Analysis of video server and encoding technology and its development trend

As my country is comprehensively building a harmonious society and a well-off society, security has become a hot topic of public concern. Whether it is the construction of a safe city or a smart city, it is to provide citizens with security and related services, realize the transformation of urban security from "post-processing" to "pre-control", and improve citizens' living satisfaction; while realizing this transformation requirement, video servers are more integrated into the system, improving their own encoding functions, and realizing long-distance transmission. This article focuses on the introduction and analysis of the principle composition, encoding technology, network technology and development trends of video servers.

2. Overview of Video Server Development

Video surveillance has evolved from traditional analog closed-circuit surveillance systems to digital-analog hybrid surveillance systems, and then to the current IP video surveillance systems. The monitoring capabilities of analog closed-circuit video surveillance systems are limited by the transmission length and amplifiers of analog video cables, so they can only achieve local monitoring. The second-generation video surveillance system basically realizes remote access to the surveillance system. At present, with the continuous development of video and audio encoding technology and broadband network technology, network video servers make it easier and more cost-effective to achieve long-distance video transmission.

As we all know, the earliest video surveillance system used coaxial cables to transmit video signals. With the continuous expansion of video surveillance systems and the continuous increase in transmission distances, traditional CATV can no longer meet application requirements. Semi-analog/semi-digital video surveillance solutions with DVR (digital video recorder) as the core have entered the video surveillance field, but this solution still uses coaxial cables for signal transmission from the camera to the DVR. DVR can support recording and playback, and supports limited IP network access. Its main functions are recording and playback, which is suitable for local small monitoring systems and not suitable for long-distance transmission.

IP video surveillance solutions based on the network and built with video servers, with digital video processing technology as the core, and comprehensive use of digital image processing, embedded computer systems, data transmission networks, automatic control and artificial intelligence technologies have become the mainstream of today's video surveillance systems. Network video servers not only have the advantages of local digital surveillance systems such as computer fast processing capabilities, digital information anti-interference capabilities, clear video images, and single-machine display of multiple images, but also truly give play to the advantages of broadband networks. Through the IP network, the monitoring center and the monitoring targets anywhere that the network can reach are combined into one system, which truly meets the current needs for remote, real-time, and centralized video surveillance systems.

3. The principle and composition of video server

Network surveillance video server is a special device that realizes audio and video data encoding and network transmission processing. It consists of audio and video encoder, network interface, audio and video interface, RS422/RS485 serial interface, RS232 serial interface, etc.

Audio and video compression encoder: Since the amount of analog video data is very large; after the digital-to-analog conversion, the amount of data is also very large, so it is necessary to use mature encoding technology to encode the video data with a high compression ratio under the technical indicators that meet the network transmission requirements to meet the transmission requirements. In the past, network video servers generally used encoders such as M-JPEG. Users could not achieve a higher compression bit rate to suit various network environments, and could only achieve network transmission effects by reducing the frame rate. At present, various companies have launched MPEG-4 network video servers to better meet the requirements of video network transmission.

Network interface: As the networking of previous analog products mainly realized network transmission by establishing independent optical fibers, the network video server's large network interface can easily realize IP networking and data transmission. The network video server mainly uses TCP/IP and other protocols to realize the network transmission of audio and video data, control data, status detection information and other data.

Audio and video interface: The network video server is equipped with a standard analog audio and video input interface, which is convenient for monitoring the video signals of each channel. Netviewer uses Dynamic Stream Control technology to ensure real-time two-way audio transmission, automatic adjustment of video frame rate according to bandwidth, and automatic connection technology after network interruption.

RS422/RS485 serial interface: The network video server is equipped with RS422/RS485 serial communication interface, which can be connected to various peripherals such as PTZ, dome, etc. through the communication line.

The network video server can cooperate with the computer central control software to realize the large system networking solution. Some manufacturers' network video servers provide open SOK for users or third-party manufacturers to develop and build new applications.

4. Video Server Digital Coding Technology

The video server not only integrates multi-channel, recording and playback functions, but also uses M-JPEG, MPEG-4 and H.264 compression algorithms to compress video images, effectively reducing the space consumed by video storage. From the earliest application of M-JPEG\MPEG-4 compression technology to H.264 compression technology, the video server has developed from supporting only a single encoding code stream transmission to the current dual encoding code economy and even triple encoding code stream transmission. Moreover, for the same H.264 encoding, under the premise of the same video effect, the use of HIGHPROFILE level encoding can reduce the bit rate by about 40% compared with the use of BASELINE level encoding.

5. Network technology of video server

Video servers are based on IP network transmission and can realize system networking in various ways and with different architectures according to different application requirements, which is unmatched by traditional analog monitoring systems. Today's video monitoring systems are getting larger and larger, and the number of servers connected to the same system is increasing. There is often a need for interconnection between multiple systems. In the same monitoring system, each video server requires an independent IP address, and the problem of IP address anonymity has gradually been exposed. However, with the development of PV6 networks, this problem will no longer exist. At present, some manufacturers' equipment can support IPV6 networks to meet the requirements of this development.

6. Development Trend of Video Server

From urban informatization to smart cities, network video surveillance systems are an indispensable part of the development of smart cities. As the core of video surveillance systems, video servers and related technologies are in an era of rapid development and change. Video surveillance is not only for obtaining video and other information across regions, but more importantly, it is for intelligent analysis of collected information to complete the control of other devices. Video servers are the change point for the digitization and IPization of front-end video and other information. Through network video servers and monitoring platforms, the monitoring resources originally scattered in various regions can be integrated into a metropolitan, integrated monitoring resource, and then the metropolitan resources can be integrated into a wide-area resource. Finally, various intelligent analysis technologies are used to identify and analyze video content, and form linkage control of other devices. In general, the technology of video servers will show the following development trends, mainly reflected in intelligence, wireless, high definition, standardization and integration.

1. Integration

The integration of video surveillance systems is also developing rapidly. From the TMS320DM36X, DM642, and DM81×× series SOCs based on DaVinci technology launched by TI (Texas Instruments), to the dedicated SOC chips launched by HiSilicon and Vimicro for video surveillance systems, they have made significant contributions to the integration and localization of intelligent video processing platforms. As an important device in the transmission and perception layers of the Internet of Things, video servers are expected to usher in further development with the development and construction of the Internet of Things, integrating standard serial data channels, multi-channel switch input and output interfaces, sensor interfaces, etc.

2. Intelligentization

Intelligence is an important trend in the development of video servers. Intelligent video systems have more powerful intelligent features than ordinary network video surveillance systems. Through the processing and analysis of front-end information by the intelligent module on the video server, it can classify the detected objects, effectively filter out non-detected objects, track multiple moving targets and analyze them at the same time, identify suspicious activities and issue relevant alarm information in advance. Therefore, before the security threat occurs, it can prompt security personnel to pay attention to the relevant monitoring images, so that the security department has enough time to prepare for potential threats. In the process of building a smart city, the standard serial data channel and multi-channel switch input and output interface provided by the video server are used to connect a variety of sensor devices. The video server is transformed into a basic device for IoT perception and transmission layer interconnection, and other supporting products form a fully functional intelligent IoT comprehensive information platform. The comprehensive information platform uses the intelligent video server to comprehensively judge the alarm information perceived by the sensor network and the collected video information, and controls the PTZ to automatically track the target object through the video server. The alarm linkage is realized by intelligent behavior analysis of the target object. In this way, the false alarm rate and missed detection rate can be effectively reduced, the alarm accuracy can be improved, and the monitoring resources can be effectively utilized.

3. Wireless

With the development of new generation wireless communication networks such as 3G and WAPI, the increase in transmission bandwidth makes it possible to use public mobile communication networks for video transmission. Wireless networks such as 3G will increasingly serve the application of network video systems. Wireless video monitoring can quickly realize the establishment of monitoring systems, can quickly deploy and replace monitoring points, and can collect real-time, first-person images. In particular, the system deployment on mobile vehicles such as buses, taxis, and inland ships can improve the timeliness and accuracy of environmental change detection and event processing. With the maturity and application of next generation wireless network technology and LTE technology, the use of wireless for video transmission will become more popular and will promote the development of wireless transmission applications of high-definition video.

4. High Definition

High-definition video has become an urgent need. The image quality of CIF resolution cannot meet the needs of high-end customers such as finance and transportation. When network bandwidth is no longer a bottleneck restricting video high-definition, video servers that can achieve high-definition and full frame rate transmission will surely be pursued by customers. The high-definition that customers pursue not only requires that the images collected by the front-end CCD or CMOS sensor are high-definition, but also requires the video server to fully consider the high-definition image quality and encoding efficiency when compressing and encoding the images collected by the front end.

5. Standardization

As far as video surveillance systems are concerned, there is no unified standard at home and abroad. Different manufacturers use their own standards in front-end, control, platform, etc., which seriously hinders the development and industrialization of video surveillance technology. At present, domestic enterprise alliances, operators, etc. have formulated some relevant standards, such as China Telecom's "Global Eye" and China Unicom's "Wide Vision" standards. At the same time, domestic manufacturers have also begun to make products compatible and interconnected with each other and between products and platforms. In the international arena, Sony, Bosch, and Axis have also jointly launched the global ONVIF standard.

VII. Conclusion

With the continuous development and integration of video server related technologies, video servers will inevitably develop in the direction of integration, intelligence, wireless, high definition and standardization. With the accelerated construction of next generation networks and the intensive progress of FTTH projects, the development of video server technology will promote the video surveillance system to quickly enter the era of digitalization, informatization and intelligence.