With the market demand and the common development of security technology, the current network camera presents a situation of blooming. Various types of network cameras are widely used in all corners of the security field. Among them, high-definition cameras and smart cameras have become applications in the video surveillance industry. Mainstream products. So what is the development status of the network camera? What are the analysis principles of the network camera? What is the advantage of the development trend of the network camera under the high-definition tide?
First, the development status of network cameras
The digitalization, networking and integration of video surveillance has become a trend. Cameras as video surveillance front-end products undoubtedly play an important role in this transformation. In recent years, the camera market has shifted from analog cameras to network cameras. According to the data, network cameras have grown at a rate of no less than 50% per year in recent years, and the network camera market has ushered in a rapid development.
From the first professional standard H.264 network camera chip solution to the 720P network camera solution to the latest third-generation monitoring solution, the network camera technology has achieved significant breakthroughs and rapid application. As the core technology of network camera, video coding technology has been restricted by network conditions and codec technology. Now it is mature, and it has the characteristics of strong pertinence, multiple coding methods, superior performance and high adaptability. This paper mainly introduces and analyzes the video coding technology of network cameras.
Second, the network camera principle architecture
The network camera is a truly all-digital product. After the video signal is collected and digitized from the image sensor (such as CCD, CMOS, etc.), the subsequent processing uses digital signals to ensure the sharpness of the image, and the network is used to package and transmit the multimedia data. (video, audio, text information, etc.).
1. Video capture
The core component of the video capture part - an image sensor, mainly CCD and CMOS, the level of sensor performance directly determines the level of the camera. The CMOS image sensor has low bandwidth and inherent anti-halation characteristics, while maintaining the advantages of small size, light weight, low power consumption, high integration, and low price. The CCD image sensor has a wide application due to its high sensitivity and low noise. With the advancement of CCD and CMOS sensor technology, the difference between the two will gradually decrease, and the two will coexist for a long time. At present, all kinds of CCD and CMOS are competing to launch, each manufacturer has its own interface standard. Even if the physical interface on the surface is the same, the internal data is still different, so it needs to interface with the original sensor. In this regard, it is necessary for the chip manufacturer and the sensor manufacturer to coordinate and cooperate to have a better effect. This is also the homework that the network camera codec chip must do. For example, the Hi3515 and Hi3520 define the SONY 720PCCD interface that originally required CPLD transfer directly into the chip. The implementation of the CPLD requires the help of the original SONY factory. This directly helps some customers solve problems that were not available.
2. Encoding algorithm
With the development of video coding and processing algorithms, multiple image and video coding compression standards have been released for different application requirements. For example, MPEG is MPEG-1, MPEG-2, MPEG-4 for multimedia storage media and digital TV applications; real-time video communication for low bit rate; ITU-T applications have developed H.261, H.263, H. 263, H.264; In the face of the current and future security application field, China's AVS (AudioVideocodingStandard) working group independently developed the advanced digital audio and video codec technology standard AVS-S. It can be said that there are many choices of video surveillance coding standards, but currently the standards used by network cameras are MJPEG, MPEG4, H.264 and so on. M-JPEG is a motion still image compression technology, but M-JPEG only compresses intra-frame spatial redundancy, and does not compress temporal redundancy between frames, so compression efficiency is not high. The focus of MPEG-4 is to solve the problem of low-bandwidth audio and video transmission, making it one of the important trends developed by current network product manufacturers. H.264 is the current mainstream solution with high compression ratio and high image quality. Good network adaptability, its application range is wide, can adapt to different occasions, but the algorithm complexity is high, and it needs strong hardware support.
3. Coding and network
Currently, due to bandwidth and cost considerations, users are required to use higher code streams at the current cost; this puts high demands on the coding efficiency of network cameras. Network cameras transmit data over the network, and the implementation of the network transmission is not good, but too large data packets will cause network congestion, so the internal control of the encoder is very strict, and the requirements cannot affect the image quality. As the actual application requirements of network cameras continue to evolve and change, the requirements for chip coding are becoming more and more demanding, and a scene closer to reality is realized under the premise of higher compression ratio. For example, the compression solution provided by HiSilicon can achieve a compression ratio of 720P@2Mbps, which is 3-4Mbps higher than that of the general product, and at least 50% compression ratio is improved. The 2Mbps code rate has another meaning, that is, the user can Upgrade to 720P experience with increased network and storage costs. With the rapid application of 3G networks in the future, the coding methods supporting various networks have also become important development directions.
Third, the application
Stability and security are two very important features of video surveillance systems. Therefore, users should pay special attention to the stability and security of surveillance systems in practical applications. In the past, monitoring systems often used the monitoring mode of the analog camera DVR to realize data acquisition, storage and management. This mode is usually applied to close-range deployment. If a natural disaster or other disaster occurs, the monitoring data will most likely be damaged.
The emergence of network cameras has completely changed the previous monitoring mode. This mode uses the network as a link to separate the encoding and storage of data. It uses a special data storage device to realize long-distance data collection, storage and management. Extremely high stability and safety. For example, Suzhou World Expo security “Moat†checkpoints use a large number of network cameras. These network cameras are installed in all important checkpoints from Suzhou to Shanghai, and the monitoring centers are located in Shanghai and Suzhou. The data storage can be realized in Beijing. Several places, such as Shanghai and Suzhou, prevent data loss and damage, which greatly facilitates the viewing, command and scheduling of the monitoring system. At present, network cameras are widely used in transportation, finance, electricity, ports and important places.
Fourth, the development trend
With the subdivision of the security industry and the development of video surveillance in the direction of networking, intelligence and integration, the development of network cameras has gradually become more and more subdivided. HD and intelligence have become the main development direction of network cameras.
1. HD
HD has always been one of the goals pursued by network cameras. At present, most network cameras can reach megapixel level, but not all network cameras can achieve high-definition applications in practical applications, which requires network cameras to have high-definition performance in addition to their own. It also supports and matches access-related devices to achieve high-definition applications. As we all know, in the era of standard definition, the cascading of chips is realized by PCI. One PCI can transmit 2~3 DI uncompressed streams, but it can't be done in HD era. HD decoding data is not transmitted through PCI. On the display chip, so many programs will scale and output the high-definition image, so that the final effect can not be reflected in the real high-definition effect. For example, the high-definition cascade channel solution introduced by HiSili can realize zero-delay multi-chip transmission effect, and can match the integrated HD VGA output of the chip, and with DHCP technology, HD can be easily realized. 