Surveillance Technology - Q&A

DVRs Versus NVRs:

What's the difference between a DVR and an NVR?

A DVR (digital video recorder) receives the video from analog security cameras and converts it to digital format for storage and playback purposes. An NVR (network video recorder) receives video that is already in a digital format, either from IP (network) cameras or from video encoders that convert analog video to digital format before passing it onto the NVR. A hybrid DVR/NVR has the ability to directly receive both analog and IP video inputs.

Do all DVRs and NVRs store digital video in the same format(s)?

The majority do. The most common algorithms used for encoding and storing digital video are H.264, M-JPEG and MPEG-4. However, there are some systems that rely on proprietary compression formats, which are often based on slight variations to the standard formats. These "closed" systems are designed to make sure that you buy all components, including cameras, from a single manufacturer. This approach will limit your ability to use the recorded video with any third-party software and hardware in the future. Buyer beware!

Is there a difference between the quality of video recorded by DVRs versus NVRs?

DVRs are limited to recording the input from analog cameras, which typically offer a standard resolution that is much lower than that captured by today's IP megapixel cameras. The level of detail displayed in a DVR's or NVR's video can only be as fine as what is captured by the camera.

Is there a limit to the number of cameras supported by a single DVR or NVR?

DVRs have a finite number of inputs. For example, if a DVR has 16 inputs and you use them all up, then adding a 17th camera means either adding an additional video capture card (if your DVR can support this option) or buying an additional DVR.

NVRs are much more flexible, as cameras are connected to it via the network. The number of cameras that can be supported is a function of the processing strength of the NVR hardware, the resolutions and frame rates of the cameras connected to it, and any limitations set by the video management software running on the NVR. By tweaking any of these variables, the maximum number of supported cameras can change. Also, multiple NVRs can work together as a unified system over the network.

Over time, it is much more cost effective and easier to add cameras to NVR based systems.

How can I create a surveillance system that monitors multiple locations?

Each DVR is limited to recording and playing back only the cameras that are physically connected to it. If, for example, a school district wanted to have surveillance systems set up at each school, with centralized monitoring available at the district office, the cameras from each DVR would need to be viewed separately.

By contrast, in an NVR system, all devices can be viewing and accessed from anywhere. Administrative controls can be put in place so that principals at each school can only view their own cameras, but the district office can quickly see all cameras across the entire network, arranged however they like – all from a single management interface.

Features and Usability:

What sort of usability features should look I for within any DVR or NVR control interface?

There is huge variation in the user experience offered by different DVR and NVR solutions, with too many features to review here in any detail. However, there are some basic controls that you should expect, and for which you should not be charged extra. These include:

  1. The ability to create and save different camera layouts. For example, you may want to create one view of the four cameras set up in your facility's parking lot. You may want a second view that displays views of the four entrances into the building. A third view might display 9 cameras, of main hallways, elevators and the lobby. Make sure you can set up and save these custom views easily and that this can be done from all viewing clients, including the mobile app. Also, make sure you can move the camera tiles around on the screen, putting them in any order you like. And, that you can save them that way, for future call up.
  2. Quick and easy playback of video from a given camera or cameras. It should be as easy as clicking on a video tile and scrolling backward and forward in time. You should not have to exit out of live viewing in order to view recorded video. Having to do so is cumbersome and time-consuming, and makes it less likely that the people assigned to monitor your cameras will make use of the playback feature as often as they should.
  3. Mapping. The easiest and most intuitive way to immediately call up video from a given camera is to click on it from a site map. This feature should be accessible from all clients, and should not cost extra.
  4. Admin features to limit access and control by user. Not everyone using your system should have the same access. You need to make sure you have ability to control what each user can see and do, including the ability to change system settings, add cameras, etc.

Are all mobile viewing apps created equal?

Absolutely not. Some apps are extremely limited, only allowing the viewer to call up live video, or view a single camera at time. Other apps provide many of the same controls available through the standard monitoring interface. If you're testing out a mobile app, make sure to try doing all the same things you would want to do from a desktop station to fully understand the capabilities and limitations of the solution.

Also, be wary of additional costs associated with setting up mobile access. Some – but not all – manufacturers require additional hardware in order to support the streaming of video to mobile devices. Also, some – but not all – integrators charge additional set up and configuration fees to support mobile devices.  

What about browser-based interfaces? What should I expect?

Some DVRs and low-end NVR solutions use browser-based controls as their primary interface. In many browser-based solutions, plug-ins are required in order to make use of at least some features.

Enterprise scale NVR systems typically offer a browser based interface in addition to a thick-client, workstation-based interface. In these types of systems, there is typically more functionality built into the thick-client than the thin client…often related to providing access to administrative controls and access to integrated third-party solutions, such as access control. Most manufacturers are continuing to introduce more robust browser-based interfaces that provide most, if not all, of the controls available through the thick client. If you intend to predominantly use the browser interface to access your system, make sure to take a test drive to understand its full capabilities and limitations.

What kind of integrations are possible with other security solutions, such as access control and license plate recognition?

Integrating your surveillance system with additional security solutions can make it far more powerful and effective. For example, imagine how useful it would be to have video clips that correlated with each time someone used an access control keypad to enter or exit the building. Or to have a record of license plates and corresponding video each time someone passed through a parking lot tollbooth. If these are the types of security capabilities you'd like for your facility – either now or someday in the future – the most important question to ask is whether the surveillance system is "open platform" versus "proprietary." An "open" system is built using industry standards that are shared across manufacturers, allowing disparate solutions to talk to and work with one another. A proprietary or "closed" system uses unique encoding and algorithms that cannot connect with other manufacturer's software.

An integrator that shows you combined video surveillance and access control that requires you to close one application to run the other, or runs the two applications side-by-side in different windows or on different monitors, is not showing you an open, integrated solution. In an integrated solution, both systems can be viewed and managed through one software interface – preferable through the video surveillance GUI.

Also, be sure to ask about pricing and licensing to add integration to a surveillance system. Some "open" systems will provide this capability to you at no charge, while others will require a set-up/configuration fee, licensing fees, or both.

How safe is my system from failure and loss of recorded video?

The best way to ensure your system will continue to operate and record in case of a drive failure is to use RAID drives for both operation and storage. A RAID array features a set of drives that work together to offer redundancy, so that when any single drive fails, others can provide back-up performance. RAID arrays can be configured in a number of ways that employ different strategies for providing redundancy. A system integrator with IT expertise would be most competent at discussing with you the pros and cons of different storage options.

What about Cameras?

Can I use any camera I want?

The answer to this question goes back to the "open" versus "closed" issue. If you want to use IP cameras, the selection you can choose from will be a function of how "open" your surveillance solution is. Some NVR systems will provide you with thousands of models to choose from – from a huge range of manufacturers. Others will provide much more limited options, or even force you to buy one specific brand.

DVR systems should be compatible with almost any analog camera on the market.

Why is there such a range in price for security cameras?

As with most things in life, you get what you pay for. There is rarely a need to opt for the most expensive cameras, but make sure that the models you choose clearly meet your specific needs. A few of the most important performance issues you should consider are listed below. Remember, each of these may add to the price of the camera, but some may also reduce installation costs.

  1. Is it an analog or IP camera? (Analog cameras cost less than IP cameras, but the gap is closing.) If it's analog and you want to connect to an NVR system, you'll also need to buy an encoder, which can negate the lower price of the analog camera. If you're looking at IP cameras, you'll obviously need to make sure that it's compatible with your specific system.
  2. How well does the camera perform in a range of lighting conditions? If you will be using the camera in low light, ask to see what this will look like. You may need a day/night camera that switches to a black and white image in the lowest lighting conditions to provide the best contrast. You might also want to consider a model with IR illuminators.
  3. How well does the camera perform with strong backlighting, such as clearly displaying a person's face who is standing in front of a bright window or open door? If this will be necessary, you need a camera with "wide dynamic range." Again, ask to see what video would look like in this condition.
  4. Can the camera operate from PoE (power-over-ethernet), eliminating the need for electrical wiring?
  5. How well will the camera housing hold up in the environment where it will be used? Can it handle an adequate range of temperatures and humidity levels? Is it resistant to tampering or vandalism?
  6. Does the camera allow you to focus the lens remotely (via a browser), without removing the cover from the camera?
  7. What is the camera's maximum resolution? How many frames-per-second can it transmit at its maximum resolution? Higher isn't always better (see the next question), but make sure you are comparing apples to apples.  

Is higher resolution always better?

Not always. The technology of today's highest resolution cameras is, in many cases, surpassing its usefulness. Even the best video monitors today don't have the ability to display more than a 3MP image. And, higher resolution video generates larger file sizes that require more bandwidth and storage. Don't be lured by the hype of a super-high megapixel camera unless you are sure that you have a practical use for it. That said, there is almost 8X as much detail captured in a 2MP image than a standard resolution image, and in many cases, it can provide the same coverage as multiple lower resolution cameras. 1MP and 2MP cameras are becoming extremely popular in the marketplace because of their superior image quality and increasingly competitive pricing.

Does the make and model of a camera matter?

Some brands cost more than other brands, due to the quality of their manufacturing, warranty policy and reputation. Those things matter, but there are plenty of less known camera manufacturers who are delivering quality products. Make your decision based upon features and performance capabilities, as well as whether there are licensing price advantages for certain brands. The cost of camera licensing across a large system can add up quickly!


Written by: Margie Gurwin, Director of Marketing. Copyright © 2015, A+ Technology & Security Solutions. Contents may not be reprinted without permission.

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