Why static UI is the easy case
When the picture behind the text does not change, the model has an unlimited supply of clean copies of it — the frames before the overlay appeared and the frames after it left. A tooltip over a toolbar, a notification over a desktop, a caption burned into a demo: all of them sit over pixels that exist unaltered elsewhere in the clip.
This is the one scenario where the result is often indistinguishable from the original at 100%, provided the box is tight. Every pixel of extra area is invented rather than copied, and invention is where artefacts come from.
- Text over a gradient or a photo wallpaper is still fine — static is static
- Keep the box tight: a generous box on a static background is the most common self-inflicted artefact
- Run the job on the shortest section that contains the overlay if you only need one segment
What breaks it
Three things. Scrolling, where the content under the text moves so the clean copy is in a different place in every frame. Video playing inside the recording, which is the same problem plus a second compression pass. And anything animated — spinners, progress bars, cursor trails — which behaves like ordinary footage with the same failure modes.
The cursor deserves its own note. It is not distinguished from background, so a cursor that crosses the box becomes part of what the model samples, and it gets smeared into the repair.
- Scrolling page: split the job at the point where the text stops moving with the page
- Blinking caret: include its full blink cycle, or it returns as a flicker
- Hover states: box the region only for the frames where the overlay is actually there
Deciding what counts as text
A tutorial recording is not one overlay but several. A title card, tooltips, menu labels, and a burned-in subtitle track all live in the same frame, and they need different decisions. Menu labels are part of the interface and should stay; a tooltip you no longer want is a small, easy job; a subtitle band across the bottom is a wide, thin strip with the same geometry as any other caption.
Remove each overlay as its own box in one job. One large box around the whole lower half of the screen turns three easy repairs into one hard one.