It's not easy to choose the suitable DVR for your home surveillance or business.
How long my DVR will record and store video ? This is a very common question when people try to choose the DVR.
The times of record and store of DVR depends on following factors:
1. Record Mode
2. Record Image Quality
3. The record size.
4. The size of Hard drive
5. Frame Rate
1. Most of DVR can support 24 hours and Motion detection, Alarm detection record methods.
When
use different method for record, the strogage time will be different.
24 hours means the DVR record in every second, never stop, It will
requre the biggest storeage space (due to the video files is continuelly
filling harddirve space).
Motion detection recording means only
record when video camera detect movement, then it will start to record,
no motion, then no record. Motion detection & Alarm detection method
can save more space that means with more record time.
2. Record
image quality means the video file size, low quality image will occupy
less space, and extend more record time. High resolution quality images
means big file size, it will occupy more storage space and with less
record time.
3. When record video, DVR can select the record size
(or image size), record size changes the amount of data place in the
harddrive.
Commonly DVR record video at CIF (352 * 288), now some
DVR can support record size of D1(704*480). The big size of image, the
less time DVR can record.
4. For Harddrive, the bigger storage
size of the drive, the longer of record time. Typically for harddrive,
it should start from 500 GB and it can reach to 2 TB. Most of DVRs can
connect to 2 pcs of 2TB SATA harddrive.
Some big size DVR can put into 4 pcs of harddrive (like 97 series DVR).
5.
Frame Rate, movie records and plays at 24 fps (pictures/frames per
second). Real time recording for DVR systems is 30 fps. Most of time 15
frames a second looks good but may miss some details that would provide
help in theft, slip and fall, and many other incidents. Unless storage
time is a real problem we recommend 30 fps. Basically, more frames means
more pictures and more pictures means more data, also means less record
time.
At last, how many days can record of 500GB DVR with 4 camera at CIF record mode ?
For CIF record mode, each camera take almost 300M per hour, then 4 camera X300M= 1.2GB, 500GB DVR approximately 18 days.
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