As a feature Request:
On selecting the required "Video Settings" and by clicking on the "Preview" button, VideoCutTool displays the loading spinner and then encode the video in the background.
This might not be as user-friendly as the users might not know how much progress did the video encoding processed.
Solution: Implement a standard progress bar which shows the percentage of encoding video of ffmpeg.
The loading spinner code is here: https://github.com/gopavasanth/video-cut-tool/blob/master/src/components/home.js#L643
Imported in Google Code-in website here: https://codein.withgoogle.com/tasks/4690276384243712/