and simple form of digital wireless camcorders.

Wireless GSM video cameras (communication protocols GPRS, EDGE, 3G) are used when there is no Internet access via WiFi. Then they use the services of mobile operators.

USB cameras transmit a signal via Bluetooth, but such equipment works only at close range, using radio waves.

Wireless IP cameras are webcams because they are transmit video and audio signals to the Internet. The wireless webcam captures and transmits digital video using a local area network.

Wired webcams are classified as external and built-in. External webcams are usually connected to a USB port or using a FireWire interface. As a wired webcam, you can use the most ordinary video camera, if it supports such functionality.

Built-in webcams are located directly on the device itself. It's hard to imagine a modern laptop without a webcam. Albeit of mediocre quality, but such must still be present.

2. STRUCTURE AND PURPOSE OF WEB-CAMERAS

2.1 Structure of webcams

A modern webcam is a digital device that captures video, digitizes, compresses and transfers video over a computer network. Therefore, the webcam includes the following components:

CCD-matrix;

Lens;

Optical filter;

Video capture card;

Compression (compression) block of video images;

Central processing unit and built-in web server;

Flash memory;

Network interface;

Serial ports;

Alarm inputs / outputs.

As a photodetector in most webcams, a CCD matrix (CCD, CCD is a charge-coupled device) is used - a rectangular light-sensitive semiconductor plate with an aspect ratio of 3: 4, which converts the incident light into an electrical signal. The CCD consists of a large number of light-sensitive cells. In order to increase the light sensitivity of the CCD, 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 (the length of the matrix diagonal in inches), the number of effective pixels, the type of scan (non-interlaced or interlaced) and the sensitivity. A typical webcam contains a lens, an optical filter, a CCD, a digital image processing circuit, an image compression circuit, and a web server for connecting to the network / 2 /. Each network camera has its own IP address, computing functions, and firmware, which allows it to function as a web server, FTP server, FTP client and e-mail client. Most modern network cameras include many other attractive features such as motion detection, alarm in / out, and e-mail support.

The webcam consists primarily of a sensor. Very often, cheaper CMOS sensors are used instead of standard CCDs for video surveillance. Although they have lower sensitivity and not very good color reproduction, their use can greatly reduce the cost of the device, since these sensors are "all in one chip" with a digital data output.

The light sensor is the heart of any digital camera. It is he who allows you to convert light into electrical signals available for further electronic processing. The basic principle of operation of both CCD and CMOS sensors is the same: under the influence of light, charge carriers are born in semiconductor materials, which are subsequently converted into voltage. The difference between CCD and CMOS sensors lies primarily in the way of accumulating and transferring charge, as well as in the technology of converting it into an analog voltage. Without going into the details of the design of various types of sensors, we only note that CMOS sensors are much cheaper to manufacture, but also more "noisy".

The principle of operation of a webcam is similar to the principle of operation of any digital camera or photo camera. In addition to the optical lens and the photosensitive CCD or CMOS sensor, an analog-to-digital converter (ADC) is required, the main purpose of which is to convert the analog signals of the photosensitive sensor, that is, the voltage into a digital code. In addition, a color shaping system is needed / 6 /. Another important element of the camera is the circuitry responsible for compressing the data and preparing it for transmission in the desired format. In webcams, video data is transmitted to a computer via a USB interface, that is, the final camera circuit must be a USB interface controller.

Further: the network camera includes a microprocessor for video compression and motion detection (or just a compressor chip). The most popular is JPEG, as the simplest and cheapest; MPEG4 is also used quite often, the rarest and most expensive is MPEG2. With the expiration of the patent for arithmetic coding, WaveLet gains popularity. Finally, the network camera includes a 10/100 Mbps network controller.

2.2 Purpose of webcams

Webcams are part of our lives. They are used to build video systems for both geographically large and small objects. They are especially indispensable in the control and monitoring of remote points where there is a need to use unattended equipment.

The webcam can be used as a security camera, for example, to guard your car under the window, or as a web nanny, to monitor everything that happens to your child while you are not at home.

A webcam can also be useful in business, you can organize virtual exhibitions, conduct video conferences or distance learning, film meetings and meetings.

As webcam capabilities emerged in applications originally designed for text chat (programs like Instant Messenger) - including Skype, Yahoo Messenger, AOL Instant Messenger, Windows Live Messenger - millions of regular users all over the world got the opportunity to communicate with each other via videophone. Improving the quality of video data allowed webcams to compete with previous video conferencing systems / 4 /. Some webcams are equipped with new features aimed specifically at increasing the popularity and convenience of video communication (including features that provide automatic image retouching, wrinkle smoothing, etc.).

Wireless cameras allow surveillance where wiring is difficult or full mobility is required. Wireless camcorders can communicate with other wired equipment. Nowadays, wireless solutions need to be taken into account when designing any network from a small office to an enterprise. This will possibly save money, labor and time.

All wireless networks support both infrastructure mode (connecting via an access point) and ad-hoc mode (setting up work without using an access point). You can add new users at any time and install new hosts anywhere and without using power cords. Wireless networks can also be installed for temporary use in rooms where there is no cabling installed or where network cabling is difficult.

To provide wireless users with access to corporate databases or shared resources of servers and printers, you can set up an access point / 5 /. This device allows wireless workstations to communicate with an existing Ethernet network. D-Link's access points are Wi-Fi compatible and seamlessly integrate with an Ethernet network. Wireless workstations can be added without degrading network performance. Network congestion with traffic can be easily avoided by adding an access point to speed up network response times.

Sometimes webcams are used in security systems. Businesses use webcams to monitor and record what is happening in offices, hallways and warehouses, and elections. For the first time in Russia cameras for viewing and recording elections were installed on March 4, 2012. Webcams transmitted commissions and ballot boxes. Homeowners use webcams to monitor anything from the nursery to the backyard.

The webcam itself is usually not capable of storing video, but simply takes pictures; to save the video, special software is used on the computer to which the webcam is connected. Webcams can also be used in games that use simple motion detection algorithms.

LIST OF USED SOURCES

1. Informatics: Textbook for universities / Ed. prof. N.V. Makarova. - 3rd ed. revised - M .: F and S, 2004.

2. Kolesnichenko S., Shishigin I. PC Hardware. BHV 1999.

3. Christiansen T., Torkington N. Perl: Programmer's Library: Per. from English - SPb. : "Peter", 2000.

4. Ostreykovsky V.A. Informatics: Textbook for universities. - M .: Higher. shk., 1999. MS Excel 97 (2000). Step by step. Ecom 1999 (2000).

5. Svetozarova G.I., Melnikov A.A. Practicum on programming in the BASIC language. - M. - Science, 1986.

6. Figurnov V.E. IBM PC for the user. Short course. Moscow: Finance and Statistics. 1997.

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The device and principle of operation of the webcam

CCD-matrix,

lens,

optical filter,

video capture card,

video compression (compression) unit,

central processing unit and built-in web server,

flash memory,

network interface,

serial ports,

alarm inputs / outputs.

As a photodetector, most webcams use CCD (CCD, CCD - Charge Coupled Device) - a rectangular photosensitive semiconductor plate with an aspect ratio of 3: 4, which converts the incident light into an electrical signal. The CCD consists of a large number of light-sensitive cells. In order to increase the light sensitivity of the CCD, 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 (the length of the matrix diagonal in inches), the number of effective pixels, the type of scan (non-interlaced or interlaced) and the sensitivity.

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

Video capture card web cameras (digitizing unit) convert the analog electrical signal generated by the CCD matrix into 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 rate.

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

Coding. In addition to the information about the change in the signal level obtained at the previous stage, during the encoding process, bits are generated that indicate the end of the sync pulse and the beginning of a new frame, as well as additional error protection bits.

Compression unit the webcam compresses 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 network traffic, it is advisable to reduce the amount of transmitted information by reducing either the frame rate over the network or the frame resolution. Most of the compression formats that webcams use provide a reasonable compromise between the two solutions to the problem of transmitting video over a network. The currently known compression formats make it possible to obtain a digitized stream with a bandwidth of 64 Kb - 2 Mb (with such a bandwidth, video data streams can work in parallel with other data streams in networks).

Compression of video images in a webcam can be represented both by hardware and software. The software implementation of compression is cheaper, however, due to the high computational capacity of the compression algorithms, it is ineffective, especially when you need to view video from a webcam online. Therefore, most of the leading manufacturers produce webcams with hardware compression. For example, every network camera from AXIS Communications is equipped with an ARTPEC compression processor that compresses video images at high speed into JPEG / MJPEG format.

Ethernet interface serves to connect the webcam to a 10/100 Mbps Ethernet network.

For networking, the webcam may have serial port to connect a modem and work in dial-up mode in the absence of a local network. The serial port can also connect peripheral equipment to the webcam.

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 the portion of RAM reserved for recording and temporarily storing video footage captured by the webcam. The information in the video buffer is updated cyclically, i.e. the new frame is written over the oldest one. This function is necessary if the webcam performs video surveillance, since it allows you to restore the events preceding and following the alarm from the security sensors connected to the webcam.

Connecting and installing a webcam

Typically, a webcam is connected to the Internet via the 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. More often than not, a webcam does not have a default IP address; it is installed either using the appropriate function of a standard web browser, or using a DOS command that uses the serial number of the webcam assigned to it by the manufacturer for identification. In addition, manufacturers develop special programs for webcams that greatly simplify the procedure for assigning an IP address to a webcam (for example, IP Installer from AXIS Communications). With built-in software for web server, FTP server, FTP client, e-mail client, etc., the webcam connects directly to the LAN / WAN / Internet network and works as a standalone network device in it. This distinguishes webcams from other digital cameras, which require a mandatory connection to a personal computer via USB or LPT port. In addition, webcams can support custom scripts and JAVA applets.

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

Additional features and functions of the webcam

Motion Detector is a software module, the main task of which is to detect web cameras moving in the field of view at a video surveillance object. The motion detector not only detects movement in the image field, but also determines the size 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 (noise filtering), and flexible alarm processing logic is set (alarm recording, integration with other security equipment).

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

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

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

Webcam software

Typically, the webcam image can be viewed using a standard web browser such as Internet Explorer or Netscape Navigator. However, many manufacturers develop exclusive webcam software.

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

Connecting the webcam to the network

Currently, a webcam can connect to the network in several ways, which are based on various 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 rarely used due to the sensitivity of the coaxial cable to external noise. The 100BaseTX standard uses twisted pair cables and provides a data transfer rate of 100 Mbps.

1000 Mbit Ethrnet, Gigabit Ethernet. The 1000BaseTX standard used here is an enhanced version of 100BaseTX. This standard is mainly used for building LAN backbones.

Standard telephone modems. This is a cheap and fairly common way to connect your webcam to the global network. The main disadvantage of this connection method is the low data transfer rate (the maximum data download speed is 56 kbps, the maximum swap speed is 33.6 kbps). The webcam is connected to the modem through 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 up to 128 kbps over two channels.

xDSL modems. DSL (Digital Subscriber Line) is a technology that provides high bandwidth over simple copper telephone wires. The data transfer rate of the webcam may vary depending on the service provider. On average, it is 1 Mbps for data download and 250 kbps for swap.

Cable modems. A cable modem is a modem that provides Internet access over cable television networks. Cable modems use asymmetric technology that is best suited for the user's Internet access. 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 usually it does not exceed 1 Mbit / s), and the data transfer rate is about 10 Mbit / s.

Cellular modems. With a cellular modem, you can connect your webcam to the Internet using cellular communication lines. The data transfer rate is usually 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 characteristics and prices for webcams are given in the ARMO-System online store.

How to access your webcam over the Internet

How to access your webcam over the Internet.

Example: After you have already received the image from the webcam on your computer, you decide that it would be nice to be able to access the camera wherever the Internet is. For example, as a store owner, you want to monitor 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 Internet Service Provider (ISP), just set up an account, switch the network camera through 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. A dedicated software or utility for the webcam will be helpful 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 customers), you can find out how you can assign a specific IP address to the camera in Step 4 below.

Scenario B)

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

broadband modem for an asymmetrical digital subscriber line connection (usually supplied by your ISP) or cable TV

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

a switch that allows various 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

remote surveillance computer

Step 2: Assign an IP address for your camera

Since a broadband router typically assigns automatic, local IP addresses to devices on the local network, such IP addresses have properties to change. A static (permanent) IP address is recommended for a network camera. To assign a static IP, find out the IP range of your router, for example, it could be 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 run the risk of your device colliding 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 that access to the camera is restricted.

Step 3: port forwarding

A broadband router, as mentioned earlier, provides an interface between the Internet, ISP and LAN. The router obtains an external IP address from an ISP and supplies internal (local) IP addresses for devices on the local network.

To access a network camera that is permanently located on the local network, you must identify the external IP address of your router (see your router 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 port opening; that is, when you print the external IP address of the router from any networked computer, the Internet locates your router, in turn redirects your request to the local IP address that is assigned to the network camera.

Launch a web browser and access the embedded web pages of the router by Logging In to Router Configuration Pages.

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

Service name	Start port	End port	Server IP address
FTP	21	21	Not configured
HTTP (Network)	80	80	Not configured
			Not configured

Since the camera sends its video over HTTP, you must configure the HTTP service as follows:

Service name	Start port	End port	Server IP address
FTP	21	21	Not configured
HTTP (Network)	80	80	192.168.0.100
Unofficial port	80xx	80xx	192.168.0.10x

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

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

Step 4: What You Can Do If Your ISP Changes Dfi's External IP Address Frequently

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

The device and principle of operation of the webcam

CCD-matrix,

lens,

optical filter,

video capture card,

video compression (compression) unit,

central processing unit and built-in web server,

flash memory,

network interface,

serial ports,

alarm inputs / outputs.

As a photodetector, most webcams use CCD ( CCD, CCD - Charge Coupled Device) is a rectangular photosensitive semiconductor plate with an aspect ratio of 3: 4, which converts the incident light into an electrical signal. The CCD consists of a large number of light-sensitive cells. In order to increase the light sensitivity of the CCD, 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 (the length of the matrix diagonal in inches), the number of effective pixels, the type of scan (non-interlaced or interlaced) and the sensitivity.

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

Optical infrared cut-off filters that are installed in webcams are optically accurate plane-parallel plates that are mounted on top of the CCD. They work as optical low-pass filters with a cutoff frequency of about 700 nm, near red. They cut off the infrared component of the light waves, ensuring the webcam has the correct color reproduction. However, many black-and-white webcams do not have such filters, which makes monochrome webcams more sensitive.

Video capture card web cameras (digitizing unit) convert the analog electrical signal generated by the CCD matrix into 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 rate.

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

Compression unit the webcam compresses 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 network traffic, it is advisable to reduce the amount of transmitted information by reducing either the frame rate over the network or the frame resolution. Most of the compression formats that webcams use provide a reasonable compromise between the two solutions to the problem of transmitting video over a network. The currently known compression formats make it possible to obtain a digitized stream with a bandwidth of 64 Kb - 2 Mb (with such a bandwidth, video data streams can work in parallel with other data streams in networks).

CPU is the computing core of the webcam. It performs operations for the output of digitized and compressed video, and is also responsible for performing the functions of an embedded web server and control program for webcams.

Ethernet interface serves to connect the webcam to a 10/100 Mbps Ethernet network.

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 the portion of RAM reserved for recording and temporarily storing video footage captured by the webcam. The information in the video buffer is updated cyclically, i.e. the new frame is written over the oldest one. This function is necessary if the webcam performs video surveillance, since it allows you to restore the events preceding and following the alarm from the security sensors connected to the webcam.

Alarm inputs / outputs serve to connect alarm sensors to the webcam. When one of the sensors is triggered, an alarm is generated, as a result of which the webcam processor assembles 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

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

Additional features and functions of the webcam

Motion Detector Is a software module, the main task of which is to detect web cameras moving in the field of view at a video surveillance object. The motion detector not only detects movement in the image field, but also determines the size 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 (noise filtering), and flexible alarm processing logic is set (alarm recording, integration with other security equipment).

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

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

Webcam software

Typically, the webcam image can be viewed using a standard web browser such as Internet Explorer or Netscape Navigator. However, many manufacturers develop exclusive webcam software.

Connecting the webcam to the network

Currently, a webcam can connect to the network in several ways, which are based on various 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 rarely used due to the sensitivity of the coaxial cable to external noise. The 100BaseTX standard uses twisted pair cables and provides a data transfer rate of 100 Mbps.

1000 Mbit Ethrnet, Gigabit Ethernet. The 1000BaseTX standard used here is an enhanced version of 100BaseTX. This standard is mainly used for building LAN backbones.

Standard telephone modems. This is a cheap and fairly common way to connect your webcam to the global network. The main disadvantage of this connection method is the low data transfer rate (the maximum data download speed is 56 kbps, the maximum swap speed is 33.6 kbps). The webcam is connected to the modem through 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 up to 128 kbps over two channels.

xDSL modems. DSL (Digital Subscriber Line) is a technology that provides high bandwidth over simple copper telephone wires. The data transfer rate of the webcam may vary depending on the service provider. On average, it is 1 Mbps for data download and 250 kbps for swap.

Cable modems. A cable modem is a modem that provides Internet access over cable television networks. Cable modems use asymmetric technology that is best suited for the user's Internet access. 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 usually it does not exceed 1 Mbit / s), and the data transfer rate is about 10 Mbit / s.

Cellular modems. With a cellular modem, you can connect your webcam to the Internet using cellular communication lines. The data transfer rate is usually between 5 and 20 kbps.

How to access your webcam over the Internet

How to access your 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 an asymmetrical digital subscriber line connection (usually supplied by your ISP) or cable TV

a switch that allows various 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

remote surveillance computer

Step 2: Assign an IP address for your camera

Step 3: port forwarding

Launch a web browser and access the embedded web pages of the router by Logging In to Router Configuration Pages.

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

Since the camera sends its video over HTTP, you must configure the HTTP service as follows:

Step 4: What You Can Do If Your ISP Changes Dfi's External IP Address Frequently

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 ISP.

A webcam is a device that is most often bought at the same time as a computer and does not attach much importance to it. However, it is worth paying attention to the characteristics, otherwise disappointment and irritation may appear already at the first shooting or communication session.

By following our tips, you can learn all about the capabilities, functions and applications of webcams. We hope that this information will help readers make the right choice when purchasing a device.

What is a webcam, how does it work and where it is used

A webcam is a fairly small device, which is a photo or video camera that is connected to a computer or laptop. Webcams capture the image in real time and then transmit it to the addressee using the Internet. The difference from a digital camera, first of all, lies in the power supply by wires and the impossibility of functioning without a computer, at least fully.

Webcams are used for video chats and video calls, video conferencing, security purposes, for monitoring and surveillance, etc.

Main characteristics of webcams

The characteristics of webcams affect both the quality of the device and its price, which can vary greatly from model to model. What are the main parameters and what should not be missed when choosing a webcam?

Webcam matrix type. The webcam matrix can be created using one of the technologies:

a) CCD- technology used in digital cameras and also used for webcams. Among its advantages: high sensitivity, high duty cycle, efficiency - about 95%, lower noise level during operation. It is worth remembering that a power supply that is too weak is likely to fail at the time of maximum load of the system or even of its individual elements. A power supply that is too powerful can reduce the efficiency of the entire computer;

b) CMOS is a cheaper-to-manufacture technology used in most webcams. Such matrices have a low cost, shoot up to 500 frames per second, and consume quite little power during operation. Among their shortcomings, experts point out a large amount of noise in the image, a low pixel fill factor and, as a result, low sensitivity;

c) BSI CMOS- when using such a matrix, it becomes easier for light to hit the photodiodes. These sensors are also called "backlit sensors" - they are much more sensitive to light. Due to this, the amount of noise in the image is reduced compared to conventional CMOS.

Camera resolution is another of the most important characteristics. The quality of the transmitted image depends on it. Note that the resolution can be direct and interpolated. With software interpolation, the number of pixels in the original image is processed using mathematical methods, multiplied by a certain number, and then an enlarged image is formed. In this case, the original image resolution does not change, and the quality may deteriorate. When choosing a camera, you should pay attention to the real resolution of 1.3 megapixels - this is enough for HD quality.
Frame frequency- a characteristic responsible for the smoothness of shooting. An acceptable rate of shooting is 15 frames per second - this will be enough for communication on the Web. For high-quality video broadcasts, you need at least 30 frames per second.
Focusing webcams allow you to influence the clarity of the image. It can be either manual or automatic. Manual is carried out by rotating the wheel located at the lens. Automatic focusing assumes that the webcam itself sets the distance to the object and calculates the focal length. Autofocus speed and quality may vary significantly from model to model.
Sensitivity- the parameter of the minimum allowable illumination at which it is possible to use the camera. However, when buying a camera with infrared illumination, this characteristic will immediately be presented at a decent level.
Connection type... Typically, webcams are connected via USB port version 1.1, 2.0, or 3.0. The latter type is faster, but only found on modern computers.

Additional functions of webcams:

Built-in microphone. It frees you from the need to buy another device, allows you to make video calls to large companies. Almost all cameras now have a built-in microphone.
The ability to use your webcam as a camera. Modern models of webcams allow these devices to be used as digital cameras. If you choose a camera for these purposes, pay attention to devices with a higher resolution, otherwise the quality of the photos will hardly suit you. Some cameras are also equipped with a photo button on the body - pressing it can activate the photo mode and launch the graphics editor.
Availability of special software. Each webcam manufacturer offers its own software for users to install or use. In addition to standard functions, it can add personalized features to the camera. For example, Logitech offers a built-in graphics editor.

What else should you pay attention to?

When choosing and buying a webcam, pay attention to its mount, tilt and swivel capabilities, as well as the viewing angle.

Explore the characteristics, compare webcam models, take into account the tips from our review and enjoy comfortable and pleasant video communication.