没有getUserMedia的声音分析 [英] Sound analysis without getUserMedia

问题描述

我正在尝试分析浏览器的音频输出，但是我不希望出现getUserMedia提示(要求获得麦克风许可). 声音源是SpeechSynthesis和Mp3文件. 这是我的代码:

return navigator.mediaDevices.getUserMedia({
        audio: true
      })
      .then(stream => new Promise(resolve => {
        const track = stream.getAudioTracks()[0];
        this.mediaStream_.addTrack(track);
        this._source = this.audioContext.createMediaStreamSource(this.mediaStream_);
        this._source.connect(this.analyser);
        this.draw(this);

      }));

此代码可以正常工作，但正在寻求使用麦克风的许可！我对麦克风一点都不感兴趣，我只需要测量音频输出即可.如果我检查所有可用设备:

navigator.mediaDevices.enumerateDevices()
.then(function(devices) {
  devices.forEach(function(device) {
    console.log(device.kind + ": " + device.label +
            " id = " + device.deviceId);
  });
})

我获得了浏览器中可用设备的列表，包括音频输出". 那么，是否有一种方法可以将音频输出路由到媒体流中，然后可以在'createMediaStreamSource'函数中使用它? 我已经检查了音频API的所有文档，但找不到它. 感谢任何可以提供帮助的人！

解决方案

有多种方法来获取源自gUM的MediaStream，但您将无法捕获所有可能的音频输出...

但是，对于您的mp3文件，如果您通过MediaElement(<audio>或<video>)，和来读取该文件，并且在没有破坏CORS的情况下提供了该文件，则可以使用 MediaElement.captureStream . 如果您是从WebAudioAPI上阅读的，或者是针对不支持captureStream的浏览器的，则可以使用 setSinkId 方法.

I am trying to analyse the audio output from the browser, but I don't want the getUserMedia prompt to appear (which asks for microphone permission). The sound sources are SpeechSynthesis and an Mp3 file. Here's my code:

return navigator.mediaDevices.getUserMedia({
        audio: true
      })
      .then(stream => new Promise(resolve => {
        const track = stream.getAudioTracks()[0];
        this.mediaStream_.addTrack(track);
        this._source = this.audioContext.createMediaStreamSource(this.mediaStream_);
        this._source.connect(this.analyser);
        this.draw(this);

      }));

This code is working fine, but it's asking for permission to use the microphone! I a not interested at all in the microphone I only need to gauge the audio output. If I check all available devices:

navigator.mediaDevices.enumerateDevices()
.then(function(devices) {
  devices.forEach(function(device) {
    console.log(device.kind + ": " + device.label +
            " id = " + device.deviceId);
  });
})

I get a list of available devices in the browser, including 'audiooutput'. So, is there a way to route the audio output in a media stream that can be then used inside 'createMediaStreamSource' function? I have checked all the documentation for the audio API but could not find it. Thanks for anyone that can help!

解决方案

There are various ways to get a MediaStream which is originating from gUM, but you won't be able to catch all possible audio output...

But, for your mp3 file, if you read it through an MediaElement (<audio> or <video>), and if this file is served without breaking CORS, then you can use MediaElement.captureStream. If you read it from WebAudioAPI, or if you target browsers that don't support captureStream, then you can use AudioContext.createMediaStreamDestination.

For SpeechSynthesis, unfortunately you will need gUM... and a Virtual Audio Device: first you would have to set your default output to the VAB_out, then route your VAB_out to VAB_in and finally grab VAB_in from gUM...

Not an easy nor universally doable task, moreover when IIRC SpeechSynthesis doesn't have any setSinkId method.

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