Shake detection
Also known as: stability measurement, jitter detection
Measuring how unsteady a clip is, so footage too rough to watch can be weighted down before anybody is asked to look at it.
Updated
What it means
Shake detection measures frame to frame instability rather than movement itself. A smooth Tracking shot moves a great deal and is perfectly watchable, while a clip jittering a few pixels every frame is neither.
The distinction is what makes the measurement useful. Separating intentional camera motion from vibration is the whole problem, and getting it wrong penalises exactly the shots that were shot well.
On action footage it is a quality signal rather than a fault report. Almost everything shakes, so the question is never whether a clip is steady but whether it is steadier than the alternatives.
How it works in practice
The measurement usually comes from tracking how the whole frame drifts between frames and looking at the high frequency part of that movement. Low frequency drift is a pan; rapid oscillation is vibration.
The same signal is available cheaply from the file, since Motion vector analysis already describes whole frame movement without decoding anything, which makes a first pass over a long upload affordable.
Results feed weighting rather than rejection. A rough clip stays available when it holds the only usable moment, and Quality scoring is where that trade is actually made.
What to watch out for
Stabilisation confuses the measurement in both directions. Footage already fixed by HyperSmooth measures as steady regardless of how it was shot, and warped edges from aggressive correction can read as instability.
Vibration from a motor is a different beast from a bumpy trail. A quad produces a tight, high frequency pattern that barely registers as drift but ruins the picture, so amplitude alone misses it.
Rolling shutter adds a trap of its own, because the wobble it produces is a distortion inside the frame rather than movement of the frame, and frame tracking cannot see it at all.
How RawClip handles it
Clips are measured for steadiness before the search for moments begins, and rough footage is weighted down rather than discarded. That way a shaky clip holding the only good run still reaches the cut, while an equally interesting but steadier alternative wins when there is one.