Storage
The single question which is thrown at me often is.. How much Hard Disk Space is required for storing x days of
Recordings?
Normally this is thrown at me by the installing technician /
engineer / project manager and it often amazes me that these guys can actually
operate in our industry without even knowing the basics.
Let me explain why this amazes me..
A system has cameras, a recording system and corporate
standards which are to be followed. So to me it becomes simple to provide for storage estimation.
Lets break this down to even more questions to answer this
question..
- How many cameras?
- Recording Resolution?
- Recording Frame rate?
- Number of hours of recording?
- What’s the type of activity in front of the cameras?
- Motion Based or Continuous Recording?
- Compression standard? Normally H.264
- Number of days to store the Video?
Most times people will answer question (g) immediately and
tell you x number of days.
Now why is it important to ask all those questions to answer
a simple question?
Compression plays an important factor and the resolution
used then provides the basis for the answer..Infact a number of online tools provide for a simple method
to arrive at a answer which would most times be dependable.
Given below are 3 links which are available
Once you have gone through the links above you will
understand why the question asked to me always amazes me..
While these links will provide you with the hard drive requirement at most times these estimates will have to be taken with some percentage variations…
These variations take place due to bit rates being considered, image quality during night time due to noise interference and also the kind of activity in front of the cameras. In an area which has very high activity each frame would have higher data and this will impact the storage requirements.
Most times people and here I mean the manufacturer’s sales guy will play around with the bit rate settings to ensure that they provide low figures thus trying to imply and show that their product is the best for bandwidth and storage requirements.
Be aware that what they will not tell you is that
H264 has a de-blocking filter which will ensure that fine detail in an image with a great depth of field / view will get lost. Should this be a case where the camera is installed in an atrium area of a shopping mall or in a public surveillance kind of environment the foreground image will probably meet approval while the background objects will lose detail. Worse still H264 is also very poor at handling low light scenes.
In such situations bit rate becomes important and should be applied with due consideration.
Here is an article which actually makes for interesting reading..http://www.initsys.net/attachments/Compression%20and%20DigitisationPDF.pdf
At the end all I can say is that if the Security Manager is clear with what he needs then the installer will have very little room to play with storage figures.
After all numbers are the all important factor. It’s numbers that deliver sales volume, it’s numbers which reduces cost from a commercial manager’s perspective and it’s numbers which the security manager is worried about since he has to have everything within the numbers given to him by the management!
God forbid if the requirement is recording with redundancy then the numbers become even more important!
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