The solution to the problem of vast amounts of video data and relatively slow computer systems is to introduce a computer compatible device that can capture the data from the cameras and can then process parts of the image under the control of a computer which can interpret the current image and make decisions based on those elements of the picture.

Video processor for connecting between camera and desktop/laptop computer.

The video processor is connected between the camera and the computer. It captures images from coloured CCTV cameras and interfaces to the computer to transfer requested data points as needed. A software program running in the computer requests the relevant areas of interest from the processor, makes decisions about that data and then requests other parts of the data depending on those decisions. In this manner the load requirements on the computer are low and almost any older generation computer could be used.

The image on the left is what is seen by the CCTV camera 50 times per second. This image has a lot of data on areas that we are not interested in watching, such as activity on the open fields to the left of the roadway. Our interest is to monitor the roadway and pathway to the right of the roadway and record any passing traffic. To do this the computer software applies a mathematical equation to to the image data to determine if conditions exist requiring an image to be stored. Should this happen then only a portion of the image around the area of interest is stored with time and date stamp. The image on the right is typical of a stored image.

Higher resolution cameras can be used with smaller fields of view if details such as identity of vehicles etc are needed such as in the image below.
Images are stored on the computer harddrive and can be viewed from other computers that are networked to the image processing computer. Image files are stored in directories organised in date order which can be deleted when interest in the images expires.

Advantages
The use of the Trolley Scan (Pty) Ltd Video processor with software, a CCTV camera and an old computer can give an very effective and low cost monitoring system that users can instal themselves. Many users will have an old computer lying around, or have a new computer at home that is seldom turned on. With this system you can monitor activities around your establishment when you are not there with a few extra parts of hardware.

Battle tested
The following sequence was recorded by the system while still under development. It shows a sequence of robbers watching the premises before attempting a robbery. They did attempt the robbery but were immediately chased away having left just fingerprints for the police and their future criminal record.

The system automatically took 29 images of the robbers during their 16 minute stake out. The high resolution images were so clear that we could see the quality of their shoes.

Selection of cameras
The market is flooded with a range of cameras, some very poor while others giving good images at reasonable prices. In selecting a camera we recommend the following be borne in mind

1. Ignore cameras with built in LEDs claiming to be infra red. The quality of the image is so poor and the range of the infra red features so short that they degrade to operation of the system.
2. Choose colour cameras.
3. Choose cameras with lens that are auto iris to control the light.
4. Choose cameras with high resolution - 540 TVL is great.
5. Choose cameras with varifocal lenses so you can adjust the field of view to your situation.
6. Choose cameras with electronic shutters to get a wide range of light conditions.
7. Choose cameras with cabled video and power, the RF versions for the data link get spurious noise which causes the computer to record lots of images.
8. Choose camera able to operate on a low LUX - 0.5 LUX or less is great.
9. If you want to record images of cars at night choose a camera with an eclipse feature. This darkens all bright features such as the headlights and lets the camera detect the other details.
10. Mount the camera in a weatherproof box.
11. Mount the camera on a firm base. Otherwise it will move in the wind and cause spurious detection.
12. Use RG59 coax cable for the video data from the camera to the video processor.

Future developments
With this system it is possible to monitor a property, a secure area or even goods being transported on a truck. The trigger lines are set up along the perimeter of the area you are watching and whenever this perimeter is breached, an image is taken.

It is also possible with the video processor and different software to monitor situations where people/items are moving around the image, such as monitoring players on a sports field. To do this the individual items/people are initially identified by looking at the entire image, and thereafter by just looking at the pixels around the people, their position is updated without having to analyse the whole picture meaning a high scan rate.