Does audio pitch change when I change the speed?

The audio is adjusted using the atempo filter, which changes playback speed while preserving the original pitch. Voices and music should sound natural at 0.5×–2× speeds. At extreme values (0.25× or 4×), some pitch artefacts may be noticeable.

What is the speed range?

The tool supports speeds from 0.25× (4× slower) to 4× (4× faster). The FFmpeg atempo filter only accepts 0.5–2× per pass, so values outside that range are chained automatically.

Does changing speed affect video quality?

Yes, because speed change requires re-encoding the video frames. The tool uses the ultrafast preset with CRF 23, which provides good quality at manageable file sizes.

How long does speed change take?

Speed change re-encodes the entire video. Expect 2–8 minutes per minute of 1080p video on a modern laptop. The processing time is similar to video compression.

Which input formats are supported?

ffmpeg.wasm supports MP4, WebM, MOV, AVI, MKV, and most other common video formats as input.

Is my video uploaded during processing?

No. ffmpeg.wasm runs entirely inside your browser. Your video is processed locally and never sent to any server.

What format is the output?

The output is MP4 (H.264 + AAC). The file duration changes proportionally to the speed multiplier — a 1× 60-second clip becomes 30 seconds at 2× and 120 seconds at 0.5×.

What are common uses for speed change?

Common uses include creating timelapse videos (2×–4×), slowing down sports or tutorial footage (0.5×–0.75×), speeding up long screen recordings for quicker review, and generating looping background videos with adjusted pacing.

Video Speed Changer

Speed up or slow down any video from 0.25× to 4× with synced audio — entirely in your browser.

100% client-side · no upload

How to change video speed

Select your video file. MP4 and WebM are best supported.
Choose a speed preset or enter a custom multiplier (0.25×–4×).
Click Apply speed change and wait for ffmpeg.wasm to re-encode.
Download the speed-adjusted MP4.

Common use cases

Timelapse (2×–4×): Speed up a long recording to create a timelapse effect for presentations or social media.
Slow motion (0.5×): Slow down sports or instructional footage to make details easier to follow.
Tutorial review (1.5×): Speed up a screen recording for quicker sharing without losing comprehension.
Audio tempo (0.75×): Slow down a music performance to analyse technique.

常见问题

Does audio pitch change when I change the speed?: The audio is adjusted using the atempo filter, which changes playback speed while preserving the original pitch. Voices and music should sound natural at 0.5×–2× speeds. At extreme values (0.25× or 4×), some pitch artefacts may be noticeable.
What is the speed range?: The tool supports speeds from 0.25× (4× slower) to 4× (4× faster). The FFmpeg atempo filter only accepts 0.5–2× per pass, so values outside that range are chained automatically.
Does changing speed affect video quality?: Yes, because speed change requires re-encoding the video frames. The tool uses the ultrafast preset with CRF 23, which provides good quality at manageable file sizes.
How long does speed change take?: Speed change re-encodes the entire video. Expect 2–8 minutes per minute of 1080p video on a modern laptop. The processing time is similar to video compression.
Which input formats are supported?: ffmpeg.wasm supports MP4, WebM, MOV, AVI, MKV, and most other common video formats as input.
Is my video uploaded during processing?: No. ffmpeg.wasm runs entirely inside your browser. Your video is processed locally and never sent to any server.
What format is the output?: The output is MP4 (H.264 + AAC). The file duration changes proportionally to the speed multiplier — a 1× 60-second clip becomes 30 seconds at 2× and 120 seconds at 0.5×.
What are common uses for speed change?: Common uses include creating timelapse videos (2×–4×), slowing down sports or tutorial footage (0.5×–0.75×), speeding up long screen recordings for quicker review, and generating looping background videos with adjusted pacing.

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