Drop in an mp3 and get a StepMania song folder: the tempo fitted across the whole track, the first downbeat located, and the steps written against that grid. Verify the sync against a click track before you commit to anything.
The tempo is fitted across the whole track rather than tapped from the intro, and the grid is drawn over the waveform with a click track you can play against it. Nudge the offset by hand if the detector was close but not right.
Stack charts the way real stepfiles do — a spread from Beginner to Challenge, or four varieties at one rating. Slots are assigned so no two charts can collide and become unplayable.
Point at a video ripped from the same source and its audio is
cross-correlated against the song's, so #BGCHANGES starts on
the beat it should rather than on a guess.
Open a folder that already has an .sm in it and the new chart
is merged in, not written over: the banner, the preview sample and every
other difficulty survive, with a timestamped backup beside them.
Paste a video URL and the audio and video are pulled together, so they are aligned by construction rather than by measurement.
Step patterns come from a model built from thousands of official charts, so staircases, candles and crossover entries look like something a person would write.
Almost nothing. Chart generation runs on a model built into the tool, so it is free with an account. Only the optional AI chart mode calls a language model, and that is metered by the tokens it actually uses.