begin webaudio package

packages/webaudio/webaudio.mjs

@@ -0,0 +1,69 @@
+import { Pattern } from '@strudel.cycles/core';
+
+let audioContext;
+export const getAudioContext = () => audioContext || new AudioContext();
+
+const lookahead = 0.2;
+
+const adsr = (attack, decay, sustain, release, velocity, begin, end) => {
+  const gainNode = getAudioContext().createGain();
+  gainNode.gain.setValueAtTime(0, begin);
+  gainNode.gain.linearRampToValueAtTime(velocity, begin + attack); // attack
+  gainNode.gain.linearRampToValueAtTime(sustain * velocity, begin + attack + decay); // sustain start
+  gainNode.gain.setValueAtTime(sustain * velocity, end); // sustain end
+  gainNode.gain.linearRampToValueAtTime(0, end + release); // release
+  // for some reason, using exponential ramping creates little cracklings
+  return gainNode;
+};
+
+Pattern.prototype.withAudioNode = function (createAudioNode) {
+  return this._withEvent((event) => {
+    return event.setContext({
+      ...event.context,
+      createAudioNode: (e) => createAudioNode(e, event.context.createAudioNode?.(event)),
+    });
+  });
+};
+
+Pattern.prototype._osc = function (type) {
+  return this.withAudioNode((e) => {
+    const osc = getAudioContext().createOscillator();
+    osc.type = type;
+    osc.frequency.value = e.value; // expects frequency..
+    osc.start(e.whole.begin.valueOf() + lookahead);
+    osc.stop(e.whole.end.valueOf() + lookahead); // release?
+    return osc;
+  });
+};
+Pattern.prototype.adsr = function (a = 0.01, d = 0.05, s = 1, r = 0.01) {
+  return this.withAudioNode((e, node) => {
+    const velocity = e.context?.velocity || 1;
+    const envelope = adsr(a, d, s, r, velocity, e.whole.begin.valueOf() + lookahead, e.whole.end.valueOf() + lookahead);
+    node?.connect(envelope);
+    return envelope;
+  });
+};
+Pattern.prototype.filter = function (type = 'lowshelf', frequency = 1000, gain = 25) {
+  return this.withAudioNode((e, node) => {
+    const filter = getAudioContext().createBiquadFilter();
+    filter.type = type;
+    filter.frequency.value = frequency;
+    filter.gain.value = gain;
+    node?.connect(filter);
+    return filter;
+  });
+};
+
+Pattern.prototype.out = function () {
+  const master = getAudioContext().createGain();
+  master.gain.value = 0.1;
+  master.connect(getAudioContext().destination);
+  return this.withAudioNode((e, node) => {
+    if (!node) {
+      console.warn('out: no source! call .osc() first');
+    }
+    node?.connect(master);
+  });
+};
+
+Pattern.prototype.define('osc', (type, pat) => pat.osc(type), { patternified: true });