如何使用 javascript 从 Audio Element 录制音频

Question

我正在使用 HTML5 和 Javascript 制作录音机，并且不想包含任何第三方 API，我的第一步是使用<audio>标签和navigator.webkitGetUserMedia函数创建音频检索器和播放器，从麦克风获取音频并通过<audio>元素播放，但是此时我无法获取数组中的音频数据，我不知道该使用哪个函数做什么。

Answer 1

简单，只需创建一个音频节点，下面是来自 MattDiamond 的 RecorderJS 的调整代码：

function RecordAudio(stream, cfg){

    var config = cfg || {};
    var bufferLen = config.bufferLen || 4096;
    var numChannels = config.numChannels || 2;
    this.context = stream.context;
    var recordBuffers = [];    
    var recording = false;
    this.node = (this.context.createScriptProcessor ||
                 this.context.createJavaScriptNode).call(this.context,
                 bufferLen, numChannels, numChannels);


    stream.connect(this.node);
    this.node.connect(this.context.destination);    

    this.node.onaudioprocess = function(e){
      if (!recording) return;
      for (var i = 0; i < numChannels; i++){
          if(!recordBuffers[i])  recordBuffers[i] = [];
          recordBuffers[i].push.apply(recordBuffers[i], e.inputBuffer.getChannelData(i));
      }
    }

    this.getData = function(){
        var tmp = recordBuffers;
        recordBuffers = [];
        return tmp;     // returns an array of array containing data from various channels
    };

    this.start() = function(){
        recording = true;
    };

    this.stop() = function(){
        recording = false;
    };

}

用法示例：

var recorder = new RecordAudio(userMedia);
recorder.start();
recorder.stop();
var recordedData = recorder.getData();