将两个音频缓冲区叠加到一个缓冲区源中

Question

试图将两个缓冲区合并为一个缓冲区; 我已经能够从音频文件创建两个缓冲区并加载和播放它们.现在我需要将两个缓冲区合并到一个缓冲区中.他们怎么能合并？

  context = new webkitAudioContext();
  bufferLoader = new BufferLoader(
    context,
    [
      'audio1.mp3',
      'audio2.mp3',
    ],
    finishedLoading
    );

  bufferLoader.load();

function finishedLoading(bufferList) {
  // Create the two buffer sources and play them both together.
  var source1 = context.createBufferSource();
  var source2 = context.createBufferSource();
  source1.buffer = bufferList[0];
  source2.buffer = bufferList[1];

  source1.connect(context.destination);
  source2.connect(context.destination);
  source1.start(0);
  source2.start(0);  
}

现在这些来源分别加载并同时播放; 但是如何将这两个源合并到一个缓冲源中呢？我不想附加它们,我想覆盖/合并它们.

解释和/或片段会很棒.

Answer 1

在音频方面,以混合两个音频流(在这里,缓冲区)合为一体,你可以简单地添加每个样本值在一起.实际上,我们可以在您的代码段上构建此代码:

/* `buffers` is a javascript array containing all the buffers you want
 * to mix. */
function mix(buffers) {
  /* Get the maximum length and maximum number of channels accros all buffers, so we can
   * allocate an AudioBuffer of the right size. */
  var maxChannels = 0;
  var maxDuration = 0;
  for (var i = 0; i < buffers.length; i++) {
    if (buffers[i].numberOfChannels > maxChannels) {
      maxChannels = buffers[i].numberOfChannels;
    }
    if (buffers[i].duration > maxDuration) {
      maxDuration = buffers[i].duration;
    }
  }
  var out = context.createBuffer(maxChannels,
                                 context.sampleRate * maxDuration,
                                 context.sampleRate);

  for (var j = 0; j < buffers.length; j++) {
    for (var srcChannel = 0; srcChannel < buffers[j].numberOfChannels; srcChannel++) {
      /* get the channel we will mix into */
      var out = mixed.getChanneData(srcChannel);
      /* Get the channel we want to mix in */
      var in = buffers[i].getChanneData(srcChannel);
      for (var i = 0; i < in.length; i++) {
        out[i] += in[i];
      }
    }
  }
  return out;
}

然后,只需影响从此函数返回到新函数AudioBufferSourceNode.buffer,并像往常一样播放它.

一些注意事项:为简单起见,我的代码段假定:

• 如果您有单声道缓冲器和立体声缓冲器,您将只能听到混合缓冲器左声道中的单声道缓冲器.如果你想要它被复制到左边和右边,你将不得不做我们被称为up-mixing ;
• 如果你想让一个缓冲区比另一个缓冲区更安静或更响亮(比如你在混音控制台上移动了一个音量推子),只需将该toMix[i]值乘以小于1.0的数字即可使其调整,大于1.0以使其更响亮.

然后,Web Audio API为您完成所有这些,所以我想知道您为什么需要自己做,但至少现在您知道如何:-).