psbs

A pitch shifting AudioBufferSourceNode built with Rubber Band

This should be a drop in replacement of AudioBufferSourceNode with a few new AudioParam

• transpose — pitch in semitones, independent of speed
• detune — pitch in cents, also independent of speed
• loopFade — crossfade across the loop seam, in seconds

playbackRate changes speed only. start(when, offset, duration), stop(when) and the ended event work as usual.

Usage

import { PitchShiftBufferSource } from "pitch-shift-buffer-source"

const ctx = new AudioContext();
await PitchShiftBufferSource.init(ctx);

// then construct synchronously, just like AudioBufferSourceNode
const source = new PitchShiftBufferSource(ctx);

const buf = await ctx.decodeAudioData(await (await fetch('audio.wav')).arrayBuffer());
source.buffer = buf;
source.transpose.value = 4;   // up a major third, speed unchanged

source.connect(ctx.destination);
source.start();

Pick the Rubber Band algorithm at construction time:

const source = new PitchShiftBufferSource(ctx, { engine: 'finer', formant: 'preserved' });

Options (each fixed at construction): engine, formant, pitchMode, transients, detector, phase, window, smoothing, channels.

The defaults work well enough for me.

Build

Needs the Emscripten SDK

npm run build

License

GPL-2.0-or-later as per rubberband. See LICENSE.