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Frequently Asked Questions
Hard Disk Requirements
How do I determine how much hard disk space I need?
There are a number of factors to consider when calculating storage needs. They following factors
are:
•
Number of cameras
•
Number of hours per day the camera(s) will be recording
•
Length of storage (how long the data must be stored)
•
Type of recording (motion detection, event/sensor-triggered, scheduled or continuous)
•
Other parameters such as frame rate, resolution and compression
Calculating your hard disk requirements on a DVR using hardware MPEG-4
compression:
In MPEG-4, the images are received in a continuous data stream. It is the bit rate which
determines the corresponding storage requirements. The bit rate is a result of a specific
frame rate, resolution and compression, as well as the level of motion.
Hardware MPEG-4 compression has an approximate file size from 1-5Kb per frame (CIF)
360x240.
Let's say you have 4 cameras and you need to continuously record video at real-time 30fps
at 360x240 resolution. How much hard disk do you need for one month of continuous
recording?
Calculation: 5 x F (frame rate) x 60 (sec) x 60 (min) x C (number of cameras)
Ex: 5Kb x 30fps = 150Kbps = 9,000 Kb per min = 540Mb per hour
540Mb x 4 (number of cameras) = 2,160Mb x 24 (hours) = 51,840Mb in one day
In one month, you would need 1,555,200Mb or 1,555Gb of hard disk space
Storage Requirements in GB, Continuous Recording for High Quality 30fps CIF
Cameras
Retention
Period (in
weeks)
1
2
3
4
5
6
7
8
1
79
159
238
317
396
476
555
634
2
159
317
476
634
793
951
1,110
1,268
3
238
476
713
951
1,189
1,427
1,665
1,903
4
317
634
951
1,268
1,585
1,903
2,220
2,537
5
396
793
1,189
1,585
1,982
2,378
2,775
3,171
6
476
951
1,427
1,903
2,378
2,854
3,329
3,805
7
555
1,110
1,665
2,220
2,775
3,329
3,884
4,439
8
634
1,268
1,903
2,537
3,171
3,805
4,439
5,073
9
713
1,427
2,140
2,854
3,567
4,281
4,994
5,708
10
793
1,585
2,378
3,171
3,964
4,756
5,549
6,342
11
872
1,744
2,616
3,488
4,360
5,232
6,104
6,976
12
951
1,903
2,854
3,805
4,756
5,708
6,659
7,610
