Closed Circuit Video System
What features should I look for in a CCTV Digital Video Recorder (DVR)?
There are several factors that are critical to consider when purchasing a DVR, especially when comparing price. The most important factors to look at are the number of cameras supported, frames per second (fps), compression technology, hard drive space, network connection / remote viewing capability, motion detection, scheduling, and ability to save video and audio to a CD or flash drive. You should also look for easy and comprehensive search capabilities (check out our ‘Smart Search’ technology) and audio support. The setup and user interface should be intuitive and easy to operate.
What is frames per second?
The frames per second (fps) relates to how many pictures the DVR will record in a second. Real time recording is about 30 fps on each camera. To calculate the fps per camera take the total fps in the system and divide it by the number of video inputs. For example, a 60 fps digital video recorder with 4 video inputs would result in about 15 fps per camera. The technology has finally gotten to the point now where real time recording is affordable. If you are recording cash registers or something similar then you should definitely invest in real time recording.
How big a hard drive do I need?
The amount of hard drive space is very important because it will limit how many days of recording you can store before the system has to start recording over the oldest video. Each DVR will have its storage capacity listed in the specifications. But this calculation is just a rough estimate as there are many factors that affect hard drive use. The most critical factor being the compression format used by the DVR (for more info on compression formats click here). But also the type of cameras that are connected to the DVR make a difference (specifically the chip size and resolution) and also the features that are selected on the DVR. If you use the scheduling or motion detection features or tune down the frame rate that will extend the storage capacity of the unit. Even the field of view (what you are recording) will affect the storage capacity – the more complex the image, the more hard drive space it will take to capture the complexity.
How does a CCTV digital video recorder work?
A CCTV digital video recorder (or “DVR” for short) is essentially a computer that saves security video images to a hard drive. Most security cameras in use today capture an analog picture. The DVR converts the analog signal to digital and then compresses it.
Many cameras can be connected to one DVR. DVRs generally come with 4, 8, 16, or 32 camera inputs. The DVR will allow you to view all of these images at once or one at a time, and all of the video is saved to the hard drive. Additional switches, quads, or multiplexors are not required.
How do I see pictures from a remote site?
You can view the camera video over the internet using a modem which is slow but can display 1 or 2 frames every 5 seconds. Better is a DSL or cable modem connection which can generally display 1 frame per second. When viewing remotely, the refresh rate is restricted by the communications medium (your internet connection speed). When viewing or playing back locally, the display is dependent of the unit’s frame rate (fps). You will need a static ip address available to assign to the DVR (more about this in your documentation).