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simplified envelope follower

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This commit is contained in:
Yotam Mann 2014-07-23 15:22:46 -04:00
parent 73c10a90c4
commit cdd0d3d610
2 changed files with 12 additions and 82 deletions
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2
.gitignore vendored
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@ -10,3 +10,5 @@ examples/scratch.html
build/node_modules/*
TODO.txt
Tone/component/FollowerOld.js

92
Tone/component/Follower.js
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@ -2,19 +2,20 @@ define(["Tone/core/Tone", "Tone/signal/Abs", "Tone/signal/Negate", "Tone/signal/
/**
* @class Follow the envelope of the incoming signal
* Note: due to the nature of low-pass filters,
* there is some rippling which is proportional
* to the smoothTime
*
* @constructor
* @extends {Tone}
* @param {Tone.Time=} [attackTime = 0.01]
* @param {Tone.Time=} [releaseTime = 0.1]
* @param {Tone.Time=} [smoothTime = 0.1]
*/
Tone.Follower = function(attackTime, releaseTime){
Tone.Follower = function(smoothTime){
Tone.call(this);
//default values
attackTime = this.defaultArg(attackTime, 0.01);
releaseTime = this.defaultArg(releaseTime, 0.1);
smoothTime = this.defaultArg(smoothTime, 0.1);
/**
* @type {Tone.Abs}
@ -23,106 +24,33 @@ define(["Tone/core/Tone", "Tone/signal/Abs", "Tone/signal/Negate", "Tone/signal/
this._abs = new Tone.Abs();
/**
* the lowpass filter
* the lowpass filter which smooths the input
* @type {BiquadFilterNode}
* @private
*/
this._filter = this.context.createBiquadFilter();
this._filter.type = "lowpass";
this._filter.frequency.value = 0;
this._filter.frequency.value = this.secondsToFrequency(smoothTime);
this._filter.Q.value = -10;
/**
* @type {WaveShaperNode}
* @private
*/
this._frequencyValues = this.context.createWaveShaper();
/**
* @type {Tone.Negate}
* @private
*/
this._negate = new Tone.Negate();
/**
* @type {Tone.Negate}
* @private
*/
this._delay = this.context.createDelay();
this._delay.delayTime.value = 0.002;//2ms 'lookahead'
/**
* @type {GainNode}
* @private
*/
this._difference = this.context.createGain();
/**
* this keeps it far from 0, even for very small differences
* @type {Tone.Multiply}
* @private
*/
this._mult = new Tone.Multiply(100000);
//the smoothed signal
this.chain(this.input, this._abs, this._filter, this._delay, this.output);
//the difference path
this.chain(this._abs, this._negate, this._difference);
this._delay.connect(this._difference);
//threshold the difference and use the thresh to set the frequency
this.chain(this._difference, this._mult, this._frequencyValues, this._filter.frequency);
//set the attack and release values in the table
this._setAttackRelease(this.secondsToFrequency(attackTime), this.secondsToFrequency(releaseTime));
//the connections
this.chain(this.input, this._abs, this._filter, this.output);
};
Tone.extend(Tone.Follower);
/**
* sets the attack and release times in the wave shaper
* @param {number} attack
* @param {number} release
* @private
*/
Tone.Follower.prototype._setAttackRelease = function(attack, release){
var curveLength = 1024;
attack /= 2;
release /= 2;
var curve = new Float32Array(curveLength);
for (var i = 0; i < curveLength; i++){
var normalized = (i / (curveLength - 1)) * 2 - 1;
var val;
if (normalized < 0.5){
val = attack;
} else {
val = release;
}
curve[i] = val;
}
this._frequencyValues.curve = curve;
};
/**
* dispose
*/
Tone.Follower.prototype.dispose = function(){
this._filter.disconnect();
this.input.disconnect();
this._frequencyValues.disconnect();
this.output.disconnect();
this._abs.dispose();
this._delay.dispose();
this._negate.dispose();
this._difference.dispose();
this._mult.dispose();
this._filter = null;
this.input = null;
this._delay = null;
this._frequencyValues = null;
this.output = null;
this._abs = null;
this._negate = null;
this._difference = null;
this._mult = null;
};
return Tone.Follower;