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1, warranty issues
The issue of warranty is one of the most important issues for the contractor. As the contractor directly faces the end-user, unsatisfactory warranty service will directly affect the reputation of the contractor. General manufacturers implement one-year free warranty on products.
2. Actual bandwidth requirements for transmitting standard real-time moving images
This is one of the important indicators to measure the overall performance of the network video server. High bandwidth means the increase in network usage costs. For end users, this will shake their determination to adopt a digital surveillance model. After all, economics is a problem that any business unit has to consider.
Due to different image states (static, normal activity, high-speed motion), image resolution, and transmission image frame rate, the occupied network bandwidth varies greatly. Therefore, many network video server manufacturers always try to blur this when introducing products. An indicator. In this regard, we can set a more unified image state, that is, for a normal moving image, the image bandwidth reaches 352*288, and the frame rate is 25 frames/s. According to our understanding, the bandwidth requirements of a considerable number of manufacturers including Taiwan and South Korea are between 500-600K, and some even require 800-900K.
3, the delay of remote video transmission
Although the transmission delay is unavoidable for any network video server, different network video servers have different delay values. The level of delay will directly affect the effect of digital monitoring. Imagine that when the monitoring staff mouse-controlled the front-end camera head at the monitoring center, he clicked on the mouse five times within five seconds, and after tenth second saw the first time after the first click on the display What will happen if you control the effect?
Due to different transmission delays at different frame rates (the same product, the higher the frame rate, the lower the transmission delay), for the sake of contrast uniformity, the condition is set to 25 frames per second. Guangzhou Xiangte Information Technology Co., Ltd.'s "Xian Vision" network video server uses MPEG-4 enhanced coding technology, transmission delay does not exceed one second, greatly improving the performance of the cloud mirror control, remote real-time monitoring.
4, image resolution
The resolution of the digitized video image will directly affect the sharpness of the surveillance image. The so-called standard image resolution in the current line refers to 352*288 pixels and is adjustable downwards. This can be achieved by an ordinary network video server. However, in some special occasions, such as in an unattended power room, monitoring of an almost static meter through an online video server (need to see the meter scale value) requires higher resolution. Guangzhou Xiangte Information Technology Co., Ltd.'s "View" network video server uses a unique sampling technology that can achieve up to 704 * 576 image resolution.
5, image compression algorithm standard
The current mainstream network video server compression algorithm standards are nothing more than MJPEG, MPEG-1, MPEG-4.
MJPEG compression technology is based on JPEG image compression technology. It is a simple intra-frame JPEG compression. After compression, the image clarity is better. However, due to the technical limitations of this method, it can not be compressed in large proportion, the data volume is high, the video is 1-2G space per hour, and the network transmission consumes a large amount of bandwidth resources, which is not suitable for the compression of moving objects and is not so large. Suitable for domestic long-term security video needs.
MPEG-1 compression technology uses compression algorithms for multi-frame prediction before and after frames, which has great compression flexibility and is the most widely used. This algorithm technology is mature and the data compression rate is higher than that of MJPEG, but the data volume is still large. Video 300-400M space per hour, if used for long-term bank real-time video recording, taking up more space on the hard disk, especially the network transmission occupying a larger bandwidth, is not really used for long-distance video image transmission.
WHITE-SPACE:normal;LETTER-SPACING:normal;BACKGROUND-COLOR:rgb(255,255,255);orphans:2;widows:2;-webkit-text-size-adjust:auto;-webkit-text-stroke-width:0px ">MPEG-4 compression technology is the most advanced compression technology currently in practical use. It uses a very narrow bandwidth and compresses and transmits images through frame reconstruction techniques to obtain the best image quality with the least amount of data. 4 features make it more suitable for interactive AV services and remote monitoring, the use of MPEG-4 compression algorithm, image compression is relatively high, video 100-200M per hour space, high image resolution, network transmission occupies a small bandwidth, can be through various Transmission mode for remote video transmission.
6. The number of video channels that the monitoring center can simultaneously monitor and record
Since the network video surveillance server is used for remote, real-time, centralized monitoring of multiple distributed network points, the number of video channels that the monitoring center can monitor and record at the same time is an important indicator to measure the effect of remote centralized monitoring.
7, the number of frames transmitted by the multi-channel network video server
The current network video server supports one or two or four video input. As the number of supported image channels increases, the product technology and processing performance requirements are higher, so most products are single-channel or “quasi-multiple†products.
What we call a true multi-channel network video server that can support 25 frames/s of digital video output per channel is truly “real timeâ€. The “quasi-multi-channel†product, regardless of two or four channels, outputs 25 frames per second of the total frame number of digital video images, that is, multi-channel sharing of 25 frames per second, in terms of image processing technology and single-channel products. There is almost no difference. This point can be easily distinguished from the price, some manufacturers of single and two-way product prices only differ by a thousand or so, basically can determine its two-way products as "quasi-two products."
8, alarm pre-trigger video function
Various network video servers on the market are quite perfect in video recording functions. There are real-time recordings, scheduled recordings, and alarm recordings. Alarm recordings can be divided into mobile triggered recordings, manual triggered recordings, and external sensors (such as infrared detectors) to trigger recording. Wait. However, if an alarm is triggered manually, it is basically started before the end of the accident. The video recording can only be the image after the alarm is triggered. For postmortem tracking of events, their records are incomplete.
At present, there are a few manufacturers of network video servers already have alarm pre-triggered video recording function, and can save image signals from a few seconds to several tens of seconds before the alarm is triggered. This function is of special significance to the user's subsequent alarm event tracking judgment.
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