When pictures are taken using the cctv cameras, normally they are recorded in digital forms. Such recordings are stored in the hard disks of your computer in lieu of recorders of video cassettes.

One of the methods used to expand the storage capabilities of digital recording is compressing the data.  Different vendors however use different methods of compression.  The standards and compression ratios also vary widely.

The formula that is used to assess the storage capabilities in binary forms is as follows -

Capacity =  n X f X s X a X d
K
Where n denotes the number of CCTV cameras used, f denotes the rate of frames per second, s denotes the size in terms of kilobytes of the compressed frames, a denotes the percentage of activity periods of each camera; d denotes the duration in terms of days used, and k denotes the constant that is equal to 1213.6.

With the coming into operation of closed circuit digital still cameras with resolution of 1600 X 1200 pixels.  The advantage with these cameras is that they have higher resolution compared to typical video cameras and also have greater storage capabilities. You can also use low cost digital still cameras for CCTV tasks using the CCDP software.  The camera then will be controlled directly from your computer system.

So far as recording and storage is concerned the cctv dvr can be replaced conveniently with the combination of digital still cameras with CCDP software.  However for monitoring purposes the CCTV combination works better.