JavaScript get permission for Audio.setSinkId

问题

I'm trying to change the sinkId at an Audio-Element in a chrome app.

Code:

var audio = new Audio();
audio.setSinkId("communications");

I'll get this error:

DOMException: No permission to use requested device

So to get the permission I tried to do that:

navigator.webkitGetUserMedia({
    audio: true
}, (stream) => {
    console.log("stream: ", stream);
}, (error) => {
    console.log("error: ", error);
});

But now I get this:

error:
NavigatorUserMediaError {name: "InvalidStateError", message: "", constraintName: ""}

I don't know, whether

• 'audio' is not available (but actually it should)
• I need a secure connection (but how do I get this at a chrome app?)

回答1:

Per specs, there should be a Permissions.request() method, which should accept a PermissionDescriptor object which itself should support a PermissionName of value "speaker".

So per specs, that would give us

 await navigator.permissions.request( { name: "speaker" } );
 const all_devices = await navigator.mediaDevices.enumerateDevices();
 const audio_outs = all_devices.filter( ({ kind }) => kind === "audiooutput" );
 // ...
 audioElem.setSinkId( audio_outs[ n ].deviceId );

---

---

But as of today december of 2019, no browser supports any of this...

Chrome (which is the only one currently supporting MediaElement.setSinkId()) does expose the Permission.request() method under chrome://flags/#enable-experimental-web-platform-features, but they still don't support the PermissionName "speaker" yet.

So we still need the less than optimal workaround of requesting for the "microphone" one instead.

(async () => {
  const query = await navigator.permissions.query( { name: "microphone" } );
  switch( query.state ) {
    case "denied": throw new Error('denied');
    case "prompt":
      await queryUserMedia();
      await getListOfDevices();
      break;
    case "granted": await getListOfDevices();
  }
  function queryUserMedia() {
    return navigator.mediaDevices.getUserMedia( { audio: true } );
  }
  async function getListOfDevices() {
    const all_devs = await navigator.mediaDevices.enumerateDevices();
    const audioouts = all_devs.filter( ({ kind }) => kind === "audiooutput" );
    const options = audioouts.map( ( dev, index ) => {
      const name = dev.label || ('audio out ' + index );
      return new Option( name , dev.deviceId );
    } );
    sel.append.apply( sel, options );
    sel.onchange = e => aud.setSinkId( sel.value );
  }

})().catch( console.error );

As a fiddle since Stack-Snippets iframes won't allow for the use of the microphone.

---

Ps: Note that if/when browsers were supporting the specs defined API, then it would even be possible to run this code on non-secure contexts.

来源：https://stackoverflow.com/questions/48854159/javascript-get-permission-for-audio-setsinkid