# audio audio [![test](https://github.com/audiojs/audio/actions/workflows/test.yml/badge.svg)](https://github.com/audiojs/audio/actions/workflows/test.yml) [![npm](https://img.shields.io/npm/v/audio?color=white)](https://npmjs.org/package/audio) _Audio in JavaScript_ ```js audio('raw.wav').trim(-30).normalize('podcast').fade(0.3, 0.5).save('clean.mp3') ``` * **Any Format** — fast wasm codecs, no ffmpeg. * **Streaming** — playback during decode. * **Immutable** — safe edits, infinite undo/redo. * **Page Cache** — open 10Gb+ files. * **Analysis** — loudness, spectrum, and more. * **Modular** – pluggable ops, tree-shakable. * **CLI** — playback, unix pipes, tab completion. * **Isomorphic** — node / browser. * **Audio-first** – dB, Hz, LUFS, not bytes and indices.
#### [Quick Start](#quick-start)   [Recipes](#recipes)   [API](#api)   [CLI](#cli)   [FAQ](#faq)   
[Ecosystem](#ecosystem)   [Plugins](docs/plugins.md)   [Architecture](docs/architecture.md)   
## Quick Start ### Node `npm i audio` ```js import audio from 'audio' let a = audio('voice.mp3') a.trim().normalize('podcast').fade(0.3, 0.5) await a.save('clean.mp3') ``` ### Browser ```html ``` Codecs load on demand via `import()` — map them with an import map or your bundler.
Import map example ```html ```
### CLI ```sh npm i -g audio audio voice.wav trim normalize podcast fade 0.3s -0.5s -o clean.mp3 ``` ## Recipes ### Clean up a recording ```js let a = audio('raw-take.wav') a.trim(-30).normalize('podcast').fade(0.3, 0.5) await a.save('clean.wav') ``` ### Podcast montage ```js let intro = audio('intro.mp3') let body = audio('interview.wav') let outro = audio('outro.mp3') body.trim().normalize('podcast') let ep = audio([intro, body, outro]) ep.fade(0.5, 2) await ep.save('episode.mp3') ``` ### Render a waveform ```js let a = audio('track.mp3') let [mins, peaks] = await a.stat(['min', 'max'], { bins: canvas.width }) for (let i = 0; i < peaks.length; i++) ctx.fillRect(i, h/2 - peaks[i] * h/2, 1, (peaks[i] - mins[i]) * h/2) ``` ### Render as it decodes ```js let a = audio('long.flac') a.on('data', ({ delta }) => appendBars(delta.max[0], delta.min[0])) await a ``` ### Voiceover on music ```js let music = audio('bg.mp3') let voice = audio('narration.wav') music.gain(-12).mix(voice, { at: 2 }) await music.save('mixed.wav') ``` ### Split a long file ```js let a = audio('audiobook.mp3') let [ch1, ch2, ch3] = a.split(1800, 3600) for (let [i, ch] of [ch1, ch2, ch3].entries()) await ch.save(`chapter-${i + 1}.mp3`) ``` ### Record from mic ```js let a = audio() a.record() await new Promise(r => setTimeout(r, 5000)) a.stop() a.trim().normalize() await a.save('recording.wav') ``` ### Extract features for ML ```js let a = audio('speech.wav') let mfcc = await a.stat('cepstrum', { bins: 13 }) let spec = await a.stat('spectrum', { bins: 128 }) let [loud, rms] = await a.stat(['loudness', 'rms']) ``` ### Generate a tone ```js let a = audio.from(t => Math.sin(440 * Math.PI * 2 * t), { duration: 2 }) await a.save('440hz.wav') ``` ### Custom op ```js audio.op('crush', (chs, ctx) => { let steps = 2 ** (ctx.args[0] ?? 8) return chs.map(ch => ch.map(s => Math.round(s * steps) / steps)) }) a.crush(4) ``` ### Serialize and restore ```js let json = JSON.stringify(a) // { source, edits, ... } let b = audio(JSON.parse(json)) // re-decode + replay edits ``` ### Remove a section ```js let a = audio('interview.wav') a.remove({ at: 120, duration: 15 }) // cut 2:00–2:15 a.fade(0.1, { at: 120 }) // smooth the splice await a.save('edited.wav') ``` ### Ringtone from any song ```js let a = audio('song.mp3') a.crop({ at: 45, duration: 30 }).fade(0.5, 2).normalize() await a.save('ringtone.mp3') ``` ### Detect clipping ```js let a = audio('master.wav') let clips = await a.stat('clipping') if (clips.length) console.warn(`${clips.length} clipped blocks`) ``` ### Stream to network ```js let a = audio('2hour-mix.flac') a.highpass(40).normalize('broadcast') for await (let chunk of a) socket.send(chunk[0].buffer) ``` ### Glitch: stutter + reverse ```js let a = audio('beat.wav') let v = a.clip({ at: 1, duration: 0.25 }) let glitch = audio([v, v, v, v]) glitch.reverse({ at: 0.25, duration: 0.25 }) await glitch.save('glitch.wav') ``` ### Tremolo / sidechain ```js let a = audio('pad.wav') a.gain(t => -12 * (0.5 + 0.5 * Math.cos(t * Math.PI * 4))) // 2Hz tremolo in dB await a.save('tremolo.wav') ``` ### Sonify data ```js let prices = [100, 102, 98, 105, 110, 95, 88, 92, 101, 107] let a = audio.from(t => { let freq = 200 + (prices[Math.min(Math.floor(t / 0.2), prices.length - 1)] - 80) * 10 return Math.sin(freq * Math.PI * 2 * t) * 0.5 }, { duration: prices.length * 0.2 }) await a.save('sonification.wav') ``` ## API ### Create * **`audio(source, opts?)`** – decode from file, URL, or bytes. Returns instantly — decodes in background. * **`audio.from(source, opts?)`** – wrap existing PCM, AudioBuffer, silence, or function. Sync, no I/O. ```js let a = audio('voice.mp3') // file path let b = audio('https://cdn.ex/track.mp3') // URL let c = audio(inputEl.files[0]) // Blob, File, Response, ArrayBuffer let d = audio() // empty, ready for .push() or .record() let e = audio([intro, body, outro]) // concat (virtual, no copy) // opts: { sampleRate, channels, storage: 'memory' | 'persistent' | 'auto' } await a // await for decode — if you need .duration, full stats etc let a = audio.from([left, right]) // Float32Array[] channels let b = audio.from(3, { channels: 2 }) // 3s silence let c = audio.from(t => Math.sin(440*TAU*t), { duration: 2 }) // generator let d = audio.from(audioBuffer) // Web Audio AudioBuffer let e = audio.from(int16arr, { format: 'int16' }) // typed array + format ``` ### Properties ```js // format a.duration // total seconds (reflects edits) a.channels // channel count a.sampleRate // sample rate a.length // total samples per channel // playback a.currentTime // position in seconds (smooth interpolation during playback) a.playing // true during playback a.paused // true when paused a.volume = 0.5 // 0..1 linear (settable) a.muted = true // mute gate (independent of volume) a.loop = true // on/off (settable) a.ended // true when playback ended naturally (not via stop) a.seeking // true during a seek operation a.played // promise, resolves when playback starts a.recording // true during mic recording // state a.ready // promise, resolves when fully decoded a.source // original source reference a.pages // Float32Array page store a.stats // per-block stats (peak, rms, etc.) a.edits // edit list (non-destructive ops) a.version // increments on each edit ``` ### Structure Non-destructive time/channel rearrangement. All support `{at, duration, channel}`. * **`.trim(threshold?)`** – strip leading/trailing silence (dB, default auto). * **`.crop({at, duration})`** – keep range, discard rest. * **`.remove({at, duration})`** – cut range, close gap. * **`.insert(source, {at})`** – insert audio or silence (number of seconds) at position. * **`.clip({at, duration})`** – zero-copy range reference. * **`.split(...offsets)`** – zero-copy split at timestamps. * **`.pad(before, after?)`** – silence at edges (seconds). * **`.repeat(n)`** – repeat n times. * **`.reverse({at?, duration?})`** – reverse audio or range. * **`.speed(rate)`** – playback speed (affects pitch and duration). * **`.remix(channels)`** – channel count: number or array map (`[1, 0]` swaps L/R). ```js a.trim(-30) // strip silence below -30dB a.remove({ at: '2m', duration: 15 }) // cut 2:00–2:15, close gap a.insert(intro, { at: 0 }) // prepend; .insert(3) appends 3s silence let [pt1, pt2] = a.split('30m') // zero-copy views let hook = a.clip({ at: 60, duration: 30 }) // zero-copy excerpt a.remix([0, 0]) // L→both; .remix(1) for mono ``` ### Process Amplitude, mixing, normalization. All support `{at, duration, channel}` ranges. * **`.gain(dB, opts?)`** – volume. Number, range, or `t => dB` function. `{ unit: 'linear' }` for multiplier. * **`.fade(in, out?, curve?)`** – fade in/out. Curves: `'linear'` `'exp'` `'log'` `'cos'`. * **`.normalize(target?)`** – remove DC offset, clamp, and normalize loudness. * `'podcast'` – -16 LUFS, -1 dBTP. * `'streaming'` – -14 LUFS. * `'broadcast'` – -23 LUFS. * `-3` – custom dB target (peak mode). * no arg – peak 0dBFS. * `{ mode: 'rms' }` – RMS normalization. Also `'peak'`, `'lufs'`. * `{ ceiling: -1 }` – true peak limiter in dB. * `{ dc: false }` – skip DC removal. * **`.mix(source, opts?)`** – overlay another audio (additive). * **`.pan(value, opts?)`** – stereo balance (−1 left, 0 center, 1 right). Accepts function. * **`.write(data, {at?})`** – overwrite samples with raw PCM. * **`.transform(fn)`** – inline processor: `(chs, ctx) => chs`. Not serialized. ```js a.gain(-3) // reduce 3dB a.gain(6, { at: 10, duration: 5 }) // boost range a.gain(t => -12 * Math.cos(t * TAU)) // automate over time a.fade(0.5, -2, 'exp') // 0.5s in, 2s exp fade-out a.normalize('podcast') // -16 LUFS; also 'streaming', 'broadcast' a.mix(voice, { at: 2 }) // overlay at 2s a.pan(-0.3, { at: 10, duration: 5 }) // pan left for range ``` ### Filter Biquad filters, chainable. All support `{at, duration}` ranges. * **`.highpass(freq)`**, **`.lowpass(freq)`** – pass filter. * **`.bandpass(freq, Q?)`**, **`.notch(freq, Q?)`** – band-pass / notch. * **`.lowshelf(freq, dB)`**, **`.highshelf(freq, dB)`** – shelf EQ. * **`.eq(freq, gain, Q?)`** – parametric EQ. * **`.filter(type, ...params)`** – generic dispatch. ```js a.highpass(80).lowshelf(200, -3) // rumble + mud a.eq(3000, 2, 1.5).highshelf(8000, 3) // presence + air a.notch(50) // remove hum a.filter(customFn, { cutoff: 2000 }) // custom filter function ``` ### I/O Read PCM, encode, stream, push. Format inferred from extension. * **`await .read(opts?)`** – rendered PCM. `{ format, channel }` to convert. * **`await .save(path, opts?)`** – encode + write. `{ at, duration }` for sub-range. * **`await .encode(format?, opts?)`** – encode to `Uint8Array`. * **`for await (let block of a)`** – async-iterable over blocks. * **`.clone()`** – deep copy, independent edits, shared pages. * **`.push(data, format?)`** – feed PCM into pushable instance. `.stop()` to finalize. ```js let pcm = await a.read() // Float32Array[] let raw = await a.read({ format: 'int16', channel: 0 }) await a.save('out.mp3') // format from extension let bytes = await a.encode('flac') // Uint8Array for await (let block of a) send(block) // stream blocks let b = a.clone() // independent copy, shared pages let src = audio() // pushable source src.push(buf, 'int16') // feed PCM src.stop() // finalize ``` ### Playback / Recording Live playback with dB volume, seeking, looping. Mic recording via `audio-mic`. * **`.play(opts?)`** – start playback. `{ at, duration, volume, loop }`. `.played` promise resolves when output starts. * **`.pause()`**, **`.resume()`**, **`.seek(t)`**, **`.stop()`** – playback control. * **`.record(opts?)`** – mic recording. `{ deviceId, sampleRate, channels }`. ```js a.play({ at: 30, duration: 10 }) // play 30s–40s await a.played // wait for output to start a.volume = 0.5; a.loop = true // live adjustments a.muted = true // mute without changing volume a.pause(); a.seek(60); a.resume() // jump to 1:00 a.stop() // end playback or recording let mic = audio() mic.record({ sampleRate: 16000, channels: 1 }) mic.stop() ``` ### Analysis `await .stat(name, opts?)` — without `bins` returns scalar, with `bins` returns `Float32Array`. Array of names returns array of results. Sub-ranges via `{at, duration}`, per-channel via `{channel}`. * **`'db'`** – peak amplitude in dBFS. * **`'rms'`** – RMS amplitude (linear). * **`'loudness'`** – integrated LUFS (ITU-R BS.1770). * **`'dc'`** – DC offset. * **`'clipping'`** – clipped samples (scalar: timestamps, binned: counts). * **`'silence'`** – silent ranges as `{at, duration}`. * **`'max'`**, **`'min'`** – peak envelope (use together for waveform rendering). * **`'spectrum'`** – mel-frequency spectrum in dB (A-weighted). * **`'cepstrum'`** – MFCCs. ```js let loud = await a.stat('loudness') // LUFS let [db, clips] = await a.stat(['db', 'clipping']) // multiple at once let spec = await a.stat('spectrum', { bins: 128 }) // frequency bins let peaks = await a.stat('max', { bins: 800 }) // waveform data await a.stat('rms', { channel: 0 }) // left only → number await a.stat('rms', { channel: [0, 1] }) // per-channel → [n, n] let gaps = await a.stat('silence', { threshold: -40 }) // [{at, duration}, ...] ``` ### Utility Events, lifecycle, undo/redo, serialization. * **`.on(event, fn)`** / **`.off(event?, fn?)`** – subscribe / unsubscribe. * `'data'` – pages decoded/pushed. Payload: `{ delta, offset, sampleRate, channels }`. * `'change'` – any edit or undo. * `'metadata'` – stream header decoded. Payload: `{ sampleRate, channels }`. * `'timeupdate'` – playback position. Payload: `currentTime`. * `'play'` – playback started or resumed. * `'pause'` – playback paused. * `'volumechange'` – volume or muted changed. * `'ended'` – playback finished (not on loop). * `'progress'` – during save/encode. Payload: `{ offset, total }` in seconds. * **`.dispose()`** – release resources. Supports `using` for auto-dispose. * **`.undo(n?)`** – undo last edit(s). Returns edit for redo via `.run()`. * **`.run(...edits)`** – apply edit objects `{ type, args, at?, duration? }`. Batch or replay. ```js a.on('data', ({ delta }) => draw(delta)) // decode progress a.on('timeupdate', t => ui.update(t)) // playback position a.undo() // undo last edit b.run(...a.edits) // replay onto another file JSON.stringify(a); audio(json) // serialize / restore ``` ### Plugins Extend with custom ops and stats. See [Plugin Tutorial](docs/plugins.md). * **`audio.op(name, fn)`** – register op. Shorthand for `{ process: fn }`. Full descriptor: `{ process, plan, resolve, call }`. * **`audio.op(name)`** – query descriptor. **`audio.op()`** – all ops. * **`audio.stat(name, descriptor)`** – register stat. Shorthand `(chs, ctx) => [...]` or `{ block, reduce, query }`. ```js // op: process function receives (channels[], ctx) per 1024-sample block audio.op('crush', (chs, ctx) => { let steps = 2 ** (ctx.args[0] ?? 8) return chs.map(ch => ch.map(s => Math.round(s * steps) / steps)) }) // stat: block function collects per-block, reduce enables scalar queries audio.stat('peak', { block: (chs) => chs.map(ch => { let m = 0; for (let s of ch) m = Math.max(m, Math.abs(s)); return m }), reduce: (src, from, to) => { let m = 0; for (let i = from; i < to; i++) m = Math.max(m, src[i]); return m }, }) a.crush(4) // chainable like built-in ops a.stat('peak') // → scalar from reduce a.stat('peak', { bins: 100 }) // → binned array ``` ## CLI **`npm i -g audio`** ```sh audio [file] [ops...] [-o output] [options] # ops eq mix pad pan crop fade gain stat trim notch remix speed split insert remove repeat bandpass highpass lowpass reverse lowshelf highshelf normalize # options -p play -l loop -o output -f force --format ``` ### Playback Audiojs demo ␣ pause · ←/→ seek ±10s · ⇧←/⇧→ seek ±60s · ↑/↓ volume ±3dB · l loop · q quit ```sh # Play fragment of the song audio song.mp3 10s..15s -p # Play clip (not full song) audio song.mp3 clip 10s..20s -p -l # Normalize before ``` ### Edit ```sh # clean up audio raw-take.wav trim -30db normalize podcast fade 0.3s -0.5s -o clean.wav # ranges audio in.wav gain -3db 1s..10s -o out.wav # filter chain audio in.mp3 highpass 80hz lowshelf 200hz -3db -o out.wav # join audio intro.mp3 + content.wav + outro.mp3 trim normalize fade 0.5s -2s -o ep.mp3 # voiceover audio bg.mp3 gain -12db mix narration.wav 2s -o mixed.wav # split audio audiobook.mp3 split 30m 60m -o 'chapter-{i}.mp3' ``` ### Analysis ```sh # all default stats (db, rms, loudness, clipping, dc) audio speech.wav stat # specific stats audio speech.wav stat loudness rms # spectrum / cepstrum with bin count audio speech.wav stat spectrum 128 audio speech.wav stat cepstrum 13 # stat after transforms audio speech.wav gain -3db stat db ``` ### Batch ```sh audio '*.wav' trim normalize podcast -o '{name}.clean.{ext}' audio '*.wav' gain -3db -o '{name}.out.{ext}' ``` ### Stdin/stdout ```sh cat in.wav | audio gain -3db > out.wav curl -s https://example.com/speech.mp3 | audio normalize -o clean.wav ffmpeg -i video.mp4 -f wav - | audio trim normalize podcast > voice.wav ``` ### Tab completion ```sh eval "$(audio --completions zsh)" # add to ~/.zshrc eval "$(audio --completions bash)" # add to ~/.bashrc audio --completions fish | source # fish ``` ## FAQ
How is this different from Web Audio API?
Web Audio API is a real-time audio graph for playback and synthesis. This is for work on audio files specifically. For Web Audio API in Node, see web-audio-api.
What formats are supported?
Decode: WAV, MP3, FLAC, OGG Vorbis, Opus, AAC, AIFF, CAF, WebM, AMR, WMA, QOA via audio-decode. Encode: WAV, MP3, FLAC, Opus, OGG, AIFF via audio-encode. Codecs are WASM-based, lazy-loaded on first use.
Does it need ffmpeg or native addons?
No, pure JS + WASM. For CLI, you can install globally: npm i -g audio.
How big is the bundle?
~20K gzipped core. Codecs load on demand via import(), so unused formats aren't fetched.
How does it handle large files?
Audio is stored in fixed-size pages. In the browser, cold pages can evict to OPFS when memory exceeds budget. Stats stay resident (~7 MB for 2h stereo).
Are edits destructive?
No. a.gain(-3).trim() pushes entries to an edit list — source pages aren't touched. Edits replay on read() / save() / for await.
Can I use it in the browser?
Yes, same API. See Browser for bundle options and import maps.
Does it need the full file before I can work with it?
No, playback and edits work during decode. The 'data' event fires as pages arrive.
TypeScript?
Yes, ships with audio.d.ts.
## Ecosystem * [audio-decode](https://github.com/audiojs/audio-decode) – codec decoding (13+ formats) * [encode-audio](https://github.com/audiojs/audio-encode) – codec encoding * [audio-filter](https://github.com/audiojs/audio-filter) – filters (weighting, EQ, auditory) * [audio-speaker](https://github.com/audiojs/audio-speaker) – audio output * [audio-mic](https://github.com/audiojs/audio-mic) – audio input * [audio-type](https://github.com/nickolanack/audio-type) – format detection * [pcm-convert](https://github.com/nickolanack/pcm-convert) – PCM format conversion

MIT · ॐ