dart - 如何保存麦克风音频输入？

Question

我需要保存麦克风输入以便稍后在 AudioElement 中使用。我这样做是为了获得麦克风输入:

window.navigator.getUserMedia(audio: true).then((MediaStream stream) {
  # what should go here?
});

我应该怎么做才能保存音频？

Answer 1

有许多可怕的愚蠢示例，您可以在当前浏览器窗口中播放当前录音。有没有这个用例。对于视频，我可以想象有人想要构建一个类似 Skype 的应用程序，并有一个预览窗口来查看你在视频上看起来是否愚蠢，但音频......

不过我发现了一篇不错的帖子:From microphone to .WAV with: getUserMedia and Web Audio

我移植了链接文章中的部分代码，展示了如何获取数据。

import 'dart:html';
import 'dart:async';
import 'dart:web_audio';

void main() {
  window.navigator.getUserMedia(video: true, audio: true).then((MediaStream stream) {
  var context = new AudioContext();
  GainNode volume = context.createGain();
  MediaStreamAudioSourceNode audioInput = context.createMediaStreamSource(stream);
  audioInput.connectNode(volume);

  int bufferSize = 2048;
  ScriptProcessorNode recorder = context.createJavaScriptNode(bufferSize, 2, 2);

  recorder.onAudioProcess.listen((AudioProcessingEvent e) {
    print('recording');
    var left = e.inputBuffer.getChannelData(0);
    var right = e.inputBuffer.getChannelData(1);
    print(left);
    // process Data
  });

  volume.connectNode(recorder);
  recorder.connectNode(context.destination);


/**
 * [How to get a file or blob from an object URL?](http://stackoverflow.com/questions/11876175)
 * [Convert blob URL to normal URL](http://stackoverflow.com/questions/14952052/convert-blob-url-to-normal-url)
 *  Doesn't work as it seems blob urls are not supported in Dart
 */
//    String url = Url.createObjectUrlFromStream(stream);
//    var xhr = new HttpRequest();
//    xhr.responseType = 'blob';
//    xhr.onLoad.listen((ProgressEvent e) {
//      print(xhr.response);
//      var recoveredBlog = xhr.response;
//      var reader = new FileReader();
//
//      reader.onLoad.listen((e) {
//        var blobAsDataUrl = reader.result;
//        reader.readAsDataUrl(blobAsDataUrl);
//      });
//    });
//    xhr.open('GET', url);
//    xhr.send();


/**
 * only for testing purposes
 **/
//    var audio = document.querySelector('audio') as AudioElement;
//    audio.controls = true;
//    audio.src = url;
  });
}