Fix sample rate

Remove hard coded 44100 sample rate. Get sample rate from audio context.
mmontag · Nov 30, 2021 · 1e63b89 · 1e63b89
1 parent c626487
commit 1e63b89
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Showing 4 changed files with 18 additions and 23 deletions.
diff --git a/src/app.js b/src/app.js
@@ -14,8 +14,6 @@ var Visualizer = require('./visualizer');
 var config = require('./config');
 var defaultPresets = require('./default-presets');
 
-var BUFFER_SIZE_MS = 1000 * config.bufferSize / config.sampleRate;
-var MS_PER_SAMPLE = 1000 / config.sampleRate;
 var PARAM_START_MANIPULATION = 'param-start-manipulation';
 var PARAM_STOP_MANIPULATION = 'param-stop-manipulation';
 var PARAM_CHANGE = 'param-change';
@@ -25,6 +23,9 @@ var app = Angular.module('synthApp', ['ngStorage']);
 var synth = new Synth(FMVoice, config.polyphony);
 var midi = new MIDI(synth);
 var audioContext = new (window.AudioContext || window.webkitAudioContext)();
+config.sampleRate = audioContext.sampleRate;
+var BUFFER_SIZE_MS = 1000 * config.bufferSize / config.sampleRate;
+var MS_PER_SAMPLE = 1000 / config.sampleRate;
 var visualizer = new Visualizer("analysis", 256, 35, 0xc0cf35, 0x2f3409, audioContext);
 var scriptProcessor = null;
 

diff --git a/src/config.js b/src/config.js
@@ -1,7 +1,4 @@
-var SAMPLE_RATE = 44100;
-var LFO_RATE = 441;
-var LFO_SAMPLE_PERIOD = Math.floor(SAMPLE_RATE / LFO_RATE);
-var PERIOD = Math.PI * 2;
+var LFO_SAMPLE_PERIOD = 100;
 var BUFFER_SIZE = 1024;
 var POLYPHONY = 12;
 
@@ -11,12 +8,10 @@ if (/iPad|iPhone|iPod|Android/.test(navigator.userAgent)) {
 }
 
 var Config = {
-	sampleRate: SAMPLE_RATE,
-	lfoRate: LFO_RATE,
+	sampleRate: 44100, // gets updated with audio context rate
 	lfoSamplePeriod: LFO_SAMPLE_PERIOD,
-	period: PERIOD,
 	bufferSize: BUFFER_SIZE,
 	polyphony: POLYPHONY
 };
 
-module.exports = Config;
+module.exports = Config;
diff --git a/src/lfo-dx7.js b/src/lfo-dx7.js
@@ -1,9 +1,8 @@
 var config = require('./config');
 
-var PERIOD = config.period;
-var PERIOD_HALF = config.period / 2;
-var PERIOD_RECIP = 1 / config.period;
-var LFO_RATE = config.lfoRate;
+var PERIOD = Math.PI * 2;
+var PERIOD_HALF = PERIOD / 2;
+var PERIOD_RECIP = 1 / PERIOD;
 var LFO_SAMPLE_PERIOD = config.lfoSamplePeriod;
 var LFO_FREQUENCY_TABLE = [ // see https://github.com/smbolton/hexter/tree/master/src/dx7_voice.c#L1002
 	0.062506,  0.124815,  0.311474,  0.435381,  0.619784,
@@ -84,7 +83,7 @@ function LfoDX7(opParams) {
 
 LfoDX7.prototype.render = function() {
 	var amp;
-	if (this.counter % LFO_SAMPLE_PERIOD == 0) {
+	if (this.counter % LFO_SAMPLE_PERIOD === 0) {
 		switch (params.lfoWaveform) {
 			case LFO_MODE_TRIANGLE:
 				if (this.phase < PERIOD_HALF)
@@ -154,12 +153,13 @@ LfoDX7.setParams = function(globalParams) {
 
 LfoDX7.update = function() {
 	var frequency = LFO_FREQUENCY_TABLE[params.lfoSpeed];
-	phaseStep = PERIOD * frequency/LFO_RATE; // radians per sample
+	var lfoRate = config.sampleRate/LFO_SAMPLE_PERIOD;
+	phaseStep = PERIOD * frequency/lfoRate; // radians per sample
 	ampModDepth = params.lfoAmpModDepth * 0.01;
 	// ignoring amp mod table for now. it seems shallow LFO_AMP_MOD_TABLE[params.lfoAmpModDepth];
-	delayTimes[LFO_DELAY_ONSET] = (LFO_RATE * 0.001753 * Math.pow(params.lfoDelay, 3.10454) + 169.344 - 168) / 1000;
-	delayTimes[LFO_DELAY_RAMP] = (LFO_RATE * 0.321877 * Math.pow(params.lfoDelay, 2.01163) + 494.201 - 168) / 1000;
+	delayTimes[LFO_DELAY_ONSET] = (lfoRate * 0.001753 * Math.pow(params.lfoDelay, 3.10454) + 169.344 - 168) / 1000;
+	delayTimes[LFO_DELAY_RAMP] = (lfoRate * 0.321877 * Math.pow(params.lfoDelay, 2.01163) + 494.201 - 168) / 1000;
 	delayIncrements[LFO_DELAY_RAMP] = 1 / (delayTimes[LFO_DELAY_RAMP] - delayTimes[LFO_DELAY_ONSET]);
 };
 
-module.exports = LfoDX7;
+module.exports = LfoDX7;
diff --git a/src/operator.js b/src/operator.js
@@ -2,8 +2,7 @@ var config = require('./config');
 
 // http://www.chipple.net/dx7/fig09-4.gif
 var OCTAVE_1024 = 1.0006771307; //Math.exp(Math.log(2)/1024);
-var PERIOD = config.period;
-var SAMPLE_RATE = config.sampleRate;
+var PERIOD = Math.PI * 2;
 
 function Operator(params, baseFrequency, envelope, lfo) {
 	this.phase = 0;
@@ -20,7 +19,7 @@ Operator.prototype.updateFrequency = function(baseFrequency) {
 	var frequency = this.params.oscMode ?
 		this.params.freqFixed :
 		baseFrequency * this.params.freqRatio * Math.pow(OCTAVE_1024, this.params.detune);
-	this.phaseStep = PERIOD * frequency / SAMPLE_RATE; // radians per sample
+	this.phaseStep = PERIOD * frequency / config.sampleRate; // radians per sample
 };
 
 Operator.prototype.render = function(mod) {
@@ -41,4 +40,4 @@ Operator.prototype.isFinished = function() {
 	return this.envelope.isFinished();
 };
 
-module.exports = Operator;
+module.exports = Operator;