sw-synth/dist/index.js

Lightweight sound synthesizer designed for real-time user interaction using the Web Audio API

import { AperiodicVoice, OscillatorVoice, UnisonVoice, } from './voice/oscillator.js';
import { BufferVoice } from './voice/buffer.js';
export * from './voice/index.js';
// Tracking numbers for voice stealing
// Technically we could run out of note identifiers,
// but who is going to play 9007199254740991 notes in one session?
let NOTE_ID = 1;
/**
 * Simple web audio synth of finite polyphony.
 */
export class Synth {
    constructor(audioContext, destination, log) {
        this.audioContext = audioContext;
        this.destination = destination;
        if (log === undefined) {
            // eslint-disable-next-line @typescript-eslint/no-unused-vars
            this.log = (msg) => { };
        }
        else {
            this.log = log;
        }
        this.voices = [];
        this.pitchBendNode = new ConstantSourceNode(this.audioContext, { offset: 0 });
        this.pitchBend = this.pitchBendNode.offset;
        this.pitchBendNode.start();
    }
    _newVoice() {
        return new OscillatorVoice(this.audioContext, this.destination, this.log);
    }
    setPolyphony(maxPolyphony) {
        if (!Number.isFinite(maxPolyphony) ||
            maxPolyphony < 0 ||
            !Number.isInteger(maxPolyphony)) {
            throw new Error('Invalid max polyphony');
        }
        while (this.voices.length > maxPolyphony) {
            const voice = this.voices.pop();
            if (voice.pitchBend) {
                this.pitchBendNode.disconnect(voice.pitchBend);
            }
            voice.dispose();
        }
        while (this.voices.length < maxPolyphony) {
            const voice = this._newVoice();
            if (voice.pitchBend) {
                this.pitchBendNode.connect(voice.pitchBend);
            }
            this.voices.push(voice);
        }
    }
    get maxPolyphony() {
        return this.voices.length;
    }
    set maxPolyphony(value) {
        this.setPolyphony(value);
    }
    _allocateVoice() {
        // Allocate voices based on age.
        // Boils down to:
        // a) Pick the oldest released voice.
        // b) If there are no released voices, replace the oldest currently playing voice.
        let oldestVoice;
        for (const voice of this.voices) {
            voice.age++;
            if (oldestVoice === undefined || voice.age > oldestVoice.age) {
                oldestVoice = voice;
            }
        }
        return oldestVoice;
    }
    /**
     * Start playing a note at the specified frequency and velocity.
     * @param frequency Frequency in Hertz.
     * @param velocity Voice amplitude. Recommended range is 0 to 1.
     * @param pitchBendRange Asymmetric pitch bend range. Determines the effect of {@link Synth.pitchBend} on this note.
     * @returns A callback that stops playing the note.
     */
    noteOn(frequency, velocity, pitchBendRange) {
        const oldestVoice = this._allocateVoice();
        if (oldestVoice === undefined) {
            return () => { };
        }
        if (this.voiceParams === undefined) {
            throw new Error('Synth.voiceParams must be set before calling Synth.noteOn');
        }
        return oldestVoice.noteOn(frequency, velocity, NOTE_ID++, this.voiceParams, pitchBendRange);
    }
    /**
     * Trigger panic and release all notes.
     */
    allNotesOff() {
        for (const voice of this.voices) {
            if (voice.lastNoteOff !== undefined) {
                voice.lastNoteOff();
            }
        }
    }
}
/**
 * Web audio synth of finite polyphony where the voices are stacked in unison.
 */
export class UnisonSynth extends Synth {
    _newVoice() {
        return new UnisonVoice(this.audioContext, this.destination, this.log);
    }
}
/**
 * Web audio synth of finite polyphony that supports inharmonic timbres.
 */
export class AperiodicSynth extends Synth {
    _newVoice() {
        return new AperiodicVoice(this.audioContext, this.destination, this.log);
    }
}
/**
 * Web audio synth of finite polyphony with user-provided audio buffers.
 */
export class BufferSynth extends Synth {
    _newVoice() {
        return new BufferVoice(this.audioContext, this.destination, this.log);
    }
}
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