FAQ — DVRs and NVRs

Recorders are what turn a camera you watch into a camera that watches for you. These were the questions Handykam answered about them.

What are DVRs and NVRs?

Short for Digital Video Recorder and Network Video Recorder. Both record camera footage to a hard drive; the difference is what they connect to.

What is the difference between them?

An NVR records networked IP cameras, receiving already-digital streams over a network cable. A DVR records analogue cameras, digitising the incoming video itself. Hybrid units that do both existed and were common during the transition — which is what most people with a mixed installation actually needed.

How long can the drive record for?

There is no single answer, because the length of recording is determined by a stack of factors:

• Size of the hard drive
• The number of cameras
• The length of recording — continuous, scheduled or motion-triggered
• The recording resolution, or more precisely the bit rate
• The frame rate of the footage
• The resolution of the camera
• The compression used
• Whether it is day or night — daytime footage is slightly larger, because there is more detail changing
• Whether audio is recorded as well

A worked example

Four cameras, 720p, 20 frames per second, recording 24/7 in H.264 at standard settings comes to roughly 777.6GB of footage. That is the kind of arithmetic that determines whether a 1TB drive gives you a week or a month.

Two conclusions follow from that example, and they are the ones that save money. First, motion-triggered recording is dramatically more efficient than continuous recording for anything that is mostly still — a nest box, a yard at night, a gateway. Second, going from 720p to 4K multiplies your storage requirement several times over, so resolution should be chosen for what you actually need to identify, not for the highest number available. The H.264 family of codecs, and its successors, are what make any of this feasible at all.

How do I connect a camera to an NVR?

With a network cable — Cat5 or Cat6 — from the camera into the NVR. Many NVRs have built-in Power over Ethernet ports, which means the recorder powers the camera down the same cable. That is much the neatest installation: one cable per camera, doing everything.

How do I connect a camera to a DVR?

With a composite cable, usually with round RCA phono plugs: yellow to video in, white to audio in. Some DVRs use BNC connectors instead — the twist-and-lock type used in professional video — in which case a small BNC converter screws onto the DVR and lets you plug the phono leads into it.

How do I put an NVR on the network?

NVRs are designed to be networked. Connect a network cable from the recorder's network port to your router or switch, having first made sure the recorder is set to DHCP so it obtains an address automatically. Then look at your router's list of connected devices to find the recorder's IP address, type that address into a browser, and the live streams should appear.

Can I get to my recorder on my phone?

Generally yes — most recorders have an app for phone, tablet and computer. As with cameras, change the default password before doing anything else, and prefer the manufacturer's app or a VPN over exposing the recorder directly to the internet.

What size drive should I use?

Work backwards from how much history you want. Decide the retention period first, then apply the arithmetic above. It is also worth using a drive rated for continuous write — ordinary desktop drives are not designed to be written to twenty-four hours a day for years and do not last as long in that duty.

What about the footage itself?

Recorded footage of people is personal data. If your cameras cover anything beyond your own property, the ICO's guidance sets out what that obliges you to do about retention, access and signage.

Related pages: Digital IP versus analogue · Camera resolution · Software links and downloads · CCTV glossary