Does Keep Audio And Pitch Guarantee Perfect Sound?

No. Chained tempo filters preserve pitch far better than changing sample rate, but 0.25× and 4× processing can still sound synthetic or introduce artifacts.

How Is The New Duration Calculated?

The source duration is divided by the selected speed. Encoded output can differ by a video frame or audio packet because containers quantize timestamps.

Can It Process More Than One Audio Track?

The focused export retains and retimes the primary audio track only. Other audio, subtitle, attachment and data tracks are omitted.

Video Speed Changer

Retime video from 0.25× to 4× with predicted duration and optional pitch-preserving primary audio.

Local processing: your media stays on this device.First export downloads about 31 MB of FFmpeg WebAssembly

01 · Source

Source Video

Retime picture from 0.25× to 4× and choose how the primary audio behaves.

Drop a video hereor choose a local file · maximum 250 MB / 30 minutes

02 · Settings

Output Controls

Settings are validated before the runtime starts.

Speed PresetPlayback Speed · 1.00×

Primary Audio

BEFORE 00:00:00.00AFTER --:--:--.--

Keep Audio And Pitch uses chained tempo filters. Extreme changes can sound processed even when pitch is preserved.

Output ContainerQuality (CRF 24)Lower values preserve more detail and make larger files.

Remove Container Metadata

03 · Output

Output Workspace

The completed file and processing receipt will appear here.

Open a source, confirm the settings, then run Change Speed.

Codec note: exports run in FFmpeg WebAssembly after a first-use download of about 31 MB. The 250 MB / 30 minutes picker ceiling is not a success guarantee: the complete source and output occupy browser memory, available decoders vary, and large 4K or unusual-codec media may still fail. Processing uses a duration-aware 5–45 minute job timeout. Fast trimming follows source keyframes and is not frame-perfect; re-encoded timing can still vary slightly on variable-frame-rate media.

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What Is the Video Speed Changer?

The Video Speed Changer retimes picture between 0.25× and 4×, predicts the resulting duration and either removes audio or changes the primary audio tempo while preserving pitch. Extreme factors are split into safe chained tempo stages, video timestamps are rebuilt for high-speed stability, and the exact video/audio filters, tempo factors, delivery settings and output facts are saved in a versioned receipt.

How It Works

Open a video, choose a preset or use the speed slider, compare Before and After durations, and choose Keep Audio And Pitch or Remove Audio. The browser preview follows the selected rate for auditioning; the final MP4/WebM is produced locally by FFmpeg WebAssembly.

When to Use It

Use it for time-lapse-style acceleration, slowed demonstrations, condensed tutorials, pacing experiments or duration matching. Pitch preservation avoids the obvious chipmunk or low-pitch effect, but extreme changes can still create audible artifacts and frame timing can vary slightly after encoding.

Frequently Asked Questions

Does Keep Audio And Pitch Guarantee Perfect Sound?: No. Chained tempo filters preserve pitch far better than changing sample rate, but 0.25× and 4× processing can still sound synthetic or introduce artifacts.
How Is The New Duration Calculated?: The source duration is divided by the selected speed. Encoded output can differ by a video frame or audio packet because containers quantize timestamps.
Can It Process More Than One Audio Track?: The focused export retains and retimes the primary audio track only. Other audio, subtitle, attachment and data tracks are omitted.

Found an issue? Send Feedback. See our data sources and update policy for tools that depend on changing information.