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In recent years, with the development of digital technology, millions of high-definition monitoring systems have become increasingly sophisticated, which has greatly promoted the development of the entire monitoring industry. High-definition monitoring systems have become an inevitable trend. At present, many high-definition manufacturers have been able to provide complete front-end, back-end and related platform solutions to meet the needs of most projects.
After many years of accumulation, the original monitoring system has laid a large number of coaxial cables (video cables) and two-core cables (control cables or power cables) in numerous buildings. The original pipelines and decoration have also ended. Sub-wiring is very difficult to set up a network, and these cables are still far from their useful life. How can these large amounts of copper be used twice, shorten the construction period of the project, reduce construction costs, and reduce personnel costs? Based on the monitoring system of analog equipment, how can we quickly upgrade and upgrade to high-definition monitoring systems without rewiring? The urgent demand in the field of security applications challenges the industry's innovative strength.
HD monitoring three transmission technology analysis
At present, the high-definition products that are widely used are based on network transmission technologies, and the direct transmission method is almost extinct in the era of high-definition, but the debate about whether network transmission is suitable for monitoring image transmission has never ceased. Therefore, finding a transmission mode that is consistent with the actual application, the technology can be satisfied, and the cost is as low as possible is particularly critical for the application of monitoring.
1, analog signal transmission
At present, the vast majority of standard-definition video signals still use the analog signal transmission method. The application of coaxial cable transmission 100 meters, at the expense of some high-frequency details, can transmit 200-300 meters, or even farther. Because of this performance, this transmission mode has not changed since the beginning of monitoring applications. However, in the era of high-definition, due to the expansion of the transmission of high-definition signal bandwidth, the use of traditional coaxial cable transmission, a few meters to attenuate, and can not be used in the monitoring project, and HD network camera transmission mode and standard definition compared to no change , so when the era of high-definition comes, it has become a monopod of network cameras, direct transmission mode is rarely used.
2, digital transmission mode
Since the HD analog transmission method cannot be used in monitoring actual applications, the only method is digital transmission. Before discussing digital high-definition transmission technology, first analyze the digital characteristics of the high-definition signal. At 30 frames per second, the theoretical bandwidth of the 1080P image signal does not exceed 1 G, and the theoretical bandwidth of the 720P image signal does not exceed 500 M. In the field of data communication technology, There are many transmission methods for such large data traffic. Commonly used media include coaxial cables, twisted pairs, and optical fibers.
3, coaxial cable transmission technology
Coaxial cable transmission technology is widely used in standard definition era for the transmission of standard definition analog video signals. The standard for digital video signals corresponding to standard definition analog video signals is the SD-SDI interface (270 Mb/s). This interface is due to cost and performance reasons. , rarely used in monitoring. The HD digital signal standard is HD-SDI (1.485Gb/s). The transmission distance can be extended to 100 meters under the premise of application of descrambling technology, originating pre-emphasis technology and receiving end equalization technology.
However, there are still many problems in practical applications by extending pre-emphasis and equalization techniques to extend the signal transmission distance of SDI. The characteristics of the cable have a great influence on the transmission distance. In addition, the coaxial cable transmission is a single-end transmission system. Mode interference. In the analog monitoring, if the line on the project site is not good, it will cause interference, which will seriously affect the transmission distance of SDI signals. It is not difficult to understand why the current HD-SDI transmission distance is inconclusive. The theoretical transmission distance and actual difference are too large, and the most tangled is that if the HD-SDI signal exceeds its transmission distance, the receiving end cannot solve any signal, which is far worse than the performance of the conventional SD analog transmission system. Therefore, there are still many problems and difficulties in the application of HD-SDI transmission technology to large-area surveillance systems.
Simultaneous transmission of digital and analog signals
It can be seen that with the rapid development of analog monitoring and network monitoring, how to upgrade the analog to the network faster and less costly has become the focus of attention in the industry. SLOC (SecurityLinkoverCoax Coax Secured Link) composite video transmission technology was born from this application.
The SLOC coaxial cable composite video transmission solution is an advanced modem solution developed by Intersil, a global leader in high-performance analog mixed-signal semiconductor design and manufacturing. It can transmit analog CVBS video and high-definition digital IP video at the same time through a coaxial cable, namely SLOC = analog video + IP code stream. The high-efficiency hybrid video surveillance technology helps to enable megapixel IP cameras to operate on existing CCTV coaxial infrastructure with a maximum monitoring distance of up to 300 meters. It also supports latency-free analog CCTV and network IP monitoring capabilities. The appearance of SLOC technology will bring good news to the seamless transition of video surveillance system from analog CCTV to network IP monitoring.
Ma Dalun, global marketing director of Intersil’s video signal processing product line, introduced the outside world. The SLOC solution consists of a SLOC-based camera modem PHY chip TW3801 and a SLOC-based receiver modem PHY chip TW3811. SLOC technology makes full use of the installed coaxial cable infrastructure and supports networked IP functions without major changes to IP camera design or DVR design. The TW3801 and TW3811 are highly integrated modem PHY subsystems that include an analog front end (AFE), a digital modem, and two Ethernet media independent interfaces (MII). The TW3801 combines the CVBS signal it receives with the Ethernet MII signal one-on-one into a proprietary output signal transmitted over the coaxial cable, and the TW3811 equates it with the signal received by the SLOC-based camera modem PHYIC. decoding.
During the Shenzhen CPSE Anbo Expo in 2011, Intersil held a special SLOC technology forum. According to their analysis, the popularity of IP cameras faces three major challenges in terms of transmission: First, engineering companies have become accustomed to coaxial cables; second, IP cameras have been limited by a transmission distance of 150 meters; again, ordinary WAN IP cameras preview video delays. Usually between 1 and 4 seconds (mainly caused by video encoding buffer, video decoding buffer, and network transmission delay). The schematic SLOC technology of Intersil's SLOC solution completely solves the three major problems facing the IP surveillance system. First, the technology supports the transmission of 1080P high-definition IP streams based on the existing coaxial cable; secondly, it supports the local transmission distance of the IP code stream extending to 300 meters; in addition, it simultaneously transmits real-time analog video for real-time preview or PTZ control, through A series of transmission solutions completely solved the problem of IP transmission delay. In addition, this technology also supports CVBS analog video transmission, optimizes the IP networking system, and can seamlessly upgrade to the high-definition IP network on the original traditional monitoring system.
For this purpose, he spoke to Joseph Spisak, Senior Strategic Marketing Manager at Intersil, a developer of SLOC technology. He introduced that Intersil currently cooperates with hundreds of customers, including OEMs, ODMs, and many design companies. Currently there are more than 100 related designs in the world, and the market is very excited, dynamic and interested in this hybrid solution. strong. Intersil will start the production of important transmitter and receiver SLOC devices in mid-2012 and is currently being promoted at customer sites around the world and at all major industry trade shows. In addition, he also revealed that Intersil will release a camera transmitter and a DVR/switch receiver solution this year, and there are other products under development that will bring further cost savings and system BOM (bill of materials) )optimization.
It is understood that in order to promote SLOC technology and solve the problem of consistency standards, Intersil is working with SONY to promote the HVSA (HybridVideoSurveillanceAlliance Hybrid Video Surveillance Alliance) organization process. Regarding the progress of the organization, Joseph Spisak said that the current progress is good and there is a lot of momentum behind it. They plan to cooperate with not only Sony but also other first-tier security OEMs in the first half of this year. Joseph Spisak said that the current awareness of SLOC technology in the field of overseas security is gradually established, and many foreign customers who have started to design are designing prototype products or are conducting trial production. “We have a total of more than 100 design wins for various security products globally. The Chinese market is expected to fully accept SLOC. We have more than 30 designs to win, and more will be later.â€
Joseph Spisak said that the value of hybrid video and why it is different from other existing coaxial solutions is the main challenge currently facing the promotion of SLOC technology. "From the very beginning of design and definition, the purpose of SLOC is to become a security protocol, not just a re-use of existing technologies. Existing technologies have limitations such as distance, and distance is extremely important in the security field."
SLOC technology security product application
Since the SLOC scheme allows megapixel-class IP cameras to use existing CCTV coax infrastructure without the use of new lines or cable modifications, significant cost and resource savings are achieved, leaving the security surveillance industry free from traditional analog surveillance systems. Switching to digital IP security monitoring systems becomes extremely simple. Since its launch in October 2010, the SLOC program has received a lot of feedback in the industry because SLOC's features are very practical. SLOC supports digital IP camera functions based on existing coaxial line infrastructure without interfering with existing CCTV services. Its embedded analog CVBS video also supports real-time viewing and control of digital IP cameras without delay, which allows manufacturers of surveillance systems to Immediately build an effective hybrid monitoring system that supports latency-free analog CCTV functionality and networked IP monitoring capabilities.
In April 2011, Intersil enough announced that Sony had decided to use SLOC technology widely in its industry-leading security network camera product line. During the 2011 Shenzhen Expo, Sony first introduced a series of hybrid high-definition solutions that include five new hybrid cameras and two camera signal receivers, which can easily convert the original analog infrastructure to a network high-definition video surveillance system. This greatly reduces the cost of system upgrades and effectively protects upfront investment.
Conclusion
At present, security monitoring has gradually moved toward high-definition, SLOC technology is mature, can quickly upgrade old systems to high-definition systems, greatly shorten the construction period, and reduce the associated cost. It can be foreseen that SLOC technology will provide high-definition webcam solutions for existing SD infrastructure, which will help realize the seamless transition from analog CCTV to network IP monitoring for video surveillance systems, and will provide strong impetus for the growth of the IP security system market.
Transmission is the most basic and critical link in many aspects of the video surveillance system. Early analog monitoring was based on coaxial cable transmission. With the increasing scale of monitoring and the development of network monitoring and remote monitoring, the original coaxial cable can no longer meet application needs. With the rapid development of analog monitoring and network monitoring, how to upgrade the analog to the network at a faster and less cost has become the focus of attention in the industry. SLOC (SecurityLinkoverCoax Coax Secure Link) composite video transmission technology was born out of this application. It transmits analog video and digital video at the same time through a coaxial cable, which greatly facilitates the use of high-definition IP cameras in the existing CCTV coaxial infrastructure. Cabling operation.