What is Fractional FPS in OBS Studio

This article explains the “Fractional FPS” setting in OBS Studio, detailing what it is, why content creators and broadcasters use it, and how to configure it. You will learn how this setting allows for precise frame rate adjustments to match legacy broadcast standards, preventing synchronization issues during streams and recordings.

Understanding Fractional FPS

In OBS Studio, the Fractional FPS setting is a video configuration tool that allows you to define an exact, non-integer frame rate using a fraction (a numerator and a denominator). While most users are familiar with whole-number frame rates like 30 or 60 frames per second (FPS), professional video production often requires highly specific, fractional frame rates.

By selecting “Fractional FPS Value” in your OBS Video settings, you can manually input the numerator and denominator to achieve these exact values.

Why is Fractional FPS Used?

The primary reason to use Fractional FPS is to comply with television and broadcasting standards, specifically the NTSC standard used in North America and parts of Asia.

• NTSC Compatibility: Legacy television standards run at 29.97 FPS or 59.94 FPS rather than a flat 30 or 60 FPS.
• Preventing Audio Desync: If your cameras, capture cards, or external hardware are capturing video at 29.97 FPS, but OBS is rendering the stream at a strict 30 FPS, a gradual drift between the audio and video tracks can occur over long broadcasts.
• Hardware Alignment: Many professional DSLR cameras, camcorders, and capture cards output fractional frame rates by default. Matching your OBS settings to your hardware output prevents screen tearing, stuttering, and dropped frames.

Common Fractional FPS Values

To set these common broadcast frame rates in OBS, you use the following fractional inputs:

• 29.97 FPS: Numerator 30000 / Denominator 1001
• 59.94 FPS: Numerator 60000 / Denominator 1001
• 23.976 FPS (Cinematic): Numerator 24000 / Denominator 1001

How to Configure Fractional FPS in OBS Studio

1. Open OBS Studio and click on Settings in the bottom right corner.
2. Select the Video tab on the left menu.
3. Locate the FPS dropdown menu (which defaults to “Common FPS Values”).
4. Change this dropdown to Fractional FPS Value.
5. Enter your desired Numerator and Denominator in the designated boxes.
6. Click Apply and then OK to save your changes.