What is Frame Rate (fps) and Why Does it Matter in Live Streaming?

This post addresses frame rate (fps) and the role that it plays in creating a great quality live stream. It's part of our series on HD live streaming.

While many factors affect the quality of your live video, resolution and frame rate are the most prominent. In this post, we'll talk about the latter.

Note: You can read more on video resolution here.

What is Frame Rate?

When you create a video, you capture thousands of individual images in a video sequence. Those individual images are frames. The frequency with which those frames appear in a given amount of time is the frame rate.

Frame rate affects the way we perceive motion in a video.

When you capture and display only a few frames per second, you miss some of the detail of the movement. As a result, the video may appear choppy.

On the flip side, when you capture and display more frames per second, you uncover the motion within your shot. With a higher frame rate, you see smoother action.

How is Frame Rate Measured?

The most common measurement of video frame rate is frames-per-second (fps). If your video displays 24 frames every second, we would say your video is 24 fps.

You may commonly see frame rates tagged onto the back of a video resolution. For example, the term '1080p30' represents a video resolution of 1080x1920 pixels and a frame rate of 30 fps.

Sometimes you'll see measurements denoted 'Hz' or 'hertz.' In the context of video, hertz refers to the refresh rate of a viewing device, rather than to the frame rate of the actual content. The refresh rate is the number of times your viewing device refreshes the screen in a second.

Refresh rate and frame rate are related but separate. Your device's refresh rate can limit your ability to view high frame rates.

Say your television has a refresh rate of 60 Hz:

• If you have video content playing at 60 fps, there will be precisely one new frame loaded each time your screen refreshes.
• If you have video content playing at 30 fps, your device will still refresh 60 times, but a new frame will only appear on every other refresh.
• If you have video content playing at 120 fps (hypothetically), your 60 Hz television would limit that video to playback at 60 fps, as your device would not be able to show 120 frames in one second.

What Are Frame Rate Standards?

Established in the mid-1900s, the frame rate standard for the film industry is 24 fps. A few experimental directors are now challenging that norm as movie theaters upgrade to support higher frame rates.

Traditional analog television standards of the 20th and early 21st centuries dictated either 29.97 fps or 25 fps, depending on your country of residence.

However, the full transition to digital television between 2007 and 2012 delivered new opportunities for high frame rate video. Broadcast television now supports up to 60 fps. Most online streaming services also back the higher rate.

As with video resolution, frame rate affects bandwidth requirements. Video content with a higher frame rate has more data to transmit than video with a lower frame rate.

As high frame rate compatibility and increased bandwidth capacity reach more viewing devices, you can expect higher frame rates to become the new normal.

When to Care About High Frame Rates

For post-produced video, higher frame rates are essential for capturing slow motion. However, in live video, slow motion is less important.

Live streaming broadcasters use high frame rates to capture fast-paced action more completely. The faster the movement in your live content, the more valuable high frame rate becomes.

Frame rate significantly improves sporting events—like a soccer match— because it helps capture the speed and movements of the athletes.

If you live stream a panel discussion, frame rate is less critical, because your subjects are relatively still. That said, the movements the panelists make will still look buttery smooth with a higher frame rate.

Here at BoxCast, our BoxCaster Pro enables high frame rate streaming for broadcasters. With the ability to stream up to 1080p60, organizations use the BoxCaster Pro to deliver higher quality live video than their viewers usually see on live broadcast television.

Here's a quick video summary addressing a few of the things we've talked about:

Final Thoughts + Further Reading

There is a limit to the number of frame rates the human eye can see. Technologists and scientists continue to argue about the location of the upper bound, but there's still space to improve.

If you've found this post interesting, you might also want to check out our post on video resolution or this one on what to consider when starting to live stream.

Happy streaming 😃 !