AudioToText
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Turn an MP4 video into MP3 audio

Upload the video and get just the audio. Processed in your browser: no upload, no watermark, no need to sign up.

  1. 1File
  2. 2Settings
  3. 3Processing
  4. 4Download
  • MP4
  • MOV
  • MKV
  • WEBM
  • AVI
  • M4V

About this tool

An MP4 file contains a video track and an audio track. Converting it to MP3 keeps the second and discards the first, which accounts for 95% of the file's size. That's why a one-gigabyte recording becomes an MP3 of a few dozen megabytes, with the same sound.

The process runs entirely in your browser, using the same engine (ffmpeg) that online services use, but without uploading the file to any server.

Features

  • The video track is discarded, not converted: that's where most of the file size came from.
  • With no upload required, the process is fast: an hour of video converts in about a minute on a standard computer.
  • Supports files of up to 500 MB, processed in chunks to avoid running out of browser memory.
  • No watermark, no sign-up and no daily conversion limit.

How it works

  1. 1

    Upload the MP4

    Also accepts MOV, MKV, WEBM or AVI. The file opens from your disk and isn't transmitted.

  2. 2

    Choose the quality

    192 kbps is a safe choice. If it's only speech, 96 kbps gives the same result at half the size.

  3. 3

    Download the MP3

    To listen to, save on your phone, or upload directly for transcribing.

In detail

Why only forty megabytes are left of a gigabyte

In a typical MP4, the video track accounts for 90% to 95% of the file, while the audio travels separately at 128 or 192 kbps, a little over a megabyte per minute. Keeping only the audio isn't the result of any special compression: it simply discards the part that takes up nearly all the space.

The result can be calculated in advance by multiplying bitrate by duration. At 192 kbps that's 1.4 MB per minute, about 85 MB per hour; at 96 kbps, half that. The size of the source video doesn't factor into that calculation: an hour-long talk produces the same result whether the original file weighed 300 MB or 4 GB.

What determines the conversion time

The process runs in your browser, using a single processor core. A desktop version of ffmpeg would spread the work across every core available; the version that runs in a browser is limited to one by design, since the multi-threaded variant requires response headers incompatible with the rest of the site, including the payment form. In practice, about fifteen minutes of video are processed per minute of waiting.

The quality level chosen barely affects that time; what determines it is your computer's processing power. While the process runs, the tab must remain open: closing it interrupts the conversion.

Frequently asked questions

Need to transcribe a video?

Upload it and get the text with timestamps, each voice identified and a summary. No account needed to start.

Transcribe my recordingSee pricing

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