How To Calculate Dvr Recording Time

By Author: Moshe Goldberg
Total Articles: 4762
Comment this article

First there was the on-site guard, just keeping an eye on things. Then came the camera/monitor combination, so guards did not have to make notes and walk around all the time. Then the Video Cassette Recorder (VCR) came on the scene, recording a single video stream to a tape (good for up to three hours at first) at 25 fps, or frames per second, and triggered by switches, alarms or other input devices, whether proactive or reactive. Technology swiftly moved along, and brought the multiplexer, recording multiple streams of video on one tape that are separated into individually viewable streams. Then came time-lapse VCRs that could drop frames and make a three-hour tape cover much longer time periods, although you would lose some information.

As soon as the digital era got into full swing, hard drives became commodity items. Computers got much faster, and video compression resulted in real space savings (MPEG-4, etc.). The Digital Video Recorder (DVR) can be understood as being a multiplexer with hard disk storage instead of tape, combined into a single device with connectivity ports added. A DVR will provide random (non-linear) ...
... access, to any part of the data at any time, which you can choose by camera ID, time and/or the date. Unless you use the highest compression at the slowest frame rates, the quality of recorded images will be far superior to those caught on tape

DVRs can be hooked up in many ways, either by direct port connections or over an Ethernet network. The amount of storage you will need will depend on image resolution, number of cameras, the frame rate (fps), triggering options, start and stop times, hours of use and other variables. It can get complicated, but there are shortcuts to finding out how to calculate DVR recording time.

So, how long will it record?
Like most things in life, actual results differ from the advertisements, and ease of use, build quality and reliability will differ according to manufacturers, while your own use of the device will also affect performance. Of course, the question, "How long will this DVR record?" is a very popular one, but it really one that cannot be answered with a one-size-fits-all reply. Analog VCRs, for example, run up against a finite maximum time limit because of tape length and recording speeds, but DVRs have virtually unlimited combinations of various settings (fps, quality, resolution or image size and scheduling, as mentioned above) that affect this calculation. Because DVR technology is what is called scalable, the best answer to that question is another question, "How long would you like it to record?"

To calculate the required storage space, remember that the more recording time you want, the more hard drive capacity you will need. This is your first rule of thumb. The easy way to calculate the numbers you want is to use one of the many DVR storage calculators found online, some of which are even made to work with specific brands and models of DVRs. Check with your manufacturer before using a generic, as there may be special considerations for your model. Before using any calculator, you should review some basic, practical information about how to approach the matter.

Preliminary decisions
No one has an unlimited budget, so the first thing to do is figure out where you really need cameras, and where you do not. There is rarely a reason (unless you are a casino or other business required to record in real-time, 30 fps) to record fast rates, and in low security areas a 1 fps rate is fine. You should also use motion detection to minimize the amount of recording. Who needs a digital recording of any empty alley? You can also find some DVRs that will record at 1 fps until motion is detected, and then increase to 30 fps until the motion stops.

Once you know how many cameras you will be running, at what different frame rates, you have a good start. You will then need to decide on resolution (image size, not monitor size) and some other variables, at which time you will then be ready to plug your figures into a DVR storage calculator. The key is not to rush into things. Do your homework, educate yourself about the technology and find out what you really need to do. This will end up saving you a lot of money compared to doing what the salesperson recommends, or just calculating everything at a real-time frame rate when you do not need to. Slow down and do things right, and you will not only save money, you will have a better DVR security system, too.
About Author:
Home Security equipment and timeslips software are only the beginning of what we have to offer at Gemini Computers. Visit online to peruse our spectrum of products including POS System, Point Of Sale Software, ELO Touch Screens, symbol Barcode Scanners, Printers, Cash Registers, MSR, Scales, Intercom/Video Phones, IP Cameras, Accounting Software, and much more.