Four Misunderstandings and Two Key Considerations for Network Camera Selection
In the current video surveillance field, IPC network HD cameras have become a trend. In engineering projects, there are various forms of IPC, and there are some misunderstandings in resolution, infrared distance, compatibility and remote access.
Analog Cameras We generally use the number of lines (TVL) to indicate the clarity of the camera. Network cameras generally use resolution to indicate sharpness.
The current mainstream IPC resolutions are:
720P: 1280*720, corresponding to 1 million pixels, recommended code stream: 2M;
960P: 1280*960, corresponding to the pixel 1.3 million, recommended code stream: 3M;
1080P: 1920*1080, corresponding to 2 million pixels, recommended code stream: 4-5M;
1536P: 2048*1536, corresponding to 3 million pixels, recommended code stream: 5M;
4K: 3840*2160, corresponding to 8 million pixels, code stream: 8M or more;
Myth 1: The higher the resolution, the better.
High resolution, high code stream: Choosing the right resolution depends on the actual needs of the project. The current encoding is H.264 algorithm. The higher the resolution, the larger the code stream, and the more hard disk space is occupied per unit time. The cost of IPC is getting lower and lower, but the cost of hard disk that can't be ignored is rising. Therefore, the IPC resolution of most projects is mainly 960P and 1080P.
In addition, the current market is mixed, manufacturers who do not pay attention to the brand image, usually use high-rate low-stream to attract attention, but if the number of frames is not enough (less than 25 frames / sec), the picture is not real-time, the resolution is high and egg;
Myth 2: The higher the resolution, the better the night vision effect.
Not necessarily, the night vision effect is mainly to see the photographic capability of IPC's CMOS chip, the chip illumination is not strong, and the resolution is high and the night vision effect is not good.
Infrared illumination distance error:The infrared distance is usually marked on the infrared gun machine parameter table, for example, the infrared distance is 50 meters. However, in the actual use process, some engineering companies generally reflect that the infrared distance is not enough, and the parameters marked have moisture.
Aside from the falseness of the product parameters, the parameter mark 50 meters generally refers to the infrared illumination distance under the appropriate lens. The infrared light we see is actually used to collect the light cup. The light cup is angled. The principle of a flashlight cup is the same. The narrow angle of illumination is far, and the wide angle is close. The size of the lamp cup is matched to the lens of the camera.
This is a good understanding, with an infrared distance of 50 meters, the actual matching 4mm wide-angle lens, the infrared gun's illumination distance is certainly less than 50 meters.
Therefore, in the design stage of the project plan, the layout of the infrared camera needs to pay attention to simultaneously: the angle of view, the lens, the infrared distance and other factors. Otherwise, the source of the design phase is wrong, and the final effect is not good.
At present, the most widely used HD network monitoring system is the ONVIF-compatible protocol, and has become the platform standard for unified management of domestic network cameras. Therefore, the high-definition network cameras provided by the manufacturers should be able to support the latest version of the ONVIF protocol, which is compatible with the use of more products and unified management to achieve interconnection and data sharing.
Even so, compatibility issues in IPC selection still deserve attention.
Different brands in the front and back end, although most of the IPC functions can be realized through the ONVIF protocol, due to the limitations of the public protocol, some functions of the backend to the camera cannot be used, such as: modification of IP address, parameter setting, alarm linkage, etc. . Although the camera's client or IE browser can maximize the function of the camera, considering the integrity, the front and rear end of the same brand using the proprietary protocol docking is the best choice.
In addition, there are still some uncertainties in the interconnection problem of different brands of ONVIF protocol. If it is not self-tested, it is best to listen to the opinions of the manufacturers. The compatibility issues are given by the manufacturers to the test opinions and results.
Entering the era of network monitoring, remote access has become an essential requirement for monitoring engineering. However, the effects usually made are often unsatisfactory. The engineers often feedback the remote access screen too card, or they are often dropped. Now do some analysis on the root cause of this problem:
P2P penetration technology
P2P is short for English Peer-to-Peer (peer-to-peer), also known as "peer-to-peer." P2P (Peer-to-Peer Communication) technology is a new network technology that relies on the computing power and bandwidth of participants in the network, rather than concentrating on a small number of servers.
Advantages: no port mapping is required, each device has a unique ID identifier registered, simple and convenient to set up, point-to-point connection, plug and play, suitable for the environment where the access end has no fixed IP;
Disadvantages: Devices generally need to rely on third-party P2P servers for registration. The stability of cloud servers is the key to stable access;
The front-end IPC publicizes a fixed external network IP, self-built forwarding service, and remote addressing directly accesses the fixed IP.
Advantages: Do not rely on third-party platforms, own fixed IP, and good stability.
Disadvantages: high cost, technical difficulty, and difficult maintenance.
Bandwidth is key:Usually, the broadband we access is ADSL or fiber-optic line. The bandwidth is generally 10M or 100M. This figure generally refers to the downlink bandwidth. However, our remote access IPC occupies the upstream bandwidth of the visited end. In general, 10M fiber optic line, the upstream bandwidth will not exceed 2M, that is to say, if the remote access to use 720P resolution screen, all the way is very reluctant.
In order to solve this problem, in the actual application of the project, remote access is usually uploaded by sub-stream, such as D1/CIF. If the remote image quality is to be synchronized with the scene, only the self-built private network or the leased line will be used, but the cost is not affordable for the general project.
Therefore, the engineering business friend during the project negotiation phase, remote access is the highlight of the project, but can not pull Party A's expectations too high, should let Party A have a clear understanding of the bandwidth issue, otherwise, the effect will not meet the design expectations, It is not worth the loss for the engineering acceptance.
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