Network Monitoring Application Problem Analysis
The network infrastructure is one of the important factors for the development of the network video surveillance market. At present, China's network video surveillance market lacks a good network infrastructure, which makes the application of network video surveillance, especially high-definition network video, obstructed. While the HD network cameras have made a qualitative leap in image clarity, they have also brought a series of problems to the network monitoring system:
· Network bandwidth is tight: The larger the resolution and the higher the resolution, the larger the code stream will be transmitted, which will increase the network bandwidth pressure. The storage space is large: the data traffic will double, increasing the storage capacity and increasing the network storage. The pressure; management platform hardware and software load intensified; construction costs doubled.
Therefore, while pursuing high image quality, the manufacturers of network video surveillance equipment have proposed solutions to the above problems. Therefore, there is a need for continuous development of video stream processing and control techniques to deal with high-bandwidth, high-capacity storage and other issues brought about by high-definition video.
Video compression technology development
In the field of video surveillance, the video compression coding format has evolved from M-JPEG, H.263, MPEG4 to H.264, and currently H.264 is a compression algorithm for mainstream applications. Its biggest advantage is that it has a very high data compression rate. Under the same image quality conditions, the compression ratio of H.264 is 1.5-2 times that of MPEG-4. H.264 also has high-quality and smooth images while having a high compression ratio. Because of this, H.264-compressed video data requires less bandwidth and is more economical in the network transmission process, resulting in significant savings. User's download time and data traffic.
Technically, H.264 concentrates on the advantages of previous standards and absorbs experience gained in standard setting. Compared with H.263 and MPEG4, H.264 achieves a significant reduction in bit rate, which can save up to 50% of code rate, and effectively achieves bit stream control. There are more manufacturers of network video products are using advanced H.264 compression algorithm.
Stream Processing Technology Analysis
Even with advanced H.264 compression algorithms, HD 720P requires 3-4M stream, HD 1080P also requires 4-6M stream, still can not solve the network, storage pressure and other issues, so there is a variety of streams Treatment method.
Flow mode selection function
Network cameras generally transmit audio and video streams, but support optional stream modes, namely, audio and video streams, pure video streams, and cameras that support pure audio stream mode. In accordance with different audio and video needs, select the appropriate flow mode, can greatly ease the network pressure, storage pressure, reduce investment costs.
Multiple encoding techniques
Most HD network cameras support three encoding technologies, namely, three different compression formats, JPEG/MPEG-4/H.264. These three kinds of code streams can be set according to the actual situation of customers. For example: D1 images of the lower bit rate H.264 video compression format are sent to the remote site for real-time monitoring, and the real-time image of the megapixel H.264 video compression format is transferred to the storage server for recording. It is also possible to transmit a megapixel JPEG image at the time of the alarm so that it can be enlarged and confirmed afterwards, and suspicious objects can be found. The co-application of multiple coding technologies also solved the problem of mitigating network pressure and storage pressure.
Dual-stream processing technology
Dual stream, that is, simultaneously coexisting two kinds of code streams in the network camera. Dual-streaming is achieved by encoding at the encoder side using two formats. One kind of code stream is used for network transmission, and the other kind of code stream is used for high-quality real-time storage. Dual code stream also takes into account local storage and remote network transmission, which solves the bottleneck of network transmission. The implementation of dual stream, opened a new page for local storage. Separately encoded and stored separately, the size of the stream can be flexibly selected according to the network bandwidth, making it possible to coexist locally with high-definition storage and low-stream transmission.
Multi-stream processing technology
Compared to dual-stream, multi-stream provides multiple sets of independent choices for the output of the stream, and multiple clients respectively access the multiple streams preset by the camera. For example: 3 million (15 frames/second), 1080P (25 frames/second), 720P (25 frames/second), and D1 (25 frames/second), each client can synchronously receive the preset stream. The technology is to achieve a variety of application requirements in the environment, the camera can provide a variety of independent code stream selection at the same time, and can also reduce the network load and pressure. For example, 3 million for storage, 1080P for local client access, 720P for video wall display, and D1 for remote client access, and smaller resolutions such as CIF or QCIF for mobile phone users, which have no effect on each other and can be sent at the same time . As a result, there is only one choice in the network camera, which not only meets the need for 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, modifying any parameter configuration of one stream, such as resolution, frame rate, etc., all other stream configurations will change. It cannot be truly multi-stream control. With true multi-stream technology, multiple streams are completely independent and can be configured with different resolutions, different frame rates, different compression ratios, or different encoding methods. At the same time, multistream performance Supports multiple concurrent full resolution, full frame rate independent concurrent streams. In the industry, existing vendors' network video products have this multi-streaming separate processing technology.
Flow control mechanism
For network cameras, to handle multiple streams, for each independently configured video stream, a good flow control mechanism is implemented, which also plays an important role in the application. The stream control includes a variable stream, a constant stream, and a maximum stream restriction mode.
·Variable stream, maintaining the set video configuration parameters, such as resolution, frame rate, etc., the bitrate of the video stream will fluctuate up and down as the content of the video changes; keeping the video stream at a constant bitrate, and the image quality The stream will be adjusted as the content of the video changes. The user can also select the picture quality priority or frame rate priority while maintaining a constant bit rate; the maximum stream restriction allows the bit rate of the video stream to fluctuate up and down, but sets the maximum limit threshold when the bit rate reaches At the maximum limit, 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 accordingly, in order to ensure the real availability of network video products in practical use and the rationalization of network video streams. Management to better meet the needs of practical applications.
Conclusion
In short, to achieve better code stream processing and control, to solve the network, storage and other pressure issues, in order to better meet the actual needs of high-definition network video surveillance. just now. Some H.264 compression algorithms and multi-stream processing technologies of network security product manufacturers of security companies are relatively mature. Their network video products have been able to meet the needs of large-scale high-definition network video surveillance systems and reduce the overall input costs of customers. The technology will also promote the larger-scale application of high-definition network video surveillance in the security industry.
The network infrastructure is one of the important factors for the development of the network video surveillance market. At present, China's network video surveillance market lacks a good network infrastructure, which makes the application of network video surveillance, especially high-definition network video, obstructed. While the HD network cameras have made a qualitative leap in image clarity, they have also brought a series of problems to the network monitoring system:
· Network bandwidth is tight: The larger the resolution and the higher the resolution, the larger the code stream will be transmitted, which will increase the network bandwidth pressure. The storage space is large: the data traffic will double, increasing the storage capacity and increasing the network storage. The pressure; management platform hardware and software load intensified; construction costs doubled.
Therefore, while pursuing high image quality, the manufacturers of network video surveillance equipment have proposed solutions to the above problems. Therefore, there is a need for continuous development of video stream processing and control techniques to deal with high-bandwidth, high-capacity storage and other issues brought about by high-definition video.
Video compression technology development
In the field of video surveillance, the video compression coding format has evolved from M-JPEG, H.263, MPEG4 to H.264, and currently H.264 is a compression algorithm for mainstream applications. Its biggest advantage is that it has a very high data compression rate. Under the same image quality conditions, the compression ratio of H.264 is 1.5-2 times that of MPEG-4. H.264 also has high-quality and smooth images while having a high compression ratio. Because of this, H.264-compressed video data requires less bandwidth and is more economical in the network transmission process, resulting in significant savings. User's download time and data traffic.
Technically, H.264 concentrates on the advantages of previous standards and absorbs experience gained in standard setting. Compared with H.263 and MPEG4, H.264 achieves a significant reduction in bit rate, which can save up to 50% of code rate, and effectively achieves bit stream control. There are more manufacturers of network video products are using advanced H.264 compression algorithm.
Stream Processing Technology Analysis
Even with advanced H.264 compression algorithms, HD 720P requires 3-4M stream, HD 1080P also requires 4-6M stream, still can not solve the network, storage pressure and other issues, so there is a variety of streams Treatment method.
Flow mode selection function
Network cameras generally transmit audio and video streams, but support optional stream modes, namely, audio and video streams, pure video streams, and cameras that support pure audio stream mode. In accordance with different audio and video needs, select the appropriate flow mode, can greatly ease the network pressure, storage pressure, reduce investment costs.
Multiple encoding techniques
Most HD network cameras support three encoding technologies, namely, three different compression formats, JPEG/MPEG-4/H.264. These three kinds of code streams can be set according to the actual situation of customers. For example: D1 images of the lower bit rate H.264 video compression format are sent to the remote site for real-time monitoring, and the real-time image of the megapixel H.264 video compression format is transferred to the storage server for recording. It is also possible to transmit a megapixel JPEG image at the time of the alarm so that it can be enlarged and confirmed afterwards, and suspicious objects can be found. The co-application of multiple coding technologies also solved the problem of mitigating network pressure and storage pressure.
Dual-stream processing technology
Dual stream, that is, simultaneously coexisting two kinds of code streams in the network camera. Dual-streaming is achieved by encoding at the encoder side using two formats. One kind of code stream is used for network transmission, and the other kind of code stream is used for high-quality real-time storage. Dual code stream also takes into account local storage and remote network transmission, which solves the bottleneck of network transmission. The implementation of dual stream, opened a new page for local storage. Separately encoded and stored separately, the size of the stream can be flexibly selected according to the network bandwidth, making it possible to coexist locally with high-definition storage and low-stream transmission.
Multi-stream processing technology
Compared to dual-stream, multi-stream provides multiple sets of independent choices for the output of the stream, and multiple clients respectively access the multiple streams preset by the camera. For example: 3 million (15 frames/second), 1080P (25 frames/second), 720P (25 frames/second), and D1 (25 frames/second), each client can synchronously receive the preset stream. The technology is to achieve a variety of application requirements in the environment, the camera can provide a variety of independent code stream selection at the same time, and can also reduce the network load and pressure. For example, 3 million for storage, 1080P for local client access, 720P for video wall display, and D1 for remote client access, and smaller resolutions such as CIF or QCIF for mobile phone users, which have no effect on each other and can be sent at the same time . As a result, there is only one choice in the network camera, which not only meets the need for 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, modifying any parameter configuration of one stream, such as resolution, frame rate, etc., all other stream configurations will change. It cannot be truly multi-stream control. With true multi-stream technology, multiple streams are completely independent and can be configured with different resolutions, different frame rates, different compression ratios, or different encoding methods. At the same time, multistream performance Supports multiple concurrent full resolution, full frame rate independent concurrent streams. In the industry, existing vendors' network video products have this multi-streaming separate processing technology.
Flow control mechanism
For network cameras, to handle multiple streams, for each independently configured video stream, a good flow control mechanism is implemented, which also plays an important role in the application. The stream control includes a variable stream, a constant stream, and a maximum stream restriction mode.
·Variable stream, maintaining the set video configuration parameters, such as resolution, frame rate, etc., the bitrate of the video stream will fluctuate up and down as the content of the video changes; keeping the video stream at a constant bitrate, and the image quality The stream will be adjusted as the content of the video changes. The user can also select the picture quality priority or frame rate priority while maintaining a constant bit rate; the maximum stream restriction allows the bit rate of the video stream to fluctuate up and down, but sets the maximum limit threshold when the bit rate reaches At the maximum limit, 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 accordingly, in order to ensure the real availability of network video products in practical use and the rationalization of network video streams. Management to better meet the needs of practical applications.
Conclusion
In short, to achieve better code stream processing and control, to solve the network, storage and other pressure issues, in order to better meet the actual needs of high-definition network video surveillance. just now. Some H.264 compression algorithms and multi-stream processing technologies of network security product manufacturers of security companies are relatively mature. Their network video products have been able to meet the needs of large-scale high-definition network video surveillance systems and reduce the overall input costs of customers. The technology will also promote the larger-scale application of high-definition network video surveillance in the security industry.
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