Turn one line of a clip into streaks on every frame. The row or column under the line is repeated toward an edge, so a subject standing above it stands on a smear of its own colours, and whatever moves through the line flows down the streaks.
A fixed line and a moving picture
The line sits at a fixed share of the frame, and the clip moves behind it. That is the whole character of the effect on video: the streaks are repainted every frame from what is on the line at that instant. A still line, through a floor or a backdrop, gives steady bands of colour. A line through a moving subject gives streaks that pulse and shift as it passes.
Direction, length and band
Direction picks which edge the streaks run to, and Up and down or Left and right stretch from the line both ways, leaving a thin band of the original. Stretch length stops them short of the edge, fading back into the frame over the last quarter. Band averages the lines around the sampled one first, which steadies the colours on a noisy clip.
Jitter
Jitter varies each streak’s start and length, which breaks the hard line where the stretch begins and gives a wind-blown edge. The arrangement is fixed across the clip, so the ragged edge holds still while the colours run through it.
Cost
The step copies pixels, so it is among the cheapest on the site: a few milliseconds per 720p frame. Export at source size is fine for clips of any length.