@trackr/effects-gain/lib/envelope.js

A subpackage of trackr that contains gain effects.

export const envelope = (options) => {
    return (audioContext, eo) => {
        const adsr = audioContext.createGain();
        if (options) {
            const t0 = eo.startTime;
            // vol:0
            adsr.gain.setValueAtTime(0, t0);
            // attack
            const t1 = t0 + options.attack;
            adsr.gain.linearRampToValueAtTime(1, t1);
            // decay
            const t2 = options.decay;
            adsr.gain.setTargetAtTime(options.sustainLevel, t1, t2);
            // release
            adsr.gain.setTargetAtTime(0, t1 + t2, options.release);
        }
        eo.latestSource.connect(adsr);
        return adsr;
    };
};