react实现audio/webm的blob转pcm流

要实现blob转pcm流，需要使用Web Audio API。以下是一个基本的示例代码：

const blobToPcm = async (blob) => {
  const audioContext = new AudioContext();
  const buffer = await blob.arrayBuffer();
  const audioBuffer = await audioContext.decodeAudioData(buffer);
  const source = audioContext.createBufferSource();
  source.buffer = audioBuffer;
  const channelData = audioBuffer.getChannelData(0);
  const pcm = new DataView(new ArrayBuffer(channelData.length * 2));
  let offset = 0;
  for (let i = 0; i < channelData.length; i++) {
    const sample = channelData[i];
    if (sample < 0) {
      sample = 32767 * sample;
    } else {
      sample = 32768 * sample;
    }
    pcm.setInt16(offset, sample, true);
    offset += 2;
  }
  return pcm;
};

const audioBlob = new Blob([/* audio/webm blob */]);
const pcm = await blobToPcm(audioBlob);
const pcmStream = new ReadableStream({
  start(controller) {
    const chunkSize = 4096;
    let offset = 0;
    const write = () => {
      const end = Math.min(offset + chunkSize, pcm.byteLength);
      const chunk = pcm.slice(offset, end);
      offset = end;
      controller.enqueue(chunk);
      if (end < pcm.byteLength) {
        requestAnimationFrame(write);
      } else {
        controller.close();
      }
    };
    write();
  }
});

这段代码将音频blob转换为PCM格式，并且创建了一个可读流，用于逐块读取PCM数据。注意，此代码只适用于单声道音频。如果你需要处理多声道音频，需要修改代码以正确处理所有声道的数据。