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HD monitoring problems
HD network cameras have made a qualitative leap in image clarity, but they have also brought a series of real problems to high-definition surveillance systems. The three core issues to be solved by HD monitoring are: bandwidth issues, display problems, and storage problems.
Bandwidth problem: Due to the current limited network bandwidth, the high bit rate brought by high-definition video has become its biggest promotion bottleneck. How to transmit as high quality video as possible with the lowest possible bit rate is the top issue that HD surveillance needs to solve. At the same time, due to the heterogeneity of the network, different networks have different channel characteristics. Different users enjoy different network bandwidths. Even the bandwidth of the same user may change at any time. With the development of the monitoring field, various user terminals have the need to connect to monitoring video. For example, the network bandwidth of the local area network monitoring network is ideal. Users want to browse high-quality video. In the field of mobile phone monitoring, because the bandwidth is limited, users value the low code. Rate video fluency. How to adapt to these different bandwidth environments is also a problem that HD surveillance devices need to solve.
Display problem: Compared with standard definition video, the amount of high-definition video information is abundant, and the corresponding requirements for decoding display performance are also greatly improved. For example, the current mainstream PC can easily achieve 8-channel D1 standard definition video decoding display, but if the front end is 1080P high-definition video, can only barely decode and display 1 way. For large-scale video surveillance platforms, if all use high-definition video, server decoding pressure will be great.
Storage issues: The increase in image resolution will inevitably consume more storage space. Taking 1920×1080@30 frames of video as an example, using the H264 encoding algorithm, to ensure clarity, the code stream needs to be maintained at more than 6Mbps, which is about 4-8 times of standard definition video. Under standard definition video conditions, a 16-channel DVR built-in 8 fast 2T hard disk can meet the long-term video storage requirements. In high-definition monitoring, this time will be greatly shortened, which will bring about increased storage costs.
Application of Video Coding Technology in High-definition Monitoring System
The development of video coding technology has brought a new method to solve the above-mentioned high-definition monitoring problems. Through the improvement of the encoding method, the applicability of high-definition video can be greatly improved, enabling it to adapt to more monitoring scenarios.
An enterprise in the industry has been committed to the research, development and promotion of high-definition video surveillance equipment. It has achieved a number of technological breakthroughs in the core algorithms of video compression. Currently, there are areas of interest that include compression coding technology, scalable coding technology, and intelligence. "Front-end" dynamic coding adaptive technology.
Region of Interest Compression Coding (ROI): Video compression ratio and video quality are contradictory bodies. The higher the compression ratio, the more video loss, and the worse the corresponding video quality. However, when watching video surveillance, people usually only interested in a specific area (usually the central area of ​​the video). The images in this area should be as clear as possible, and other parts of the image may be relatively blurred. Based on the above requirements, a compression coding technique for an image region of interest arises, that is, lossless compression or lossless compression of a region of interest in an image, and lossy compression of a background region. This can not only make the reconstructed image have higher video quality, but also get a higher compression ratio, which solves the contradiction between compression ratio and image quality.
Picture 1 is the original image; Picture 2 is compressed and generated by an ordinary video encoding algorithm without ROI processing. Obviously, the entire picture has become blurred due to the loss caused by video compression; the face image that is more interested in monitoring has been performed. ROI processing, coding to get picture 3. It can be seen that the sharpness of the background area is similar to that of the picture 2, but since the face is subjected to ROI processing, more details are saved and visually clearer than the picture 2. In high-definition equipment, compression is performed using a high compression ratio, and the central area of ​​interest for monitoring is processed using ROI technology to obtain lower bit rate, high-vision-quality video.
Scalable video coding technology: It is achieved by dividing a single stream into several layers. If the codestream generated by the video encoder after one-time compression can be decoded by the decoder at different code rates, frame rates, spatial resolutions, and video quality, the codec system is said to have "scalability". From this definition, we can see that scalable encoding only needs to encode the video program source once, and then it can reconstruct the video with various resolutions, bit rates, or quality levels by transmitting, extracting, and decoding the corresponding part of the compressed code stream. Compared with the currently used simulcast encoding method, this encoding method has a stronger ability to satisfy various different needs and greatly improves the encoding efficiency.
The single code stream provided by the encoder has a scalable feature and can automatically adapt to the user network's network status and terminal equipment. In a network with a good bandwidth, high-resolution and high-quality video can be transmitted, and in a low-bandwidth environment such as mobile phone monitoring, only low-resolution and low-stream video can be transmitted.
The basic idea of ​​scalable video coding is described as follows: The encoder encodes the video sequence into a base layer and multiple enhancement layers, as shown in FIG. The base layer has the lowest video quality, and the enhancement layer can improve the quality of the base layer. High-definition monitoring equipment can select the amount of data to send based on bandwidth and terminal requirements.
For example, in a space scalable encoding application, the resolution of the mobile video is small. In this case, there is no need to transmit more enhancement layers (corresponding to a higher spatial resolution), and only the basic layer suitable for the resolution of the mobile phone can be transmitted. . The receiving end decodes the corresponding quality video according to the received data.
The more enhancement layers received, the better the decoded video quality. It is usually assumed that the base layer data is lower than the minimum transmission bandwidth, so the decoder can always decode the lowest quality video. By using a high-definition video encoder that uses scalable video coding technology, it can adapt to the video monitoring requirements under various network bandwidth conditions, and the bandwidth problem is no longer a problem. At the same time, the decoding end can also choose to solve only the basic layer according to its own decoding capability. The video still decodes more enhanced video, which greatly eases the problem of insufficient display capability when displaying high-definition video.
"Smart front end" dynamic coding adaptive technology: Through the application of "region of interest coding technology" and "scalable video coding technology", the pressure on network bandwidth and decoding display capability in high-definition surveillance video is greatly reduced, but it takes up much storage space. The problem has not been solved in nature. The development of intelligent video analytics technology has brought new ways to solve this problem.
Most of the videos in the surveillance industry are redundant. Users are more concerned with the specific video when abnormal events occur. The "smart front-end" high-definition network cameras, combined with intelligent analysis algorithms, can achieve cross-border, mixed lines, and regional stays. Remaining behavior analysis. In the normal state, "insignificant" video streams are recorded in SD format. Once an abnormal state occurs, the video is automatically switched to HD video, which ensures the details of the surveillance video without causing excessive pressure on the storage. Improve the efficiency of effective video retrieval. Verified, can save 30% -50% of storage space.
Conclusion
The progress of video coding technology has brought new developments to high-definition surveillance, effectively alleviating the bottlenecks that high-definition video surveillance has encountered in terms of network bandwidth, decoding and display capabilities, and storage resources, becoming the most powerful boost for the overall high-definition monitoring industry. power. Some security companies are positioning themselves as technology-leading enterprises, adhering to the development direction of high-definition and intelligentization, giving full play to their core technology advantages in video coding, and continuously blazing new trails, serving the society, and serving users, helping the security industry to achieve full HD development of.
In recent years, the construction and application of high-definition surveillance systems has become a trend. Video surveillance has evolved from the "visible" standard-definition video security system to "visible" high-definition video surveillance systems. In 2011, as the outbreak year of high-definition products in the surveillance field, more and more manufacturers have joined this field and launched a series of high-definition video surveillance products. The front-end lens manufacturers and chip makers are also adopting high-definition video solutions. In the market, high-definition solutions have gradually become popular in areas such as transportation and bayonet, and the market share of high-definition surveillance in the traditional surveillance areas is also gradually increasing. According to a report released by the international authoritative electronics industry research organization IMSRESEARCH, the next five years, high-definition monitoring The market share of products will exceed the traditional standard definition monitoring products.