Upload worklet.js

worklet.js

@@ -0,0 +1,86 @@
+/** @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);