Video Framerate Converter

Convert video framerates between PAL (25fps), NTSC (29.97/30fps), and cinema (24fps) formats. Get ready-to-use ffmpeg and sox commands for both conform (speed change) and interpolate (frame drop/add) methods.

Input

Conversion Settings

Conform = total frames stay same, playback speed changes. Interpolate = duration stays same, frames added/dropped.

Results

Input Duration

Seconds
1500 frames
60 sec(s)
Minutes
60 secs / 60
1 min(s)

Conversion 'conform': 25 → 24fps

Definition
The total # of frames stays the same
1500 frames
Speed
video is slowed down from 25 to 24 fps
-4%
Audio
As a result, the audio will sound lower
Correct audio
pitch up by +4.167% (0.707 semitones)
104.17%
Convert video
ffmpeg -i [input] -r 24 -filter:v "setpts=1.0417*PTS" -y [output]
Convert audio
sox [input] [output] tempo 0.96
ffmpeg -i [input] -filter:a "atempo=0.96" -vn [output]
Duration: time
1500 frames / 24 fps
62.50 sec

Conversion 'interpolate': 25 → 24fps

Definition
The total duration stays the same
60 sec
New length
60 seconds * 24 fps
1440 frames
Naive conversion
drop a frame every
25 frames
Convert video
ffmpeg -i [input] -r 24 -y [output]
Convert audio
audio stays exactly the same

How to Use

  • Calculate frames from duration: 93 sec @ 24fps = 2232 frames
  • Get ffmpeg/sox commands to change framerate
  • Common use case: convert PAL (25fps) or NTSC (30fps) to cinema (24fps)
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Frequently Asked Questions

What is the difference between conform and interpolate?

Conform keeps all original frames but changes playback speed (and audio pitch). Interpolate keeps the original duration but adds or removes frames to match the new framerate.

When should I use conform vs interpolate?

Use conform when you want to preserve every frame (like slow-motion). Use interpolate when duration must stay the same (syncing to external audio, matching other clips).

Why does conform affect audio pitch?

Conform changes playback speed. Slowing down video also slows audio (lower pitch). Use sox or ffmpeg atempo filter to correct pitch while keeping the new speed.

How do I convert PAL to NTSC or vice versa?

PAL is 25fps, NTSC is 29.97fps. Use conform for ~20% speed change with pitch correction, or interpolate to add/drop frames while keeping original duration.

What framerate should I use for cinema?

Traditional cinema uses 24fps. High Frame Rate (HFR) cinema uses 48fps or 60fps. Most streaming platforms accept 24, 25, or 30fps.