Remove frames from the middle of a movement, or repeat the same frame, so the motion jerks along. A person's movement turns stiff and mechanical, which feels eerie.
When a ghost or monster closes in, found footage with a flickering signal, dream or hallucination scenes. Use it for just 1–2 seconds.
When you generate, make a clip with clear movement (a pale figure standing still, jerking its head side to side). In editing, cut out only the section you want to break up and drop its frames. Applying fps=6,fps=30 keeps only 6 frames per second, so the motion looks choppy. To repeat the same frame a few times, use loop or tpad. For a fast tremble like in Jacob's Ladder, first speed the clip up 4x with setpts=PTS/4, then reduce the frames. Add a crackling sound effect on each stutter.
Make the picture skip like a damaged tape by dropping frames to 6 fps, then returning to 24 fps: ffmpeg -i clip.mp4 -vf "fps=6,fps=24" -an out.mp4. Apply it to a short 1 to 2 second clip and cut it in right before the scare, so the stutter breaks the viewer's rhythm.
Jacob's Ladder (1990) — An actor's head shake was filmed at 4 frames per second and played back at normal speed (24 frames per second). The head seems to vibrate wildly, like a machine (366 Weird Movies)
Not verified