What Size Hard Disk Will You Need?
This is a great question that will appeal to your inner geek. If you don’t consider yourself to be technically minded though, let’s go over this in layman’s terms.
You also don’t need to be a brilliant mathematician to work out how much hard disk space you’ll need for X number of days recording, because there are some fantastic software tools available, often provided by CCTV manufacturers, that will do the calculations for you.
Hikvision’s Storage and Network Calculator is a free tool available to download from their website.
These are the key elements that influence CCTV video size:
- Frame rate
- Scene complexity
The number of security cameras you have installed will of course largely affect the storage required.
Camera resolution is defined in megapixels (MP), or the number of pixels crammed into the frame.
One resolution we all may be familiar with is the resolution of our high definition (HD) TVs: 1080P. 1080P HD which is 1920 pixels along the width by 1080 pixels along the height (1920×1080).
Ultra HD or 4K can be from 8MP (3840×2160) to 12MP (4000×3000). So, better quality images, but larger video files.
Simply put, the more pixels squeezed into the frame, the more data there is to be processed, streamed or stored.
Measured in frames per second (FPS) this is how many still images are being captured/displayed per second.
Think of a flip book where you would draw one picture on each page and flip the pages to animate the drawing. This is essentially what is happening.
The higher the frame rate, the smoother the ‘animation’ of the on-screen video. And the higher the frame rate, the more data is being processed, streamed or stored.
This page goes into more detail about frame rate if you would like further reading.
A frame rate of 12 or 15 fps is usually more than adequate for CCTV purposes.
As we already know, the number of pixels on screen and the number of frames per second as they increase, means more data to be processed, and therefore more data to be stored.
And the complexity of what is on screen / being captured by camera is also going to have an influence on CCTV storage.
More movement and detail in front of the camera means more pixels changing more often. Vehicles passing, people moving, trees and shrubs moving in the wind, these will all add to scene complexity.
To reduce the size of CCTV data files, compression algorithms such as H.264, H.264+, H.265 were developed. With the resolution of CCTV cameras becoming greater, improved compression became a necessity and with that, Hikvision developed and released H.265+.
These compression techniques can greatly reduce the amount of storage space required as well as the bandwidth needed to stream such high resolution images, without losing image quality.
H.265+ can reduce the size of files by up to 82.5% compared with H.264, and a 66.4% saving on H.265.