IP Cameras - the most asked question

The single most asked question with IP cameras is also the single hardest question to answer. How much bandwidth/storage will i need for my cameras? Seriously it gets embarrassing when you have to say i do not know. That said however there are reasons why we can not say, such as how many cameras, frame rate image size, image quality, codec used, recording schedule and type of trigger if any to activate recording. There are some guides out there such as the one developed by Overland Storage and Mobotix, but they are only a guide. A rough estimate for Mobotix cameras is about 2 to 3 gig a day based on movement triggers.

Taking it a step further lets look at some numbers to show how difficult it is to pin a number down. The best an analogue camera can do is about the same as VGA(640x480) 0.3M pixels, its actually 4 CIF(704x576) 0.4M pixels, you would not find a mobile with this limited camera abilities today. Mobotix cameras however wade in at an impressive genuine 3M pixels so if we just take that number at 10 frames per second how does it compare to poor analogue cameras? Well 10 x 3Mpx is equal to 100Fps at 4 CIF (BTW CIF stands for Common Intermediate Format used to standardise the horizontal and vertical resolutions in pixels) or 400FPS at 1CIF.

This is a scary thought i here you say.....not really you see with IP cameras you can get the camera to do a lot of the work on the camera and only send what is of real interest. There is no point recording an empty room or a quiet street so the camera is set up to to only send to the recording device when movement is detected, this does 2 things it reduces storage requirements dramaticly even at 3Mpx and makes events easier to find during and after the event. The size and sensitivity of the trigger box can have a big impact on reducing false posatives too as a small trigger box could be constantly set off by any thing passing, so to detect cars entering a gate a car size trigger box is used so a person walking past would not be able to change the pixels sufficiently to cause an event.

So getting back to the question it should really be worded like so - If i had 5 cameras all running at 3Mpx at 12 FPS using MXpeg on an out of hours schedule with motion detection triggered recording stored for 31 days how much diskspace will i need? Answer ABOUT 760GB - 1TB planning this sort of system means worst case scenario a 2TB system will required.

Next time we will discuss the pros and cons of camera codecs.