First, what is meant by "HD"?
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For video surveillance, image clarity is undoubtedly the most critical feature. The clearer the image, the more obvious the details, the better the viewing experience, and the higher the accuracy of application services such as smart analytics. Therefore, image clarity is the eternal pursuit of video surveillance.
The standard for measuring image sharpness is resolution, in pixels. The larger the value, the clearer the image. The so-called high-definition, standard definition, the difference is also reflected here. The dividing line between the two is megapixel or 720p, which is HD in megapixel or 720p.
(1) 1080i format is a standard digital TV display mode. 1125 vertical scanning lines, 1080 visible vertical scanning lines, 16:9, resolution 1920×1080, interlaced/60Hz, horizontal frequency 33.75KHz.
(2) 720p format, which is a standard digital TV display mode. 750 vertical scanning lines, 720 visible vertical scanning lines, 16:9, resolution 1280×720, progressive/60Hz, line frequency 45KHz.
(3) 1080p format is a standard digital TV display mode. 1125 vertical scan lines, 1080 visible vertical scan lines, 16:9, resolution 1920×1080 progressive scan, professional format.
Second, the advantages of high-definition monitoring
Whether in terms of resolution, display or fluency, HD is more advantageous than standard definition. In terms of resolution, the resolution of 720p is 9 times that of CIF, and the resolution of 1080i/1080p is 20 times that of CIF. In the same display environment, HD is much clearer. From the display effect, HD supports both large screen display and 16:9 widescreen display, which can greatly enhance the user's viewing experience. In terms of fluency, HD supports higher frame rates, such as 720p and 1080i/1080p, which can support 60 frames per second or 60 fields per second, and its image fluency is twice as high as that of standard definition. Therefore, high-definition surveillance is one of the most mainstream trends in the monitoring industry.
For customers, HD only makes sense when it includes front-end, platform, storage, browsing, display and so on. Therefore, in order to achieve true high-definition monitoring, it is necessary to fully support HD from the aspects of video source acquisition, video signal encoding and compression, video signal transmission, video browsing, and video file playback.
Third, high-definition monitoring in intelligent buildings
front end
Previously, the intelligent building industry mostly used analog systems. Compared with these traditional closed-circuit television monitoring systems, HD cameras do not need coaxial cables and do not need huge video distributors. At the same time, high-definition network cameras use broadband networks to transmit images, which are very cheap, can fully utilize network resources, enhance the flexibility of monitoring range, and can directly realize remote monitoring by using network update software.
transmission
The monitoring system transmission technology mainly includes six kinds of transmission modes: video baseband transmission, optical fiber transmission, network transmission, microwave transmission, twisted pair balanced transmission, and broadband common cable transmission. Each technology has its own characteristics and application level. In the past, fiber optic transmission has been the best way to solve high-speed transmission of long-distance video surveillance because of its small attenuation, frequency bandwidth, immunity to electromagnetic interference, and good confidentiality. With the rapid development of network technology, various broadband networks are emerging one after another. In addition to the self-built fiber-optic private network reaching gigabit bandwidth, the local area network is gradually developing towards 1000M and 10000M.
At the same time, major operators are also vigorously developing EPON and GPON optical networks, making the bandwidth reach Gbit or higher. These provide a better carrier for efficient transmission of high-definition video images in the network, and make network transmission an excellent choice for long-distance audio and video transmission.
At present, the uncompressed high-definition video signal after acquisition has both analog and digital transmission modes. The analog transmission generally uses YPbPr component transmission, and one high-definition video signal requires three coaxial cables to transmit at the same time. Digital transmission generally uses DVI, HDMI or HD-SDI transmission. The transmission distance of DVI or HDMI is only a few meters, which is not suitable for monitoring transmission. Although HD-SDI can transmit about 100 meters, the requirements for coaxial cable are very high. The price of the cable is also very expensive. If the high-definition video is efficiently compressed at the front end and then transmitted over the IP network, the transmission cost is equivalent to the standard-line monitoring network transmission cost.
Due to the limitation of high-definition video transmission over the WAN, strengthening bandwidth construction is an important way to solve the problem of high-definition transmission and network bandwidth. In addition, because HD takes up more network bandwidth, the use of network bandwidth should be carefully designed when building high-definition systems, especially large-channel HD systems. For example, 100M Ethernet can only carry 5~6 HD images at the same time (considering the collision detection feature of Ethernet). If there are multiple users accessing the same video source, the occupied bandwidth will be larger. Therefore, the use of technologies such as system design, multicast, and forwarding is particularly important.
storage
At present, the storage methods commonly used in security systems include DAS direct connection, NAS network hard disk and IPSAN. The IPSAN mode uses IP-based Ethernet transmission, which has good scalability, sharing and low application cost. At present, one of the main technologies used in large and medium-sized centralized monitoring and storage. These storage methods are very mature technologies in the IT industry. Most of the storage media are data hard disks that are commonly used on IT. The capacity is generally terabytes or more. (1G data is calculated per hour per data, and 1TB data hard disk can store about 720P. The video image is 1000 hours or 1000 cameras simultaneously recording 1 hour of data), and now 2TB of data hard disk has gradually entered people's sight. As the scale of specific HD monitoring projects continues to expand, large-scale HD monitoring system PB-level mass storage solutions will be widely used.
For high-definition surveillance systems, the security requirements for high-definition video storage are also high, especially for stored video playback. Whether video can be played back depends on several aspects:
First, whether the storage device has sufficient mixed read and write performance to ensure that the storage can satisfy the playback of multiple channels of video while writing a large amount of high-definition video. Insufficient mixed read and write performance may not only affect normal video writing and playback, but also may cause subsequent video to be completely unwritten.
Second, the security and stability of the storage system, advanced RAID technology, high-reliability enterprise-class disk can effectively reduce the possibility of data loss due to disk damage, and ensure that HD video is available in real time.
Third, data backup, images of important places or important images of a certain time in a common place often need to be backed up to ensure that the video is always available for a period of time. Generally, it can be saved to multiple storages during video capture, or save a single file first, and then copy to another storage. Multiple saves or backups of important video files are issues that must be considered when designing a high-definition surveillance system.
Fourth, the effectiveness of the platform software media management system is mainly the database structure design of the media management system background. Whether the target video can be retrieved quickly, accurately and efficiently through keywords is an important indicator of the media management system. Otherwise, even if the HD video is saved, it may not be retrieved and cannot be used for image recall and image analysis. It makes no sense.
In addition, intelligent analysis and data mining capabilities also fully demonstrate their application value in storage systems. Taking the intelligent building project as an example, the storage time can be extended from three months or half a year to one year, and the later expansion of the front-end monitoring point requires a larger storage capacity. If the intelligent analysis module is installed in combination with time and alarm trigger storage, the space required for video storage will be greatly reduced. In some important occasions (such as airports, customs) entrance and exit, you can also compare the face or license plate video captured by the HD camera with the blacklist in the back-end storage database to determine whether it is a criminal suspect or illegal vehicle, etc. If it is blacklisted If the information is consistent, the alarm parallel connection system will be implemented.
Management platform
Faced with the trend of increasingly large and complex projects in the intelligent building industry, and the trend of system integration is becoming more and more obvious, a powerful supporting and dispatching software is indispensable, especially for the vertically centralized management mechanism platform, and authorization management (whether or not for a certain user) Operation authority) and level control (different levels of users have different control management, operation rights) is particularly prominent. In the software architecture, the C/S structure and the B/S structure have their own advantages, and the different requirements of the monitoring system can be selected as needed. However, the functional application of the C/S architecture software system can be more abundant and the communication overhead is less. It is recommended to adopt the C/S structure.
On the hardware, considering the original investment and future expansion requirements, the high integration and large integration functions of the hardware platform are also very important. For example, whether it supports both analog and digital access, whether it supports both HD and SD systems, whether it supports intelligent analysis, whether it has a complete codec function, whether it supports large-scale networking, etc.
display
High-definition effects must be represented using good display devices. The display devices on the back end generally have three types: CRT, LCD, and PDP. The high-definition display effect must be displayed using a large-size display. Now there are splicing wall technologies, such as large-scale command centers in stadiums and buildings, most of which use spliced ​​large screens. At present, DLP is the most mature in the splicing screen, but the LCD splicing wall is gradually occupying the market. In terms of definition, the LCD can fully meet the requirements of 1080p. In addition, new display technologies (such as OLED high-definition screens) have placed high-definition indicators in the most important position, and various types of displays have also made 16:9 widescreens a stereotype for HD products.
For example, the transmission of the DVI interface is completely digital, which ensures the integrity of the information from the video source to the display terminal, and can achieve faster transmission speed and clearer images. Another example is the HDMI interface, which avoids the disadvantages of excessive DVI interface area and inability to transmit audio. Although the maximum transmission speed of HDMI is less than DVI (DVI can reach 8Gbps, HDMI is 5Gbps, HDTV signal transmission of the highest quality requires 2Gbps), but its support Eight-channel or mono digital audio transmission, eliminating the need for separate audio cables. At the same time, the length of the connecting line can reach more than 20 meters (DVI line above 8 meters will affect the image quality). Compared with the DVI interface, HDMI not only has higher bandwidth and higher resolution, but also integrates video transmission and audio transmission, which greatly simplifies cable connection.
Third, Hikvision high-definition monitoring overall solution
In summary, to achieve high-definition monitoring, you must have complete HD monitoring equipment and solutions to achieve. In order to fully meet the needs of high-definition surveillance, especially for the high-definition surveillance needs of the intelligent building industry, Hikvision has launched an overall HD surveillance solution, with a complete product line covering front-end video capture, encoding, transmission, storage, and control. , decoding output, to the central management platform, etc., these products and programs have been widely used in many landmark projects of the 2010 Shanghai World Expo.
For example, a 2 megapixel CCD HD network camera can realize real-time transmission of 2 megapixel HD video images; DS-9000 series hybrid DVR, which has the functions of DVR and NVR, can support both analog and digital access, and can be connected to HD Network camera for high-definition video recording and playback; HD decoding card/device, support for HD decoding; video integrated management platform, complete matrix function, support for HD, SD and network IP matrix, support for analog and digital access, support Large-scale networking, support for mass storage and many other functions.
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