Technical guide to network video. Technologies and factors to consider for the successful deployment of IP-based security surveillance and remote monitoring applications.
Welcome to the Axis technical guide to network video The move to open video systems—combined with the benefits of networking, digital imaging, and camera intelligence—constitutes a far more effective means of security surveillance and remote monitoring than has ever been reached before. Network video provides everything that analog video offers, plus a wide range of innovative functions and features that are only possible with digital technology.
TABLE OF CONTENTS Table of contents Network video: overview, benefits and applications 7 1.1 1.2 1.3 1.3.1 1.3.2 1.3.3 1.3.4 1.3.5 1.3.6 1.3.7 1.3.8 Overview of a network video system Benefits Applications Retail Transportation Education Industrial City surveillance Government Healthcare Banking and finance 7 8 12 12 12 12 13 13 13 13 14 Network cameras 15 Camera elements 27 2.1 2.2 2.2.1 2.2.2 2.2.3 2.3 2.4 2.5 3.1 3.2 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.3 3.3.1 3.3.2 3.3.3 3.4 3.4.1 3.4.2 3.
TABLE OF CONTENTS Camera protection and housings 39 Video encoders 45 Resolutions 51 Video compression 55 Audio 63 4.1 4.2 4.3 4.4 4.5 4.5.1 4.5.2 4.5.3 4.5.4 4.6 4.6.1 4.6.2 4.6.3 4.6.4 5.1 5.1.1 5.1.2 5.2 5.3 5.4 5.5 5.6 6.1 6.2 6.3 6.4 7.1 7.1.1 7.1.2 7.2 7.2.1 7.2.2 7.2.3 7.3 7.4 8.1 8.2 8.3 8.3.1 8.3.2 8.3.
TABLE OF CONTENTS 8.4 8.5 8.5.1 8.5.2 8.5.3 8.6 Audio detection alarm Audio compression Sampling frequency Bit rate Audio codecs Audio and video synchronization 66 66 67 67 67 67 Network technologies 69 Wireless technologies 87 Video management systems 91 9.1 9.1.1 9.1.2. 9.1.3 9.2 9.2.1 9.2.2 9.3 9.4 9.5 9.5.1 9.5.2 9.5.3 9.5.4 9.5.5 10.1 10.2 10.2.1 10.2.2 10.2.3 10.3 11.1 11.1.1 11.1.2 11.2 11.2.1 11.2.2 11.2.3 11.2.4 11.2.5 11.3 11.3.1 11.3.2 11.3.3 11.3.4 11.3.5 11.3.6 11.3.
TABLE OF CONTENTS 11.4 11.4.1 11.4.2 11.4.3 11.4.4 11.4.5 11.4.6 Integrated systems Application programming interface Point of Sale Access control Building management Industrial control systems RFID 104 104 104 105 105 106 106 Bandwidth and storage considerations 107 Tools and resources 115 Axis Communications’ Academy 117 Contact information 118 12.1 12.1.1 12.1.2 12.2 12.3 12.4 12.
Network video: overview, benefits and applications - CHAPTER 1 7 Network video: overview, benefits and applications Network video, like many other kinds of communications such as e-mail, web services and computer telephony, is conducted over wired or wireless IP (Internet Protocol) networks. Digital video and audio streams, as well as other data, are communicated over the same network infrastructure.
CHAPTER 1 - Network video: overview, benefits and applications Axis network cameras Home Office I/O AUDIO 1 2 3 4 5 6 OUT IN Axis video encoders PS1 NETWORK PS2 ACTIVITY 1 2 3 4 0 - FANS LOOP IP NETWORK INTERNET Web browser Power-one FNP 30 100-240 AC 50-50 Hz 4-2 A AC 0 - Power-one FNP 30 AXIS Q7900 Rack 100-240 50-50 Hz 4-2 A AC POWER POWER AXIS Q7406 Video Encoder Blade AXIS Q7406 Video Encoder Blade Analog cameras Computer with web browser Computer with video manag
Network video: overview, benefits and applications - CHAPTER 1 9 location to view and manage video, and off-site video access would not be possible without such equipment as a video encoder or a network digital video recorder (DVR). A DVR is the digital replacement for the video cassette recorder. > High image quality: In a video surveillance application, high image quality is essential to be able to clearly capture an incident in progress and identify persons or objects involved.
CHAPTER 1 - Network video: overview, benefits and applications Figure 1.2a Setting up an event trigger using a network camera’s user interface. Event management functionalities can be configured using the network video product’s user interface or a video management software program. Users can define the alarms or events by setting the type of triggers to be used and when. Responses can also be configured (e.g.
Network video: overview, benefits and applications - CHAPTER 1 11 viewing/recording station. Separate audio cables must also be used if audio is required. Network video products can also be placed and networked from virtually any location, and the system can be as open or as closed as desired. > Cost-effectiveness: An IP-Surveillance system typically has a lower total cost of ownership than a traditional analog CCTV system.
CHAPTER 1 - Network video: overview, benefits and applications 1.3 Applications Network video can be used in an almost unlimited number of applications; however, most of its uses fall under security surveillance or remote monitoring of people, places, property and operations. The following are some typical application possibilities in key industry segments. 1.3.1 Retail Network video systems in retail stores can significantly reduce theft, improve staff security and optimize store management.
Network video: overview, benefits and applications - CHAPTER 1 13 which to base their decisions. Network video can also be used for remote learning; for example, for students who are unable to attend lectures in person. 1.3.4 Industrial Network video can be used to monitor and increase efficiencies in manufacturing lines, processes and logistic systems, and for securing warehouses and stock control systems. Network video can also be used to set up virtual meetings and get technical support at a distance.
CHAPTER 1 - Network video: overview, benefits and applications 1.3.8 Banking and finance Network video is used in security applications in bank branches, headquarters and ATM (automated teller machine) locations. Banks have been using surveillance for a long time, and while most installations are still analog, network video is starting to make inroads, especially in banks that value high image quality and want to be able to easily identify people in a surveillance video.
NETWORK CAMERAS - CHAPTER 2 15 Network cameras There is a wide range of network cameras to meet a variety of requirements. This chapter describes what a network camera is and explains the different camera types. Information is also provided about day and night, and megapixel network cameras. A camera selection guide is included at the end of the chapter. For more on camera elements, see Chapter 3. 2.
CHAPTER 2 - Network CAMERAS A network camera can be configured to send video over an IP network for live viewing and/or recording either continuously, at scheduled times, on an event or on request from authorized users. Captured images can be streamed as Motion JPEG, MPEG-4 or H.264 video using various networking protocols, or uploaded as individual JPEG images using FTP, e-mail or HTTP (Hypertext Transfer Protocol).
Network CAMERAS - CHAPTER 2 17 2.2.1 Fixed network cameras A fixed network camera, which may come with a fixed or varifocal lens, is a camera that has a fixed field of view (normal/telephoto/wide-angle) once it is mounted. A fixed camera is the traditional camera type where the camera and the direction in which it is pointing are clearly visible. This type of camera represents the best choice in applications where it is advantageous to make the camera very visible.
CHAPTER 2 - Network CAMERAS 2.2.3 PTZ cameras and PTZ dome cameras A PTZ camera or a PTZ dome camera can manually or automatically pan, tilt and zoom in and out of an area or object. All PTZ commands are sent over the same network cable as for video transmission; no RS-485 wires need to be installed as is the case with an analog PTZ camera. Some of the features that can be incorporated in a PTZ camera or a PTZ dome camera include: > Electronic image stabilization (EIS).
Network CAMERAS - CHAPTER 2 19 > Preset positions. Many PTZ cameras and PTZ dome cameras enable a number of preset positions, normally between 20 and 100, to be programmed. Once the preset positions have been set in the camera, it is very quick for the operator to go from one position to the next. > E-flip. When a PTZ dome camera is mounted on a ceiling and is used to follow a person in, for example, a retail store, there will be situations when a person will pass just under the camera.
CHAPTER 2 - Network CAMERAS Mechanical PTZ network cameras Mechanical PTZ cameras are mainly used indoors and in applications where an operator is employed. The optical zoom on PTZ cameras typically ranges from 10x to 26x. A PTZ camera can be mounted on a ceiling or wall. Figure 2.2d PTZ network cameras. From left to right: AXIS 212 PTZ-V (non-mechanical), AXIS 213 PTZ, AXIS 214 PTZ and AXIS 215 PTZ.
Network CAMERAS - CHAPTER 2 21 digital zoom, the zoomed-in image often loses detail and sharpness. A non-mechanical PTZ camera is ideal for discreet, wall-mounted installations. PTZ dome network cameras PTZ dome network cameras can cover a wide area by enabling greater flexibility in pan, tilt and zoom functions. They enable a 360-degree, continuous pan, and a tilt of usually 180 degrees.
CHAPTER 2 - Network CAMERAS Near-infrared light, which spans from 700 nanometers (nm) up to about 1000 nm, is beyond what the human eye can see, but most camera sensors can detect it and make use of it. During the day, a day and night camera uses an IR-cut filter. IR light is filtered out so that it does not distort the colors of images as the human eye sees them. When the camera is in night (black and white) mode, the IR-cut filter is removed, allowing the camera’s light sensitivity to reach down to 0.
Network CAMERAS - CHAPTER 2 23 Day and night cameras are useful in environments that restrict the use of artificial light. They include low-light video surveillance situations, covert surveillance and discreet applications, for example, in a traffic surveillance situation where bright lights would disturb drivers at night.
CHAPTER 2 - Network CAMERAS 2.5 Guidelines for selecting a network camera With the variety of network cameras available, it is useful to have some guidelines when selecting a network camera. > Define the surveillance goal: overview or high detail. Overview images aim to view a scene in general or view the general movements of people. High detail images are important for identification of persons or objects (e.g., face or license plate recognition, point-of-sales monitoring).
Network CAMERAS - CHAPTER 2 25 > Overt or covert surveillance. This will help in selecting cameras, in addition to housing and mounts, that offer a non-discreet or discreet installation. Other important feature considerations that may be required of a camera include: > Image quality. Image quality is one of the most important aspects of any camera, but it is difficult to quantify and measure it. The best way to determine image quality is to install different cameras and look at the video.
CHAPTER 2 - Network CAMERAS Another important consideration, outside of the network camera itself, is the selection of the network video product vendor. Since needs grow and change, the vendor should be seen as a partner, and a long-term one. This means that it is important to select a vendor that offers a full product line of network video products and accessories that can meet the needs now and well into the future.
CAMERA ELEMENTS - CHAPTER 3 27 Camera elements There are a number of camera elements that have an impact on image quality and field of view and are, therefore, important to understand when choosing a network camera. The elements include the light sensitivity of a camera, the type of lens, type of image sensor and scanning technique, as well as image processing functionalities, all of which are discussed in this chapter. Some guidelines on installation considerations are also provided at the end. 3.
CHAPTER 3 - CAMERA ELEMENTS Many manufacturers specify the minimum level of illumination needed for a network camera to produce an acceptable image. While such specifications are helpful in making light sensitivity comparisons for cameras produced by the same manufacturer, it may not be helpful to use such numbers to compare cameras from different manufacturers. This is because different manufacturers use different methods and have different criteria for what is an acceptable image.
CAMERA ELEMENTS - CHAPTER 3 29 The field of view can be classified into three types: > Normal view: offering the same field of view as the human eye. > Telephoto: a narrower field of view, providing, in general, finer details than a human eye can deliver. A telephoto lens is used when the surveillance object is either small or located far away from the camera. A telephoto lens generally has less light gathering capability than a normal lens.
CHAPTER 3 - CAMERA ELEMENTS > Varifocal lens: This type of lens offers a range of focal lengths, and hence, different fields of view. The field of view can be manually adjusted. Whenever the field of view is changed, the user has to manually refocus the lens. Varifocal lenses for network cameras often provide focal lengths that range from 3 mm to 8 mm. > Zoom lens: Zoom lenses are like varifocal lenses in that they enable the user to select different fields of view.
CAMERA ELEMENTS - CHAPTER 3 31 3.2.3 Lens mount standards When changing a lens, it is also important to know what type of lens mount the network camera has. There are two main standards used on network cameras: CS-mount and C-mount. They both have a 1-inch thread and they look the same. What differs is the distance from the lenses to the sensor when fitted on the camera: > CS-mount. The distance between the sensor and the lens should be 12.5 mm. > C-mount.
CHAPTER 3 - CAMERA ELEMENTS Limits to the exposure time and gain can be set in some Axis cameras. The longer the exposure time, the more light an image sensor receives. Bright environments require shorter exposure time, while low-light conditions require longer exposure time. It is important to be aware that increasing the exposure time also increases motion blur, while increasing the iris opening has the downside of reducing the depth of field, which is explained in section 3.2.6 below.
CAMERA ELEMENTS - CHAPTER 3 33 3.2.6 Depth of field A criterion that may be important to a video surveillance application is depth of field. Depth of field refers to the distance in front of and beyond the point of focus where objects appear to be sharp simultaneously. Depth of field may be important, for instance, in monitoring a parking lot, where there may be a need to identify license plates of cars at 20, 30 and 50 meters (60, 90 and 150 feet) away.
CHAPTER 3 - CAMERA ELEMENTS 3.3 Image sensors As light passes through a lens, it is focused on the camera’s image sensor. An image sensor is made up of many photosites and each photosite corresponds to a picture element, more commonly known as “pixel”, on an image sensor. Each pixel on an image sensor registers the amount of light it is exposed to and converts it into a corresponding number of electrons. The brighter the light, the more electrons are generated.
CAMERA ELEMENTS - CHAPTER 3 35 possibilities and more functions. CMOS sensors also have a faster readout (which is advantageous when high-resolution images are required), lower power dissipation at the chip level, as well as a smaller system size. Megapixel CMOS sensors are more widely available and are less expensive than megapixel CCD sensors. 3.3.3 Megapixel sensors For cost reasons, many megapixel sensors (i.e.
CHAPTER 3 - CAMERA ELEMENTS However, when interlaced video is shown on progressive scan monitors such as computer monitors, which scan lines of an image consecutively, the artifacts become noticeable. The artifacts, which can be seen as “tearing”, are caused by the slight delay between odd and even line refreshes as only half the lines keep up with a moving image while the other half waits to be refreshed. It is especially noticeable when the video is stopped and a freeze frame of the video is analyzed.
CAMERA ELEMENTS - CHAPTER 3 37 3.5 Image processing Three features that may be supported in network cameras to improve image quality are backlight compensation, exposure zones and wide dynamic range. 3.5.1 Backlight compensation While a camera’s automatic exposure tries to get the brightness of an image to appear as the human eye would see a scene, it can be easily fooled. Strong backlight can cause objects in the foreground to be dark.
CHAPTER 3 - CAMERA ELEMENTS 3.6 Installing a network camera Once a network camera has been purchased, the way it is installed is just as important. Below are some recommendations on how to best achieve high-quality video surveillance based on camera positioning and environmental considerations. > Surveillance objective.
CAMERA Protection and housings - CHAPTER 4 39 Camera protection and housings Surveillance cameras are often placed in environments that are very demanding. Cameras may require protection from rain, hot and cold environments, dust, corrosive substances, vibrations and vandalism. Manufacturers of cameras and camera accessories employ various methods to meet such environmental challenges.
CHAPTER 4 - CAMERA protection and housings 4.2 Transparent covering The “window” or transparent covering of an enclosure is usually made of high-quality glass or durable, polycarbonate plastic. As windows act like optical lenses, they should be of high quality to minimize its effect on image quality. When there are built-in imperfections in the clear material, clarity is compromised. Higher demands are placed on the windows of housings for PTZ cameras and PTZ dome cameras.
CAMERA Protection and housings - CHAPTER 4 41 4.4 Environmental protection The main environmental threats to a camera—particularly one that is installed outdoors—are cold, heat, water and dust. Housings with built-in heaters and fans (blowers) can be used in environments with low and high temperatures. In hot environments, cameras can be placed in enclosures that have active cooling with a separate heat exchanger. To withstand water and dust, housings (often with an IP66 rating) are carefully sealed.
CHAPTER 4 - CAMERA protection and housings ing or hitting) than more discretely designed housings or casings for a fixed dome or PTZ dome camera. The smooth, rounded covering of a fixed dome or PTZ dome makes it more difficult, for example, to block the camera’s view by trying to hang a piece of clothing over the camera. The more a housing or camera blends into an environment or is disguised as something other than a camera—for example, an outdoor light—the better the protection against vandalism.
CAMERA Protection and housings - CHAPTER 4 43 4.5.3 Camera placement Camera placement is also an important factor in deterring vandalism. By placing a camera out of reach on high walls or in the ceiling, many spur-of-the-moment attacks can be prevented. The downside may be the angle of view, which to some extent can be compensated by selecting a different lens. 4.5.4 Intelligent video Axis’ active tampering alarm feature helps protect cameras against vandalism.
CHAPTER 4 - CAMERA protection and housings 4.6.2 Wall mounts Wall mounts are often used to mount cameras inside or outside a building. The housing is connected to an arm, which is mounted on a wall. Advanced mounts have an inside cable gland to protect the cable. To install an enclosure at a corner of a building, a normal wall mount, together with an additional corner adapter, can be used.
Video ENCODERS - CHAPTER 5 45 Video encoders Video encoders, also known as video servers, enable an existing analog CCTV video surveillance system to be integrated with a network video system. Video encoders play a significant role in installations where many analog cameras are to be maintained. This chapter describes what a video encoder is and its benefits, and provides an overview of its components and the different types of video encoders available.
CHAPTER 5 - VIDEO ENCODERS By using video encoders, analog video cameras of all types, such as fixed, indoor/outdoor, dome, pan/tilt/zoom, and specialty cameras such as highly sensitive thermal cameras and microscope cameras can be remotely accessed and controlled over an IP network. A video encoder also offers other benefits such as event management and intelligent video functionalities, as well as advanced security measures.
Video ENCODERS - CHAPTER 5 47 > Serial port (RS-232/422/485) often used for controlling the pan/tilt/zoom functionality of an analog PTZ camera. > Input/output connectors for connecting external devices; for example, sensors to detect an alarm event, and relays to activate, for instance, lights in response to an event. > Audio in for connecting a microphone or line-in equipment and audio out for connecting to speakers.
CHAPTER 5 - VIDEO ENCODERS Figure 5.2a An illustration of how a small, single-channel video encoder can be positioned next to an analog camera in a camera housing. 5.3 Rack-mounted video encoders Rack-mounted video encoders are beneficial in instances where there are many analog cameras with coaxial cables running to a dedicated control room. They enable many analog cameras to be connected and managed from one rack in a central location.
Video ENCODERS - CHAPTER 5 49 enable analog PTZ cameras to be controlled over long distances, even through the Internet. (In an analog CCTV system, each PTZ camera would require separate and dedicated serial wiring from the control board—with joystick and other control buttons—all the way to the camera.) To control a specific PTZ camera, a driver must be uploaded to the video encoder. Many manufacturers of video encoders provide PTZ drivers for most analog PTZ cameras and PTZ dome cameras.
CHAPTER 5 - VIDEO ENCODERS Adaptive interpolation offers the best image quality. The technique involves using only one of the two consecutive fields and using interpolation to create the other field of lines to form a full image. Blending involves merging two consecutive fields and displaying them as one image so that all fields are present. The image is then filtered to smooth out the motion artifacts or ‘comb effect’ caused by the fact that the two fields were captured at slightly different times.
RESOLUTIONS - CHAPTER 6 51 Resolutions Resolution in an analog or digital world is similar, but there are some important differences in how it is defined. In analog video, an image consists of lines or TV-lines since analog video technology is derived from the television industry. In a digital system, an image is made up of square pixels. The sections below describe the different resolutions that network video can provide. They include NTSC, PAL, VGA, megapixel and HDTV. 6.
CHAPTER 6 - RESOLUTIONS D1 720 x 576 D1 720 x 480 When shown on a computer screen, digitized analog video may show interlacing effects such as tearing and shapes may be off slightly since the pixels generated may not conform to the square pixels on the computer screen.
RESOLUTIONS - CHAPTER 6 53 6.3 Megapixel resolutions A network camera that offers megapixel resolution uses a megapixel sensor to deliver an image that contains one million or more pixels. The more pixels a sensor has, the greater the potential it has for capturing finer details and for producing a higher quality image. Megapixel network cameras can be used to allow users to see more details (ideal for identification of people and objects) or to view a larger area of a scene.
CHAPTER 6 - RESOLUTIONS 4:3 16:9 Figure 6.3a Illustration of 4:3 and 16:9 aspect ratios. 6.4 High-definition television (HDTV) resolutions HDTV provides up to five times higher resolution than standard analog TV. HDTV also has better color fidelity and a 16:9 format. Defined by SMPTE (Society of Motion Picture and Television Engineers), the two most important HDTV standards are SMPTE 296M and SMPTE 274M.
VIDEO COMPRESSION - CHAPTER 7 55 Video compression Video compression technologies are about reducing and removing redundant video data so that a digital video file can be effectively sent over a network and stored on computer disks. With efficient compression techniques, a significant reduction in file size can be achieved with little or no adverse effect on the visual quality.
CHAPTER 7 - VIDEO COMPRESSION A pair of algorithms that works together is called a video codec (encoder/decoder). Video codecs of different standards are normally not compatible with each other; that is, video content that is compressed using one standard cannot be decompressed with a different standard. For instance, an MPEG-4 decoder will not work with an H.264 encoder.
VIDEO COMPRESSION - CHAPTER 7 57 Figure 7.1b With difference coding, only the first image (I-frame) is coded in its entirety. In the two following images (P-frames), references are made to the first picture for the static elements, i.e. the house. Only the moving parts, i.e. the running man, are coded using motion vectors, thus reducing the amount of information that is sent and stored. Other techniques such as block-based motion compensation can be applied to further reduce the data.
CHAPTER 7 - VIDEO COMPRESSION An I-frame, or intra frame, is a self-contained frame that can be independently decoded without any reference to other images. The first image in a video sequence is always an I-frame. I-frames are needed as starting points for new viewers or resynchronization points if the transmitted bit stream is damaged. I-frames can be used to implement fast-forward, rewind and other random access functions.
VIDEO COMPRESSION - CHAPTER 7 59 Besides difference coding and motion compensation, other advanced methods can be employed to further reduce data and improve video quality. H.264, for example, supports advanced techniques that include prediction schemes for encoding I-frames, improved motion compensation down to sub-pixel accuracy, and an in-loop deblocking filter to smooth block edges (artifacts). For more information on H.264 techniques, see Axis’ white paper on H.264 at www.axis.
CHAPTER 7 - VIDEO COMPRESSION 7.2.2 MPEG-4 When MPEG-4 is mentioned in video surveillance applications, it is usually referring to MPEG-4 Part 2, also known as MPEG-4 Visual. Like all MPEG (Moving Picture Experts Group) standards, it is a licensed standard, so users must pay a license fee per monitoring station. MPEG-4 supports low-bandwidth applications and applications that require high quality images, no limitations in frame rate and with virtually unlimited bandwidth. 7.2.3 H.
VIDEO COMPRESSION - CHAPTER 7 61 7.3 Variable and constant bit rates With MPEG-4 and H.264, users can allow an encoded video stream to have a variable or a constant bit rate. The optimal selection depends on the application and network infrastructure. With VBR (variable bit rate), a predefined level of image quality can be maintained regardless of motion or the lack of it in a scene.
CHAPTER 7 - VIDEO COMPRESSION Figure 7.4a Axis’ H.264 encoder generated up to 50% fewer bits per second for a sample video sequence than an MPEG-4 encoder with motion compensation. The H.264 encoder was at least three times more efficient than an MPEG-4 encoder with no motion compensation and at least six times more efficient than with Motion JPEG.
AUDIO - CHAPTER 8 63 Audio While the use of audio in video surveillance systems is still not widespread, having audio can enhance a system’s ability to detect and interpret events, as well as enable audio communication over an IP network. The use of audio, however, can be restricted in some countries, so it is a good idea to check with local authorities.
CHAPTER 8 - AUDIO 8.2 Audio support and equipment Audio support can be more easily implemented in a network video system than in an analog CCTV system. In an analog system, separate audio and video cables must be installed from endpoint to endpoint; that is, from the camera and microphone location to the viewing/recording location. If the distance between the microphone and the station is too long, balanced audio equipment must be used, which increases installation costs and difficulty.
AUDIO - CHAPTER 8 65 Many Axis network video products do not come with a built-in speaker. An active speaker— a speaker with a built-in amplifier—can be connected directly to a network video product with audio support. If a speaker has no built-in amplifier, it must first connect to an amplifier, which is then connected to a network camera/video encoder.
CHAPTER 8 - AUDIO 8.3.2 Half duplex Loudspeaker Audio sent by operator Audio sent by camera LAN/WAN Video sent by camera Headphones PC Network camera Microphone Figure 8.3c In half-duplex mode, audio is sent in both directions, but only one party at a time can send. This is similar to a walkie-talkie. 8.3.3 Full duplex Loudspeaker Full duplex audio sent and received by operator LAN/WAN Video sent by camera Headphones PC Network camera Microphone Figure 8.
AUDIO - CHAPTER 8 67 8.5.1 Sampling frequency There are many different audio codecs supporting different sampling frequencies and levels of compression. Sampling frequency refers to the number of times per second a sample of an analog audio signal is taken and is defined in hertz (Hz). In general, the higher the sampling frequency, the better the audio quality and the greater the bandwidth and storage needs. 8.5.
NETWORK TECHNOLOGIES - CHAPTER 9 69 Network technologies Different network technologies are used to support and provide the many benefits of a network video system. This chapter begins with a discussion about the local area network, in particular, Ethernet networks and the components that support it. The use of Power over Ethernet is also covered.
CHAPTER 9 - NETWORK TECHNOLOGIES type of fiber. Depending on the type of twisted pair or fiber optic cables used, data rates today can range from 100 Mbit/s to 10,000 Mbit/s. Figure 9.1a Twisted pair cabling includes four pairs of twisted wires, normally connected to a RJ-45 plug at the end. A rule of thumb is to always build a network with greater capacity than is currently required. To future-proof a network, it is a good idea to design a network such that only 30% of its capacity is used.
NETWORK TECHNOLOGIES - CHAPTER 9 71 categories are recommended for network video systems. Most interfaces are backwards compatible with 10 and 100 Mbit/s Ethernet and are commonly called 10/100/1000 interfaces. For transmission over longer distances, fiber cables such as 1000BASE-SX (up to 550 m/1,639 ft.) and 1000BASE-LX (up to 550 m with multimode optical fibers and 5,000 m with single-mode fibers) can be used. Figure 9.1b Longer distances can be bridged using fiber optic cables.
CHAPTER 9 - NETWORK TECHNOLOGIES Switches typically indicate their performance in per port rates and in backplane or internal rates (both in bit rates and in packets per second). The port rates indicate the maximum rates on specific ports. This means that the speed of a switch, for example 100 Mbit/s, is often the performance of each port. Figure 9.
NETWORK TECHNOLOGIES - CHAPTER 9 73 9.1.3 Power over Ethernet Power over Ethernet (PoE) provides the option of supplying devices connected to an Ethernet network with power using the same cable as for data communication. Power over Ethernet is widely used to power IP phones, wireless access points and network cameras in a LAN. The main benefit of PoE is the inherent cost savings. Hiring a certified electrician and installing a separate power line are not needed.
CHAPTER 9 - NETWORK TECHNOLOGIES According to IEEE 802.3af, a PSE provides a voltage of 48 V DC with a maximum power of 15.4 W per port. Considering that power loss takes place on a twisted pair cable, only 12.95 W is guaranteed for a PD. The IEEE 802.3af standard specifies various performance categories for PDs. PSE such as switches and midspans normally supply a certain amount of power, typically 300 W to 500 W.
NETWORK TECHNOLOGIES - CHAPTER 9 75 Uninterruptible Power Supply (UPS) 3115 Network camera with built-in PoE Network camera without built-in PoE Network switch Midspan Power Ethernet Active splitter Power over Ethernet Figure 9.1d An existing system can be upgraded with PoE functionality using a midspan and splitter. The midspan, which adds power to an Ethernet cable, is placed between the network switch and the powered devices.
CHAPTER 9 - NETWORK TECHNOLOGIES another based on IP addresses. It forwards only data packages that are to be sent to another network. A router is most commonly used for connecting a local network to the Internet. Traditionally, routers were referred to as gateways. Firewalls A firewall is designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both.
NETWORK TECHNOLOGIES - CHAPTER 9 77 Ports A port number defines a particular service or application so that the receiving server (e.g., network camera) will know how to process the incoming data. When a computer sends data tied to a specific application, it usually automatically adds the port number to an IP address without the user’s knowledge. Port numbers can range from 0 to 65535. Certain applications use port numbers that are pre-assigned to them by the Internet Assigned Numbers Authority (IANA).
CHAPTER 9 - NETWORK TECHNOLOGIES NAT (Network address translation) When a network device with a private IP address wants to send information via the Internet, it must do so using a router that supports NAT. Using this technique, the router can translate a private IP address into a public IP address without the sending host’s knowledge.
NETWORK TECHNOLOGIES - CHAPTER 9 79 Port forwarding is traditionally done by first configuring the router. Different routers have different ways of doing port forwarding and there are web sites such as www.portfoward.com that offer step-by-step instruction for different routers.
CHAPTER 9 - NETWORK TECHNOLOGIES 9.2.1.2 IPv6 addresses An IPv6 address is written in hexadecimal notation with colons subdividing the address into eight blocks of 16 bits each; for example, 2001:0da8:65b4:05d3:1315:7c1f:0461:7847 The major advantages of IPv6, apart from the availability of a huge number of IP addresses, include enabling a device to automatically configure its IP address using its MAC address.
NETWORK TECHNOLOGIES - CHAPTER 9 81 Transport protocol Port Common usage Network video usage FTP (File Transfer Protocol) TCP 21 Transfer of files over the Internet/ intranets Transfer of images or video from a network camera/video encoder to an FTP server or to an application SMTP (Send Mail Transfer Protocol TCP 25 Protocol for sending e-mail messages A network camera/video encoder can send images or alarm notifications using its built-in e-mail client. 80 Used to browse the web, i.e.
CHAPTER 9 - NETWORK TECHNOLOGIES 9.3 VLANs When a network video system is designed, there is often a desire to keep the network separate from other networks, both for security as well as performance reasons. At first glance, the obvious choice would be to build a separate network. While the design would be simplified, the cost of purchasing, installing and maintaining the network would often be higher than using a technology called virtual local area network (VLAN).
NETWORK TECHNOLOGIES - CHAPTER 9 83 The term, Quality of Service, refers to a number of technologies such as Differentiated Service Codepoint (DSCP), which can identify the type of data in a data packet and so divide the packets into traffic classes that can be prioritized for forwarding.
CHAPTER 9 - NETWORK TECHNOLOGIES 9.5 Network Security There are different levels of security when it comes to securing information being sent over IP networks. The first is authentication and authorization. The user or device identifies itself to the network and the remote end by a username and password, which are then verified before the device is allowed into the system. Added security can be achieved by encrypting the data to prevent others from using or reading the data.
NETWORK TECHNOLOGIES - CHAPTER 9 85 server instructs the switch or access point to open the port to allow data from the network camera to pass through the switch and be sent over the network. 1 Supplicant (Network camera) 2 Authenticator (Switch) 3 Authentication Server (RADIUS) or other LAN resources Figure 9.5a IEEE 802.1X enables port-based security and involves a supplicant (e.g., a network camera), an authenticator (e.g., a switch) and an authentication server.
CHAPTER 9 - NETWORK TECHNOLOGIES HTTPS or SSL/TLS encryption DATA VPN tunnel PACKET Secure Non-secure Figure 9.5b The difference between HTTPS (SSL/TLS) and VPN is that in HTTPS only the actual data of a packet is encrypted. With VPN, the entire packet can be encrypted and encapsulated to create a secure “tunnel”. Both technologies can be used in parallel, but it is not recommended since each technology will add overhead and decrease the performance of the system.
WIRELESS TECHNOLOGIES - CHAPTER 10 87 Wireless technologies For video surveillance applications, wireless technology offers a flexible, cost-efficient and quick way to deploy cameras, particularly over a large area as in a parking lot or a city center surveillance application. There would be no need to pull a cable through the ground. In older, protected buildings, wireless technology may be the only alternative if standard Ethernet cables may not be installed.
CHAPTER 10 - WIRELESS TECHNOLOGIES 10.1 802.11 WLAN standards The most common wireless standard for wireless local area networks (WLAN) is the 802.11 standard by IEEE. While there are also other standards as well as proprietary technologies, the benefit of 802.11 wireless standards is that they all operate in a license-free spectrum, which means there is no license fee associated with setting up and operating the network. The most relevant extensions of the standards are 802.11b, 802.11g, 802.
WIRELESS TECHNOLOGIES - CHAPTER 10 89 10.2.1 WEP (Wired Equivalent Privacy) WEP prevents people without the correct key from accessing the network. There are, however, weaknesses in WEP. They include keys that are relatively short and other flaws that allow keys to be reconstructed from a relatively small amount of intercepted traffic.
VIDEO MANAGEMENT SYSTEMS - CHAPTER 11 91 Video management systems An important aspect of a video surveillance system is managing video for live viewing, recording, playback and storage. If the system consists of only one or a few cameras, viewing and some basic video recording can be managed via the built-in web interface of the network cameras and video encoders. When the system consists of more than a few cameras, using a network video management system is recommended.
CHAPTER 11 - VIDEO MANAGEMENT SYSTEMS other systems such as access control, building management, and industrial control. This allows users to manage video and other building controls through a single program and user interface. For more on servers and storage, see Chapter 12.
VIDEO MANAGEMENT SYSTEMS - CHAPTER 11 93 systems where the number of cameras stays within the limits of an NVR’s designed capacity. An NVR is normally easier to install than a system based on a PC server platform. Axis network video recorder (NVR) Viewing PC AXIS 262 Network Video Recorder IP NETWORK Axis network cameras Figure 11.1b A network video surveillance system that uses an NVR. 11.2 Software platforms Different software platforms can be used to manage video.
CHAPTER 11 - VIDEO MANAGEMENT SYSTEMS With a Windows client-based program, the video management software must first be installed on the recording server. Then a viewing client software program can be installed on the same recording server or any other PC, whether locally on the same network where the recording server resides, or remotely at a viewing station located on a separate network.
VIDEO MANAGEMENT SYSTEMS - CHAPTER 11 95 11.3.1 Viewing A key function of a video management system is enabling live and recorded video to be viewed in efficient and user-friendly ways. Most video management software applications enable multiple users to view in different modes such as split view (to view different cameras at the same time), full screen or camera sequence (where views from different cameras are displayed automatically, one after the other).
CHAPTER 11 - VIDEO MANAGEMENT SYSTEMS Remote recording/ viewing at medium frame rate and medium resolution Analog camera I/O AUDIO 1 2 3 4 5 6 OUT IN Video encoder Local recording/ viewing at full frame rate and high resolution Viewing with a mobile telephone at medium frame rate and low resolution Figure 11.3b Multiple, individually configurable video streams enable different frame rate video and resolution to be sent to different recipients. 11.3.
VIDEO MANAGEMENT SYSTEMS - CHAPTER 11 97 Once the type of recording method is selected, the quality of the recordings can be determined by selecting the video format (e.g., H.264, MPEG-4, Motion JPEG), resolution, compression level and frame rate. These parameters will affect the amount of bandwidth used, as well as the size of storage space required. Network video products may have varying frame rate capabilities depending on the resolution.
CHAPTER 11 - VIDEO MANAGEMENT SYSTEMS network video product and flagged to the management software program for further actions to be taken. This process offers a number of benefits: > It enables a more efficient use of bandwidth and storage space since there is no need for a camera to continuously send video to a video management server for analysis of any potential events. Analysis takes place at the network video product and video streams are sent for recording and/or viewing only when an event occurs.
VIDEO MANAGEMENT SYSTEMS - CHAPTER 11 99 > Video motion detection: When a camera detects certain movement in a camera’s motion detection window, an event can be triggered. For more on video motion detection see page 102. > Camera tampering: This feature, which allows a camera to detect when it has been intentionally covered, moved or is no longer in focus, can be used to trigger an event. For more on active tampering alarm, see page 102.
CHAPTER 11 - VIDEO MANAGEMENT SYSTEMS > Activate output port: The output port(s) on a network camera or video encoder can be connected to external devices such as alarms. (More details are provided below on output ports.) > Send e-mail notification: This notifies users that an event has occurred. An image can also be attached in the e-mail. > Send HTTP/TCP notification: This is an alert to a video management system, which can then, for example, initiate recordings.
VIDEO MANAGEMENT SYSTEMS - CHAPTER 11 101 Device type Description Usage Door contact Simple magnetic switch that detects the opening of doors or windows. When the circuit is broken (door is opened), images/video as well as notifications can be sent from the camera. Passive infrared detector (PIR) A sensor that detects motion based on heat emission. When motion is detected, the PIR breaks the circuit and images/video as well as notifications can be sent from the camera.
CHAPTER 11 - VIDEO MANAGEMENT SYSTEMS Video motion detection Video motion detection (VMD) is a common feature in video management systems. It is a way of defining activity in a scene by analyzing image data and differences in a series of images. With VMD, motion can be detected in any part of a camera’s view.
VIDEO MANAGEMENT SYSTEMS - CHAPTER 11 103 Software programs that help simplify the management of network cameras and video encoders in an installation often provide the following functionalities: > > > > > > Locating and showing the connection status of video devices on the network Setting IP addresses Configuring single or multiple units Managing firmware upgrades of multiple units Managing user access rights Providing a configuration sheet, which enables users to obtain, in one place, an overview of all
CHAPTER 11 - VIDEO MANAGEMENT SYSTEMS 11.4 Integrated systems When video is integrated with other systems such as point-of-sale and building management, information from other systems can be used to trigger functions such as event-based recordings in the network video system, and vice versa. In addition, users can benefit from having a common interface for managing different systems. 11.4.
VIDEO MANAGEMENT SYSTEMS - CHAPTER 11 105 Figure 11.4a An example of a PoS system integrated with video surveillance. This screenshot displays the receipts together with video clips of the event. Picture courtesy of Milestone Systems. 11.4.3 Access control Integrating a video management system with a facility’s access control system allows for facility and room access to be logged with video. For example, video can be captured at all doors when someone enters or exits a facility.
CHAPTER 11 - VIDEO MANAGEMENT SYSTEMS > Intelligent video can be used to detect reverse flow of people into a building due to an open or unsecured door from events such as evacuations. > Information from the video motion detection functionality of a camera that is located in a meeting room can be used with lighting and heating systems to turn the light and heat off once the room is vacated, thereby saving energy. 11.4.
BANDWIDTH and STORAGE CONSIDERATIONS - CHAPTER 12 107 Bandwidth and storage considerations Network bandwidth and storage requirements are important considerations when designing a video surveillance system. The factors include the number of cameras, the image resolution used, the compression type and ratio, frame rates and scene complexity. This chapter provides some guidelines on designing a system, along with information on storage solutions and various system configurations. 12.
CHAPTER 12 - BANDWIDTH AND STORAGE CONSIDERATIONS When implementing 10 or more cameras, the network load can be estimated using a few rules of thumb: > A camera that is configured to deliver high-quality images at high frame rates will use approx. 2 to 3 Mbit/s of the available network bandwidth. > With more than 12 to 15 cameras, consider using a switch with a gigabit backbone.
BANDWIDTH and STORAGE CONSIDERATIONS - CHAPTER 12 109 MPEG-4 calculation: Approx. bit rate / 8(bits in a byte) x 3600s = KB per hour / 1000 = MB per hour MB per hour x hours of operation per day / 1000 = GB per day GB per day x requested period of storage = Storage need Note: The formula does not take into account the amount of motion, which is an important factor that can influence the size of storage required. Camera Resolution Approx.
CHAPTER 12 - BANDWIDTH AND STORAGE CONSIDERATIONS A helpful tool in estimating requirements for bandwidth and storage is the AXIS Design Tool, which is accessible from the following web address: www.axis.com/products/video/design_tool/ Figure 12.1a The AXIS Design Tool includes advanced project management functionality that enables bandwidth and storage to be calculated for a large and complex system. 12.
BANDWIDTH and STORAGE CONSIDERATIONS - CHAPTER 12 111 Separate storage Axis network cameras Network switch, broadband router or corporate firewall Computer server with video management software Figure 12.3a Network-attached storage NAS provides a single storage device that is directly attached to a LAN and offers shared storage to all clients on the network. A NAS device is simple to install and easy to administer, providing a low-cost storage solution.
CHAPTER 12 - BANDWIDTH AND STORAGE CONSIDERATIONS 12.4 Redundant storage SAN systems build redundancy into the storage device. Redundancy in a storage system allows video, or any other data, to be saved simultaneously in more than one location. This provides a backup for recovering video if a portion of the storage system becomes unreadable.
BANDWIDTH and STORAGE CONSIDERATIONS - CHAPTER 12 113 12.5 System configurations Small system (1 to 30 cameras) A small system usually consists of one server running a surveillance application that records the video to a local hard disk. The video is viewed and managed by the same server. Although most viewing and management will be done at the server, a client (local or remote) can be connected for the same purpose. IP NETWORK Application and storage server Workstation client (optional) Figure 12.
CHAPTER 12 - BANDWIDTH AND STORAGE CONSIDERATIONS IP NETWORK Surveillance workstations Master server 1 Master server 2 Storage server 1 Storage server 2 Figure 12.5c A large centralized system. Large distributed system (25 to +1000 cameras) When multiple sites require surveillance with centralized management, distributed recording systems may be used. Each site records and stores the video from local cameras. The master controller can view and manage recordings at each site.
TOOLS AND RESOURCES 115 Tools and resources Axis offers a variety of tools and information resources to help design IP-Surveillance systems. Many are accessible from the Axis website: www.axis.com/tools Lens Calculators This tool helps you calculate the focal length of the lens you will need in order to capture a specific scene at a certain distance.
AXIS COMMUNICATIONS’ ACADEMY 117 Axis Communications’ Academy Number one in network video knowledge. Learn more about network video technologies with Axis’ training program. > > > > Broad course offering Hands-on training Training from the leading experts Gain a competitive edge The video surveillance market is changing as older analog systems converge towards network video technology. New technologies, applications and integration possibilities are driving the convergence.
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About Axis Communications Axis is an IT company offering network video solutions for professional installations. The company is the global market leader in network video, driving the ongoing shift from analog to digital video surveillance. Axis products and solutions focus on security surveillance and remote monitoring, and are based on innovative, open technology platforms.
