Frame-rate
converter.
Fix progressive subtitle drift by rescaling between 23.976/24/25/29.97/30/60 fps.
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Frequently asked
How do I know I have a frame-rate mismatch?+
If your subtitles drift further off as the video plays — they're fine at the start but minutes off by the end — that's a frame-rate mismatch. A constant offset (using a shifter) will not fix it; you need to rescale.
What's the difference between 23.976 and 24?+
23.976 fps (technically 24000/1001) is the NTSC film standard, used by most US Blu-rays and streaming. 24 fps is the cinema standard. They differ by 0.1% — small per second, but minutes drift across a feature.
Which way should I rescale?+
Set Source fps to the rate the subtitles were timed at, and Target fps to your video's actual rate. If you don't know the source, try common pairs: 23.976 ↔ 25 (PAL/NTSC), 24 ↔ 25, 29.97 ↔ 25.
How can I check my video's frame rate?+
On macOS, open the file in QuickTime → Window → Show Movie Inspector. On Windows, right-click → Properties → Details. ffprobe and MediaInfo also show fps.
Will it round timestamps?+
Output is preserved to millisecond precision (SRT) or millisecond precision (VTT). The rescale itself uses full floating-point math — no extra rounding error beyond the format's native granularity.