Take you to understand the clear principle of Wuxi HD monitoring
Wuxi HD monitoring is the traditional HD monitoring, which is divided into three types: analog, digital and network. The front end of analog monitoring is analog video camera The back end is a matrix. The front end of digital monitoring is also an analog camera, and the back end is a DVR.
For video surveillance, image clarity is undoubtedly the key feature. The clearer the image, the more obvious the details, the better the viewing experience, and the higher the accuracy of intelligent and other applications. Therefore, image clarity is the eternal pursuit of video surveillance.
The standard for measuring image clarity is resolution, and the unit is pixel. The higher the value, the clearer the image. The difference between HD and SD is also reflected here. The dividing line between the two is megapixel or 720p, and the one reaching megapixel or 720p is high-definition. Based on such a standard, CIF and D1, which currently occupy the mainstream in the video surveillance market, belong to Standard Definition.
HD has more advantages than SD in terms of resolution, display effect and smoothness. In terms of resolution, 720p resolution is 9 times the CIF resolution, and 1080i/1080p resolution is 20 times the CIF resolution. In the same display environment, HD will be much clearer. From the perspective of display effect, HD supports both large screen display and 16:9 widescreen display, which can greatly enhance the viewing experience of users.
From the perspective of smoothness, HD supports a higher frame rate. For example, 720p and 1080i/1080p can both support 60 frames/second or 60 fields/second, and its image smoothness is twice as high as standard definition. Therefore, HD monitoring will inevitably replace SD monitoring.
In order to realize true HD monitoring, HD must be fully supported from the aspects of video source acquisition, video signal coding and compression, video signal transmission, video browsing, video file playback, etc. For customers, HD is meaningful only when it includes front-end, platform, storage, browsing, display and other aspects.
The uncompressed HD video signal after acquisition has two transmission modes: analog and digital. The analog transmission generally adopts YPbPr component transmission. One channel of HD video signal requires three coaxial cables to transmit simultaneously. Digital transmission generally adopts DVI, HDMI or HD-SDI transmission. The transmission distance of DVI or HDMI is only a few meters, which is not suitable for monitoring transmission. HD-SDI can transmit about 100 meters, but it has high requirements for coaxial cables and is very expensive. However, if the HD video is compressed efficiently at the front end and then transmitted over the IP network, the transmission cost is equivalent to the standard definition monitoring network transmission cost.
At present, the video signal processing of DVR is divided into two parts: video capture and video coding. In the video signal acquisition part, most of the current DVRs are analog video inputs, using CVBS (composite video signal) signal input of BNC interface. The resolution of composite video signal is D1, and the composite video signal is collected and quantized according to D1 resolution in DVR. At present, there is no analog component interface of YPbPr or digital video interface of DVI, HDMI, HD-SDI, etc. for DVRs. In the encoding part, DVR can encode each collected video signal into CIF, 2CIF, DCIF, D1 and other resolutions, but the encoding resolution can only be D1, and does not have the encoding capability of 720p or 1080i, 1080p.
