Refactor waveWorker to typescript

Author: BafS

src/audio.ts

@@ -1,4 +1,4 @@
-import WaveWorker from './waveWorker.js';
+import WaveWorker from './waveWorker';
 
 /**
  * Process javascript code to audio buffer

src/waveWorker.js

@@ -0,0 +1,115 @@
+// Adapted from https://stackoverflow.com/a/42632646
+
+/* eslint-disable no-restricted-globals */
+/* eslint-disable no-bitwise */
+
+class WavePCM
+{
+  sampleRate: number;
+  bitDepth: number;
+  recordedBuffers: Uint8Array[];
+  bytesPerSample: number;
+  numberOfChannels: number|null = null;
+
+  constructor(config: {sampleRate: number, bitDepth: number} = {
+    sampleRate: 48000,
+    bitDepth: 16,
+  }) {
+    this.sampleRate = config.sampleRate;
+    this.bitDepth = config.bitDepth;
+    this.recordedBuffers = [];
+    this.bytesPerSample = this.bitDepth / 8;
+  }
+
+  record(buffers: number[][]) {
+    this.numberOfChannels = this.numberOfChannels ?? buffers.length;
+    const bufferLength = buffers[0].length;
+    const reducedData = new Uint8Array(bufferLength * this.numberOfChannels * this.bytesPerSample);
+
+    // Interleave
+    for (let i = 0; i < bufferLength; i++) {
+      for (let channel = 0; channel < this.numberOfChannels; channel++) {
+        const outputIndex = (i * this.numberOfChannels + channel) * this.bytesPerSample;
+        let sample = buffers[channel][i];
+
+        // Check for clipping
+        if (sample > 1) {
+          sample = 1;
+        } else if (sample < -1) {
+          sample = -1;
+        }
+
+        // bit reduce and convert to uInt
+        switch (this.bytesPerSample) {
+          case 4:
+            sample *= 2147483648;
+            reducedData[outputIndex] = sample;
+            reducedData[outputIndex + 1] = sample >> 8;
+            reducedData[outputIndex + 2] = sample >> 16;
+            reducedData[outputIndex + 3] = sample >> 24;
+            break;
+
+          case 3:
+            sample *= 8388608;
+            reducedData[outputIndex] = sample;
+            reducedData[outputIndex + 1] = sample >> 8;
+            reducedData[outputIndex + 2] = sample >> 16;
+            break;
+
+          case 2:
+            sample *= 32768;
+            reducedData[outputIndex] = sample;
+            reducedData[outputIndex + 1] = sample >> 8;
+            break;
+
+          case 1:
+            reducedData[outputIndex] = (sample + 1) * 128;
+            break;
+
+          default:
+            throw Error('Only 8, 16, 24 and 32 bits per sample are supported');
+        }
+      }
+    }
+
+    this.recordedBuffers.push(reducedData);
+  }
+
+  requestData () {
+    const bufferLength = this.recordedBuffers[0].length;
+    const dataLength = this.recordedBuffers.length * bufferLength;
+    const headerLength = 44;
+    const wav = new Uint8Array(headerLength + dataLength);
+    const view = new DataView(wav.buffer);
+
+    view.setUint32(0, 1380533830, false); // RIFF identifier 'RIFF'
+    view.setUint32(4, 36 + dataLength, true); // file length minus RIFF identifier length and file description length
+    view.setUint32(8, 1463899717, false); // RIFF type 'WAVE'
+    view.setUint32(12, 1718449184, false); // format chunk identifier 'fmt '
+    view.setUint32(16, 16, true); // format chunk length
+    view.setUint16(20, 1, true); // sample format (raw)
+    view.setUint16(22, (this.numberOfChannels ?? 2), true); // channel count
+    view.setUint32(24, this.sampleRate, true); // sample rate
+    view.setUint32(28, this.sampleRate * this.bytesPerSample * (this.numberOfChannels ?? 2), true); // byte rate (sample rate * block align)
+    view.setUint16(32, this.bytesPerSample * (this.numberOfChannels ?? 2), true); // block align (channel count * bytes per sample)
+    view.setUint16(34, this.bitDepth, true); // bits per sample
+    view.setUint32(36, 1684108385, false); // data chunk identifier 'data'
+    view.setUint32(40, dataLength, true); // data chunk length
+
+    for (let i = 0; i < this.recordedBuffers.length; i++) {
+      wav.set(this.recordedBuffers[i], i * bufferLength + headerLength);
+    }
+
+    // @ts-ignore
+    self.postMessage(wav, [wav.buffer]);
+    self.close();
+  }
+}
+
+self.onmessage = function (e) {
+  const wavPCM = new WavePCM(e.data.config);
+  wavPCM.record(e.data.pcmArrays ?? [[]]);
+  wavPCM.requestData();
+};
+
+export default WavePCM;