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/** @module worklet */
// Called with `audioWorker.addModule('worklet.js')`
// Defines the following global variables:
// - sampleRate
// - registerProcessor
/**
* The `Processor` class is an AudioWorkletProcessor that resamples the input audio to a target sample rate.
*/
class Processor extends AudioWorkletProcessor {
/**
* @param {object} options - The options object.
* @param {object} options.processorOptions - The processor options object.
* @param {number} options.processorOptions.targetSampleRate - The target sample rate.
*/
constructor(options) {
super(options);
this.targetSampleRate = options.processorOptions.targetSampleRate;
this.inputBuffer = new Float32Array(this.inputFrameSize);
this.inputBufferSize = 0;
this.outputBuffer = new Float32Array(this.targetFrameSize);
}
/**
* The size of the input frame.
* @type {number}
*/
get inputFrameSize() {
return Math.round(sampleRate / 50);
}
/**
* The size of the target frame.
* @type {number}
*/
get targetFrameSize() {
return Math.round(this.targetSampleRate / 50);
}
/**
* Flushes the input buffer to the output buffer, resampling the audio.
* Then sends the output buffer to the main thread using the port.
*/
async flush() {
const ratio = sampleRate / this.targetSampleRate;
this.outputBuffer.fill(0);
for (let i = 0; i < this.targetFrameSize; i++) {
const index = i * ratio;
const left = Math.floor(index);
const right = Math.min(left + 1, this.targetFrameSize - 1);
const weight = index - left;
this.outputBuffer[i] = this.inputBuffer[left] * (1 - weight) + this.inputBuffer[right] * weight;
}
await this.port.postMessage(this.outputBuffer);
}
/**
* Pushes audio to the input buffer.
* @param {Float32Array} inputArray - The input audio.
*/
pushAudio(inputArray) {
const inputLength = inputArray.length;
const remainingLength = this.inputFrameSize - this.inputBufferSize;
if (inputLength < remainingLength) {
this.inputBuffer.set(inputArray, this.inputBufferSize);
this.inputBufferSize += inputLength;
return;
}
this.inputBuffer.set(inputArray.subarray(0, remainingLength), this.inputBufferSize);
this.flush();
this.inputBufferSize = 0;
this.pushAudio(inputArray.subarray(remainingLength));
}
/**
* Processes the input audio (the main worklet loop).
*/
process(inputArray, outputArray, parameters) {
this.pushAudio(inputArray[0][0]);
return true;
}
}
// Registers the processor with the name "hey-buddy".
registerProcessor("hey-buddy", Processor);
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