[Webkit-unassigned] [Bug 192932] New: Can not disable audio processing (lowpass)

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Thu Dec 20 08:44:59 PST 2018


            Bug ID: 192932
           Summary: Can not disable audio processing (lowpass)
           Product: WebKit
           Version: Safari 12
          Hardware: All
                OS: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Web Audio
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: franz.bender at icloud.com

Created attachment 357815

  --> https://bugs.webkit.org/attachment.cgi?id=357815&action=review

Page 1: Chrome picks up high frequency audio; Page 2: Safari doesn't pick up high frequencies

There is no way to disable the pre-preprocessing of audio (coming from the microphone). Even with the 'echoCancellation'-Flag set to false high frequencies get filtered out.

What did I try to do:
I'm trying to analyze audio coming from the microphone:

let stream = await navigator.mediaDevices.getUserMedia({
    audio: {
        optional: [
            {autoGainControl: false},
            {noiseSuppression: false},
            {echoCancellation: false}
    video: false
let inputSource = this.audioCtx.createMediaStreamSource(stream);

I wrote a script implementing an algorithm which detects certain frequencies (called Goertzel algorithm). I noticed that it only works for low frequencies (in the range of human hearing). In Chrome however it did work so I assume that there is still some kind of audio processing going even though I tried to disable it.

In the attached PDF-File you can see two screenshots of exactly the same page. The left box is a plot of the raw audio data (512 Samples) and on the right is an indicator that shows the level of 18000Hz. I set my iPad up to play a 18000Hz signal at high volume. Chrome (page 1) processes the audio correctly. Safari on the other hand doesn't pick up those high frequencies.

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