Hi-Tech Security Solutions Hi-Tech Security Solutions
Follow us on:
Follow us on Facebook  Share via Twitter  Share via LinkedIn
   
 




















 

DVR vs NVR
1 March 2009, CCTV, Surveillance

Phil Ridgeon discovers why investing in NVRs is better than spending money on DVRs.

Why are NVRs better than DVRs? It would seem appropriate to start this article by clearly defining, for the purpose of the article what I mean by DVR and NVR so that my arguments can be applied against a clearly defined base.

Let us define DVR as digital video recorder, a device which normally records analogue cameras ie, cameras which generate 1 V peak-to-peak composite video signals. IP cameras can be recorded on DVRs but this is not common; as a codec is needed for each camera to convert the IP video stream back to an analogue signal so it can be recorded, an expensive process. DVRs are characterised by having the following internal components:

* An analogue to digital converter, or encoder, which converts the composite analogue video signals into the digital domain.

* Digital storage, usually hard disks, where the digital representation of the analogue signals are stored ready for use.

* A database, relating the digital information to references; time, alarms and other metadata, enabling the video information to be retrieved and displayed quickly and easily.

* Digital to analogue conversion and replay controls. These are usually found more in smaller, standalone DVRs and less common in enterprise level DVRs.

* An operating system, which runs the whole DVR.

* A computer network interface, found in more recent DVRs, to allow the DVR to be interrogated remotely.

Figure 1. Typical DVR block diagram
Figure 1. Typical DVR block diagram

DVRs are also characterised by having an input for every camera connected ie, there is a direct connection, typically by BNC, UTP or fibre between each camera and the DVR. For example a 16 channel DVR will have 16 physical connections, one for each of the cameras.

Let us move on to the NVR. Similarly NVR is defined as network video recorder, a device for recording digitised IP video streams, originating either from analogue cameras connected via IP encoders and/or IP cameras where the IP video streams are created inside each camera. NVRs are characterised by having the following internal components.

* Digital storage, usually hard disks, where the digital IP video signals are stored ready for use.

* A database, relating the digital information to references; time, alarms and other metadata, so that the video information required can be retrieved and displayed quickly and easily.

* Digital to analogue conversion and replay controls. These are usually found more in smaller, standalone NVRs and less common within enterprise level NVRs.

* An operating system, which runs the whole NVR.

* A computer network interface, which is the primary input for IP video streams in to the NVR and also the primary way of connecting playback equipment in large systems.

Figure 2. Typical NVR block diagram
Figure 2. Typical NVR block diagram

As mentioned above; the difference between NVRs and DVRs is that NVRs have a single common input, a network connection, for all the IP video inputs. This common connection is also used for the connection of playback client PCs. A network switch connects individual IP cameras, IP encoders and playback PCs to this common single connection.

Why are NVRs better?

1. NVRs are less expensive than DVRs.

As you can see from the difference between the internal components there is actually less inside an NVR than a DVR, as all of the analogue to digital encoding takes place outside of an NVR in the IP cameras and IP encoders. Essentially, the very minimum that one needs in an NVR is a single network connection, operating system, database and some storage and that is it. The operating system and database can be software only meaning that only a minimum amount of hardware is needed. The analogue to digital conversion circuit needed in the DVR is completely eliminated, saving cost.

2. NVRs are more reliable than DVRs.

This relates to the first advantage. The more components there are in any electronic device the more there is to go wrong and the lesser the reliability of the device. As NVRs are simpler devices with fewer parts they are inherently more reliable than DVRs as there is less to go wrong.

3. NVRs can produce more detailed images than DVRs.

DVRs record analogue video signals. The maximum resolution able to be recorded is that produced by the analogue cameras themselves. For a black and white (or monochrome) camera the maximum resolution available is about 600 television lines (TVL), (the number of TV lines is the number of black-to-white transitions which can be identified across the TV screen). For a colour camera the limit, until recently, was about 450 TVL. However, the recent introduction of day/night technology where image processing or mechanical switching gives colour pictures in the day and monochrome pictures at night, now delivers an overall resolution of about 540 TV lines. The limitations in resolution for analogue composite video signals are a consequence of bandwidth limits for monochrome and by the presence of the colour burst and filters needed for colour.

This level of detail can be captured effectively by the current generation of DVRs which have a recording resolution of 4CIF (704 pixels horizontal by 576 pixels vertical). In effect, there is little logic in increasing the number of pixels in a DVR because there is no more detail available from the camera, through the limitations imposed by the analogue composite video signal. Multiplying the horizontal and vertical pixels – 704 x 576 gives a total of 405 – 504 pixels or 0,4 megapixels (a megapixel is one million pixels).

This is much lower than we are accustomed to these days with lowly camera phones which have 3 megapixel (MP) cameras in them let alone digital stills cameras which have resolutions of 10 MP. This is the reason that we still have the problem of effective zooming in on a playback image generated by a DVR viewing a wide-angle surveillance scene. We struggle to see the fine detail in the scene because the number of pixels on the screen diminishes very quickly and the image becomes blocky or pixellated.

The current generation of megapixel CCTV cameras have resolutions of 1, 2, 5 or even 10 MP, delivering much more detail than analogue cameras. The limitations imposed by analogue composite video signals means that composite video cannot be used to send megapixel images from one place to another. Instead megapixel camera manufacturers have chosen computer network connection, or IP, as the output connection for megapixel cameras. Effectively, this means that NVRs which can record IP video streams can record megapixel cameras, but DVRs cannot. In this way NVRs can deliver much more high-definition recordings than DVRs, allowing fine detail to be discerned from a surveillance view even when the image is zoomed in digitally.

4. NVRs are more flexible in their application than DVRs.

As we can see from above; NVRs can record analogue cameras (via IP encoders) and IP cameras of both standard and megapixel resolution. DVRs can only practically record analogue cameras. This allows NVRs to be used for a wider range of applications than DVRs. For system integrators, CCTV installation and maintenance companies or even end users this means that a smaller spares holding is required because only NVRs need to be supported even if both analogue and IP cameras are installed.

A second part of this flexibility comes from the very nature of the simplicity of NVRs themselves, as mentioned earlier. Essentially an NVR is a network input, operating system, storage element and a database. These are all characteristics of digital data storage servers which are used in all sorts of other applications in computer networks. This means that standard computer parts and assemblies can be used in NVRs and one is not tied to proprietary electronic hardware as one is with a DVR.

The analogue to digital conversion circuits in DVRs are all proprietary, meaning that when you buy a DVR you are buying a black box from a manufacturer and for any service, repair and maintenance you must go back to that manufacturer alone.

An NVR can consist of off-the-shelf hardware, such as server PC and hard disk storage array which can be purchased and maintained from multiple different sources. The only proprietary bit is the NVR software which runs on the server PC (and client PCs used to replay the recordings). It is true that there will be software licence costs, perhaps with annual maintenance charges but the tie in to buying and maintaining NVR hardware can be broken.

In addition, large purchasers of IT hardware can leverage volume purchasing advantages from their existing or preferred sources of IT hardware. The opportunity also emerges for advantageous new business and purchasing models in the supply of NVR systems through different schemes for the purchase of NVR software licences.

5. NVRs can offer reduced time to repair and higher availability than DVRs.

The fact that proprietary hardware ties repair to the manufacturer also ties the speed of repair to the capability of that manufacturer. Nearly all manufacturers offer just return to base repairs. A few offer 24 hour repair turn-around times but typically repair times are much longer, requiring end users to have to invest money in service spares to keep their cameras recording while a faulty DVR is repaired.

The opportunity that NVRs offer to use off-the-shelf IT hardware also opens the door to the level of service available in the IT industry by IT manufacturers. For example, rather than return to base, some IT manufacturers, such as IBM, offer repair on-site with a 4-hour response time, at a very reasonable cost. This is practically unheard of from DVR manufacturers.

To summarise, NVRs are indeed better than DVRs in many ways. NVRs are less expensive to buy than DVRs and there are different ways in which you can buy them. NVRs are more reliable than DVRs but when they do go wrong the opportunity exists to get them repaired and working again much more quickly. NVRs can produce more detailed video information than DVRs as a consequence of being able to exploit megapixel camera technology. Finally, because NVRs, as I have explained, are more flexible and so can be applied more universally they deliver lower costs of ownership and an improved return on investment.

For more information contact Lisa Karam, Out The Square, +27 (0)11 886 9931, lisa@outthesquare.co.za


  Share via Twitter   Share via LinkedIn      

Further reading:

  • Hacker-resistant CCTV stops criminals
    July 2014, TeleEye (South Africa), CCTV, Surveillance
    The devices people are relying on to provide a new layer of security are actually back doors that crooks can easily exploit.
  • Hikvision secures Makro distribution centre
    July 2014, Hikvision, CCTV, Surveillance
    Makro officials wanted a new IP surveillance solution that reduced theft, established excellent overall security, provided better warehouse management, and a means to monitor workers in sensitive areas; as well as reducing shrinkage.
  • Avigilon adds intelligent video analytics
    July 2014, CCTV, Surveillance
    The introduction of the Rialto analytics appliances bring high-performance analytics and high-definition imaging together to provide increased protection.
  • Servest partnering with juwi Renewable Energies
    July 2014, CCTV, Surveillance
    Servest has designed, commissioned and installed the latest CCTV surveillance systems at all of juwi Renewable Energies’ South African solar energy power plants.
  • Beyond surveillance
    July 2014, Cathexis Technologies, CCTV, Surveillance
    Need to increase the return on investment of your video security system, Daryl Buhrmann, product manager at Cathexis Technologies has some ideas.
  • FNB improves security at Fairland building
    July 2014, Jasco Security Solutions (Multivid), CCTV, Surveillance
    FNB turned to Jasco Security and the latest version of the Bosch Video Management System (VMS) to upgrade the video solution at one of its branches.
  • Tri-brid HDCVI DVR embraces interoperability
    July 2014, Dahua Technology, Products, CCTV, Surveillance
    Dahua Technology has introduced its tri-brid HDCVI DVR (DH-HCVR7000-series), a digital video recorder compatible with three signals – HDCVI, analogue and network. The hybrid DVR is a good solution to ...
  • Entry-level IP security camera
    July 2014, Duxbury Networking, Products, CCTV, Surveillance
    The ACTi D Series is targeted at indoor and outdoor monitoring applications and consists of cube, dome and bullet cameras with one to three megapixel resolution high definition (HD) lens options.
  • Professional IP camera solution
    July 2014, Regal Distributors SA, Products, CCTV, Surveillance
    The new range of Hikvision 4-Line Smart IP cameras are designed to meet all professional market applications such as casinos, banks, residential communities, transport solutions for airports, harbours and motorways.
  • Video security upgrade for Alexander House
    June 2014, Geutebrück SA, CCTV, Surveillance
    Alexanderhaus in Berlin’s Alexanderplatz is making the move to convert its old analogue security systems to the digital age with a hybrid solution from Geutebrück.
  • Underground mine security with Vivotek
    June 2014, CCTV, Surveillance
    The Guido Coal Mine provides its employees and tourists with the best in mine security.
  • Camera displays in control rooms
    June 2014, Leaderware, CCTV, Surveillance
    Dr Craig Donald visits a large number of control rooms and discusses the systems that are installed, camera displays, and why people are looking at various views.

 
 
 
Search...
Hi-Tech Security Solutions Business Directory


         
Contact:
Technews Publishing (Pty) Ltd
1st Floor, Stabilitas House
265 Kent Ave, Randburg, 2194
South Africa
Publications by Technews
Dataweek Electronics & Communications Technology
Electronic Buyers Guide (EBG)

Hi-Tech Security Solutions
Hi-Tech Security Business Directory (HSBD)

Motion Control in Southern Africa
Motion Control Buyers’ Guide (MCBG)

South African Instrumentation & Control
South African Instrumentation & Control Buyers’ Guide (IBG)
Other
Terms & conditions of use, including privacy policy
PAIA Manual
         
    Mobile | Classic

Copyright © Technews Publishing (Pty) Ltd. All rights reserved.