static/mic-processor.js

class GargiMicProcessor extends AudioWorkletProcessor {
  constructor() {
    super();
    this.pending = new Float32Array(0);
    this.offset = 0;
    this.ratio = sampleRate / 16000;
  }

  process(inputs) {
    const input = inputs[0]?.[0];
    if (!input?.length) return true;

    const joined = new Float32Array(this.pending.length + input.length);
    joined.set(this.pending);
    joined.set(input, this.pending.length);

    const samples = [];
    while (this.offset + 1 < joined.length) {
      const left = Math.floor(this.offset);
      const mix = this.offset - left;
      const value = joined[left] * (1 - mix) + joined[left + 1] * mix;
      samples.push(Math.max(-1, Math.min(1, value)));
      this.offset += this.ratio;
    }

    const consumed = Math.floor(this.offset);
    this.pending = joined.slice(consumed);
    this.offset -= consumed;

    if (samples.length) {
      const pcm = new Int16Array(samples.length);
      for (let index = 0; index < samples.length; index++) {
        pcm[index] = samples[index] < 0
          ? samples[index] * 32768
          : samples[index] * 32767;
      }
      this.port.postMessage(pcm.buffer, [pcm.buffer]);
    }
    return true;
  }
}

registerProcessor("gargi-mic-processor", GargiMicProcessor);