Welcome to the world of video surveillance! As business owners stepping into this fascinating field, you might have heard terms like DVR and NVR thrown around. But what do they really mean, and how do they differ? Let’s break it down into simple, easy-to-understand language.
What is a DVR?
A DVR, or Digital Video Recorder, is a device that records video in a digital format to a disk drive, USB flash drive, SD memory card, or other local or networked mass storage device. It’s most commonly used with analog cameras. Think of it as the brain of your surveillance system that collects and stores the video footage from your cameras.
What is an NVR?
An NVR, or Network Video Recorder, is similar to a DVR but is designed for use with IP (Internet Protocol) cameras. NVR systems record and store video footage digitally, but the significant difference is that NVRs capture the video directly from the network. This means that IP cameras can send their video footage to the NVR over a network cable.
Let’s simplify the journey of video footage from both IP cameras to an NVR and analog cameras to a DVR, breaking it down into an easy-to-understand process.
IP Camera to NVR:
- Capture: An IP camera captures video footage as digital data from the get-go. Think of it as taking a series of digital photos and putting them together to create a video.
- Transmission: This digital data is then sent over a network cable, similar to how computers send data to each other in your home or office network. This is like sending an email with a video attachment to a friend.
- Reception and Storage: The NVR, which is connected to the same network, receives this digital data. Since the NVR is designed to work with digital data, it can directly store this data onto its disk without needing to convert it. It’s akin to receiving the email on your computer and saving the video attachment to your hard drive.
Analog Camera to DVR:
- Capture: Analog cameras capture footage as an analog signal, which is a continuous wave that varies in amplitude. Imagine this as recording a video on an old VHS tape; it’s not in digital form but rather a continuous magnetic recording.
- Transmission: This analog signal is then sent over a coaxial cable (a thick cable used for various types of analog transmissions) directly to the DVR. It’s somewhat like sending a signal through a long wire directly into your television.
- Conversion and Storage: Since the DVR receives analog signals, it must convert these signals into digital format to store them on a disk. This is similar to copying a video from a VHS tape onto a DVD; the content needs to be converted into a format that the DVD can understand and store.
In your research you have undoubtedly come across the terms DVR (Digital Video Recorder) and NVR. (Network Video Recorder). You may have been told that one works with analog cameras (DVR) and the other works with IP/Ethernet/Network cameras (NVR). Both ultimately record a digital signal onto a hard drive or other storage medium. I am not sure that the explanation means much to a business owner researching video surveillance solutions.
So let’s look at the actual difference between these two devices. An NVR receives video footage from an IP camera in digital form. The camera captures the footage as digital data from the get go, and sends it on to the NVR – which then saves the data to a storage medium.
The analog camera on the other hand captures the video footage as an analog signal. It sends this analog signal as a continuous magnetic wave form to the DVR. In order to save this signal to a storage medium, the DVR needs to convert the signal from an analog format to a digital format.
Now one asks – so what is the benefit of an NVR, since ultimately both feeds are saved as digital data? I cringe at the many responses sales people give to their customers when answering this question. Most responses are just not true.
They say:
Higher Video Quality – Digital cameras can transmit HD (High Definition) or even 4K Resolution. But – with HD analog formats like HD-TVI (Hikvision) , HD-CVI (Dahua) and AHD – analog cameras can also transmit HD and 4K resolution
Easier Installation and Scalability – You can scale the system by adding more cameras without worrying about the limitation of coaxial cable length. Ethernet cable has distance limitations – namely 90m after which it must be extended by more switches. We can use a category 5/6 class ethernet cable and send 4 camera signals hundreds of meters on a single cable. It’s true that Multiple IP camera signals can be extended 100m at a time, over a single cable – also with limitations. IP cameras have the advantage of Power Over Ethernet (PoE) they say. We are currently sending power over coax alongside the analog video signal on the same cable. Both power eco-systems have similar limitations in terms. If NVR’s can be distributed rather than centralised, so can DVR’s. If IP cameras can be transmitted on Fibre Optic cable, so can analog signals. If NVR data can be transmitted over WI-FI , so can DVR data.
Improved Accessibility: Digital video can be easily accessed and managed remotely, users can connect to the NVR from anywhere. But hold on a minute – aren’t both devices storing the data digitally? The argument holds true for DVR’s as well. I suspect that this answer is intended when accessing a single camera.
Integration and Flexibility:Digital surveillance systems can be easily integrated with other digital systems and technologies they claim. But, once again – both devices are storing digital data. Once again I imagine this is meant for integrating individual cameras, and not systems. Modern DVR’s now known as XVR’s can even receive digital feeds directly from IP Cameras, and entire other DVR’s.
Compression: Some sales people even use this one – IP cameras use more efficient compression standards like H.264 and H.265. They compress files with less impact on image quality. Ouch – analog systems have been using H.264 and H.265 compression standards for ages.
Purpose Built: They say that XVR’s may be compromised in handling the full features of an IP camera. When pressed they admit that that’s not guaranteed. XVR’s are now the modern DVR – X as in cross over or hybrid. Just because an XVR is designed to integrate analog camera technologies with IP cameras -that’s no argument for the XVR not being able to handle modern functions of an IP camera.
DVR’s and now XVR’s can match the performance and use case of NVR’s – and they can do that at around 40% less cost.
So with all the hype set aside, what is the actual benefit of NVR’s when compared to DVR’s
In conclusion to this part – it’s clear that I am not a fan of expensive NVR’s.
The entire argument brings us back to one specific issue. The conversion of analog data to digital data.
Analog signals are continuous and subject to noise and distortion. Manipulation of analog signals is usually limited to simple signal amplification or filtering. While performing advanced computations directly on an analog signal is not impossible – it’s just impractical. Digital signals are far easier to manipulate with mathematical precision. Why is this relevant? Because tasks like image recognition, or motion detection are complex processing tasks, which require mathematical precision.
Here is an argument for the digital camera , or IP/Network camera as we may call it – not necessarily for the NVR. A DVR that must convert multiple analog signals into a digital form and then run these computational processes on multiple video streams – would be a kind of supercomputer. It wouldn’t come cheap likewise! It’s impractical to place the compute burden of multiple streams on a single processor , whether that’s a DVR, XVR or NVR.
So we have arrived at the digital camera. A device that handles the computational processes required for advanced analytics, for itself. Dealing with it’s own video data – only! We can call this distributed computation, or edge processing. Multiple devices handle their own processing, and then send the processed digital data onward for storage and display. It can be a DVR, an XVR, NAS, Server or an NVR that receives that data for storage, and which displays it.
An NVR is simply a device that minimalistically needs to focus on storing and displaying the pre-processed digital data. It only makes sense to use IP cameras for pre-processing. Most devices, including NVR’s, could not handle complex computation on multiple streams – hence onboard computational devices like DVR’s and XVR’s become redundant. The lowly basic NVR is all that’s needed to store and retrieve the pre-processed data.
Let’s try and make simple sense of the discussion!
- If you plan to use large scale video analytic in your video surveillance system – then you are best served by IP cameras and NVR’s.
- If you already have an analog video surveillance system, and plan to gradually introduce video analytics. Deploy an XVR that accommodates your existing cameras and allows you to introduce additional IP cameras on the same system – with the ability to process the features of those IP cameras.
These recommendations are already becoming dated, before the ink has dried. At gensix we have found that we need more computational capacity than standard IP cameras can provide. Complex AI and ML scenario’s have led to the demand for integration of our SuperMini AI machines. These machines are packed with computational capacity – enabling robust handling of the most modern computational tasks.
In Summary: The decision to deploy DVR’s, XVR’s or NVR’s all center around the degree to which you will be adopting advanced video analytics. I have specifically not discussed WI-FI IP cameras – which I think are a bad idea in most cases, but do provide options in terms of reduced cabling infrastructure.
Speak with your gensix representative about the solution that best fits your requirements.
