How to Speed Up or Slow Down Video with FFmpeg

FFmpeg changes video speed with the setpts filter. If the video has audio, use the atempo filter too so the audio stays in sync.

For the short command page, see Speed Up Video with FFmpeg.

Speed Up Video and Audio to 2x

ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" fast.mp4

This makes the video play twice as fast and speeds up the audio to match.

ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=2.0*PTS[v];[0:a]atempo=0.5[a]" -map "[v]" -map "[a]" slow.mp4

This doubles the presentation timestamps, so the output plays at half speed.

If you do not need audio:

ffmpeg -i input.mp4 -vf "setpts=0.5*PTS" -an fast-no-audio.mp4

The -an option removes audio.

Goal	Video filter	Audio filter
2x faster	`setpts=0.5*PTS`	`atempo=2.0`
4x faster	`setpts=0.25*PTS`	`atempo=2.0,atempo=2.0`
Half speed	`setpts=2.0*PTS`	`atempo=0.5`
Quarter speed	`setpts=4.0*PTS`	Chain audio carefully or remove audio

For video, the setpts multiplier is the inverse of the speed. For audio, atempo uses the direct speed factor.

For large speed changes, chaining smaller atempo values is more reliable:

ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=0.25*PTS[v];[0:a]atempo=2.0,atempo=2.0[a]" -map "[v]" -map "[a]" fast-4x.mp4

This creates 4x speed by applying 2x audio speed twice.

The audio is out of sync.
Use filter_complex and process video and audio in the same command.

The video changed speed but audio did not.
You probably used only -vf setpts. Add atempo or remove audio with -an.

The audio sounds bad at extreme speeds.
For very fast timelapses or very slow motion, remove audio or replace it with music.

The output file is too large.
Add H.264 settings such as -c:v libx264 -crf 23 -preset medium.