GOP / Keyframe interval

[FranckB]

Hello,
a question about the Keyframe interval.
I use OBS for recordings my screen. I want the best possible quality when capturing. Until now the value I use is 120 or every 4 seconds (30 fps). In X264 the quality is good and a controlled file size. But in video editing software, the timeline is quickly slowed down when there are many cuts in the video. I recently learned the concept of GOP and therefore its relationship with the keyframe interval. I just made recordings at 15 frames for the interval (1/2s). The size of the files is multiplied by 5 (normal) I do not notice a difference in quality (it is low)

My question is, is there an ideal value? both to control the size of the file, for the quality, and above all to avoid slowdowns in the timelines?
What value are you using? 15, 30, 60? 120 would be too much... (at 30fps)

Thanks

 

[FranckB]

anyone have an idea?
I specify for the recording, not for the stream

 

[sandrix]

This is a rather complex and extensive topic for discussion. There are many factors that influence the choice of key factors and it is impossible to simply say how much is best to use. Everything depends on the tasks.
There are only recommended values. Encoding a key frame every 2 seconds for a 60 fps video would be the optimal value.
Usually for dynamic video it is customary to reduce the keyframe interval, while for static video it is better to specify a higher keyframe interval.
It will take me a long time to explain why this is needed, so here is a great article.

Keyframes, InterFrame & Video Compression

Learn what keyframes are in relation to video compression while describing the interframe process. Includes best practices to follow for live streaming while setting this up in the encoder.

blog.video.ibm.com

Keyframe spacing is not your main concern.

 

[FranckB]

Hello,
thanks for taking the time to respond. I will read the article.
Also the two second value, I apply it for 30 fps, for software capture where it's relatively static.

I made a capture of one hour at the value 15 (1/2s at 30fps), for the timeline it's better, but the size of the file becomes enormous without improving the quality (it's better but not a lot of difference)