PostMicroTools
Reference + calculator
Pulldown & audio sync
When footage moves between frame rates, speed and audio change. This works out the speed shift, pitch, the audio sample-rate to "pull", and how far sound drifts out of sync over time.
Common conversions
| From → To | Speed | Audio | Name |
|---|---|---|---|
| 24 → 23.976 | −0.1% | 48000 → 47952 Hz | NTSC pulldown |
| 23.976 → 24 | +0.1% | 47952 → 48000 Hz | NTSC pullup |
| 30 → 29.97 | −0.1% | pull down 0.1% | NTSC pulldown |
| 24 → 25 | +4.17% | pitch ~+0.7 st | PAL speed-up |
| 25 → 24 | −4.0% | pitch ~−0.7 st | PAL slow-down |
What is 1000/1001?
NTSC "drops" the rate by a factor of exactly 1000/1001 (≈0.0999%) for historical color-subcarrier reasons. So 24 fps becomes 23.976, 30 becomes 29.97, and 48 kHz audio paired with them is sometimes run at 47.952 kHz.
Pull vs frame-rate conversion
A "pull" just reinterprets existing frames/samples at a slightly different rate (no new frames). A true frame-rate conversion (e.g. 24→25 for content, not speed) creates new frames via blending or optical flow and is a different operation.