adsr-gain-node/dist/adsr-gain-node.js

A simple and small nodejs module for creating an adsr gain node

/* Package: adsr-gain-node. Version: 2.0.0. License: MIT. Author: dennis iversen. Homepage: https://github.com/diversen/adsr-gain-node#readme   */ (function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.adsrGainNode = f()}})(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
function AdsrGainNode(ctx) {

    this.ctx = ctx;

    this.options = {
        attackAmp: 0.1, 
        decayAmp: 0.3,
        sustainAmp: 0.7,
        releaseAmp: 0.01,
        attackTime: 0.1,
        decayTime: 0.2,
        sustainTime: 1.0, 
        releaseTime: 3.4,
        autoRelease: true
    };

    /**
     * Set options or use defaults
     * @param {object} options 
     */
    this.setOptions = function (options) {
        this.options = Object.assign(this.options, options);
    };

    this.gainNode
    this.audioTime
    
    /**
     * Get a gain node from defined options
     * @param {float} audioTime an audio context time stamp
     */
    this.getGainNode =  (audioTime) => {

        this.gainNode = this.ctx.createGain();
        this.audioTime = audioTime

        this.gainNode.gain.setValueAtTime(0, audioTime)        
        
        // Attack
        this.gainNode.gain.exponentialRampToValueAtTime(
            this.options.attackAmp, 
            audioTime + this.options.attackTime)

        // Decay
        this.gainNode.gain.exponentialRampToValueAtTime(
            this.options.decayAmp, 
            audioTime + this.options.attackTime + this.options.decayTime)

        // Sustain
        this.gainNode.gain.exponentialRampToValueAtTime(
            this.options.sustainAmp, 
            audioTime + this.options.attackTime + this.options.sustainTime)

        // Check if auto-release
        // Then calculate when note should stop
        if (this.options.autoRelease) {
            this.gainNode.gain.exponentialRampToValueAtTime(
                this.options.releaseAmp,
                this.audioTime + this.options.attackTime + this.options.decayTime + this.options.sustainTime + this.options.releaseTime)
            
            // Disconnect the gain node 
            this.disconnect(this.options.attackTime + this.options.decayTime + this.options.sustainTime + this.options.releaseTime)
        }
        return this.gainNode;
    };

    /**
     * Release the note dynamicaly
     * E.g. if your are making a keyboard, and you want the note
     * to be released according to current audio time added the ADSR release time 
     */
    this.releaseNow = () => {
        this.gainNode.gain.exponentialRampToValueAtTime(
            this.options.releaseAmp,
            this.releaseTime()) 
        this.disconnect(this.options.releaseTime)
    }

    /**
     * Get release time according to audio ctx time and the adsr release time
     */
    this.releaseTime = function() {
        return this.ctx.currentTime + this.options.releaseTime
    }
    
    /**
     * 
     * @param {float} disconnectTime the time when gainNode should disconnect 
     */
    this.disconnect = (disconnectTime) => {
        setTimeout( () => {
            this.gainNode.disconnect();
        },
        disconnectTime * 1000);
    };
}

module.exports = AdsrGainNode;

},{}]},{},[1])(1)
});