web/PCMPlayerWorklet.js

class PCMPlayerProcessor extends AudioWorkletProcessor {
  constructor() {
    super();
    this.queue = [];
    this.offset = 0;
    this.bufferedSamples = 0;
    this.started = false;
    this.startThreshold = Math.round(sampleRate * 0.25);
    this.port.onmessage = (event) => {
      if (event.data.type === "reset") {
        this.queue = [];
        this.offset = 0;
        this.bufferedSamples = 0;
        this.started = false;
        return;
      }
      if (event.data.type === "audio") {
        const samples = new Float32Array(event.data.samples);
        this.queue.push(samples);
        this.bufferedSamples += samples.length;
      }
    };
  }

  process(_inputs, outputs) {
    const output = outputs[0][0];
    output.fill(0);
    if (!this.started) {
      this.started = this.bufferedSamples >= this.startThreshold;
      if (!this.started) {
        return true;
      }
    }

    let outputOffset = 0;
    while (outputOffset < output.length && this.queue.length) {
      const current = this.queue[0];
      const count = Math.min(output.length - outputOffset, current.length - this.offset);
      output.set(current.subarray(this.offset, this.offset + count), outputOffset);
      outputOffset += count;
      this.offset += count;
      this.bufferedSamples -= count;
      if (this.offset === current.length) {
        this.queue.shift();
        this.offset = 0;
      }
    }
    if (this.started && outputOffset < output.length) {
      this.port.postMessage({ type: "underrun" });
    }
    return true;
  }
}

registerProcessor("audex-pcm-player", PCMPlayerProcessor);