mirror of
https://codeberg.org/uzu/strudel
synced 2026-08-19 02:34:22 -04:00
Felix Roos
42 lines
2.1 KiB
JavaScript
42 lines
2.1 KiB
JavaScript
/*
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clockbridge.mjs
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Copyright (C) 2022 Strudel contributors - see <https://codeberg.org/uzu/strudel/src/branch/main/packages/superdough/index.mjs>
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This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details. You should have received a copy of the GNU Affero General Public License along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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// thanks freya https://youtu.be/LSNQuFEDOyQ?si=ukZI2IGgWV_NDZzP&t=2979
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export function expDecay(a, b, decay, dt) {
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return b + (a - b) * Math.exp(-decay * dt);
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}
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// translates between audio and performance clock
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export class ClockBridge {
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p; // smoothed clock offset
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lastTime;
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audioContext;
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constructor(audioContext) {
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this.audioContext = audioContext;
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}
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// delta between audio and performance time in ms
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getOffset() {
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const { contextTime, performanceTime } = this.audioContext.getOutputTimestamp();
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if (!contextTime || !performanceTime) {
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return;
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}
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const offset = performanceTime - contextTime * 1000; // clock offset in ms
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const dt = performanceTime - (this.lastTime ?? performanceTime); // delta time since last hap
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const decay = 1 / 10000; // how fast offset changes have an effect
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this.p = expDecay(this.p ?? offset, offset, decay, dt); // smooth clock offset
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this.lastTime = performanceTime;
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return this.p;
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}
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getPerformanceTime(audioContextTime) {
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const offset = this.getOffset();
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return audioContextTime * 1000 + offset; // this is now correct in performance time (ms)
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}
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getAudioContextTime(performanceTime) {
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const offset = this.getOffset();
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return (performanceTime - offset) / 1000; // this is now correct in audio context time (seconds)
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}
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}
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