README
SoundTouch-TS
A port of a port to TypeScript. Pitchshift and Timestretch in JS/TS. This library is LGPL2.1 due to SoundTouch. A more tested port of this library, with more utilities, is available in soundtouch-js. This TS port exists because I wanted the types, and didn't know soundtouch-js existed until recently.
However, as long as you allow a user, at runtime, to swap out this library, it should fall under section 6b of https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html. But JS/TS and LGPL are legally ambiguous, so use at your own risk.
Usage
// It's TS, but JS is fine too!
import { SoundTouch } from "soundtouch-ts";
const st = new SoundTouch(44100);
const tempo = 0.5;
// Audio will take 2x as long to play with no pitch changes
st.tempo = tempo;
const ctx = new AudioContext();
fetch("http://test-audio.somewhere.mp3")
.then(res => res.arrayBuffer())
.then(ab => ctx.decodeAudio(ab))
.then(ab => {
const interleaved = asInterleaved(ab);
st.inputBuffer.putSamples(interleaved);
st.process();
const channels = 2;
const receiver = new Float32Array((channels * ab.length) / tempo);
const requested = 256;
let received = 0;
while (st.outputBuffer.frameCount) {
const queued = st.frameCount;
st.process();
st.outputBuffer.receiveSamples(receiver.subarray(received), requested);
const remaining = st.outputBuffer.frameCount;
received = (queued - remaining) * channels;
}
const audio = asPlanar(receiver, 44100, 2);
const abnode = new AudioBufferSourceNode(ctx, { buffer: audio });
ctx.destination.connect(abnode);
abnode.start();
});
function asInterleaved(ab: AudioBuffer): Float32Array {
const channels = ab.numberOfChannels;
const output = new Float32Array(channels * ab.length);
for (let i = 0; i < ab.length; i++) {
for (let c = 0; c < channels; c++) {
const chan = ab.getChannelData(c);
output[i * channels + c] = chan[i];
}
}
return output;
}
function asPlanar(
buffer: Float32Array,
sampleRate: number,
channels: number = 2
): AudioBuffer {
const channelLength = Math.floor(buffer.length / channels);
const output = new AudioBuffer({
numberOfChannels: channels,
length: channelLength,
sampleRate: sampleRate
});
for (let c = 0; c < channels; c++) {
const chan = output.getChannelData(c);
for (let i = 0; i < channelLength; i++) {
chan[i] = buffer[i * channels + c];
}
}
return output;
}
Publishing
$ npm version [xxx]
$ npx pack build && pushd pkg && npm publish
$ git push origin HEAD --tags
History
This port was modified from the following:
- Original Port (LGPL 2.1): https://github.com/also/soundtouch-js/tree/master/src/js
- Modularized / Expanded (MIT): https://github.com/jakubfiala/soundtouch-js
- Modified and included in a UI (MIT): https://github.com/ZVK/stretcher (http://zackzukowski.com/TAP-audio-player/)
- Converted to TypeScript: src/index.ts.