scratchfoundation/scratch-audio
1
0
Fork 0
mirror of https://github.com/scratchfoundation/scratch-audio.git synced 2024-12-22 14:02:29 -05:00
Code Issues Projects Releases Packages Wiki Activity Actions

vocoder effect, because ROBOTS

Browse source
This commit is contained in:
Eric Rosenbaum 2016-11-07 17:30:00 -05:00
parent cd4d80b3b6
commit 28c9bffe4d
1 changed files with 272 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

272
src/vocoder.js Normal file
View file

@ -0,0 +1,272 @@
var Tone = require('tone');
var modulatorNode = null;
var carrierNode = null;
var vocoding = false;
var FILTER_QUALITY = 6; // The Q value for the carrier and modulator filters
// These are "placeholder" gain nodes - because the modulator and carrier will get swapped in
// as they are loaded, it's easier to connect these nodes to all the bands, and the "real"
// modulator & carrier AudioBufferSourceNodes connect to these.
var modulatorInput = null;
var carrierInput = null;
var modulatorGain = null;
var modulatorGainValue = 1.0;
// noise node added to the carrier signal
var noiseBuffer = null;
var noiseNode = null;
var noiseGain = null;
var noiseGainValue = 0.2;
// Carrier Synth oscillator stuff
var oscillatorNode = null;
var oscillatorType = 4; // CUSTOM
var oscillatorGain = null;
var oscillatorGainValue = 1.0;
var oscillatorDetuneValue = 0;
var FOURIER_SIZE = 4096;
var SAWTOOTHBOOST = 0.40;
// These are the arrays of nodes - the "columns" across the frequency band "rows"
var modFilterBands = null; // tuned bandpass filters
var modFilterPostGains = null; // post-filter gains.
var heterodynes = null; // gain nodes used to multiply bandpass X sine
var powers = null; // gain nodes used to multiply prev out by itself
var lpFilters = null; // tuned LP filters to remove doubled copy of product
var lpFilterPostGains = null; // gain nodes for tuning input to waveshapers
var carrierBands = null; // tuned bandpass filters, same as modFilterBands but in carrier chain
var carrierFilterPostGains = null; // post-bandpass gain adjustment
var carrierBandGains = null; // these are the "control gains" driven by the lpFilters
var vocoderBands;
var numVocoderBands;
var hpFilterGain = null;
var outputGain;
function Vocoder() {
Tone.Effect.call(this);
outputGain = new Tone.Gain();
this.generateVocoderBands(55, 7040, 28);
this.initBandpassFilters();
this.createCarrier();
this.effectSend.connect(modulatorInput);
outputGain.connect(this.effectReturn);
}
Tone.extend(Vocoder, Tone.Effect);
// this function will algorithmically re-calculate vocoder bands, distributing evenly
// from startFreq to endFreq, splitting evenly (logarhythmically) into a given numBands.
// The function places this info into the vocoderBands and numVocoderBands variables.
Vocoder.prototype.generateVocoderBands = function (startFreq, endFreq, numBands) {
// Remember: 1200 cents in octave, 100 cents per semitone
var totalRangeInCents = 1200 * Math.log( endFreq / startFreq ) / Math.LN2;
var centsPerBand = totalRangeInCents / numBands;
var scale = Math.pow( 2, centsPerBand / 1200 ); // This is the scaling for successive bands
vocoderBands = [];
var currentFreq = startFreq;
for (var i=0; i<numBands; i++) {
vocoderBands[i] = new Object();
vocoderBands[i].frequency = currentFreq;
//console.log( "Band " + i + " centered at " + currentFreq + "Hz" );
currentFreq = currentFreq * scale;
}
numVocoderBands = numBands;
};
Vocoder.prototype.initBandpassFilters = function() {
// When this function is called, the carrierNode and modulatorAnalyser
// may not already be created. Create placeholder nodes for them.
modulatorInput = Tone.context.createGain();
carrierInput = Tone.context.createGain();
if (modFilterBands == null)
modFilterBands = new Array();
if (modFilterPostGains == null)
modFilterPostGains = new Array();
if (heterodynes == null)
heterodynes = new Array();
if (powers == null)
powers = new Array();
if (lpFilters == null)
lpFilters = new Array();
if (lpFilterPostGains == null)
lpFilterPostGains = new Array();
if (carrierBands == null)
carrierBands = new Array();
if (carrierFilterPostGains == null)
carrierFilterPostGains = new Array();
if (carrierBandGains == null)
carrierBandGains = new Array();
var waveShaperCurve = new Float32Array(65536);
// Populate with a "curve" that does an abs()
var n = 65536;
var n2 = n / 2;
for (var i = 0; i < n2; ++i) {
var x = i / n2;
waveShaperCurve[n2 + i] = x;
waveShaperCurve[n2 - i - 1] = x;
}
// Set up a high-pass filter to add back in the fricatives, etc.
// (this isn't used by default in the "production" version, as I hid the slider)
var hpFilter = Tone.context.createBiquadFilter();
hpFilter.type = "highpass";
hpFilter.frequency.value = 8000; // or use vocoderBands[numVocoderBands-1].frequency;
hpFilter.Q.value = 1; // no peaking
modulatorInput.connect( hpFilter);
hpFilterGain = Tone.context.createGain();
hpFilterGain.gain.value = 0.0;
hpFilter.connect( hpFilterGain );
hpFilterGain.connect( outputGain );
//clear the arrays
modFilterBands.length = 0;
modFilterPostGains.length = 0;
heterodynes.length = 0;
powers.length = 0;
lpFilters.length = 0;
lpFilterPostGains.length = 0;
carrierBands.length = 0;
carrierFilterPostGains.length = 0;
carrierBandGains.length = 0;
var rectifierCurve = new Float32Array(65536);
for (var i=-32768; i<32768; i++)
rectifierCurve[i+32768] = ((i>0)?i:-i)/32768;
for (var i=0; i<numVocoderBands; i++) {
// CREATE THE MODULATOR CHAIN
// create the bandpass filter in the modulator chain
var modulatorFilter = Tone.context.createBiquadFilter();
modulatorFilter.type = "bandpass"; // Bandpass filter
modulatorFilter.frequency.value = vocoderBands[i].frequency;
modulatorFilter.Q.value = FILTER_QUALITY; // initial quality
modulatorInput.connect(modulatorFilter);
modFilterBands.push(modulatorFilter);
// Now, create a second bandpass filter tuned to the same frequency -
// this turns our second-order filter into a 4th-order filter,
// which has a steeper rolloff/octave
var secondModulatorFilter = Tone.context.createBiquadFilter();
secondModulatorFilter.type = "bandpass"; // Bandpass filter
secondModulatorFilter.frequency.value = vocoderBands[i].frequency;
secondModulatorFilter.Q.value = FILTER_QUALITY; // initial quality
modulatorFilter.chainedFilter = secondModulatorFilter;
modulatorFilter.connect(secondModulatorFilter);
// create a post-filtering gain to bump the levels up.
var modulatorFilterPostGain = Tone.context.createGain();
modulatorFilterPostGain.gain.value = 6;
secondModulatorFilter.connect(modulatorFilterPostGain);
modFilterPostGains.push(modulatorFilterPostGain);
// Create the sine oscillator for the heterodyne
var heterodyneOscillator = Tone.context.createOscillator();
heterodyneOscillator.frequency.value = vocoderBands[i].frequency;
heterodyneOscillator.start(0);
// Create the node to multiply the sine by the modulator
var heterodyne = Tone.context.createGain();
modulatorFilterPostGain.connect(heterodyne);
heterodyne.gain.value = 0.0; // audio-rate inputs are summed with initial intrinsic value
heterodyneOscillator.connect(heterodyne.gain);
var heterodynePostGain = Tone.context.createGain();
heterodynePostGain.gain.value = 2.0; // GUESS: boost
heterodyne.connect(heterodynePostGain);
heterodynes.push(heterodynePostGain);
// Create the rectifier node
var rectifier = Tone.context.createWaveShaper();
rectifier.curve = rectifierCurve;
heterodynePostGain.connect(rectifier);
// Create the lowpass filter to mask off the difference (near zero)
var lpFilter = Tone.context.createBiquadFilter();
lpFilter.type = "lowpass"; // Lowpass filter
lpFilter.frequency.value = 5.0; // Guesstimate! Mask off 20Hz and above.
lpFilter.Q.value = 1; // don't need a peak
lpFilters.push(lpFilter);
rectifier.connect(lpFilter);
var lpFilterPostGain = Tone.context.createGain();
lpFilterPostGain.gain.value = 1.0;
lpFilter.connect(lpFilterPostGain);
lpFilterPostGains.push(lpFilterPostGain);
var waveshaper = Tone.context.createWaveShaper();
waveshaper.curve = waveShaperCurve;
lpFilterPostGain.connect(waveshaper);
// Create the bandpass filter in the carrier chain
var carrierFilter = Tone.context.createBiquadFilter();
carrierFilter.type = "bandpass";
carrierFilter.frequency.value = vocoderBands[i].frequency;
carrierFilter.Q.value = FILTER_QUALITY;
carrierBands.push(carrierFilter);
carrierInput.connect(carrierFilter);
// We want our carrier filters to be 4th-order filter too.
var secondCarrierFilter = Tone.context.createBiquadFilter();
secondCarrierFilter.type = "bandpass"; // Bandpass filter
secondCarrierFilter.frequency.value = vocoderBands[i].frequency;
secondCarrierFilter.Q.value = FILTER_QUALITY; // initial quality
carrierFilter.chainedFilter = secondCarrierFilter;
carrierFilter.connect(secondCarrierFilter);
var carrierFilterPostGain = Tone.context.createGain();
carrierFilterPostGain.gain.value = 10.0;
secondCarrierFilter.connect(carrierFilterPostGain);
carrierFilterPostGains.push(carrierFilterPostGain);
// Create the carrier band gain node
var bandGain = Tone.context.createGain();
carrierBandGains.push(bandGain);
carrierFilterPostGain.connect(bandGain);
bandGain.gain.value = 0.0; // audio-rate inputs are summed with initial intrinsic value
waveshaper.connect(bandGain.gain); // connect the lp controller
bandGain.connect(outputGain);
}
};
Vocoder.prototype.createCarrier = function () {
oscillatorNode = new Tone.Oscillator(110, 'sawtooth8').start();
oscillatorNode.connect(carrierInput);
noiseNode = new Tone.Noise('white').start();
noiseGain = new Tone.Gain(noiseGainValue);
noiseNode.connect(noiseGain);
noiseGain.connect(carrierInput);
}
module.exports = Vocoder;