Video transmission rate and size in disk or storage device.

[1337.807 0]

Alright, I've been bothered by this if this is really correct. About data transmission rates and the size being stored in the hard disk. Correct me if I'm wrong for example I have a camera that transfers 88 KBps so does it mean that the recorder is saving 88KB of data per second in the hard disk? Am I right? If no then how do I compute it?

[Harrar 0]

How are you storing on your DVR? 160x80, 320x240, 640x480, 720x480? What frame rate? Motion detect or continuous record? Those and more will determine how much storage you'll be using.

[1337.807 0]

for example I have a CIF resolution of 352x240 and 15fraps at a quality of Very High and I have continuous record. I understand as well that the images per frame varies depending on the background and light that the camera processes and transfer.

[Soundy 1]

"Images per frame" means nothing - one image = one frame.

 

The amount of motion will still make a difference, even with continuous recording. Depending on the codec used, in general, less motion means less data, as most of the time the compression is looking only at what has changed from one frame to the next. Little or no motion means little or no change, which means that frame requires very little data.

 

Light AS SUCH won't matter much... COMPLEXITY of the scene will. A solid grey wall can be compressed a LOT... a random multi-color pattern cannot.

[1337.807 0]

Thank you for correcting me buddy... I am new to this field and I'm glad to find this forum I can learn a lot. Our DVR's uses MPEG4, H.264, and MJPEG. So that means that we cannot really tell how big the size of an image is? Because we have lot of factors to consider. In other words what we can only tell are predections? Can you give me an example with the same variables I mentioned earlier adding my codec is MPEG4 without an audio and I have 2TB of HDD space how long will it take until the DVR fills the hard disk? I'm assuming that it will take 15 to 20 days.

[Soundy 1]

CIF @ 15fps constant... you don't say how many cameras, but I would expect with 2TB, you'd get at least a couple months.

[1337.807 0]

CIF @ 15fps constant... you don't say how many cameras, but I would expect with 2TB, you'd get at least a couple months.

 

 

So in other words soundy all we can do are predictions on how long would it take till the hard disk fills? In summary the size of the recording in each second will depend on the settings such as Frame rate, resolution, compression method the DVR is using, record type if it's continuous or motion detect, the complexity of the scene, and many more. Do you have a computation table soundy? By experience is it ok if you share some stories ?

[Soundy 1]

There are a number of disk-space calculators out there, some online, some downloadable... many are on IP-camera-manufacturers' sites and geared more towards calculating the requirements for their cameras. Generally you can plug the same info into three different calculators and get four different answers, that's how much of a black art it really is.

 

I don't really have any experience that would be meaningful to your particular situation... I deal mainly with Vigil DVRs, and besides most sites being fewer cameras, the bulk of them only use 1-2fps, maybe 80% CIF, 20% 4CIF for the analog units, Vigil also has their own proprietary Aztech codec which claims up to 90% storage reduction for MJPEG streams.

[Erron S. 0]

Soundy is exactly right. There are a few storage calculators out there that will 'error on the side of caution' and give you a high number while others want their product to have a good perception and will swing the other way. The real issue is that no matter what it's just a ball park figure. Depending on the compression and the compression technique it can vary a lot. Not only that, but it can vary from day to day depending on what it is looking at. I know a number of systems currently installed in retail locations that get an excess of 3 months in recording time, but as soon as the holidays roll around they drop down to 1 month. Why? For a couple of reasons really. For one, their hours are extended to accommodate the holiday shoppers. Two, they used to have say 50 shoppers a day while now they are getting 250 a day. It's a -more- complex image to compress due to the additional activity and movement so the files sizes are larger as well as the motion based recording is longer. When it's all said and done the best way of calculating storage is to have experience with whatever recorder you are using and estimate it to the best of your ability. I've been selling the same recorder for getting close to a decade now so I can get pretty close but I'll never be 100% accurate because the scene is always changing due to the human element. If we are looking at say a production line (lighting never changes, movement is always the same, etc) then we could accurately quote a recording time frame but not until we saw what (enter your favorite compression technology here) compression was compressing the file size down to. Then with some basic math we could extrapolate the record time from the frames per second x 60 for the minute, x 60 for the hour, x 24 for the day and so on. You get the idea anyway. Hope that helps in some way!