Why do some CCTV footages look crappy while
others play smoothly?
On an ordinary day an ordinary person enters the corner shop. Looks like an average Joe from the neighbourhood. He moves quickly, never looking up. His hoody somewhat covers his face but nothing suspicious. He suddenly steps to the counter holding a gun-like object in his hand. In 2 minutes he is out in the street.
Everything is not lost: the CCTV system has recorded the incident. The police arrive and check the footage. To their surprise and the owner’s horror, there is no clear picture to identify the criminal: the camera recorded only 120 pictures – 1 in a second – during the 2-minute scene. How devastating!
How could this have been avoided? Let’s look at this problem closely.
What is FPS?
Watching movies and films we rarely think about how we perceive movement from them. We do not really think about separate images when we see videos, movies or cartoons. But true thing: a video file is produced by a sequence of images.
What determines the smoothness of a movement in footages? Or, in other words, what determines the clarity in the movement? Well, it is determined by the number of images taken in a second. The more frames per second you record with a DVR, the better the quality will be. We call this number ‘frames per second’ or FPS.
Different FPS in different applications
In the early days we did not have to deal with frames as magnetic tapes were used in CCTV whose speed of the recording was pre-defined.
Different areas require different frames rates: a movie is shot at 24 frames per second, a broadcast film in Europe at 25 frames, a USA broadcast film at 30 frames and screen capture videos at 10-15 frames. Old B&W films were shot at 16 to 18 frames per second.
As digital technology emerged, it became possible to set or change the frame rate.
So, what is the ideal frame rate in a CCTV system?
Answers vary. It all depends on the environment we want to survey. Let’s take a couple of examples here.
If you are supposed to record images in a warehouse where you don’t get frequent moving objects, you don’t need to record the images at a high frame rate, probably 10-15 FPS will do. This will save you a lot of space and provide you with more recording time.
On the other hand, if it is a McDonald‘s outlet or a supermarket, you probably need smooth recording and thus you should go for a higher frame rate, e.g. 25 FPS.
Device wise, what do you really have to take into consideration?
When it comes to CCTV, the digital video recorder plays a vital role. As the recorder will record the images, it is important to make sure that you buy the right recorder.
400 FPS DVR – Wow! Should I be amazed?
Frames per second is used as a marketing tool by a lot of manufacturer. A lot of companies print and promote 400 fps in their box and marketing materials.
What is really meant by 400 fps? It means that the device can handle as many as 400 frames per second. In other words, you have to divide 400 by the number of cameras to determine the frame rate you can achieve.
For example, if you have 400 fps in 16 cameras, it means that each camera can record footages at 25 fps.
It is the same frequency as used in DVDs! It means the footages will be as smooth as those seen on TV. It simply means realistic films.
How is it affected by remote viewing?
You should also consider the frame rate in remote viewing. The number of frames per sec that a DVR can send through the internet may be lower. Sometimes drastically lower: normally around 10 to 12 fps.
It is really hard to guarantee the frame rate in remote viewing as there are several factors that will influence it. For example, bandwidth, remote viewing computer, internet speed at the other end and so on.
How does frame rate affect cameras?
When you decide that you need smooth and realistic recordings, you have to go with higher fps. If so, you also have to consider a higher TVL camera to go with. As most DVRs will give you the option to decide or change the frame rate on each camera, you will have the option of selecting the right frame rate for the each of your cameras.
- FPS means frames per second
- FPS determines how smooth a footage is
- FPS used in DVDs and broadcasting is 25 – in Europe
- If you use a CCTV system in premises with little movement, 10-15 FPS will do. If you need realistic recording, go with 25 FPS
- 25 FPS requires cameras that are capable to record at this frequency
- A DVR determines how many cameras it can handle at what FPS.
Remember the hoody guy? How could the owner have protected his domain? If he had understood that a CCTV system is not a guarantee per se; if he had set it properly i.e. increased the FPS to 25, the police could have used the footage to find and arrest the perpetrator.
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