Sitemap    Feedback
Home About us Products Service Contact Us
NVR vs. DVR
        Over the last 20 years, rapid development of video compression algorithms (MJPEG, MPEG-4, H264 etc.), computer processing speeds and a reduction in the physical size of data storage devices gave rise to the DVR; essentially a multiplexer (a video recorder that allows several streams of video to be recorded onto the same tape and separated out into discrete, viewable streams) that uses a computer disk for storage. The DVR provided a convenient replacement for early multiplexer and VCR combinations and provided non-linear access to recorded material usually selected by the camera ID, time and date.



        DVRs however presented many limitations, the most problematic of which being that if it fails all recordings are lost.

        The advent of NVRs (Network Video Recorders) represents the arrival of the next natural point in the development of recording technology.

        It is important to differentiate between DVRs and NVRs, as both are often termed ‘digital’. A DVR digitally compresses analogue video feeds and stores them on a hard-drive, the term ‘digital’ referring to the compression and storage technology, not the transmitted video images. The DVR therefore has to be located near the analogue feeds. In contrast an NVR stores digital images directly from the IP-network.

        Therefore the most obvious difference between the DVR and NVR is that whereas the DVR records from analogue streams provided from analogue cameras, the NVR records video streams that have already been encoded at the cameras. Thus you find no video connectors anywhere on a NVR; it’s input and output is IP data comprising compressed and encoded video. This will typically be in either MPEG-4 or H.264 formats which have enjoyed widespread adoption in the CCTV industry as the compression technology of choice, due largely to their efficiency.

NVR

DVR

NVRs utilize 'off the shelf' PCs with a standard Ethernet interface for receiving video and controlling PTZ devices.

DVRs utilize proprietary PC based devices containing analog to digital capture cards.

NVR technology allows secure, direct access to the video feeds independent of the NVR itself.

Remote video access is only available through the DVR.

NVR failures can be repaired or replaced by the user, PC manufacturer or retail point of purchase very quickly.

DVR failures require the DVR manufacturer to service the unit or replace it

NVRs can be replaced and upgraded in a matter of minutes. Performance can be significantly augmented over short periods of time. This allows new technology offerings to be immediately implemented.

DVR performance is basically fixed. It can not be easily augmented and has physical limits. Performance augmentation requires premium cost components sold by the manufacturer.

Retired NVRs are completely viable PCs which can be sold or used for other services.

DVRs require manufacturer approved components and accessories.

NVR maximum resolution is effectively unlimited. As camera resolutions continue to increase, NVRs can receive and decode the images without modification.

DVR maximum resolution is limited by analog camera technology and capture card design. Native analog resolutions have approached their limits.


 

        The biggest advantage of an architecture based on NVRs is that they can be located anywhere on a network – at the monitoring center, adjacent to camera clusters, on the edge of a network, collected together in a hardened environment, basically anywhere at all. The location of an NVR is transparent to the operator – he or she simply calls up the recorded video stream to be viewed, provided they have the necessary authorization to do so. NVRs record and replay simultaneously, and recordings on any one machine can be remotely viewed by a number of operators spread across the network simultaneously and independently and without affecting each other.

        The importance of the independence of physical location, well away from the cameras if necessary, should not be underestimated – IT Managers are notoriously obsessive in safeguarding their network capacity, but by calculating the data flow requirement across the network and strategically placing NVRs accordingly, the impact of video streaming on bandwidth usage can be minimized.

        To assist in the calculation of data flow requirement and disk storage capacity requirement, our NVR Assistant can be used to estimate these numbers using such parameters as the number of cameras, functionality of the camera (PTZ under continuous operator control / static for ID purposes etc.), picture resolution and update rate in frames-per-second requirement, and if motion-sensing is used the motion frequency and type.


Copyright © 2003 Huashi Technology Co., Limited All Rights Reserved.
Waterproof IR Camera,Dome Camera,CCTV System Kit,DVR Card,Surveillance Equipment,Digital Video Recorder(DVR),CCTV Tester,Sport Camera.