When it comes to video surveillance systems, bandwidth is an integral aspect that you definitely want to consider. This is because CCTV systems require immense amounts of bandwidth which can drastically affect your storage requirements. In this article, we’ll discuss how much bandwidth is required for CCTVs so you can adjust your storage solutions accordingly.
How bandwidth affects storage
The amount of bandwidth a CCTV system uses correlates to the overall quality of its video output. In general, a higher video quality requires more bandwidth which, in turn, requires more storage space. When it comes to video quality, there are a couple of factors to consider such as:
Frame rate (fps)
Continuous or event recording
This refers to the size of the image which is measured in pixels. In CCTV systems, the most commonly used resolutions are 1.3 MP (1280 x 1024), 2MP (1600 x 1200), 4 MP (2688 x 1520) and so on. Higher resolutions will consume more storage space but will display more intricate details of a given image.
One of the most common questions people ask is “What resolution should I use for my CCTV cameras?” The answer is it depends. You can justify using a higher resolution camera if you want to record monetary transactions, identify license plates, and recognise faces of intruders. Lower resolution cameras can be used for applications that don’t require much detail (think of monitoring hallways and entrances).
Frame rate is the speed at which images are shown on a display. This determines whether the video is smooth and fluid or choppy and robotic. The goal with CCTV systems is to display many images in a fast sequence to allow for a better sense of motion. For example, images that are displayed at 30 frames per second (fps) appear more fluid than 10 or 15 fps images.
Like with most things in CCTVs, a higher frame rate requires more bandwidth, thus increasing your storage requirements as well. Most CCTV systems use 15 fps and while this may be adequate for daily recording, you may want to use 30 fps in instances where you’ll be recording plenty of movement.
Compression algorithm (also called CODEC) works by reducing the amount of storage and bandwidth required to store a recorded video. Footage captured by CCTV cameras are often too large to be stored and it’s for this reason that codecs are used. Such algorithms like MPEG-4 and MJPEG have evolved into H.264 and H.265 which are more efficient in terms of data compression.
While there are other compression formats used in CCTVs, H.264 is the most commonly used one as it offers high-quality video transmission with low bandwidth requirements. It works with colour variations, predictions, and movement to help save on bandwidth and storage depending on how complex the scene is.
Speaking of scenes, the amount of activity in front of a camera can influence bandwidth usage. The more movement is recorded, the more information is processed, hence the need for higher bandwidth. One example is commercial establishments like malls and stores. Activity in these areas is very high and the images come out very complex, thus costing more in terms of storage and data transmission.
As a general rule, you want to consider scene activity with a margin of safety. If you’re going to record a heavily populated area, you will need to use a higher resolution camera to see more detail. This amplifies your storage needs so keep that in mind when setting up your CCTV system.
Continuous or event recording
Continuous recording is the act of recording videos at 100% length. Recording footage for hours on end creates extremely large file sizes. Even if you were to compress the file, you’d still end up with footage that consumes significant amounts of storage space. This is where event recording comes in.
Event recording is different from continuous recording in that it only records footage when it detects movement. What this does is eliminate unnecessary footage, allowing you to perform a more efficient recording that uses less storage. When using event recording, you can record on a digital video recorder (DVR) and store the videos only for a specific period generated by the alarm.
Both types of recording have their own time and place. Consider your storage solutions to determine whether or not you should record continuously or go with event recording instead.
How much storage do you really need?
There is no straightforward answer that can accurately determine your storage needs as each setup varies differently from property to property. That said, there are many online CCTV storage calculators online that give a rough estimation based on the number of cameras you have, the resolution you’re using, the number of frames per second, and so on.
For domestic applications, we generally recommend having 2TB worth of storage if you’re using a 4-6MP camera and 4TB if you’re using an 8MP system.