Many people may not understand what the Keyframe Interval stands for. However, it is a simple concept for video editors where the encoding settings determine the frequency at which the whole picture is transmitted.
The Keyframe Interval is responsible for how often a keyframe is generated within the video. A keyframe, also known as an i-frame, is a single frame that contains all of the necessary information for displaying a video. If the Keyframe Interval is set too high, it could lead to visible compression without compromising the quality of a video.
Keyframe Interval is essential in video streaming and recording, but it can be confusing. In this guide, we'll help you understand this concept to enable you to create better animations.
In this article
Part 1. What Is Keyframe Interval
Keyframe Intervals, also known as "Keyframe Frequency" in Adobe Flash Media Live Encoder (FMLE) and vMix or "GOP size" by some encoders, is the frequency at which keyframes are generated in an animated sequence. This is an important parameter to consider when creating animations, as it can impact the animation's file size, quality, and smoothness.
Keyframe Intervals are the distance in time between two keyframes. For example, if an animation is set to every 2 seconds interval and the frame rate is 30 per second, it means that every 60 frames, a keyframe is created.
Part 2. How Does Keyframe Interval Work?
Keyframes are important in video and animation because they mark specific points in time that can be used to create a smooth and consistent transition between different states or images. The Keyframe Interval is the amount of time that passes between two keyframes.
In order to create a smooth and consistent transition, the Keyframe Interval must be carefully calculated. In a 60-frame-per-second video, a keyframe is recorded every 5 or 300 frames. Delta frames are "difference" frames that provide an incremental change from the previous frame.
Keyframes are different from delta frames in that a higher keyframe value results in a clearer video with fewer transmission artifacts and vice versa.
The Keyframe Interval can be adjusted to create a faster or slower transition between two keyframes. A shorter Keyframe Interval will create a faster transition, while a longer one will create a slower transition.
For example, if you want your transition to look smoother, use a longer interval, like two seconds. Conversely, a zoom effect over a 0.2-second interval will be quicker.
Part 3. A concept closely connected to Keyframe Interval - Bitrates
The relationship between keyframes and bitrates is important to understand when creating video content. Keyframes are the frames in a video that are used to define the start and end points of an encoding process. The bitrate measures how much information is being transferred in a given time from one place to another.
When encoding video, keyframes are used to establish a consistent quality throughout the video. The bitrate is then used to determine how much information can be transferred without affecting the quality of the video. Thus, the higher the video's bitrate, the better the quality.
Your mileage may vary regarding this explanation, as different encoders manage bitrates and keyframes in different ways.
For example, if you're using an encoder like Wirecast, you might notice that broadcasting in a still background with someone talking results in a higher quality video as compared to a moving background. This can be reproduced using the same average bitrate and Keyframe Interval between them.
This happens because the delta frames have to share a lot more information to share in each frame in the video with a moving background. When you have an encoder like Wirecast, it's working to keep your stream at an average bitrate. This can result in reduced quality if there is a lot of extra information in the delta frames.
Part 4. What You Need To Know To Set A Right Keyframe Interval
After understanding the important concepts in video editing, let’s see how to set the keyframe level in our videos appropriately.
Most streaming services will automatically set it for you based on your stream's frame rate and bitrate. However, if you want to set the keyframe gap manually, there are a few things you need to keep in mind.
- Set the frame interval at 2 seconds. Do not increase it from 4 seconds.
- Disable the "auto" keyframe feature.
- To allow for b-frames, use an encoding profile higher than baseline and use IDR-based keyframes.
Part 5. How To Change The Keyframe Interval On OBS Studio
Above is the basic knowledge of the keyframe interval. Then, how to apply it to your real video-editing work? In this part, we will choose OBS to show you the application process.
OBS Studio is a powerful yet free and open-source screen recorder and live streaming tool for Windows, macOS, and Linux. One of the most useful features of OBS Studio is its ability to change the keyframe interval on the fly without having to restart your recording or stream.
The process for changing the it in OBS Studio has been made more efficient since the classic version. However, some users may have trouble locating the new setting.
Here's how to change the it on OBS Studio:
Step1 Launch the OBS Studio on your PC or laptop.
Step2 From the bottom right of the screen, open the "Settings" menu.
Step3 On the Settings Window, click "Output" and configure the output mode to "Advanced."
Step4 Finally, edit the Keyframe Interval, set it to 2 seconds, and click "OK" to save your changes.
Part 6. Will Keyframe Interval Affect Your Video’s Quality?
When you try to set the keyframe gap by yourself, you may feel confused about the difference a higher or lower interval make to your video. Then, wil-l or how it affects your video’s performance?
In a stream, it determines the balance between smoothness and picture quality. A keyframe is a point that determines how often the entire frame is sent, as opposed to just the differences from the previous frame.
Therefore, if you set the Keyframe Interval higher, your video will be more stable with fewer artifacts but requires more bandwidth and processing power. Conversely, a lower Keyframe Interval value causes more artifacts but is less resource intensive.
A lower Keyframe Interval value will result in lower video quality, while a higher keyframe value will result in higher video quality. However, the optimal Keyframe Interval value can vary depending on the specific case.
For instance, you don't need a higher Keyframe Interval for streaming a live video, but you have to use a higher Key Interval value for recording.
Video- What is the Maximum Bitrate & Keyframe Interval for OBS
The Bottom Line
In this article, we've explored Keyframe Interval, how it works, and the relationship between keyframes and bitrates. We also provided guidance on setting the Keyframe Interval correctly and changing it on OBS Studio.
Hopefully, the information provided in this guide was helpful, and you now have a better understanding of Keyframe Intervals.