static/pcm-worklet.js

class PCMRecorderProcessor extends AudioWorkletProcessor {
  process(inputs) {
    const input = inputs[0];
    if (!input || !input[0]) {
      return true;
    }

    const samples = input[0];
    const pcm16 = new Int16Array(samples.length);
    for (let i = 0; i < samples.length; i += 1) {
      const value = Math.max(-1, Math.min(1, samples[i]));
      pcm16[i] = value < 0 ? value * 32768 : value * 32767;
    }
    this.port.postMessage(pcm16.buffer, [pcm16.buffer]);
    return true;
  }
}

registerProcessor("pcm-recorder", PCMRecorderProcessor);