HDCVI An Innovative HD Video Transmission Solution

What is HDCVI

In November 2012, Dahua Technology Co., Ltd. announced the HDCVI, a coaxial HD transmission interface technology with independent intellectual property rights. HDCVI technology is a high-definition video transmission method based on the existing SYV75-3 or SYV75-5 coaxial cable, enabling reliable transmission of ultra-long-distance high-definition video signals over low-cost and low-quality coaxial cables. Compared with the HD-SDI subsystem's high requirements for transmission media in practical applications, HDCVI can adapt to long-distance, low-cost transmission media and complex deployment scenarios.

HDCVI employs baseband modulation and quadrature amplitude modulation in modulation, and modulates the video into coaxial high-definition electrical signals for transmission. It is also known as HDCVI, the high-definition composite video interface. This technology avoids the chroma crosstalk phenomenon of CVBS and completely separates the luminance and chrominance signals to further enhance the picture quality.

HDCVI includes 1920H and 1280H specifications, is compatible with standard 1080P and 720P resolutions, and uses targeted automatic signal compensation technology to ensure extremely low signal distortion over long distance transmissions. HDCVI technology also uses a system of coaxial million HD cameras and DVRs. The DVR is used as a node device, and the camera is deployed in a star topology. The coaxial cable is used for point-to-point transmission between the camera and the DVR. According to the transmission cable, a 75-3, 75-5 equivalent cable can be used within a 500-meter point-to-point transmission distance, and transmission distances over 500 meters can be transmitted using a coaxial cable with a rating of 75-5 or higher. Point-to-point transmission cables can be used in the middle of connectors or soldered connections. In the actual construction stage, HDCVI product installation, wiring, and wiring are exactly the same as the construction of analog SD products. There are no special requirements for outdoor and indoor construction, and they have strong anti-interference ability to the outside world.

In order to realize the multi-signal common cable transmission, the HDCVI embeds the audio signal and the bidirectional data communication signal in the blanking area at the same time. The audio signal is compounded in line blanking to increase synchronization with the video signal and supports up to 44.1 kHz sample rate through automatic compensation techniques. The forward and reverse data channels are compounded in the frame blanking, and the control signals are transmitted in both directions to realize the transmission information between the receiving end and the sending end, supporting control commands such as camera zoom, pan and tilt, and real-time alarm. The forward transmission data can be predicted because of the transmission time and the baud rate of the electrical signal, and the receiver has a high-performance automatic compensation technology that can support a higher transmission baud rate. The reverse transmission of data due to the existence of impedance matching and channel transmission uncertainty factors, the signal frequency is lower and the amount of data sent each time is limited, so the supported baud rate is lower. Of course, the reverse channel also uses an automatic compensation technique to perform a certain restoration of the long-range transmission signal of the electrical signal.

Therefore, HDCVI is a low-cost, long-distance, no-delay, high-efficiency, anti-jamming and easy-to-implement megapixel HD video transmission technology.

HDCVI Implementation Carrier--HDCVI Chip

In August 2013, Dahua Technology Co., Ltd. officially launched a chip solution based on HDCVI technology. The chip solutions introduced this time are divided into two parts: transmit chip (TX) and receive chip (RX). They are applied to the front-end HDCVI coaxial million HD camera and the back-end HDCVI coaxial million HD DVR, and can also be extended to the middle. Optical transmitters, distributors, and matrices.

Figure 1 shows a typical application diagram of the HDCVI transmit chip (TX). TX chip adopts BT1120/BT656 digital video interface, I2S audio interface, I2C configuration interface on the data interface, and the standard data and configuration interface make the TX chip adapt to the ISP chip and audio chip of various signals on the market, making the HDCVI coaxial The whole HDTV camera solution is very flexible. In terms of coaxial output, the TX chip is compatible with the traditional CVBS format in addition to the HDCVI format. The TX chip supports all resolutions and frame rates of the HDCVI protocol in terms of resolution and frame rate: 1280H@25fps/30fps/50fps/60fps and 1920H@25fps/30fps.


Figure 1: HDCVI Transmit Chip (TX) Application Diagram

From the application block diagram point of view, using the TX chip coaxial million high-definition camera program is very simple, and TX chip using MQFN packaging technology chip size is very small, suitable for various types of cameras.

Figure 2 shows a typical application diagram of the HDCVI receiver chip (RX). Supports 4 channels of HDCVI analog HD input and 4 channels of digital video output; supports all formats and resolutions of HDCVI protocol; supports I2S audio output and multi-chip audio cascade output; supports I2C configuration interface; supports analog video input channels and digital output channels Flexible mapping; independent of each channel; supports support for brightness, contrast, sharpness, hue, saturation and other video parameters can be configured; support bidirectional control signal transmission; each channel built-in independent equalizer.


Figure 2: HDCVI Receiver (RX) Application Diagram

From the application block diagram, the interface between the RX chip and the video AD chip used in the existing analog DVR is completely the same, so the traditional analog DVR can be seamlessly connected to the entire solution. The built-in equalizer allows the DVR to receive high-definition video signals transmitted over 500 meters over long distances.

Therefore, the release of the TX and RX chips allows the entire manufacturer to make very small modifications to the original camera and DVR solution to implement the HDCVI solution, which will certainly accelerate the popularity of high-definition video surveillance.

The advantages of HDCVI

According to HDCVI's technical features and performance, HDCVI has a competitive advantage in the field of high-definition video transmission over coaxial cable compared to HD-SDI technology. First of all, both HDCVI and HD-SDI transmission technologies can deliver high-definition video at 720p and 1080p effective resolutions, but HDCVI has a clear natural advantage in terms of transmission distance. HD-SDI can only transmit 100 meters under the better environment of transmission medium. HDCVI can transmit at least 500 meters when using a 75-3 cable, and the signal distortion is extremely low. When a cable with 75-5 or better is used, the transmission distance can be further increased while ensuring the transmission of video. the quality of. Second, HD-SDI has poor anti-interference ability, especially in high-frequency radiation environments such as mobile phones and wireless routers. Strong high-frequency wireless electromagnetic interference to HD-SDI interference, resulting in high bit error rate of video data, manifested as abnormal images, Huaping, unable to lock and so on. HDCVI adopts low-frequency coaxial high-definition modulation technology, which avoids the interference of high-frequency wireless electromagnetic radiation from the essence of technology. Even under strong interference source environment, HDCVI can still ensure high-quality image transmission. Thirdly, in the actual construction of HD-SDI, there are stringent requirements for the selection of wiring environment and construction methods, which are mainly manifested in the high quality requirements for the installed cables; the requirement of not allowing midway connections; the welding quality requirements for connecting terminals. Installation path low radiation requirements. All of these impose high requirements on the quality of construction workers, construction costs, complexity of installation and maintenance, and layout design of circuits. HDCVI technology follows the construction requirements and alignment specifications of analog SD, and ordinary weak construction personnel can rapidly deploy high-definition monitoring subsystems.

HDCVI compares with the mainstream network high-definition camera, HDCVI also shows the advantages of security industry applications. First, HDCVI uses point-to-point transmission to ensure the reliability of signal transmission. IPC adopts the Ethernet transmission technology, and the transmission path is routed and exchanged through the network, causing network jitter and packet loss risks. In order to adapt to the network environment to ensure video fluency, video buffering technology is often adopted. At present, better point-to-point energy transmission in the network environment is guaranteed within 300ms. In a poor network environment, the delay phenomenon is more serious. HDCVI technology does not have delay in the point-to-point transmission process. The HD video source is not coded and decoded from the camera to the back-end device preview. The image completely maintains the original effect and provides users with more perfect visual effects. Secondly, the current upgrading of analog SD equipment can also be seamlessly switched to HDCVI products. By replacing the camera and DVR, the need for full HD monitoring can be achieved. The construction and deployment of analog SD equipment is the most widely used, and is the system currently used by engineering and construction personnel in the construction of security projects. HDCVI technology follows the transmission method of analog standard definition and is most easily accepted by users for construction and deployment. And quickly implement the implementation. Compared with IPC construction, similar to IT construction, there are high requirements for construction personnel, topology design, flow design, and node equipment selection. Third, the HDCVI system is used in exactly the same way as the SD system. The coaxial megapixel HD camera plus the DVR deployment system is plug-and-play, with DVR interoperability as the mainstay. Compared with the use of the IPC, it is often necessary to set and initialize the camera, and there are also risks of communication or configuration exceptions caused by network protocol compatibility problems. Even with the application of standardized protocols such as Onvif, the promotion of IPC plus NVR system, the ease of use is still not comparable to analog systems.

In addition, because HDCVI uses a multi-signal common cable transmission technology, a coaxial cable video is used to complete transmission of video and audio signals and bidirectional data transmission, and audio and video synchronous transmission and reverse transmission control signals, such as pan/tilt rotation, zoom control, etc., are realized. , further reducing the complexity of construction and installation.

More importantly, because HDCVI technology not only takes into account the practical value, but also adapts to long-distance, no-delay, strong-interference transmission methods and complex deployment scenarios, it has a low-cost, cost-effective competitive advantage. The high-definition video surveillance system based on HDCVI technology will maintain the same cost as the original analog SD system, and experience the charm of high-definition surveillance at the same system cost.



Table 1: Comparison of common monitoring technologies

System Solution

HDCVI HD solution mainly uses HDCVI technology DVR and coaxial million HD camera to form the basic subsystem. The DVR and NVS are used as the converged node device and are deployed in a star topology with a coaxial million HD camera. The HDCVI technology video surveillance system not only conforms to the analog SDTV camera system in terms of usage and installation, but also has the same interactive experience for user operations. The transmission medium can also directly use coaxial cables and connectors in the SD system. The construction and deployment personnel do not need to learn a great deal of professional assembly knowledge. They also have no special requirements for the quality of the cable and the connection process. They fully inherit the advantages of the analog SD system. There is no need for new training during the deployment of the new construction project. The reconstruction project can easily realize smooth transition and seamless upgrade based on the original system.

HDCVI technology products for users, according to the monitoring scene to choose the right camera; according to the number of monitoring points to select a sufficient access channel DVR; according to the scheduled video time to select the appropriate capacity of the hard disk, you can build high-definition monitoring system. The entire selection process and follow-up installation and commissioning work are almost identical to the traditional monitoring and control systems in the SD era. The only difference is the selection of hard disk capacity. Considering high-definition video surveillance, the video stream is significantly larger than D1. Taking the 1280H Coaxial Million HD surveillance system as an example, each channel generates 720P worth of coded data, which is more than twice that of the D1 era. When selecting a hard disk, you need to use an equal multiple of the hard disk capacity.

HDCVI technology can transmit 500 meters of high-definition video signals. It is required that the distance between the camera and the DVR should not exceed this range when designing the system. In this coverage area, it is ideally suited for typical applications of video surveillance points up to 16 channels. In the application model that exceeds the HDCVI transmission range, it is recommended to use a typical application built by multiple DVR networking methods, where each DVR covers monitoring points within a valid distance and tries to average the number of accesses per DVR.

HDCVI's new features also bring new features to the coaxial million HD system, which is reflected in the deployment of auxiliary video monitoring devices such as audio and alarms. Closer to the camera, the audio monitoring equipment and alarm farther from the DVR can be connected to the camera nearby and sent to the DVR through the coaxial cable using the HDCVI technology, thereby simplifying the construction deployment plan.

Technology development trend

HDCVI transmission technology has now achieved full-featured applications, and products based on HDCVI technology need to be more widely used. Through experiencing the advantages and functional characteristics of the technology, the demand for improved technology is further explored. As an emerging technology, in addition to satisfying the curiosity of manufacturers and users, it needs to be recognized by users in practice. With the rapid advancement of marketization, this new technology will surely grow and expand, and it is expected to become one of the HD video transmission standards in the security industry.

The popularization and application of HDCVI technology is inseparable from the diversity of products and the completeness of the system. As a new technological standard, manufacturers need to make unremitting efforts to develop more competitive products. With systematic application and high cost performance, it has accelerated the popularity of high-definition video surveillance at the megapixel level and completed the structural upgrade of the analog surveillance industry.

Conclusion

Under the trend of high-definition surveillance, HDCVI HD monitoring solution is the best choice for analog surveillance system upgrade. In the face of competition between HD network surveillance systems and HD-SDI surveillance systems, HDCVI technology will become an important member of the high-definition surveillance market at a lower cost and close to the advantages of security applications. With the participation of more manufacturers, the improvement of new technologies and the improvement of supporting products, it will promote the sound development of technology and market ecological environment, and accelerate the overall shift of the security industry to high-definition monitoring.

Wen / Deputy Director of Zhejiang Dahua Technology Co., Ltd. R&D Center Xie Yun

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