[Webkit-unassigned] [Bug 180522] New: Can't analyse local MediaStream input audio level using webkitAudioContext on iOS

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=180522

            Bug ID: 180522
           Summary: Can't analyse local MediaStream input audio level
                    using webkitAudioContext on iOS
           Product: WebKit
           Version: Safari 11
          Hardware: iPhone / iPad
                OS: iOS 11
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebRTC
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: adam at tokbox.com
                CC: youennf at gmail.com

We use the following code to analyse the audio input level in a local MediaStream coming from getUserMedia. This works fine in Safari on a Mac but on iOS you get constant 0 (because timeDomainData[idx] always returns 128).

navigator.mediaDevices.getUserMedia({audio:true}).then(stream => {
  const context = new (window.AudioContext || window.webkitAudioContext)();
  const sourceNode = context.createMediaStreamSource(stream);
  const analyser = context.createAnalyser();
  sourceNode.connect(analyser);
  const timeDomainData = new Uint8Array(analyser.frequencyBinCount);

  setInterval(() => {
    analyser.getByteTimeDomainData(timeDomainData);

    let max = 0;
    for (let idx = 0; idx < timeDomainData.length; idx++) {
      max = Math.max(max, Math.abs(timeDomainData[idx] - 128));
    }
    audioLevel.innerHTML = (max / 128);
  }, 100);
}).catch(err => {
   alert(err.name + ' ' + err.message);
});


You can see it working at https://output.jsbin.com/rexolan

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