ffmpeg - How to change keyframe interval?

Question

How to set the keyframe interval to 5 seconds using FFmpeg?

Answer 1

You'll need to reencode. Set x264's keyint parameter to 5*fps and disable scenecut. If your fps is 24 for example :

ffmpeg -i <input> -vcodec libx264 -x264-params keyint=120:scenecut=0 -acodec copy out.mp4

This is obviously not optimal for quality but it'll match your demand.

Edited to change no-scenecut to scenecut=0, as per sigh-boy suggestion.