Speed ramps

A ramp is a change of speed over time. A flat setSpeed is a speed CHANGE, not a ramp; use it only when no ramp is wanted.

Workflow

1. Ramp with one curve: setKeyframeTrack with prop:"speed" and the whole curve as keyframes ({time, value, easing}) in one call. It rescales the clip so the selected source footage is kept and returns the new duration. Do not build a ramp from several addKeyframe speed calls: they leave the clip length alone, so the ramp consumes a different stretch of source than the one you chose. For a slow-motion hit: 1.0 down to 0.3 to 0.4 over about 0.3 s with easeOutCubic just before the moment, hold, then back up. For velocity edits, time the ramp in beats (beat-sync).
2. Or use the preset: applyVfxPreset "speed-ramp" writes a tested ramp in one command.
3. Motion blur sells fast moves: setMotionBlur 50 is about a 180-degree shutter. It costs nothing on a still clip.
4. Replays: duplicateClip, slow the copy (about 0.5) and place it immediately after the original; optionally label it.
5. Freeze: freezeFrame at the source-media time to hold, usually with a label and a punch.
6. Reverse: reverseClip. For a rewind beat, duplicate, reverse the copy and shorten it so the motion snaps back.

Gotchas