Network digital image transmission systems

October 2003 CCTV, Surveillance & Remote Monitoring

Digital image transmission systems on networks and the Internet have for many years been used in the surveillance industry. The ability to see images up close which occur from a long distance away is hugely compelling. Integration of information networks with video images is a growing trend as people everywhere look for ways to enhance their use of the Internet and networks.

The ability to view images remotely from a desktop computer is a goal for many organisations today. The desire for live pictures over the Internet is fuelling increased demand for new technologies that can bring images from great distances economically. Now that nearly everybody has access to a PC-based browser, the possibilities for viewing remote images exist everywhere.

Currently, new products which are entering the market such as LAN cameras, digital video recorders, video servers and digital video transmission devices which can connect directly to the LAN (local area network), are providing new and innovative remote monitoring functions. These products are able to convert images into compressed streams through the network or Internet, make it possible to perform surveillance in realtime from anywhere in the world.

The demands which are growing for security and surveillance equipment using CCTV to be managed on a network are examples which can be plainly seen. LAN digital cameras, digital video recorders are experiencing a growth as users choose to link CCTV images into computer systems and networks.

The (Net)work drives growth

Due to the dramatic growth of corporate networks, many companies are using network remote monitoring CCTV solutions, that are mostly PC driven and use specialised software with added capture cards. This allows transmission over much longer distances than normal coaxial cables. The growth of the Internet and the adoption of the World Wide Web have opened a whole new world of possibilities for using the network as a resource for CCTV imaging and transmission, replacing older, video based equipment.

The rapid development of computer networking, and massive investment in it, has benefited industries such as banking, manufacturing, medical field, supermarkets, retail outlets, petrol stations and many more. Just by applying current networking technologies to surveillance systems an event can be viewed live from any location in the world. This is pretty exciting stuff.

Unlimited opportunities

The integration of video information with existing networks offer virtually unlimited opportunities. Video network transmissions will soon change the alarm monitoring industry. The digital video server, LAN cameras and digital video recorders are ideal components for visual alarm verification. For example, Joe Soap, owner of Enterprise Systems in Joburg, used to rely on an electronic security system to alert him and the monitoring company of any alarm activations. On average the system was triggered a few times a month, with the armed response company responding to the activations. Then Joe discovered that his CCTV system could help verify activations. Joe then linked the DVR system using an ISDN modem, creating a powerful method of live surveillance and alarm verification system.

Medical monitoring via camera servers offers the possibility of sending high resolution images over networks to enable doctors to access live images for critical analysis and decision making.

The trend is definitely towards using TCP/IP and Internet technology. The change from analog to digital cannot be stopped. We all know that digital technology offers significant benefits over analog. That debate has long since been put to bed. Remote monitoring via digital networks will get faster and much more cost effective as the industry drives towards wireless networking and efficient networks.

For more information contact Abie Ali, Frank Street, 011 838 4515,,

How much storage is required?

Many CCTV installers are often stumped when it comes to calculating the amount of storage space required when using digital video recorders. There is a simple formula that one can use to help solve this storage problem. Firstly, you will require the following information from your supplier:

* Image size eg, 388 x 277 = 4 kilobytes (typical compression) 786 x 576 = 6 kilobytes (typical compression).

* Recording speed eg, 6 frames/sec per camera.

* Apply the following to aid your calculations: Frames per hour = [Frames per second] x [3600] x [no. of cameras] eg, Frames per hour = 6 x 3600 x 16 = 345 600 frames/hr.

* Image space required per hour = [Frames per hour] x [image size] eg, Image space required per hour = 345 600 x 6 kilobytes = 1,98 gigabytes.

* Therefore for 24 hour recording = [image space per hour] x 24 eg, 24 x 1,98 gigabytes = 47,5 gigabytes.

The above calculation is based on continuous recording. If motion detection recording is applied then the space capacity requirement will change.


20% motion: 48 x 20% = 9,5 gigabytes

30% motion: 48 x 30% = 14,2 gigabytes

40% motion: 48 x 40% = 19,0 gigabytes

So with a 40% motion on a 16 camera system, a 120 gigabytes hard drive will record for approximately six days.

Note: The Editor has included the long syntax for the above calculations, because there is still much confusion about what constitutes bits, bytes, kilobytes, gigabytes and the suchlike. Most times abbreviations for these descriptions are used incorrectly, including in many vendors specification sheets. One of the most confusing problems regarding PC statistics and measurements is the fact that the computing world has two different definitions for most of its measurement terms. Capacity measurements are usually expressed in kilobytes (thousands of bytes), in megabytes (millions of bytes), or gigabytes (billions of bytes). Due to a mathematical coincidence, however, there are two different meanings for each of these measures.

Computers are digital and store data using binary numbers, or powers of two, while humans normally use decimal numbers, expressed as powers of 10. As it turns out, two to the tenth power, 210, is 1024, which is very close in value to 1000 (103). Similarly, 220 is 1 048 576, which is approximately 1 000 000 (106), and 230 is 1 073 741 824, close to 1 000 000 000 (109). When computers and binary numbers first began to be used regularly, computer scientists noticed this similarity, and for convenience, 'hijacked' the abbreviations normally used for decimal numbers and began applying them to binary numbers. Thus, 210 was given the prefix 'kilo', 220 was called 'mega', and 230 'giga'.

There is a fundamental difference between the International System of Units (SI), which strictly represent powers of 10 (see and the usage of prefixes for binary multiples which have been adopted by the International Electrotechnical Commission (IEC) for use in information technology.

1 byte = 8 bits

1 kilobit = 1024 bits

1 kilobit = 128 bytes

1 kilobyte = 8192 bits

1 kilobyte = 1024 bytes

1 megabit = 1 048 576 bits

1 megabyte = 8 388 608 bits

1 megabyte = 1 048 576 bytes

1 megabyte = 1024 kilobytes

1 gigabit = 1 073 741 824 bits

1 gigabyte = 8 589 934 592 bits

1 gigabyte = 1 073 741 824 bytes

1 gigabyte = 1 048 576 kilobytes

1 gigabyte = 8192 megabits

1 gigabyte = 1024 megabytes

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