Digital Video Recorders
Digital Video Recorders (DVRs) are used with analog security cameras only and not with IP cameras. They take analog video streams, compress them, store them and provide a management interface. The developments made with DVRs over the last decade are similar to those made with digital photography – completely changed it! The days of changing tapes, watching grainy video and spending countless hours searching for footage are over!
4 channel DVR console
There are two basic types of DVRs: appliances and PC based. PC based have their place and can leverage existing equipment by adding a card that accepts camera inputs. The rest is taken care of by software that typically runs on the Microsoft Windows operating system. In the right hands, a PC based digital video recorder can be quite effective.
Digital video recorders are specialized devices that serve one and only one purpose: to digitally record analog security cameras. The operating system (typically embedded Linux) and functions needed to power the system are usually embedded on chips which are not prone to viruses, conflicts with other software or, most common, operator error. As such, appliance based DVRs are more common and are easier to implement since they are specialized devices that do not require software installations or hardware upgrades. Plug your cameras in, configure the device and record video. Easy. DVR appliances can also take on different forms including rack mountable, standalone and mobile versions which can be discreetly mounted inside a car, truck or boat.
When choosing a digital video recorder, there are several factors to consider:
- Compression – the process of taking images sent from the security camera and storing them in a more efficient format. Compression is a trade off between image quality and small file sizes. MPEG-4 is currently very common amongst DVRs with H.264 becoming more popular.
- FPS – Frames Per Second indicate how many images a DVR can process at a given time. Full motion video is 30fps. If you wanted to a DVR to record 4 security cameras at 30fps, you would need a DVR that can process 120fps. Some DVRs can have the recording fps adjusted on a per channel basis which can maximize disk space. 10fps per channel is often enough.
- Channels – the number of cameras that a DVR can accommodate, typically 4, 8, 16 or 32. If additional channels are required, another DVR will be required. For this reason, it is smart to allow room for future growth – choose a DVR that has more channels than you need today.
- Network Abilities – many DVRs provide an Ethernet connection so that the unit can be managed and viewed online using bundled software that almost always runs on Windows machines only. Some provide a built in mini-web server where multiple users can remotely view cameras in real time. Other options include email alerts, transferring images via ftp and a built in web server for remotely viewing your video security system.
- Options – built in CD or DVD burners are common allowing you to burn a clips of footage from security cameras. Some offer USB ports that can be use memory sticks to transfer surveillance footage.
- More advanced DVRs also offer storage options such as RAID arrays which combine multiple hard drives for additional storage and fault tolerance.
- Warranty – This can vary greatly between manufacturers from 1 year to 3 years. Appliance based DVRs have no moving parts apart from the hard drive and power supply fan.
- Support – Beware of budget DVR manufacturers that provide poor documentation and zero support.
DVRs cannot be used with IP cameras which already send digital video – there is no need to convert the image from analog to digital. Instead, hybrid DVRs should be used which can record a combination of analog video and digital video feeds.
Mobotix IP cameras are flexible in that they do not require centralization. Instead, each camera can be fitted with flash storage that can independently record video. If video centralization is required, Mobotix cameras can be configured record video to remote Windows, NFS or FTP servers without the need for a dedicated Network Video Recorder (NVR) appliance. This means that you can start with a 1 IP camera video security system without having to purchase any centralized recording devices.