Improving NVR network video transmission performance through dual stream

The 2009 CPSE has come to a successful conclusion. Keda's network video surveillance products have attracted much attention at the exhibition, and the excellent image clarity of Keda's NVR has been unanimously recognized. While praising the image quality, many visitors also raised the following question: How does NVR ensure image transmission under different network conditions?

We know that as the image clarity of network video surveillance products continues to improve, the bandwidth environment required for the transmission of video streams by the surveillance system is becoming increasingly stringent: the clearer the image, the higher the bandwidth required for the transmission of the video stream. Therefore, the pressure on the network to carry surveillance resources is bound to increase, and even the performance of decoding equipment is facing huge challenges. Especially as high-definition surveillance is about to emerge, the industry is increasingly concerned about how high-definition surveillance manufacturers will solve the bandwidth environment problem. It is in this context that the dual-stream technology of video surveillance systems came into being and has become a popular trend.

Dual stream, as the name implies, means that the monitoring system encodes two video streams from the same video source. These two video streams can have the same video resolution or different video resolutions. In this way, when in use, the system can allocate corresponding video streams according to user needs, thereby reducing bandwidth pressure and effectively optimizing the network bandwidth environment.

At present, some manufacturers' network video front-ends can encode two streams with the same video resolution and transmit them to the browsing client and storage server respectively. This encoding and transmission method can fully reduce the stream forwarding pressure of the monitoring host, but it is very easy to cause network congestion and can only be used in occasions where the network bandwidth is very sufficient. As shown in the following figure:

Another situation is that some manufacturers' network video front-ends can generate two streams with different video resolutions. The stream with higher video resolution is used for video storage, and the stream with lower video resolution is used for real-time browsing. This can fully reduce the pressure on the network bandwidth occupied by remote browsing, but the usage is not flexible enough. Users can only browse low-resolution images when the bandwidth is sufficient. As shown in the following figure:

Combining the advantages and disadvantages of the above two methods, Kodak NVR provides a more comprehensive and complete dual-stream function.

Keda NVR cooperates with the network front end to compile two video streams with different video resolutions. The high video resolution stream is used as NVR local storage, and during real-time browsing, the NVR can automatically adjust according to the size of the user's browsing screen and the network bandwidth. For example: when the user sets the high video resolution stream to D1, the real-time browsing stream can be automatically adjusted between D1, CIF and QCIF, so as to fully adapt to different network bandwidth environments.

Keda NVR dual-stream performance has two advantages:

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First, when the bitstream of the video resolution used for recording remains unchanged, the video resolution can be automatically adjusted according to the actual bandwidth of the user to browse the video image. In this way, when the user's bandwidth is low, the video image can be browsed in a low video resolution mode, while users with more abundant bandwidth can browse the video in a high video resolution mode. As shown in the following figure:

Second, when the bitstream of the video resolution used for recording remains unchanged, the video resolution can be automatically adjusted to browse the video image according to the different ways of screen segmentation used by the user's client. That is, when the user browses with a large screen, the NVR will transmit a high-resolution video bitstream, and when the user browses with a small screen, it will transmit a low-resolution video bitstream, thereby fully improving the performance and efficiency of the decoding device. As shown in the following figure:

It can be seen that the dual-stream feature of Kodak NVR can be flexibly set in many aspects according to the user's different application needs and bandwidth environment, so that it can better meet the requirements of network video surveillance transmission and help users browse more video images at the same time under limited computer performance conditions without affecting the quality of video recording.