AudioBuffer: getChannelData() 方法

getChannelData(channel)

const audioCtx = new AudioContext();
const button = document.querySelector("button");
const pre = document.querySelector("pre");
const myScript = document.querySelector("script");

pre.textContent = myScript.textContent;

// Stereo
const channels = 2;
// Create an empty two second stereo buffer at the
// sample rate of the AudioContext
const frameCount = audioCtx.sampleRate * 2.0;

const myArrayBuffer = audioCtx.createBuffer(2, frameCount, audioCtx.sampleRate);

button.onclick = () => {
  // Fill the buffer with white noise;
  // just random values between -1.0 and 1.0
  for (let channel = 0; channel < channels; channel++) {
    // This gives us the actual ArrayBuffer that contains the data
    const nowBuffering = myArrayBuffer.getChannelData(channel);
    for (let i = 0; i < frameCount; i++) {
      // Math.random() is in [0; 1.0]
      // audio needs to be in [-1.0; 1.0]
      nowBuffering[i] = Math.random() * 2 - 1;
    }
  }

  // Get an AudioBufferSourceNode.
  // This is the AudioNode to use when we want to play an AudioBuffer
  const source = audioCtx.createBufferSource();
  // set the buffer in the AudioBufferSourceNode
  source.buffer = myArrayBuffer;
  // connect the AudioBufferSourceNode to the
  // destination so we can hear the sound
  source.connect(audioCtx.destination);
  // start the source playing
  source.start();
};