Formula for days of recording.

[smokingjoe 0]

Could someone tell me if there is some type of formula to figure out how many days of recording you should get on a DVR while recording constantly? I think it is effected by the size of your hard drive, your memory and frames per second while recording.

[securitymonster 0]

The storage calculators are usually offered by the DVR manufacturer. What brand DVR are you using?

[smokingjoe 0]

I am looking to purchase a DVR for a small business in my area. They would like to record for 7 days without being recorded over. I have searched the net trying to find them a good deal on a system that would do this while keeping under their budgit of $1500.

I am looking at a Dell and GeoVision CD12, 12 camera DVR and PC Base System, Frame Rates (30-120 FPS), 160GB Hard drive.

Does not say how much memory it has.

Not sure if this would record for 7 days or not.

 

Seems like this hard drive is small compared to other systems that I have looked at.

[amirm 0]

The math depends on one number but otherwise is very simple. You must know the data rate for each channel. Assuming you are using full resolution analog camera, we can use an assumption of 2 mbit/sec per channel of continuous recording. This number by the way, is selectable by you. It can be lowered and with it, lower the image quality. Or higher for improved quality (I am assuming MPEG-4 compression here).

 

Now to turn that number into days of recording, you need to do the following:

 

1. Divide the data rate by 8 to convert it to megabytes/sec (8 bits in one byte).

2. Multiply by 3600 to get the rate per hour. Multiply again by 24 to get days.

3. Multiply by number of channels you have.

 

Now let's do the math for your machine:

2/8*3600*24 = 21.6 Gigabytes/day

21 * 12 cameras = 453 Gigabytes/day

 

So your 160 Gigabyte drive would not even last one day let alone 7!

 

You can reduce the frame rate of some of the cameras as to reduce their data rate but you are so far away from making this work that I can't see that being enough.

 

Fortunately, a 1.5 TByte drive goes for $130. Add a couple and you are good to go (assuming you don't need redundancy).

 

Now someone double check may math .

[ipman 0]

The storage space formula is:

 

Days = Storage Space (GB) /

( FrameSize (Kb) * #ofFramesPerSecond * #ofCameras * * 24 * 60 * 60* Activity * / 1024 * 1024 )

 

But the most hard thing is to find out Frame Size. The easy way is to use special ip camera calculators.

Edited May 16, 2011 by Guest

[Soundy 1]

Just FYI, your DVR's memory (ie. RAM) has no bearing on it.

 

Rather than constant recording, consider motion-triggered recording. Most systems will pre-buffer and post-record so you don't miss the few seconds surrounding the event. Most allow you to set the sensitivity of the motion detection so you don't miss smaller events. The ability to NOT record when there's nothing happening will usually save you TONS of space.

 

Consider too, that 30fps is almost NEVER necessary. Most people wouldn't be able to tell the difference at even 15fps, and 7.5-10fps will still give you reasonably smooth motion. At 7.5fps, you've just reduced your storage needs to 25% of that for 30fps (or quadrupled your retention time, depending on how you look at it).