D1 vs CIF?

What's the difference betwen D1 & CIF?

Firstly let's define the resolution acronyms

QCIF: 176 X 120 Pixels
CIF:    352 X 240 Pixels
2CIF:  20 X 240 Pixels
4CIF:  704 X 480 Pixels
D1:     720 X 480 Pixels
960H: 976 x 582 Pixels
HD:    1280 x 720 Pixels  ( for IP camera, 1080P)

Two elements are important when looking at DVR recording quality

1. The Resolution  : The size of the recorded image
2. The Frame Rate : How many frames are captured per secound

In the UK (PAL) For real-time recording, the frame rate is 25fps for every DVR.
So the highest recording speed for a 4 channel DVR is 4 x 25 = 100fps, etc

It is not essential to record at this real time speed because even at 3-5 fps  you will not miss anything and only use up valuable hard disk space filling up with unecessary frames.

QCIF, CIF, 2CIF, D1, 960H, HD, 1080P comparison diagram  So why is D1 recorded resolution is so important ?

There are regulatory & legal requirements in some situations e.g. casinos and governent buildings, for each channel to be originally recorded in D1 resolution.

D1 resolution (720x480 pxls) is the highest resolution that a standard DVR can record in. 
Typically, the higher the resolution you choose to record in the lower the frame rate you have to select. The higher of the recording resolution, the more data your DVR needs to process and the more Hard Disk space is required.

CIF Reslution is an image of 352 X 240 Pixels,

960H represents the number of effective pixels in the horizontal direction of the CCD image sensor which can provides 976 X 582 Pixels resolution, and is the highest resolution in an analog cctv system.