The keyframe interval controls how often a keyframe (i-frame) is created in the video. The higher the keyframe interval, generally the more compression that is being applied to the content, although that doesn't mean a noticeable reduction in quality.
For live streaming you will want to set your keyframe interval to 2. What this means is that a full video frame will be rendered every 2 seconds. If you want to learn more about keyframes, head over here.
Strictly speaking, longer keyframe intervals should result in better quality for the bitrate, but there's diminishing returns, and in the context of live encoding, its not worth going crazy on.
Let's say it's 2 minutes between I-frames -- that means if you're watching and have a slight hiccup in your connection, it's going to take upwards of 2 minutes before you can start viewing again.
Bitrate for recording and streaming should be set from 4000 Kbps to 6000 Kbps depending on your bandwidth, frame rate, and video resolution. Plus, note that Keyframe Interval should be set at 2, meaning that the video frame will be rendered every 2 seconds.
Streaming programs like OBS and XSplit let you set your Keyframe Interval manually, and for the most part, you're going to want to stick to 2. This value means '2 keyframes every second'.
Because of this, it's recommended to have your keyframe interval set at 2 seconds for live streaming.
OBS Output Settings
Of course, you can select a higher video quality if you choose. If you are only streaming audio, you can get away with bitrate settings as low as 64 kbps. However, for better quality, you should up your audio bitrate settings to 192-320 kbps.
A keyframe marks the point in time where you specify a value, such as spatial position, opacity, or audio volume. To create a change in a property over time, you set at least two keyframes—one keyframe for the value at the beginning of the change, and another keyframe for the value at the end of the change.
With their new Navi GPU series AMD added a new feature to the hardware encoders: High Motion Quality Boost. This option should allow you to get higher quality streams at the exact same bitrate, resolution and framerate, given that you own and use an AMD RX 5700 (XT/XT Anniversary).
The best bitrate for 1080p 60fps on Twitch is 6,000 kbps provided if you have a strong internet connection. However, you can opt for 1080p 30fps that requires at least 4,500kbps if you have a slower connection.
The reasons why your OBS lags depend on when you're experiencing the lag. If you're experiencing lags when streaming, culprits often boil down to network latency. But if it keeps lagging even if you're recording, or exporting your videos, it's mainly caused by your graphics card.
The (New) Nvenc encoder is easily the best OBS encoder available, assuming you have a modern NVIDIA graphics card with the improved ASIC chip. With zero performance impact while encoding and high-quality frames even at low bitrates, it is a strong contender as a streaming encoder.
For regular HD videos with a standard resolution, set bitrate between 2,500 to 4,000 kbps. For full HD videos with high resolution, set bitrate between 4,500 to 6,000 kbps. For regular HD videos with high resolution, set bitrate between 3,500 to 5,000 kbps.
Network congestion is the main culprit. Having a static bitrate can cause frames to drop because your connection is unable to keep up and will drop frames to improve the stability of your stream and minimize latency.
Assuming that you mean the keyframe interval in the video encoding properties panel (highlighted), this governs how often keyframes are written to the video stream. The default, 18, is one keyframe every 18 frames (or two-thirds of a second.)
For 720p video at 30 frames per second, bitrate should be between 2,500 and 4,000 kbps. That requires upload speeds between 3.2 Mbps and 5 Mbps. For 720p video at 60 frames per second, the bitrate should be between 3,500 and 5,000 kbps.
Although GPUs do not directly affect the streaming quality, having a low-end GPU means you have to play on lower settings for a smooth experience.