Change video speed
Speed a video up or slow it down, keeping the audio in step.
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Speed and pitch
The interesting part is the audio. Simply playing a soundtrack faster raises its pitch — the chipmunk effect — which is fine as a joke and useless for a lecture you are trying to get through.
The audio here is re-timed rather than resampled, so voices stay at their natural pitch however far you push the speed. That is what makes 2x actually usable on speech.
Extreme speeds are chained
The filter that does pitch-preserving re-timing only works between half and double speed in one pass. Anything beyond that has to be chained, which is why so many tools cap at 2x or silently produce broken audio above it. Here the chain is built automatically, so 4x and 8x work properly.
What each range is for
1.25x to 2x — lectures, tutorials, meeting recordings. Most people adjust within a minute.
4x and above — skimming footage to find a moment, or turning a long recording into a timelapse.
0.5x and below — examining something that happened quickly. Note that slow motion made this way repeats frames rather than generating new ones, so it stutters. Genuine slow motion has to be filmed at a high frame rate.
Duration changes proportionally
A four-minute clip at 2x is two minutes. The result tells you both figures, which is useful when you are aiming to fit a time limit.
Dropping the audio
Turn off keeping the audio and the output is silent, which is faster and smaller — right for timelapses, where sped-up sound is just noise.
Common questions
Will voices sound odd?
No. The audio is re-timed rather than resampled, so pitch stays natural at any speed.
Can I go faster than 2x?
Yes, up to 8x. The pitch-preserving filter is chained automatically, which is where most tools stop.
Does slow motion look smooth?
No. Slowing down repeats frames rather than creating new ones. Real slow motion has to be filmed at a high frame rate.
How much shorter will it be?
Proportionally — a 4 minute clip at 2x is 2 minutes. Both figures are shown.
Can I remove the audio?
Yes, which is faster and smaller — usually what you want for a timelapse.