Myth No.6 ~ 'Real-time recording can't be achieved with IP'

With IP we can choose exactly what sort of ‘real-time’ recording we want, tailoring the system to the application.

What do we mean by real time recording? According to the theory of persistence of vision, the human eye retains an image for a brief moment. When a series of still video images is displayed in quick succession, we get an illusion of movement (that is, we do not see the individual frames in the series).

When is real-time recording important? It is considered vital in high security applications and also
when monitoring financial transactions. Any process where it is critical not to miss any information, such as at a casino gaming table, should also use real-time recording. For most general security and surveillance applications, however, 24-hour real-time recording is not required, and generally means massive amounts of irrelevant information are being needlessly recorded and archived. It is far better in these instances to record in real time against an alarm or video motion detection.

It is essential that we don’t miss any critical information, but recording irrelevant and redundant information is a waste of money and clutters up systems. So how do we balance the two? We recommend that for high security and high speed transactions, video cameras are recorded at 25 ips, and for general applications images are recorded at 6 or 12 ips, increasing to up to 25ips
in the case of alarm or activity. 

In the PAL television system used in Europe, ‘real -time’ video records at 25 frames per second. A
technique called interlace uses persistence of vision to combine two consecutive images (or fields) to create one frame with higher detail in non-moving areas. Because the fields are exposed and displayed separately, a single TV ‘frame’ can potentially contain motion or even two distinct images, with ‘combiartifacts’ being seen on a still image where a recording system has combined the two fields. Modern IP cameras now use non-interlaced or progressive scanning for transmitting moving images in which all the lines of each frame are drawn in sequence. Real-time recording, however, is still considered to be 25 ips.