Network monitoring application problem analysis
This article refers to the address: http://
The network infrastructure is one of the important factors for the good development of the network video surveillance market. At present, China's network video surveillance market lacks a good network infrastructure, which has hindered the application of network video surveillance, especially high-definition network video.
HD network cameras have a qualitative leap in image clarity, but also bring a series of problems to the network monitoring system:
· Network bandwidth is tense: the greater the resolution and the higher the resolution, the increased code stream will increase, increasing the network bandwidth pressure;
· Large storage space: double the data traffic, increase the storage capacity, and increase the pressure of network storage;
· Management platform hardware and software load is intensified;
· Construction costs doubled.
Therefore, in the pursuit of high image quality, the manufacturers of network video surveillance equipment have put forward the requirements to solve the above problems. Therefore, it is necessary to continuously develop the processing and control technology of the video stream to cope with the problems of high bandwidth and large capacity storage brought by high definition.
Video compression technology development
In the field of video surveillance, video compression coding formats have evolved from M-JPEG, H.263, MPEG4 to H.264. Currently, H.264 is the compression algorithm for mainstream applications. Its biggest advantage is its high data compression rate. Under the same image quality, H.264 compression ratio is 1.5-2 times that of MPEG-4. H.264 also has high-quality and smooth images with high compression ratio. Because of this, H.264-compressed video data requires less bandwidth and is more economical during network transmission, which saves a lot of money. User download time and data traffic.
Technically, H.264 concentrates on the advantages of previous standards and absorbs the experience accumulated in standard setting. Compared with H.263 and MPEG4, H.264 can greatly reduce the code rate, save up to 50% of the code rate, and effectively realize the code stream control. Nowadays, more manufacturers' network video products use advanced H.264 compression algorithms.
Code stream processing technology analysis
Even with the advanced H.264 compression algorithm, HD 720P requires 3-4M code stream, HD 1080P also needs 4-6M code stream, still can not solve the network, storage pressure and other issues, so there are multiple streams Processing method.
Stream mode selection function
Network cameras generally transmit audio and video streams, but support code stream selectable modes, namely: audio and video streams, pure video streams, and cameras that support pure audio stream mode. When selecting different flow modes according to different audio and video requirements, network pressure, storage pressure, and investment cost can be greatly alleviated.
Multiple coding techniques
HD network cameras support three encoding technologies, which support three different compression formats, JPEG/MPEG-4/H.264. These three streams can be set according to the customer's actual situation. For example, the D1 image of the lower stream H.264 video compression format is transmitted to the remote end for real-time monitoring by the client, and the megapixel H.264 video compression format real-time image is transmitted to the storage server for recording, and It is also possible to transmit a megapixel JPEG image at the time of an alarm, so that it is easy to zoom in and confirm afterwards to find suspicious objects. The combination of multiple coding technologies also solves the problem of relieving network pressure and storage pressure.
Dual stream processing technology
Dual stream, that is, two streams are coexisted in the network camera at the same time. The dual stream is implemented by separately encoding in two formats on the encoding side. One code stream is used for network transmission, and the other code stream is used for high-quality real-time storage. The dual code stream takes into account local storage and remote network transmission, and solves the bottleneck of network transmission. The implementation of dual stream has opened a new page for local storage. The code is separately coded and stored separately. The code stream size can be flexibly selected according to the network bandwidth, so that the local HD storage and the low code stream can coexist.
Multi-stream processing technology
Compared with the dual code stream, the multi-stream stream provides multiple independent selections for the output of the code stream, and multiple clients access the plurality of code streams preset by the camera. Such as: 3 million (15 frames / sec), 1080P (25 frames / sec), 720P (25 frames / sec) and D1 (25 frames / sec), each client can synchronously receive the preset stream. The technology is designed to provide multiple independent stream selections in a variety of application environments, while also reducing network load and stress. For example, 3 million for storage, 1080P for local client access, 720P for video wall display, D1 for remote client access, and smaller resolutions such as CIF or QCIF for mobile mobile users, which have no effect on each other and can be sent simultaneously. . In this way, there is only one choice in the network camera, which not only satisfies the requirements of high-definition monitoring, but also saves storage space.
At present, various manufacturers have different technologies for multi-stream processing. If multiple concurrent streams are supported, but these video streams must be configured with the same parameters, modify the parameter configuration of any code stream, such as resolution, frame rate, etc., then all other stream configurations will change. It is not possible to achieve true multi-stream control. True multi-stream technology, multiple streams are completely independent, and can be different resolutions, different frame rates, different compression ratios or different encoding methods. At the same time, in multi-stream performance. Supports multiple concurrent full resolution, full frame rate independent concurrent streams. In the industry, the existing network video products of the manufacturer have the multi-stream processing technology alone.
Flow control mechanism
For the network camera, in addition to multi-stream processing, a good flow control mechanism is implemented for each independently configured video code stream, which also plays an important role in the application. The code stream control includes a variable code stream, a constant code stream, and a maximum stream limit mode.
Variable variable stream, maintaining set video configuration parameters, such as resolution, frame rate, etc., the video stream bit rate will fluctuate up and down as the video content changes;
• Keep the video stream at a constant bit rate, and the image quality and stream will be adjusted as the video content changes. The user can also select image quality priority or frame rate priority while maintaining a constant bit rate;
The maximum flow limit is to allow the bit rate of the video stream to fluctuate up and down, but the maximum defined threshold is set. When the bit rate reaches the maximum defined threshold, the video quality will be reduced accordingly to keep the video stream from exceeding The set maximum threshold.
It can be seen that the true multi-stream technology provides good chip processing support, and can provide a variety of complete flow control management mechanisms to ensure the true availability of network video products in actual use and the rationalization of network video streams. Management to better meet the needs of real-world applications.
Conclusion
In short, to achieve better stream processing and control, to solve network, storage and other stress problems, in order to better meet the actual needs of high-definition network video surveillance. just now. Some security manufacturers' network video products have matured with H.264 compression algorithm and multi-stream processing technology. Their network video products are capable of meeting the needs of large-scale high-definition network video surveillance systems, and the overall cost of customers is reduced, while advanced. The technology will also promote the larger-scale application of HD network video surveillance in the security industry.
Small size Travel Power Strip, easy to carry with traveling. 1 universal Power Socket, 3 type of Plug EU/AU/US. 4 USB charging ports, 5V 4A output. socket of grooves on the side, storage power cord, easy to use.You can charge your device more freely on your journey.
Size:145x50x35mm, weight:175g.
PC/ABS flame retardant, phosphor bronze+pure copper.
Color of socket can be customized.
Travel Power Strip
Travel Power Strip, Power Socket, Portable Industrial Socket, Portable Rechargeable Extension Socket
ZhongShan JITONGLONG Plastic Hardware Co. Ltd. , https://www.toukoo-electronics.com