Video to MP3

Extract a selected audio range from supported videos to MP3 or WAV. Choose a bitrate and download the result, with processing in your browser.

Open a video, choose the section, and Nerulio decodes only its audio track and encodes it as MP3 at 128, 192 (default), 256 or 320 kbit/s constant bitrate with the LAME 3.100 encoder, or as uncompressed 16-bit WAV. The picture is discarded without being decoded, so the video codec does not matter; the browser only has to decode the audio codec (AAC, Opus, MP3, PCM…). Fades, peak normalisation and resampling to 44.1 or 48 kHz are under Advanced.

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Bitrate, size, and what MP3 cannot restore

At a constant bitrate an MP3 spends the same number of bits every second, so its size is bitrate × duration ÷ 8. At 192 kbit/s that is 24 KB per second, about 1.4 MB a minute. WAV at 44.1 kHz, 16-bit stereo runs at 1411.2 kbit/s, about 10 MB a minute.

The audio in a video is nearly always compressed already, usually as AAC or Opus. Converting it to MP3 decodes and re-encodes it, which cannot bring back detail the first encoder removed: 320 kbit/s from a 128 kbit/s source only makes the file bigger. Pick a bitrate at or a little above the source's, or WAV when you will keep editing the audio.

Normalise measures the loudest sample in the section and scales the whole section so that this peak reaches 0.98 of full scale (about −0.2 dBFS). It does not compress dynamics, so one loud peak limits how far a quiet recording can be raised. Fades are linear and measured from the start and end of the section, up to half its length each.

kbit/s: Thousand bits per second: 192 kbit/s is 24,000 bytes per second.
CBR: Constant bitrate: every second of the MP3 uses the same number of bits.
Peak normalisation: One gain for the whole section, chosen so the loudest sample stays just below clipping.

Example: a music video of 3 min 20 s (200 s)

Size of the audio at each choice, as the result box shows it (1 MB = 1,048,576 bytes):

128 kbit/s    128,000 × 200 ÷ 8 = 3,200,000 bytes ≈ 3.1 MB
192 kbit/s    192,000 × 200 ÷ 8 = 4,800,000 bytes ≈ 4.6 MB   (default)
256 kbit/s    6,400,000 bytes ≈ 6.1 MB
320 kbit/s    8,000,000 bytes ≈ 7.6 MB
WAV 44.1 kHz 16-bit stereo   1,411,200 × 200 ÷ 8 = 35,280,000 bytes ≈ 33.6 MB
Normalise     measured peak 0.25 → gain 0.98 ÷ 0.25 = 3.92 (+11.9 dB)

File headers add a few bytes on top. If the source audio is AAC at 128 kbit/s, 192 kbit/s MP3 keeps what is there; 320 kbit/s adds 3.2 MB and nothing audible.

From the source audio to the MP3

In the source	What happens	In the result
Audio codec (AAC, Opus, MP3, PCM…)	Decoded by the browser; PCM is decoded by the reader itself	Encoded by LAME 3.100 (or written as PCM for WAV)
Sample rate	Kept, or resampled to 44.1 or 48 kHz if chosen	Same rate
Video track	Discarded without decoding	—
Section start and end	Samples outside are dropped; fades are measured from the section	Starts at 0 s
Extra audio tracks, chapters, cover art	Not read	—

Check the result

Play the result in the result player: it should start and end where the section does, with the fades you set.
Check the size in the result box against bitrate × duration ÷ 8.
If you normalised, compare the loudness with the source: the loudest moment should sit just under clipping.

Troubleshooting

Symptom	Likely cause	How to check	Fix
"This file has no audio track"	The video was recorded or exported without sound	Play the source with sound on; ffprobe lists no audio stream	There is nothing to extract; find a version with audio
It stops with a decoder error	The browser cannot decode this audio codec (for example a surround codec)	ffprobe shows the audio codec	Convert the audio with a desktop tool, or try another browser
320 kbit/s sounds no better than 192	The source audio was lossy at a lower bitrate; re-encoding cannot add detail	ffprobe shows the source audio bit_rate	Pick 192 or the source bitrate; use WAV for editing
Normalise barely changed the volume	One loud peak (a clap, a door) is already near full scale	Look for a single spike in an audio editor	Leave the spike out of the section, or use a loudness tool that compresses dynamics
Compatibility mode refuses a long file	Without WebCodecs the whole source is decoded in memory, limited to 20 minutes	The compatibility note is shown	Use a browser with WebCodecs, which reads the file in pieces without a length cap

Other ways to do it

Option	When it is the better choice
FFmpeg: `ffmpeg -i in.mp4 -vn -c:a libmp3lame -b:a 192k out.mp3`	Batch conversion or codecs your browser cannot decode; libmp3lame also offers VBR with `-q:a`.
WAV from this page	When you will edit, mix or encode the audio again later: no extra lossy step now.

What this page does not cover

MP3 is written at a constant bitrate only; there is no VBR option.
No ID3 tags (title, artist, cover) are written.
Sources with more than two channels have not been tested in this path.

Versions and sources

Checked in tests/media-browser.mjs in Chromium 153 and Firefox 155: a 4 s MP3 at 192 kbit/s and a 44.1 kHz WAV cut from a 1920 × 1080 MP4 kept their length within 0.12 s; normalising a quiet test tone measured a peak below 0.2 and raised it by more than 2×; 1 s fades left the length unchanged. MP3 encoding is LAME 3.100 compiled to WebAssembly (mediabunny-mp3-encoder 1.58.1). The FFmpeg options are from its documentation.

Official documentation used

FFmpeg codecs: libmp3lame

Video to MP3

Extract a selected audio range from supported videos to MP3 or WAV. Choose a bitrate and download the result, with processing in your browser.

How it works

Open a supported video or audio file
Choose the time range, MP3 or WAV, and audio settings
Export and listen to the beginning and end of the result

Supported formats

MP4 / WebM / MOV / MP3 / WAV / OGG / M4A → MP3 / WAV — Input decoding and output encoding depend on browser support.

What this tool does

Extract audio incrementally with selectable 96–320 kbit/s MP3 or PCM WAV.

Implementation and verified quality

advanced · ranged demux / WebCodecs / LAME WASM. Quality qualification is in progress. Pro/Flagship quality has not been established.

Before you export

Fast cut shrinks to inner keyframes. Precise mode re-encodes; codec availability varies. Temporary outputs use local browser storage when available. Compatibility recording retains its short-clip limits.

Frequently asked questions

What determines the supported size?

Actual device memory, storage and codec support. Tested examples are evidence, not a guarantee for every file.

Are my files uploaded?

This tool processes the files you open on your device without uploading them. Images you explicitly attach to community posts are uploaded separately. Optional engines and models are downloaded from third parties; those requests expose connection information such as your IP address.

Will my work be saved automatically?

No. Images and editing state stay in this tab; media output can use local temporary storage. Changing language preserves your work; reloading, closing the tab, or following a link to another page can clear it.