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Audio & video / Local FFmpeg tool

Video Compressor

Reduce MP4 size using adjustable H.264 CRF and a maximum output width.

● Files stay in your browser
Files stay in your browser

The first run loads an approximately 31 MB FFmpeg WebAssembly core from this site. It does not use a CDN or upload your files.

Files are limited to 200 MB total and 20 minutes; mobile devices use an 80 MB limit. Reverse, GIF and boomerang tools have lower duration caps.

Choose files, set the controls, then start.Progress: 0%

Processed result

The first run loads an approximately 31 MB FFmpeg WebAssembly core from this site. It does not use a CDN or upload your files.

Validated downloads will appear here after processing.

Method, example & boundaries

Video Compressor: from input to a reviewable result

Reduce an MP4 delivery file by combining an H.264 quality target with a maximum output width. The page reports actual output size after processing and does not promise a fixed compression ratio because motion, noise, duration, and the source codec determine how many bytes are required.

Worked example: prepare a 4K phone clip for messaging

Example input
3840×2160 MP4, 50 seconds; maximum width 1280; CRF 29.
Example output
One MP4 no wider than 1280 pixels, aspect ratio preserved, with measured result size and validated duration.

How to interpret it

Downscaling removes pixel detail while the higher CRF allocates fewer bits; both changes can reduce size, but the measured result remains content-dependent.

Scale-if-needed plus CRF encoding

The worker probes source dimensions, scales down only when width exceeds the selected maximum, preserves even dimensions and aspect ratio, encodes H.264 at the chosen CRF with AAC audio, and validates the output before download.

Video-size boundaries

  • No setting can guarantee an exact megabyte target for every scene and duration.
  • High CRF or aggressive downscaling can make text, faces, and fast motion visibly worse.
  • Already-small or heavily compressed sources may not shrink and can lose quality after re-encoding.

Local AI / Speech to text

Transcribe the current audio or video

Open-source Whisper Tiny runs in your browser. The file, audio and result are never uploaded.

◎ First use loads about 64 MB of model and runtime files

Choose an audio or video file in the workbench above first.

◎ The model loads only from 321Kit; MiniMax is not called and no transcript history is stored.

Transformers.js + Whisper Tiny (Apache-2.0)

Transcript

How it works

Video Compressor

Higher CRF and a smaller width generally reduce size while sacrificing visual detail.

How does this tool process my file?

Higher CRF and a smaller width generally reduce size while sacrificing visual detail. Processing uses single-thread FFmpeg.wasm. The page does not upload, store or inspect file content outside this device. Cancel, error and page close terminate the worker and revoke temporary object URLs.

What limits apply to the output?

Output size cannot be guaranteed because scene complexity and source codecs vary. Files are limited to 200 MB total and 20 minutes; mobile devices use an 80 MB limit. Reverse, GIF and boomerang tools have lower duration caps.

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