Keyframes and Scene Changes: How Face Tracking Crops Video

After face analysis, Bitcut creates a set of keyframes that define where the vertical crop should be positioned at specific moments in time. Between keyframes, the camera smoothly interpolates. At scene changes, the camera cuts instantly. Together, these create a natural-looking reframe of your horizontal footage.

What Are Keyframes?

A keyframe marks a specific crop position at a specific time. It tells Bitcut: "At this moment, center the vertical frame here." The face tracking engine creates keyframes automatically:

  • At the start of each scene — so the crop jumps immediately to the right face
  • When a face moves significantly — so the camera follows smoothly
  • When the tracked face changes — in multi-face scenes, when attention shifts

Between keyframes, spring physics produces smooth, natural camera movement rather than abrupt jumps.

Scene Changes

Bitcut automatically detects scene changes in your clip — moments where the camera angle cuts, the shot switches from close-up to wide, or a completely different frame appears. At scene boundaries:

  • The crop position cuts instantly rather than panning smoothly
  • A new face is selected as the tracking target for the new scene
  • The crop change is timed to happen just after the video cut, so the viewer sees the new shot before the crop shifts
Camera cuts vs. smooth pans. Scene changes produce instant cuts (like a real camera switch). Face movement within a scene produces smooth panning. This matches how professional multi-camera productions look.

The Face Strip

The face strip is a visual timeline that appears above your clip during face tracking mode. It shows:

  • Face thumbnails — small portraits of each detected face, positioned along the timeline where they appear
  • Scene boundaries — vertical dividers marking where scene changes occur
  • Keyframe diamonds — small markers showing where crop position keyframes are placed

Scrubbing the timeline updates the preview in real time, showing you exactly how the vertical crop will look at any point in the clip.

Transition Types

Keyframes use two transition types:

  • Cut — instant position change (used at scene boundaries)
  • Smooth — spring-physics interpolation (used for face following within a scene)