Subtitle Frame-Rate Retime Converter

When a video changes frame rate the subtitle clock changes with it. A film at 23.976 fps broadcast in PAL at 25 fps plays 4.2708% faster, so every subtitle must shrink by the factor 23.976/25 — shifting alone can never fix that, because the error grows over time (about 2.6 seconds per hour). This converter multiplies every cue start and end by the exact ratio: presets for the common PAL speedup / slowdown pairs (23.976↔25, 24↔25, 24↔23.976), arbitrary source/target frame-rate pairs, a direct duration factor, or two-point calibration — you give one cue's current and correct time, a second cue's current and correct time, and the tool solves the line t′ = a·t + b that maps both exactly, fixing drift AND offset in one pass (a mismatched frame rate is exactly a linear error). The report shows the factor applied, the first cue's shift and the accumulated drift at the last cue so you can verify the direction. Millisecond rounding only; the input is never re-formatted beyond the timing lines.