What is frame rate? And why does it matter?
Videos are becoming a very significant part of our everyday life. We record videos to share with family and friends, put on social media, for advancing our businesses, for advertisements, and other life events.
Even though it’s becoming very easy to record a video any time anywhere, the process still requires a basic understanding of some technical terms, options, and settings to get the best result desired.
Today we will focus on the video frame rate and its connection to the video motion quality, and its impact on the file size.
What is frame rate?
Every video we watch consists of a number of photographs that are displayed at a certain rate to show picture motion. Those photographs are called frames and the number of frames per second in a video is what we call frame rate.
In general, the standard frame rate is 24 to 30 Frames Per Second (FPS) for videos like those we see in movies and TV shows, and 60 Frames Per Second for sports events, gaming, and other scenes that involve fast-moving objects.
When you hear the technical term FPS (Frames Per Second) is 30 about a specific video, that means the video is flipping 30 images per second to display the video.
Why does frame rate matter in the video capturing world?
Why do you care to know whether your video has a 24 frame rate, 30, 60, or otherwise? You should because the video experience relies heavily on the frame rate. When you are watching a video that has a smooth motion and crisp details, you are watching a video with a high frame rate which is 24 FPS or more. On the contrary, lower video frame rates will show a jumpy video with rough motion.
It really matters to set up your frame rate right
Most of the time, the default frame rate will work and you won’t need to update it. But in some cases which we will talk about later in this article, you might need to do some adjustments.
To decide what is the right frame rate that will work best for you, you will have to ask yourself the following three questions:
- Do you care if the file size got big, or do you need to keep it as small as possible?
- How fast the objects in your video are going to move? How important is it for you to get every small motion detail?
- Do you need to do any video editing, any video redaction work before sharing it with the public?
Let’s start tackling these questions one by one.
Do you care if the file size got big, or do you need to keep it as small as possible?
Choosing the frame rate for your video will have a huge impact on the video file size. Here is why:
Since the frame rate of a video tells us how many images per second the video has, then we can do simple math to calculate how many images a 5 minutes video has in two different scenarios:
- The video has 25 Frames Per Second rate:
- 25 frames * 60 seconds per minute * 5 minutes = 7500 Images in 5 minute video
- The video has 60 Frames Per Second rate:
- 60 frames * 60 seconds per minute * 5 minutes =18000 Images in 5-minute video
As you can see above the five minutes video with a 25 FPS rate will have 7500 images while the 60 FPS video will have 18000 images. That will clearly have an impact on the size of the video file (more than 2 times in this example). The higher the recording frame rate is the larger the video file size will be which in turn will impact the data storage planning financially and strategically.
Now imagine you have a surveillance camera that is recording hundreds of hours of video every week, body-worn cameras, in-car cameras that stay on for hours and hours a day. In those cases, getting the frame rate right matters a lot.
How fast the objects in your video are going to move? How important is it for you to get every small motion detail?
Having a high frame rate along with video resolution will produce a sharp, clear video with great smooth motion which will easily help identify people and other objects in the video. If you are capturing a sports event, if you are recording a crime scene, if there are really fast-moving objects, that’s when you need a higher frame rate that can go up to 60 FPS.
In some cases when recording sensitive information it’s very important to make sure you have the frame rate set up to capture all the details needed. Especially if there are fast-moving objects.
Do you need to do any video editing, any object detection, any video redaction work before releasing?
Sharing your recorded video will sometimes require editing, enhancing, applying effects, detecting objects, and redacting sensitive and private information.
A Lot of video editing tools will help you edit, enhance and apply effects without worrying about the details in which those functions are being applied which makes it easy for you to not think about the frame rate when you record your videos.
However, when it comes to object detection and redaction, the frame rate plays a huge role in saving time and effort on human and machine levels.
Let’s go back to the 5 minutes video example, if we are to detect objects and apply specific effects like blur or pixelate faces, license plates, private information in screens and papers, we will need to go through the 7500 different images for the 5 minutes video when the frame rate is at 25 FPS and 18000 different images for the same video with the 60 FPS rate.
Of course, there are a good number of tools out there like CaseGuard Redaction Software that uses machine learning algorithms to detect still and moving objects in videos and can help you achieve all those different functions automatically without you worrying about doing so frame by frame. However, any video analysis software that can detect objects like faces, license plates, cars, screens, papers, and others, will have to scan every frame in your video to be able to give you the desired output. Scanning and detecting objects even if it’s done automatically will consume a lot of time and resources.
Back to our 5 minutes video example, the processing time for detecting objects like faces and license plates with a 60 FPS rate can be cut in less than half if we are working with the 25 FPS rate. That is both time and machine power. On top of that, having a high frame rate will require the video editor to go over more frames and make sure that the object detection work was done correctly and accurately. Now imagine having hundreds of hours of video with a 60 FPS rate vs 25 or 30 FPS.
Frame rates in surveillance and body-worn cameras
The standard frame rate for surveillance cameras is 15 FPS. It does not usually produce a smooth motion or crisp details but it is recommended so it captures the most action while minimizing the storage cost. The storage costs can go dramatically up or down based on the frame rate.
For body-worn cameras and in-car cameras, 30 FPS is the standard video frame rate that provides clear, natural, and realistic motion video. Too low a frame rate may miss important details, such as the direction a suspect flees, the suspect license plate number, or the use of a weapon. Frame rates lower than 25 FPS for such sensitive content will cause motion blur, which is the last thing you need here.
Understanding what the frame rate is and how to choose it right will require some thought but It will have a huge impact on how you conduct your business, how you manage and store your data in a timely manner and cost-effective way. Answering the three questions above will help you get there.