Basic Concepts in video surveillance

DVR (Digital hard disk recorder) It is the second generation monitoring system (CCTV first generation) which developed rapidly after the simulation video system in recent years.

DVR System Features: video, audio signal collection, storage is mainly digital form, high quality, system function is more powerful, perfect, and information system can exchange data, application flexibility is better. However, due to the limitations of its own technical architecture, digital DVR is unable to solve the long delay in network remote monitoring environment, can not multi-channel simultaneous monitoring, high integration and centralized monitoring and so on. The reason is that the DVR system from the monitoring point to the Monitoring Center for analog transmission, and the first generation of systems similar to the existence of many shortcomings, to achieve long-distance video transmission needs to lay (leased) optical cable, cable ends of the installation of video optical end machine equipment, high-cost system construction, difficult to maintain and maintenance costs. The system is only suitable for the transformation of the traditional monitoring system, it is not suitable for the new monitoring system and the system requiring remote video transmission (more than two kilometers).

NVR (Network video recorder) in video surveillance system, NVR is the ideal upgrade of analog video recorder and DVR, is the original DVR based on the implementation of the Windows operating system and computer-independent operation of the standalone operating equipment.

Thanks to its highly integrated chip technology, the NVR has advanced digital video recording, storage and replay capabilities, no need to replace and store videotapes, no computer coordination and routine maintenance, enabling high resolution (up to FULL-D1 resolution), high-quality real-time monitoring, and easy-to-use. In short, the NVR system will be the traditional video, audio and control signal digitization, through the network interface on the NVR device, in the form of IP packets in the network transmission, on the basis of DVR, the realization of the system network.

The difference between the two:

　　DVR's "digitization" refers to the compression and storage technology is for digital signals, rather than direct digital encoded video image transmission. So the DVR must be deployed near the analog cameras. Instead, an NVR can store digital images directly from an IP network. Therefore, the biggest difference between NVR and DVR is that the DVR to the analog video collected by codec and stored in the hard disk, and the NVR directly record the camera has been encoded digital video. So the NVR does not have a video interface, and its input and output data are both IP data and compressed encoded video.

frame rate, bitstream and resolution



frame rate concept

A frame is a static picture, a continuous frame to form an animation, such as TV images. We usually say that the number of frames, in short, is the number of frames transmitted in 1 seconds, it can be understood that the graphics processor can refresh several times per second, usually with FPS (Frames Per Second). Each frame is a stationary image, and a fast and continuous display of frames creates the illusion of motion. The high frame rate allows for smoother, more realistic animations. The greater the number of frames per second (fps), the smoother the displayed action will be.

bitstream concept

The stream (data rate), refers to the video file in the unit time the use of traffic, also called bitrate, is the video coding in the picture quality control of the most important part. At the same resolution, the larger the stream size of the video file, the smaller the compression ratio, and the higher the picture quality.

Resolution Concepts

　　Video resolution refers to the size or size of an image of a video imaging product. The common image resolution is 352x288,176x144,640x480,1024x768. In the image of the two sets of numbers, the former is the image length, the latter is the width of the picture, the two are multiplied by the image of the pixel, the aspect ratio is generally 4:3.
At the same resolution, the larger the stream size of the video file, the smaller the compression ratio, and the higher the picture quality.

Channel

　　The most earthy argument, all the way is a picture (that is, a camera), such as the monitoring of the host is 8 road that it means that the host can only connect to 8 cameras so we usually say with 8-way monitoring host or 12-way monitoring host and so on. channel means this monitor host display screen, a 8-way monitoring host You can let him display 4 channels, but also can show more (but you only have 8 way is working) if 4 screen then is Channel One, channel Two, channel three, Channel Four, each channel corresponds to a camera, For example, the Channel One shows the Ladies ' (metaphor) channel two shows the gate and so on.

Reference turn: http://bbs.cps.com.cn/forum.php?mod=viewthread&tid=566460

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Basic Concepts in video surveillance