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/**
* @class OnePoleFilter
* @extends AudioWorkletProcessor
*
* A simple One-pole filter.
*/
class OnePoleFilter extends AudioWorkletProcessor {
// This gets evaluated as soon as the global scope is created.
static get parameterDescriptors() {
return [{
name: 'frequency',
defaultValue: 250,
minValue: 0,
maxValue: 0.5 * sampleRate
}];
}
constructor() {
super();
this.updateCoefficientsWithFrequency_(250);
}
updateCoefficientsWithFrequency_(frequency) {
this.b1_ = Math.exp(-2 * Math.PI * frequency / sampleRate);
this.a0_ = 1.0 - this.b1_;
this.z1_ = 0;
}
process(inputs, outputs, parameters) {
let input = inputs[0];
let output = outputs[0];
let frequency = parameters.frequency;
for (let channel = 0; channel < output.length; ++channel) {
let inputChannel = input[channel];
let outputChannel = output[channel];
for (let i = 0; i < outputChannel.length; ++i) {
this.updateCoefficientsWithFrequency_(frequency[i]);
this.z1_ = inputChannel[i] * this.a0_ + this.z1_ * this.b1_;
outputChannel[i] = this.z1_;
}
}
return true;
}
}
registerProcessor('one-pole-filter', OnePoleFilter);
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