Framerate/frames per second (fps)

What is Video Framerate?

Framerate: how frequently the images in a video update. Each image in a video is a frame,and the images update many times per second. The framerate is measured in frames per second (fps) and the FPS tells you how many images appear in that second.

In the 'flip book" image above, each page is a frame, and the 'video' updates as fast as the user is able to flip through the pages. The higher the framerate, the more 'fluid' the motion will appear.

What are common framerates used today?

• Film is typically recorded at 24 fps.
• TV is typically 29.97 FPS or 59.94 FPS. The values were initially 30/60 - based on the common electrical frequency of 60Hz, but an artifact in black and white televisions was removed by lowering the frame rate by 0.1%, and as a result, these framerates are still common today.
• Video games are typically played at 60 fps. With fast motion, it is important to not have any jank or lag in the visuals, and it was found that 60 FPS was best for gaming.
• Cartoons: Cartoons are often 'inked' at 8 ("on threes") or 12 ("on twos") frames per second, and then repeated on screen multiple times to reach the 24 fps expected by viewers. The term "on threes" comes from how often each frame is repeated to get to the 24 fps that is ultimately broadcast.

Human perception

Until recently, it was assumed that humans cannot see faster than 60 fps.

Most TVs and monitors refresh at 60 Hz (and since Hz has the unit 'per second', you can think of that as 60 refreshes per second). Some gaming monitors refresh at 90 or even 120 Hz.

A recent study at MIT showed the brain can process an image in as low as 13ms which comes to ~ 75 fps, indicating that our eye and brain can process motion at a faster rate, if only subconsciously.

FPS at api.video

Each video uploaded to api.video is encoded into multiple sizes for streaming, and we have optimized the framerate for each stream. The frames per second varies by the size of the video, and as the video dimensions get larger, so does the fps of the video:

• 240p: 18 fps
• 360p: 24 fps
• 480p: 24 fps
• 720p: 24 fps
• 1080p: 30 fps
• 4k: 60 fps