Frequently Asked Questions

What is digital recording?

Digital recording offers the ability to convert analogue video images to a series of binary digital numbers and then store this as a data file with a name cross referenced against time and date.

Is digital recording right for me?

Despite claims from many suppliers, Digital Recording is not necessarily the best solution for all circumstances. Many systems are "oversold" to the customer with disappointing results, therefore it is important to plan before you buy. Technologies are rapidly changing at a rate comparable to the computer industry, which has its pros and cons. Chubb can advise you on the advantages and disadvantages of both analogue and digital based systems.

How much information can be digitally stored?

This varies depending on picture quality, update rate and compression method. As an example, to store the images on a standard videotape, a capacity of about 250 Gigabytes would be needed at 650 Kilobytes per image. Digital recording uses compression technology to reduce this to about 20 Kilobytes.

So how much information can I store on a digital recording system?

Using the best methods available a digital recording system requires just under 9 Gigabytes of storage per day (one camera at 5 frames per second with a file size of 20 Kilobytes). A 31 day archive requires 280 Gigabytes. The capacity of storage systems is becoming increasingly larger and cheaper, with 36 Gigabytes hard drives now commonplace.

How can this information be archived?

There are a number of methods available: 
Removable hard drive = 250 Gigabytes
Digital Versatile Disk (DVD) = 4.5 Gigabytes - rapid access and improving technology.
Rewritable Disk (cd rw) = 700 Megabytes - rapid access and commonplace.
The capacity and technology is improving and reducing in price rapidly.

Does digital video recording offer instant access?

Many manufacturers claim "instant access", however it is important to understand that the information is only "instant" once it is downloaded from the archive medium onto the hard drive. This download can take some time depending on the methods used, before "instant access" is available. One system recently evaluated had a download time of 40 minutes.

Why are many suppliers quoting different storage capacities and recording times?

Unfortunately, there are no common standards for digital video recording and storage in the CCTV industry. The various systems in the market incorporate different types of compression technologies. In addition some manufacturers quote low storage times and capacities when the image quality has been reduced to as good as useless.