How to speed up or slow down a video on Mac
Updated 2026-07-10 · Runs locally — nothing uploaded
Choose a speed from 0.25× to 4× and keep Preserve pitch enabled for speech; FFmix builds the matching video and audio filters before you confirm.
- Output
- Retimed MP4 with matched audio
- Processing
- On your Mac
- Setup
- About 1 minute to set up
- Access
- Free local task
Speed changes involve two clocks: the video frames and the audio samples. FFmix keeps them together by pairing setpts with atempo, so a 1.5× tutorial stays in sync and the speaker does not turn into a chipmunk. For a deliberate tape effect, turn pitch preservation off.
The command layer makes that choice visible before the encode. Speeds outside ffmpeg’s single-filter range are automatically chained, and multiple selected clips can reuse the same setting as separate queue jobs.
Steps
- 1 Drop the clip into FFmix and choose Change speed.
- 2 Set a speed between 0.25× and 4×.
- 3 Keep Preserve pitch on for speech, or turn it off for a tape-style effect.
- 4 Review the video and audio filters, then confirm the local encode.
Advanced: canonical ffmpeg recipe
This is the canonical recipe. FFmix adapts encoder flags to the engine on your Mac, then shows the final command; the command shown is the command run.
ffmpeg -i "input.mp4" -filter_complex "[0:v]setpts=PTS/1.5[v];[0:a]atempo=1.5[a]" -map "[v]" -map "[a]" "input-1.5x.mp4"Drop a file and go — all local, nothing uploaded.
FAQ
How does FFmix keep voices from sounding high or low?
It changes video timing with setpts and uses ffmpeg's atempo audio filter to alter duration while preserving pitch.
Why does changing speed re-encode the video?
The operation changes frame timing and duration, so the result needs a new video stream rather than a simple container copy.
Can I process several clips at the same speed?
Yes. Select them together, choose the speed once and FFmix creates a queue job for each clip.
Related guides
Join multiple clips into one video on your Mac — instant and lossless when they match, no command line, nothing uploaded. One step with FFmix.
How to rotate a video on Mac without losing qualityRotate a sideways MP4 or MOV by 90° or 180° on Mac without re-encoding when metadata rotation is enough. Local, fast and lossless.