Many factors are important in determining for how long a system can store video. Frame Rate, resolution, disk size, motion detection, compression ratio, and camera noise all effect the total storage capacity of a video surveillance system.

The storage capacity of every DVR system is different, even if the amount of disk space in the system is the same. This is the result of the the fact that every DVR has a different way to control the rate of hard disk consumption during normal usage. For example, there are different ways of changing frame rate, resolution, compression and motion detection. It is therefore often difficult to make a fair comparison between vendors.

One way to compare the storage capacity of one DVR against another is to ask (or better yet test) how many hours of video it can capture using all channels, each at the highest frame rate possible, at CIF resolution, and with motion on all channels. This test is relatively easy to perform. Simply set the DVR to the highest frame rate possible on each channel and use the output from a DVD player to drive the video. You may need a DA to split the signal from the DVD, so that there is not an impedance problem.

The rate of disk consumption is determined by dividing the amount of disk space used per hour by the number channels. This number varies widely by DVR vendor.

Also, after a couple of hours, check the temperature of the DVR. When working at full speed, a DVR can generate a lot of heat. If it is not located in a well ventilated room, it may fail after a period of time.

Important factors effecting video storage capacity

   Compression: The type of compression used effects how much disk space is used per frame. (more...)

   Resolution: As the frame resolution increases, the disk space required grows geometrically. (more...)

   Frame Rate: The number fps being recorded effects how much disk space is used per second. (more...)

   Camera Noise: A noisy signal from a camera forces the DVR to compress more data and thus uses more disk space. A camera recording under very low light conditions, i.e. at night, often produces more noise and thus disk space usage can be higher at night.

   Motion Detection: Motion detection can be used to reduce the amount of disk space used. (more...)